# Another Rupnow 1 by 1



## CFLBob (Jul 11, 2021)

Starting around the time I was first getting my Webster to run, Brian Rupnow started a build thread on a vertical 1" bore by 1" stroke engine he was designing.  I watched it within interest because I was trying to decide what to build for my second engine.  

I spent a while looking at hit and miss engines, and talked about scaling models to get closer to what I was thinking of building, but in the end I decided to build Brian's engine from his plans. 

Brian finished in a few months.  That's highly unlikely for me.  First off he's a much more experienced machinist, and second off, I'm working from 2D prints in pdf files.  While I have both a manual and a CNC lathe, my mills are only CNC, so my work flow or processes are different from most folks.  For parts that I want to CNC  that will mean turning the 2D drawings into 3D models in CAD, and then using CAM or writing manual files to get the tool paths.  There are other things the prints call for that I should do; heat treating O1 (oil-cooled) steel; silver soldering some steel parts together, and so on.  These are things I think I know how to do in concept, but I'll need to test the details.  

My CAD program (Rhino 3D, but ver. 5 while 7 is current) is supposed to import .pdf files, and it sorta does.  It doesn't import the dimensions and some things it imports (like circles) don't behave at all Rhino's native version.  It just puts lines on the screen, and the commands to create dimensions don't work for many things, so it's going to be  a completely manual process.  Before you machine a part manually, you need to study the drawings.  That doesn't go away with reading pdf files in.  

For my first experiment, I thought I'd import the crankshaft counterweights.  These have a rather complex outline, with only three straight lines in the whole part.  To do these on the rotary table would take multiple setups.  I believe that the whole part would take seven setups.  If I could do it in CNC, I thought I could reduce that to three setups.  First, I tried to import the outline, scale it in size and then convert it to a solid.  It went better than I thought.  As a test, I printed it in PLA, and it came out looking like it should. 





It seemed like the best way to make this would be to not do that rectangular cutout in the bottom until the outline was cut.  Then I could drill a hole where the center of the large radius (top in that view) is, and use that to bolt the workpiece to a tooling plate.  Starting with a roughly 2" x 6" piece of solid steel I'll drill two holes far enough apart to cut two of these counterweights; with the tool paths based on a 3/8" end mill that was 2.000" apart.  The cutout would be done using what CAM programs call "waterline" cuts: constant depth passes around the shape.  Once the outline is cut, I'll stand it up in a vise, and cut out that 0.500" wide rectangle.  After that, there are two holes, a through hole from top to bottom (you can see it in the center of the plastic model) and its counterbore.  

This shows the two pieces right after cutting them out.  I like to say it came out almost as if I knew what I was doing.  It was kind of cool watching the cutter cut the one on the right out of the steel without touching the one on the left. 






Look between the two of them where the piece of stock that hasn't been cut away has a point that's pointing out of the screen.  See the ledge between the left and right pieces?  It's an arc from that point to the right side of the left counterweight.  What you're seeing is the left one isn't cut to full depth while the right one cut through the steel into my scrap aluminum backing piece in places.  The backing piece is visible on the front left.

All that irregular depth of cut meant was that when I took them off that fixture they're on, I had to do some file work to make the problem child match the other one.

Now we get to the real meat of this task.  How do I hold those rounded parts so that I can cut out the rectangular relief that's under the mounting screw?  I want something with a concave radius that matches the convex parts, to hold it upside down in the vise.  I thought about using the rest of the steel that I cut them out of, but that's the wrong radius.  That radius is 3/8" more than the part because of the cutter going around them cutting out the parts. At some point, it occurred to me to use my 3D printer to print a fixture.  An hour and 30 cents worth of filament later I had a fixture.  





The two parts squeezed together are .620 thick, and I made the plastic thinner - like about .575 - so that the jaws wouldn't just squeeze the plastic but would lock the parts in place.   I made sure the bottoms of the blanks were parallel to the mill table with an angle gauge.  

Once I cut the rectangular cutout, the printed fixture was a perfect way to hold the two parts to drill the through hole.  Being backed by plastic and not my vise made it risk free to the vise so a no-brainer to do.  They're not technically done in this picture, there was one more step, but they're pretty close to being done. 






This is after the second setup of the three needed, with the two counterweights alongside the fixture and the 3D printed test counterweight I did to make sure the dimensions were right after I translated from .pdf files to a CAD drawing.  To do the final setup, all I needed to do was stand the two parts on their legs and center the drill bit that made the holes in the parts.  I did the 1/4" counterbore with an end mill held in the drill chuck.  The only motion is the up/down of the drill.  

I'm not sure what the next part will be, but I either plunge more deeply into porting the drawings into CAD files or do something where I can work off the pdf files.  I had been thinking of doing the crankshaft because I've never done one like this.  I noticed that in Brian's thread he had the mating piston connecting rod done first before getting into the crankshaft, so that points me toward doing the conn rod before the crankshaft.


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## Brian Rupnow (Jul 11, 2021)

Go Go Gadget!!!--Good luck Bob.--If you have questions, don't be afraid to ask. Sometimes I put way too much information on one drawing, so you have to look really close to see what I am trying to tell you.---Brian


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## werowance (Jul 12, 2021)

watching


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## CFLBob (Jul 18, 2021)

Just an update.

It was a computer-intensive week and not one single piece of metal was harmed or even inconvenienced. 

I upgraded my 3D printer setup by adding Pronterface. Pronterface gives you computer control over the printer for things that the built in interface doesn't allow, including an immediate mode line where I can tell it things to go over 100mm in X or Y (G01 X100), like I'm used to from Mach 3 on the CNC tools. Well, I can do that in the built in interface, but it's much clumsier and involves turning the selector knob about 125 clicks and presses.

There's a back story there of why it took days to do that rather than a few hours, most of which I can sum up by saying, "I hate Windows 10."  There's one exception to that, and maybe it's only important for the Creality Ender 3 V2, but let me tell anyone else in case they need it.  The micro SD card that comes with the Ender includes drivers for Windows to convert a USB port to emulate a regular serial port.  They wouldn't install.  I'd point Windows Device Manager to the files and it didn't recognize them.  It turns out the driver I wanted is called CH340 and one of the Ender documents has a screen shot showing a piece of software to install that driver that they didn't include on the memory card.  If you get into this trap, do a web search for CH340IR.EXE, run that and it'll install the drivers for you. 

The rest of the week was spent turning the pdf files of the engine drawings into solid models so I can get tool paths.  Chances are I wasted about half that time by correcting the pdf import into Rhino 3D CAD.  It doesn't import dimensions or distinguish hidden lines from regular lines, so the drawings are a mess.  The point was to just convert them into solid models and not fuss over the drawing.  As for where a hole goes and hidden lines, just keep both the pdf open in Acrobat reader and switch back and forth between them as needed.  This is one of the side plates that define the crankcase.  






I converted a few other parts to solid models, but they were much simpler than this one.  There's more aluminum left in the chip tray than the part.  I think.  

Before the cutters touch this part, I'll convert the other side plate to a solid model.


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## awake (Jul 19, 2021)

Bob, something to consider is getting a Raspberry Pi and setting it up with Octoprint. It is a very easy process, not very expensive (just the cost of the Pi), and gives you wireless control of the printer with all of the manual features that you get from Pronterface, plus the ability to upload files to print, the ability to use a camera (cheap USB webcam works) for live monitoring of the print over the wifi, etc. You can also set it up to work over the internet, so that you can control your printer away from home - some security issues to attend to, but again very easy.


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## CFLBob (Jul 19, 2021)

I have a Raspberry Pi 2, and the reason I didn't start down the road to using that is that the NUC was literally on the next workbench over, while I'd have to dig up some things for the Pi.  I might well replace the NUC with the Pi if I can get it to run the only app that was on the NUC until now.  

I looked at Octoprint but really don't care about the wireless control aspects which seemed to be the emphasis.


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## cds4byu (Jul 20, 2021)

I have set up Octoprint on my printer and will never look back.

I can do a complete job of controlling my printer through a web browser -- which is immune to Windows 10/11 issues (when they issue the required update, which eventually they will).

It makes it trivial to control my printer.  I can flash firmware very easily.  I can do all the control I want.

I get it that you have Pronterface set up.  I used to have Repetier host set up.  The best investment I've made in my 3D printer was Octoprint.

Carl


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## CFLBob (Jul 28, 2021)

I haven't updated this since the 20th, and while I don't have cut metal to show, and won't for another couple of days, I've been plodding along on the computer side of things.

Here's where things are now.  






These are (big secret) side plates 1 and 2.  The blanks aren't much bigger than the final part, and instead of laying out where to drill with Dykem and scratching, I printed the two drawings at 1:1 and taped them to the blanks.  Then I marked the point referred to as (0,0) on the drawings using a punch, and drilled them for a "tight clearance" hole of the 5/16-18 bolts holding them to a plate.  The holes in the plate were drilled and tapped the same distance apart as the drawings show for the two big holes in the side plate (1.563").  

With the (0,0) located, I know the location of all the features, but I'm intending to cut the outlines in the next step, and not drill all the matching holes.  I'll then bolt them together, like Brian did using a 3/16" drill rod in two places, and drill the five screw holes that hold the two halves together.  I'm not sure how I'll hold the two pieces to do that.  It would be good to drill, tap and counter bore all five holes first, before I cut the outlines, but don't have a cutter long enough to cut the outlines of a 2" thick plate or a good way to hold them for that.  

The next step is to create the tool paths, and since they're mirror images of each other, the tool paths have to be different.  The program I'm using is an old version of DeskProto, version 5. They appear to be offering it as a free version now, and you pay for more capabilities in the SW. I need to look at the free version and see if it's better than what I have. I approach a part like this by waterline machining and I have to arm wrestle DeskProto to get it to what I want. The problem is that even then don't get exactly what I want. This is a screen capture showing the tool paths before I save them to a file.






The red and green lines are tool paths; greens are rapid (G00), reds are regular (G01) movements.  The problem is that the program moves the cutter across the top of the part, and that will cut off my mounting bolts if I do that.  

I end up editing the tool paths in a text editor to remove those loops around the raised center area.  Then I check it in GWizard editor from CNCCookbook.com to ensure it's cutting right.  There still appears to be wasted motions that I'd like it to not make, but since I'm not trying to save every second of machine time, I won't try to edit them out.






(I'm not sure why the green tool path lines in this turned blurry when I saved it).  This is a perspective of the same side plate (2) showing that the cutter just goes around the raised area and doesn't trim it.  

The next step is to correct a mistake in my original mounting of those blanks and put them on a sacrificial piece of 1/16 thick aluminum.  I'll recheck the center of the (0,0) hole with my edge finder to ensure it hasn't shifted around the mounting holes.  Once that's done, I'll air cut the first few loops around the part to prove to myself it's not doing something I didn't expect.  If that's good, I'll cut the first one.


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## Eccentric (Jul 28, 2021)

Looks like your making good progress. A couple of questions regarding the issue of the tool paths cutting your hold down hardware: does the software allow you to set a "Clearance Height" or a "Retract Height"? Alternately, does the software allow you to select a start Z height and a finish Z height? If so you could make your model taller to include the hold down bolts, then start the actual cutting lower so as not to cut air before you get to the part.

It looks like you plan to cut the part in one go. I like to make a roughing pass and then a finishing pass. I typically leave about .020" of material all around the part with the roughing pass and then climb mill to dimension.  For the roughing pass I use an older end mill, and remove material faster than I would for a finish pass.  then I use a newer end mill moving across the work piece slower for the finishing pass. This takes longer, but I get a much better finish and I am able to hold tighter tolerances.

Do you have a band saw or some way to remove most of the material before you take it to the CNC? I have an old carbide tipped table saw blade that hit a couple of nails in a board year ago. That broke several of the carbide tips so I don't use it for wood, but it does a great job hogging out aluminum on the table saw. Much faster than my band saw for large blocks.

I really hate to have to go in and edit the G-code because I end up modifying and tweaking the tool paths a lot, and if I have to edit the G-code each time I make a little modification, it can be quite tedious.  As you stated, it is about tricking the software to give you what you want.  I usually make several version of the 3D model, either removing features or adding material in keep out areas, to force the software to give me tool paths where I want them.


Keep up the good work, I am looking forward to you making chips.


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## CFLBob (Jul 28, 2021)

Eccentric said:


> A couple of questions regarding the issue of the tool paths cutting your hold down hardware: does the software allow you to set a "Clearance Height" or a "Retract Height"? Alternately, does the software allow you to select a start Z height and a finish Z height? If so you could make your model taller to include the hold down bolts, then start the actual cutting lower so as not to cut air before you get to the part.



It has a clearance height, which I thought behaved as the retract height, but I hadn't thought of distorting the model by making it taller.  Setting the Z-height where the cutting finishes?  I think there's a way to do that.  I think that the program by default cuts the top with the paths at Z=0.000 because it has no way of knowing that you don't want to do that.  

I just downloaded the demo version of DeskProto 7.  I'll play with that at some point.

I have been planning to cut it in one operation, but I've done rough and finish passes before and I'm thinking about it for this.  The milling is going to use a 1/2" diameter cutter and is largely taking thin cuts off the vertical sides of the piece.  There's one place in the blank that turns into cutting a slot, that area on the right front, in front of the surface that angles up to the mid-line.  I use a FogBuster for cooling, not flood coolant, and I'm a little hesitant about cutting a slot that's an inch deep.  The fog buster has a hard time getting into deep slots.  

I could cut that corner off in a couple of ways; probably the easiest would be cutting the corner off in a separate operation with another end mill.  It's just going back and forth between two points, dropping the cutter for each path.  I could even do it with a saw.  That would leave the main operation as all cutting along vertical edges.  

 I'm looking forward to making chips, too.


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## CFLBob (Jul 30, 2021)

Just a small addendum.  

I've cut many things just by using the command line in Mach 3.  A few simple Go To statements (G01) back and forth, dropping the cutter every change.  So I set up to do the same with cutting off the stock between the angled edge and the rest of the blank.  

Because of the angle and needing more than just X and Y, I drew a few cylinders in the CAD drawing, found their centers and made a tool path.  This is side plate 2 and the big rectangle is a estimate at the size of the stock I'm cutting it from.  The reason 2 and 3 are farther off the edge than 1 and 2 is that I tested the points I had and the cutter didn't get off the blank.  I drew the rectangle wrong.  So I moved 2 and 3 further along the angle.






The idea is go in numerical order, and since the endpoints are all off the work piece, when I got from 4 to 1, I'll lower the cutter, too.   

With this approach I never cut a deep slot.


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## CFLBob (Jul 31, 2021)

It wouldn't be a shop project without little things to overcome, right? 

I did that little cut shown in the previous post.  It didn't take long to notice that the cuts didn't seem to be as deep as the Mach 3 display (DRO) was saying.  When the file was done, instead of being through the 1" thick piece, it was cut about halfway.  The cutter had driven the rest of the way up into the collet.  I thought I had tightened that as tight as always.  Oh, well...

I repositioned the cutter (a 1/2" carbide, 4-flute end mill), tightened very tightly and started the cut again. This time, it cut farther down, but still left a sizable ledge on the work - maybe .050 thick.  I trimmed that back but every time I cut another pass, it seemed like the cutter pushed farther up into the collet.

Since the cut had pretty much achieved its purpose of trimming away most of that corner, I said it was close enough to done and then decided to do the actual cut.   I re-zeroed the cutter in the collet yet again and thought I'd try the real outline cut.  The real outline file also left a thick ledge again.

At this point, I took the carbide cutter out and replaced it with one of my older HSS cutters that I had used several times before.  I suspected that the cutter was too small in diameter and that's why it couldn't grab it securely enough.  It was a cutter I got from some dood's table at Cabin Fever in '15, so maybe it was surplus because it was imperfect?  My mistake in retrospect was that I never stopped to analyze the problem and didn't really ask, "why is this a problem now and never has been before?"

I did the same exact file with the HSS cutter, spent about 10 minutes cutting air, and it also left part of plate uncut.  By this time, it was late enough to shut down in the shop and I said I'd look closer at the cutter and collet today.

The cutter diameter was fine.  The carbide cutter measured 0.4995 to my manual micrometer while the HSS cutter measured 0.4985.  The diameter clearly wasn't the issue, so I cleaned out the collet with a paper "shop towel" (the blue paper kind) and some mineral spirits.  I don't know how it got oil in there, and I didn't see anything on the paper towel, but I put the carbide cutter back in the collet and did the last couple of passes around the side plate (I edited the file to remove everything above cutting to -0.950).  This time, it left a thinner margin on the very left side of the blank.  Re-checking the zero showed it hadn't moved, so that meant the work probably did.  I lowered the bottom cut from the CAM set (-1.001) down to -1.004 and ran it again, this time resulting in a proper looking side plate.  I think the reason that previous try left some material on the left side is I inadvertently didn't position a backing plate under the left edge.






I think that I'm going to mirror the files to re-create that path to cutoff the corner and try to get the other side plate done tomorrow. 

These still have a lot of machining to go, but the first chips are always good.


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## CFLBob (Aug 2, 2021)

The other side plate is cut to size, and it had a peculiar aspect to it.  The CAM program neglected to cut one little area to the proper depth.   

In the red box here.  You can see the ledge better at the bottom.





That uncut area on the top is supposed to be 0.124 above the floor.  That's 4 cuts at .031; the rest of that surface is the right depth; where you see the ledge and across the right side, it's .093 - three passes.  I ran the file again, just to watch through the first four layers and the cutter just never went there.  I was concerned it might have been from my editing the file, but that was just to keep the cutter out of the uncut area.  It went into this area to cut it down to -.093, it just didn't go back to cut the last pass.  I've been using Deskproto for about 10 years and I can't think of another time it did something like this.

I have a way to use a Logitech Rumblepad - a game controller - as a pendant-like interface for Mach3 and cut that area down to 0.124 "by hand" driving the mill with the buttons on the Rumblepad.  It needs a little file work, but should be OK.

Next step is take both sides off this plate and move into my plans to bolt them together and drill the holes for the guide pins Brian designed in.


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## CFLBob (Aug 8, 2021)

Picking up where I left off last Monday, now it was time to take both pieces off the mill, de-burr them, then bolt them together, smooth them and remount to get ready to drill the holes for the two tooling pins that go into both sides to hold them in the right  positions.  That makes it easier to take them apart and put them back together precisely, which I'm going to have to do.  Other than breaking the one fine sanding belt I own before I was fully done with sanding, there were no issues.

This is where I made a silly screw-up and spent a day trying to find it.   The issue centers on the dimensions in red in this drawing. 






The problem showed up when I went to position the center drill over the hole for the tooling pin circled in red.  It looked too close to the top edge, and instead of measuring what's in the red oval, I got more like .150 to .160 instead of .220.  That led to studying it for hours, looking at other measurements and just being confused.  The overall length and width of the plates were right.  The dimensions going left to right looked fine.  The dimensions from the edges of the raised area to the part's edges were also offset.  IIRC, the top one, 0.696 was too small and the 0.625 on the bottom was too big. 

What this would mean was that the CAM program had shifted the centerline X-axis upward in this view.  I couldn't figure out how it could do that and not mess up the whole part.  

Late one night last week, after puzzling over this for hours, I took yet another look at the work and realized my mistake.  I had put the two pieces on mill upside down and backwards.  Notice the ~45 degree angle in the drawing is at lower left.  Here you can see it's on upper left.  The top of this stack is side 2.  You can tell it from side 1 by the machining marks






Since the next operation was just positioning the mill and drilling a total of 11 holes of different sizes, it didn't take as much time to finish this phase of the machining as it did to figure out what I did wrong setting up to do it.   






There are five large holes with a counterbore; those had to be done in three steps; the two tooling pin holes had to be prepared in three steps also and tooling pins cut to length.  So it wasn't simply drilling 11 holes, but it wasn't so much hard as just a lot of motions. 

These are complex pieces.  The vertical side facing you, the right and the far vertical sides all get drilled and tapped holes.  Two per side on both side plates.  The far side gets a 1.1" diameter hole bored into it, centered on the plane where the two side plates touch.  And lots more.  I'll be working on these for a while already (it only seems longer than Brian spent on the whole engine), but I think the way most of the next operations should get done is with the machining vise on the mill's table.  For some of the large features that get bored out, perhaps the four-jaw chuck on the lathe.


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## CFLBob (Aug 16, 2021)

Since I've been doing Monday updates and it's Monday, here's an update.

As the week began, the first step was to take the two sides apart.  I tapped the five  #10-24 holes in plate 2 that will get screws holding the sides together, and then it was time to take my aluminum tooling plate off the mill and put the milling vise back on to start working on some of the internal complexity of these parts.  It was time to hog out the three different cylinders inside side plate 1.  

The largest of these cylinders is 2.376" diameter and 0.557" deep.  Like most of you, I have a rotary table, a boring head for the mill, and a boring bit for my lathe.  How best to do that?  Since I think a strong feature of my shop is the CNC control, that's where the approach went.

The basic thing this is doing is cutting a circle, and the ability to cut smooth nice circles is built into G-code.  Plus, while the commercial CAM program I have can cut circles, it ends up being a fairly coarse approximation - I can see and feel the steps the CAM generates.  I've hand programmed circle cutting while making the parts for the big mill CNC conversion and while making the connecting rod for my Webster.  This post has some details on it while I found an incompatibility between the software I use to verify G-code and Mach 3. I decided to hand write G-code using the circular interpolation (G03 - cutting counterclockwise) instead of using the CAM program.

The first thing I did was use the biggest end mill I have, a 3/4" diameter cutter, in the centers of the cylinders and not cutting to final depth.  Just removing bulk metal and creating a starting point.  That's two holes.    

The basic approach is to use that 3/4" hole in the middle as an entry into the cut.  That hole is where I lower the cutter (so I'm not drilling with an end mill) and then move back out to the rim of the circle to cut around the perimeter. I have to keep straight in my head that the tool path marks the center of the cutter, not the diameter of the hole it's cutting.  When using the CAM program, it will work from the diameter it needs to cut keep track of the tool radius offset.

After testing a couple of ideas, I figured the way to cut the big cylinder is by cutting two passes around the circle, one with cutter center at the edge of the 3/4" hole, which doubles its size to 1.5", followed by a second cut with the center of the cutter 0.375 in from the final size.  Since the radius is 1.188, the cutter goes at 0.813 from the center.  This is after the first operation on cavity 1.  I have a video here showing the last few passes.






The changes in the way the bottom of the cylinder reflect the light can't be felt, and you can see marks from both passes around the circles.

With that nice result, I wrote toolpaths to enlarge and deepen the center of that cavity and then enlarge and deepen the small cavity on the right, bringing both to final size.  Except I misread the drawing and made cavity 3 too small.  It's always easier to correct making something too small as opposed to making it too big, and with the file that enlarges and deepens that cylinder taking about 15 seconds, it took me more time to fix the G-code than fix the part by running it (video of the process - 28 seconds long at actual speed). 






I think I can just revise the X and Y coordinates for the other side and be done fairly quickly.


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## CFLBob (Aug 25, 2021)

I'm late on my usual Monday updates because I wanted to be able to say I'm finished with the two side plates.  

Hollowing out the second plate using the same basic approach as shown in the last post worked fine and really didn't take much longer than running the files a week ago.   Once I found a typo that made them just a bit wrong.  






Then it was a matter of drilling and tapping holes everywhere.  On side 2.






and the rest.  The top has a 1.100" diameter hole that I cut using the exact same approach as I did for the internal hollowed out areas, as well as four tapped holes.






The right side has a tricky feature, a hole drilled at 40 degrees to the bottom, 1/2" reamed.  This really caused me about a day's delay of "think about it 30 times, measure it 20 times, machine it once"






You can see what I think is my big mistake on this one - I drilled and tapped two holes on the back side plate (2) that are extra.  I think I can fill them with a set screw and use some red LocTite to keep them sealed.  

And since you've seen every other view of it, here's the bottom side, which has a 3/8-16 tapped hole in plate 1. 






They clearly need some cosmetic work to pretty them up a bit, and some deburring, so they're not Done done, but I think all the features are there.  I honestly think this might be the most complex little assembly I've built.  There's nothing equivalent in the Webster or my Duclos Flame Eater.

I think I'm moving on to the crank shaft next, but it's also a good time to make sure I have all the raw materials.  I need to order a few pieces of metal I didn't order last time I shopped.


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## Brian Rupnow (Aug 25, 2021)

Looking good bob.----Brian


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## L98fiero (Aug 26, 2021)

CFLBob said:


> Picking up where I left off last Monday, now it was time to take both pieces off the mill, de-burr them, then bolt them together, smooth them and remount to get ready to drill the holes for the two tooling pins that go into both sides to hold them in the right  positions.  That makes it easier to take them apart and put them back together precisely, which I'm going to have to do.  Other than breaking the one fine sanding belt I own before I was fully done with sanding, there were no issues.
> 
> This is where I made a silly screw-up and spent a day trying to find it.   The issue centers on the dimensions in red in this drawing.


How do you check your part program? There are some pretty sophisticated programs for checking that will backplot solid models but a quick, easy check can be done with CNCdiscriminator Discriminator CNC Editor The download is free and as long as you're not expecting it to interpret macros and such it's free. It only plots cutter paths, not solid models but it's pretty good for even some 3D profiles, depending on what you expect from it, I use it all the time and if you want to edit the program it's better than the solid modeller in the CAM package.


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## CFLBob (Aug 26, 2021)

L98fiero said:


> How do you check your part program? There are some pretty sophisticated programs for checking that will backplot solid models but a quick, easy check can be done with CNCdiscriminator Discriminator CNC Editor The download is free and as long as you're not expecting it to interpret macros and such it's free. It only plots cutter paths, not solid models but it's pretty good for even some 3D profiles, depending on what you expect from it, I use it all the time and if you want to edit the program it's better than the solid modeller in the CAM package.



I use the CNCCookbook.com GWizard Editor.   It gives the cutter paths on a grid and not on the model.  Since the grid is 1/4" squares, I can get the dimensions of what it cuts out to a good accuracy with my hand calculator, but it still wouldn't find the problem.  No software would have.

I mounted the part upside down and backwards.  That sort of "short in the headset" just isn't going to be found by software.


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## CFLBob (Sep 7, 2021)

The last ten days or so have been focusing on making my crankshaft.  Since I've never made a real crankshaft (supported at both ends), like this one, I was interested in getting experience at it.

The final size of the rectangular stock the shaft is made from is 1.000 x 0.500, and while Brian recommends making it 1/32 on each side oversized to start with, I left it .025 on each side oversized.  Mainly because I do everything CNC from the command line and counting by .025 at a time is more familiar than counting by 0.0313






By the way, I actually threw away more steel in those chips, 7.77 cubic inches, than I ended up with.  The volume of the 1.25" diameter, foot long bar to start with was 14.73 cubic inches.  The volume that's left was 6.96 cu. in.  

After this, I did the usual trim and de-burr of all the edges, and then put the two center drill spots in both ends that will hold the piece so it gets turned to the proper sizes and shapes.  This is how that was done - verifying zero on the left and after the work on the right.  It was just about all I could do with my mill to put the center marks on the ends of an 8" long bar. The head was just about at the top of its column.






At this point, I had a real bump in the road.  I have two lathe dog sets for my Sherline lathes, but nothing for the big lathe.  It was the weekend, a holiday weekend here in the states, so now what?  

First, I tried to turn between centers without a dog to see if it could work but I could barely scrape anything off the piece.  After looking for options, I thought I could make one out of a 2" diameter piece of steel or aluminum, about an inch long.  Bore a 1.5" diameter hole in the middle.  Cut away everything that doesn't look like a lathe dog.  My immediate problem was that while I had a cutoff piece of 2" aluminum, it wasn't long enough and I had no other junk stock big enough to work on. I eventually found a piece of pipe in my junk stock that was smaller than 2" diameter but big enough to work, so today I made it into the lathe dog.  It's some sort of soft, gummy aluminum alloy, maybe the stuff they make shower curtains out of.   






It isn't strong enough, probably because the walls are too thin.  When I tighten the setscrew more, the ring stretches.   I made some test cuts with it and it seemed to worked well enough, though.  If I had some steel or something that would resist stresses more than this one, I'd make a replacement.  

I'll go ahead and try it, though.  Within a few days, I'll know if it holds up to the stresses of making this crankshaft.


----------



## Brian Rupnow (Sep 7, 2021)

Very glad that I see you continuing with the build.---This build isn't for sissies. You will learn to figure out a few things before you are done here.---Brian


----------



## Eccentric (Sep 7, 2021)

Looking great.  I think making the crankshaft is one of the most challenging, most rewarding and most nerve wracking parts of the build. I hate to admit it, but I rarely get my crank right on the first try,  hopefully you will best me in this regard. But I learn something everytime and I am getting better and learning little tricks.  Patience is the key.

I agree with you and don't think the homemade aluminum lathe dog is going to hold up, you have a lot of turning ahead of you. I recommend this set: Lathe Dog Set | Lathe Dogs for Sale | LittleMachineShop

They are only 35 bucks and have a whole progression of sizes that you will use as you turn down the crankshaft.  They are steel and will allow you to really crank down on the hold down bolt. You can see an example in the last picture of this series.








I use this type of small carbide cutter to turn down the sides of the  crank web.  Like you I use the mill to remove the material and cut the slot to size, but there is one last cut the mill cannot do.  And I use






this type of homemade HSS cutter for the crankpin.  It is relieved on the sides and has the forked snake tongue shape on the end to reduce the amount of the cutter actually in contact with the work piece.  I crank it in a couple of thou and then move the cutter back and forth.  As I approach the target dimension, I run my lathe slow, like 250 RPM to eliminate the chatter.  This is the most nerve wracking part for me, as I approach the actual dimension, you over shoot and the part is ruined.  I turn to about .0015" over then use files, stones and emery paper to finish to size.   






Here is a collection of tools used to bring the crankpin to final dimension and polish.  It is important to be cognizant of the pressure used across the pin, you don't want to make one side of the pin smaller than the other.  That is a problem with files for example, if you press evenly then move it back and forth, the middle of the pin is in contact with the file more than the edges and you get a low spot in the middle. I use the calipers and micrometer constantly throughout the process. I use strips of emery paper for the final finish.






If it is available, I use the connecting rod to test fit.  I am careful not to over tighten the cap before the pin is to dimension, but this proves that the web dimension is good and the final fit is good.

You can see the lathe dog in this picture.  Also the reason my steel is black is that I stress relieve the blank in the heat treat oven and let it oven cool overnight.  Don't know how much this helps.

Keep up the great work.


----------



## CFLBob (Sep 7, 2021)

Thanks for that excellent discussion.  Lots of good points to come back to again.  

This one really resonated 


Eccentric said:


> That is a problem with files for example, if you press evenly then move it back and forth, the middle of the pin is in contact with the file more than the edges and you get a low spot in the middle.



I think I've been there on different tasks.

My immediate problem is that I have two sets of cutters, one 1/4" shank set for the Sherline lathes and one 3/8" shank set for this big lathe, the Little Machine Shop 3540 (a SIEG SC4).  The L & R cutters are wider than the opening in the bar that I roughed out on the mill.  I used a flat ended cutter similar to the one you show except with no cutout that happened to fit.   I need to open the slot close to final width with either the square tip or something.  I'm thinking of using one of the 1/4" cutters.  




I hadn't noticed the chatter until this  picture.

Your lathe looks so much like my LMS lathe that it's spooky.


----------



## CFLBob (Sep 19, 2021)

Well, it has been almost two weeks since the last update and not much to say.  I concluded my shop-made dog wasn't going to work and after exchanging emails with Little Machine Shop about using the chuck mounting plate instead, I ordered a face plate for my lathe and their two biggest lathe dogs.  For smaller pieces, I have the equivalent tools for my Sherline, but I've never used them in the 15+ years I've had them. 

Let me note first that the people who make these accessories never include instruction sheets.  I think their view is that if you're using a lathe  you should be professionally trained and you should know how to maintain or  upgrade it.  I also wouldn't be surprised if not including instructions  might have some aspect of trying to protect themselves from spurious lawsuits. 

Now, I'm fully self-trained, I take responsibility for myself, and there really didn't seem like many ways to put it on incorrectly.  It has three bolt holes on the back which match with three through holes on the mounting  plate that's standard on the lathe.  I put the first bolt in, went to rotate the two plates to put in the next bolt and quickly found the combination wouldn't turn.  There was interference between a different bolt on the lathe and the faceplate.






That bolt (M8?) has two nuts on it, putting that spring under  tension.  It sticks maybe 1/8" inch into that cavity in the  casting.  The bent, black sheet metal you see on the left and top edges is holding a clear plastic "lathe chuck guard" that is supposed to keep your fingers away from the chuck but primarily seems to catch oil the chuck may sling.  A closer look showed that when the guard is down, the faceplate  will rub on the plastic and I'm sure eventually (a few minutes) will wear  through it.  A note on the faceplate's product page  says, “This faceplate will not fit with the plastic chuck guard in  place.”

I'm going to gloss over me looking at the lathe and trying to figure out how to remove that for several hours when the answer is visible right there in that picture.  All I had to do was unscrew the two nuts on the right end of the interfering bolt and then the cover just slides off the bolt,  Once that's done, just unscrew that bolt.   That's when I set things up to hurt myself. 






This is the faceplate, lathe dog, crankcase blank and all.

You can see above that I'm using a parting tool to shave that side of the cutout, and to minimize how much tool was exposed, cranked the cross slide and QCTP forward.  It's like this.






I'm not completely sure how it happened, but I think I put my right hand on top of the tool holder and let my finger stick out forward a little too far while getting started.  The bar was spinning and it whacked my finger.  It tore the end of my finger off breaking almost all of the fingernail, but it stayed attached by a lot of skin.  We figured it was time to go to an urgent care place.   The doctor there said the end segment of bone in that finger was broken and they don't treat "open fractures."  They told me to go to an ER.  Where I sat for 3-1/2 hours, never talked to or saw a doctor, never really had anyone look at it closely, then had a nurse leave the blood soaked and hardened gauze pad from the Urgent Care place on the finger, wrap some self-adhesive gauze around it, and refer me to a hand surgeon.   This was last Monday the 13th.

Long story shortened, the surgeon got me into the office Wednesday and did the surgery the day after that.  This is called a degloving injury but do yourself a favor and don't look for example images.  I will still have 10 full-length fingers, and might even have 10 fingernails.  I mean, I do now, but part of the fix was to sew the half or 2/3 of nail that broke off back onto the nail bed and it's going to take months to see how that grows. 

I just took off the oversized bandage I've been wearing since Thursday and switched to something smaller.  It's likely to be another week before I can get any more work done.

I need to order some more metal, so this is a good time to pay attention to those things.


----------



## Brian Rupnow (Sep 19, 2021)

Bob---Sorry you hurt yourself. I've had a few whacks from the chuck, but nothing hospital worthy. I'm not exactly afraid of my machines, but I treat them with a great deal of respect.


----------



## CFLBob (Sep 19, 2021)

Brian Rupnow said:


> Bob---Sorry you hurt yourself. I've had a few whacks from the chuck, but nothing hospital worthy. I'm not exactly afraid of my machines, but I treat them with a great deal of respect.



This is the first time I've ever needed anything beyond a plain old band-aid from anything in 40+ years of wood and metal working  It obviously could have been much worse, but it was just from a moment of inattention.  

The previous week, I was telling someone to watch out because anything that cuts metal isn't going to get slowed down by skin and bone.  Anytime we're using any machine, something bad could happen.


----------



## Eccentric (Sep 22, 2021)

Bob,

I am also sorry you got hurt, I hope everything heals OK.  The name of the injury , degloving, gives me the creeps and shivers.  Sorry it had to be you, but a little reminder now and then of how dangerous our machines can be is not a bad thing.  I'll continue to be extra vigilant in your name.

I've always had mixed feeling about those "chuck guards" on the smaller hobby lathes.  Do they give a false sense of security? Do they enable people to be lax respecting  the moving chuck?  Are they a neccessity for the beginning hobbiest? We all are aware of the chuck and work close to it, especially with files (which always have a nice fat handle so it won't be driven through the palm of our hand by accident, right?).

Take care of yourself and I hope to see you back in the workshop soon.  Your crank is coming along nicely.

Greg


----------



## CFLBob (Sep 22, 2021)

Thanks, Greg.  I've found over the last two days that I forget to use the pain meds, which clearly means I don't need them.  That's a good sign.  The finger is still a bit swollen and the range of motion isn't back but it's coming back.

My followup visit with the surgeon is Friday morning and I'm hoping to be back to more or less normal.  I don't know if that's even possible, if I'll get another 10 day followup or what, but 10 days to two weeks is about when they take out regular stitches.  That's ignoring the 6 months for the nail to grow back out.  

Meanwhile, I've been rounding up the metal stock I need but didn't pick up when I was starting because it seemed like the sizes I could buy were absurd compared to what I need.  Like I need about 1" length of a O-1 tool steel to make the cam, and the smallest bars I could find were 36" (that 1" I quote is over twice the finished length of the cam).  

I think I'm about to order a flywheel casting from Martin Models instead of doing the built up flywheel Brian did in the original.


----------



## Brian Rupnow (Sep 22, 2021)

Bob--In my opinion, no one should feel bad about buying a flywheel , a sparkplug, or a carburetor. I think everyone should build one of the above mentioned things once, just to prove to themselves that they can. Then, having proved to yourself and the world that you have actually made these things and that they are in the range of your capabilities, go ahead and buy them.---Brian


----------



## Steamchick (Sep 23, 2021)

Bob, Sorry to hear of your injury. And thanks for NOT posting pictures. I don't enjoy hearing of painful experiences... call me squeamish! I can't rememeber having any bad cuts and bruises, except from crashing motorbikes. But I have experienced (months of!) severe back-pain and sciatica, on and off for 40 years... so hope it wasn't as bad as that.
A salutary lesson in there.
Take care... 
K2


----------



## jlchapman (Sep 23, 2021)

Bob, Sorry to hear about your injury.  It happens, just be glad it wasnt more serious then it was.

Thanks for posting your CNC adventures.  I love seeing the fixtures and how the machining is done.   I'm self taught also and use these post for learning.  I'm also applying my new CNC skills to model building.

Jerry


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## CFLBob (Sep 23, 2021)

jlchapman said:


> Bob, Sorry to hear about your injury.  It happens, just be glad it wasnt more serious then it was.
> 
> Thanks for posting your CNC adventures.  I love seeing the fixtures and how the machining is done.   I'm self taught also and use these post for learning.  I'm also applying my new CNC skills to model building.
> 
> Jerry



Thanks, Jerry.

Re: the CNC adventures, I've been working on the G-code for the CAM, which combines arcs from three different circles.  I did a similar approach on the Webster's cam, but the Webster's cam was a simpler design that had a couple of straight lines in it while Brian's cam has no straight lines.  

The simple way to do that is to dump the cam into my CAM program.  The drawback is the motion is done as straight line segments, so the curves are approximated as stair steps.  First off, it's ugly, but more importantly is that I'm not sure it doesn't harm the function.


----------



## Steamchick (Sep 23, 2021)

Hi Jerry, I too am learning from all these posts. So when you see "advice" from me, take care, I'm not expert like these other guys! (I never got into CAD and CNC.... pencil drawings, chalk on the kids toy blackboard, and total hand and brain power to manage where the tools cut has been my life!). 
Cheers!
K2


----------



## L98fiero (Sep 24, 2021)

CFLBob said:


> Thanks, Jerry.
> 
> Re: the CNC adventures, I've been working on the G-code for the CAM, which combines arcs from three different circles.  I did a similar approach on the Webster's cam, but the Webster's cam was a simpler design that had a couple of straight lines in it while Brian's cam has no straight lines.
> 
> The simple way to do that is to dump the cam into my CAM program.  The drawback is the motion is done as straight line segments, so the curves are approximated as stair steps.  First off, it's ugly, but more importantly is that I'm not sure it doesn't harm the function.


Brian says he uses the same cam on all his engines, here's the cutter path for the T-head engine using a 1/4" endmill, with the XY0 at Y-.04 so you can cut it from a piece of 3/4 stock. It's for a Yasnac control with a tool changer and was originally for a 1/2" mill going full depth so feeds and speeds aren't correct and it uses adaptive cutter paths so you'll probably need/want to do some editing, at least the finish pass should be good. Hope it works for you.

%
O100  (BRIANS CAM.TXT)
N01 G17 G20 G40 G49 G80 G90 (G17= XY PLANE, G40= CANCEL CUTTER COMP, G49= CANCEL TOOL LENGTH OFFSET, G80=CANCEL CANNED CYCLES, G90=ABSOLUTE COORDINATES)
N02 G00(RAPID TRAVERSE)
N03 G91 G28 Z0(G91=INCREMENTAL MOVES, G28=GO TO HOME THROUGH SECOND POSITION)
N04 G91 G28 X0 Y0
N05 T6 M06  (1/4 FLAT ENDMILL - ROUGH)(M06=TOOL CHANGE)
N06 G90 G54 X-.5786 Y-.0622 T16 S2450 M03(T16 CALLS NEXT TOOL TO TOOL CHANGER)
N07 G43 H6 Z.1(G43=ADD TO Z FOR TOOL LENGTH COMP)
N08 Z-.7
N09 G01 Z-.8 F31.
N10 X-.5419 Y-.0665
N11 G17 G03 X-.5002 Y-.0413 I.0046 J.0395
N12 X-.4911 Y-.0116 I-.1569 J.0643
N13 X-.4871 Y.008 I-1.095 J.2373
N14 G02 X-.4754 Y.0668 I2.5641 J-.4773
N15 X-.4498 Y.1556 I.6334 J-.1349
N16 X-.3925 Y.2664 I.4821 J-.179
N17 X-.2359 Y.411 I.3959 J-.2717
N18 X-.0641 Y.4695 I.2363 J-.4127
N19 X.033 Y.475 I.0642 J-.2695
N20 X.1689 Y.4432 I-.0477 J-.5092
N21 X.3779 Y.2858 I-.1723 J-.4462
N22 X.2041 Y-.4276 I-.3779 J-.2858
N23 X.1777 Y-.4393 I-.2938 J.6294
N24 X-.1548 Y-.4487 I-.1777 J.3993
N25 X-.3557 Y-.3131 I.1601 J.454
N26 X-.4519 Y-.1423 I.3559 J.313
N27 X-.462 Y-.0883 I.2601 J.0765
N28 X-.4626 Y-.0234 I.4331 J.0364
N29 X-.4314 Y.133 I.5806 J-.0344
N30 X-.3673 Y.257 I.4667 J-.1627
N31 X-.1864 Y.4066 I.3709 J-.2643
N32 G03 X-.1802 Y.4106 I-.0145 J.0293
N33 G02 X-.147 Y.4348 I.2068 J-.2489
N34 X-.0628 Y.4698 I.147 J-.2349
N35 X.033 Y.475 I.0628 J-.2698
N36 X.1356 Y.4415 I-.0331 J-.2751
N37 X.1842 Y.4157 I-1.4699 J-2.8215
N38 X.2558 Y.3701 I-.3092 J-.565
N39 X.3523 Y.2763 I-.2901 J-.3948
N40 X.4449 Y.0449 I-.3567 J-.2769
N41 X.4271 Y-.1323 I-.4466 J-.0447
N42 X.1778 Y-.4392 I-.4272 J.0923
N43 G03 X.1828 Y-.5135 I.0164 J-.0362
N44 G01 X.1941 Y-.5169
N45 G03 X.2451 Y-.4752 I.0114 J.0381
N46 G01 Z-.7
N47 G00 Z.1
N48 X.1577 Y.5006
N49 Z-.7
N50 G01 Z-.8 F31.
N51 G03 X.0986 Y.4625 I-.0396 J-.0035
N52 G01 X.1356 Y.4415
N53 G02 X.1759 Y.4141 I-.1393 J-.2473
N54 X.2148 Y.381 I-.5345 J-.6685
N55 X.258 Y.343 I-1.216 J-1.4259
N56 X.315 Y.2835 I-.4076 J-.4477
N57 X.3825 Y.1757 I-.3583 J-.2994
N58 X.3913 Y.1546 I-.4603 J-.2035
N59 X.4269 Y-.1334 I-.3913 J-.1946
N60 G03 X.5094 Y-.1263 I.0423 J-.0092
N61 G01 X.2841 Y.4293
N62 G03 X.2148 Y.381 I-.0401 J-.0163
N63 G02 X.3826 Y.1712 I-.5602 J-.62
N64 X.3915 Y.1542 I-.4923 J-.2685
N65 G03 X.4142 Y.1344 I.0355 J.0178
N66 G02 X.425 Y.1281 I-.0145 J-.0369
N67 G01 X.4468 Y.11
N68 X.4853 Y.0781 Z-.785
N69 X.5142 Y.0541 F394.7
N70 G02 X.5283 Y.0203 I-.0252 J-.0303
N71 G01 X.5266 Y.0013
N72 X.5249 Y-.0176
N73 G02 X.5172 Y-.0723 I-.6939 J.0698
N74 G01 X.5088 Y-.1186
N75 G02 X.4835 Y-.2146 I-.6372 J.1159
N76 X.4472 Y-.2942 I-.4504 J.1577
N77 G01 X.4419 Y-.3034
N78 X.4366 Y-.3126
N79 G02 X.3627 Y-.4047 I-.3591 J.2125
N80 G01 X.3548 Y-.4121
N81 X.347 Y-.4194
N82 G02 X.2768 Y-.4712 I-.2863 J.3145
N83 X.1934 Y-.5131 I-.3535 J.5997
N84 X.1056 Y-.5451 I-.371 J.8823
N85 G01 X-.0188 Y-.5836
N86 G02 X-.0624 Y-.5688 I-.0116 J.0376
N87 G01 X-.0891 Y-.5315
N88 X-.1182 Y-.4908 Z-.8 F31.
N89 X-.1298 Y-.4745
N90 G02 X-.1329 Y-.4694 I.0334 J.0237
N91 G03 X-.1548 Y-.4487 I-.0362 J-.0162
N92 G02 X-.4265 Y.055 I.1548 J.4087
N93 X-.3789 Y.1888 I.4816 J-.0963
N94 X-.2839 Y.3107 I.3924 J-.2077
N95 X-.1807 Y.4102 I.6304 J-.5507
N96 G03 X-.2433 Y.4542 I-.0251 J.0308
N97 G01 X-.2491 Y.4379
N98 G02 X-.252 Y.4316 I-.0388 J.0138
N99 G01 Z-.7
N100 G00 Z.1
N101 X-.4982 Y-.0041
N102 Z-.7
N103 G01 Z-.8 F31.
N104 G02 X-.5085 Y.0469 I-.0346 J.0196
N105 G01 X-.4897 Y.0324
N106 G03 X-.4265 Y.055 I.0243 J.0315
N107 G02 X-.3727 Y.1884 I.4322 J-.0971
N108 X-.283 Y.3118 I.7195 J-.4287
N109 G03 X-.281 Y.3616 I-.03 J.0261
N110 G01 X-.2993 Y.3862
N111 Z-.7
N112 G00 Z.1
N113 G91 G28 Z0
N114 T6 M06  (1/4 FLAT ENDMILL - FINISHING)
N115 G90 G54 X-.0313 Y.5644 T16 S2500 M03
N116 G43 H6 Z.1
N117 G01 Z-.8 F20.
N118 G41 D46 X.1652 Y.4098 F15.(D=CUTTR COMP LOCATION)
N119 G17 G02 X.3698 Y.1735 I-.5116 J-.6498
N120 X-.3698 Y.1735 I-.3698 J-.2135
N121 X-.1652 Y.4098 I.7162 J-.4135
N122 X.1652 Y.4098 I.1652 J-.2098
N123 G03 X.5162 Y.4516 I.1546 J.1964
N124 G40 G01 X.3198 Y.6062
N125 G00 Z.1
N126 G91 G28 Z0


----------



## CFLBob (Sep 24, 2021)

L98fiero said:


> Brian says he uses the same cam on all his engines, here's the cutter path for the T-head engine using a 1/4" endmill, with the XY0 at Y-.04 so you can cut it from a piece of 3/4 stock. It's for a Yasnac control with a tool changer and was originally for a 1/2" mill going full depth so feeds and speeds aren't correct and it uses adaptive cutter paths so you'll probably need/want to do some editing, at least the finish pass should be good. Hope it works for you.
> 
> %
> O100  (BRIANS CAM.TXT)
> ...



Thanks!  I'll have to look at that in my G-code simulator and see what it looks like.  There are codes in there I've never seen before.


----------



## L98fiero (Sep 24, 2021)

CFLBob said:


> Thanks!  I'll have to look at that in my G-code simulator and see what it looks like.  There are codes in there I've never seen before.


I edited my post and added some comments for the codes you may be unfamiliar with.


----------



## Eccentric (Sep 25, 2021)

CFLBob said:


> Meanwhile, I've been rounding up the metal stock I need but didn't pick up when I was starting because it seemed like the sizes I could buy were absurd compared to what I need.  Like I need about 1" length of a O-1 tool steel to make the cam, and the smallest bars I could find were 36" (that 1" I quote is over twice the finished length of the cam).



Bob,

One thing you might want to research is case hardening.  This is where you use a low carbon mild steel and only hardend the surfaces that need it.  I have not made my camshaft yet and I am going to try this.  I will be using this: BROWNELLS SURFACE HARDENING COMPOUND | Brownells

I have not case hardended mild steel before, but I am going to give it a try. 

The cost of the hardening compound may be more than the 01 tool steel.  Also I have read posts here where the camshaft gets distorted during case hardening.  So take all of this with a grain of salt.

Greg


----------



## Steamchick (Sep 26, 2021)

Hi Greg,
Many will know more than I.... but here's my pennorth...
50 years ago, the machine shop where I worked part time made various tools and punches, usually from high-carbon or tool steel (often from annealed old files, re-forged as appropriate). Some softer tools were left in "my charge" for case-hardening. I was taught that any high carbon coating is adequate.... I even used sugar from the tea tray!. A red-hot tool end, dipped in a tin containing sugar, more heat, more sugar, and after "enough" the tool was quenched in oil (big flames, lots of smoke - outside!). Then I cleaned it with wire wool.....until shiny steel, and tempered the tool to the Boss's instruction for the colour temperature, then quenched in oil (again). The hard edge was then honed for sharpness. (Hand-dressed with a stone slip). Worked well for drills, scrapers, lathe tools, etc. I still do it when "needs must". 

Otherwise, in industry, I know the cam-shafts for car engines were cast "grey" iron, then oven hardened, quenched or whatever for the cam lobes to be ground. But I don't know the process. I used the soft core grey iron to make odd (small) parts like pistons. (1/2" DIA).
Also in industry, I experienced nitriding: steel piston rings cooked in ammonia flames in an oven for over 4 hours to nitride the surface. At school I was taught that blacksmiths would keep a donkey, feed it on turnips, then collect the strong pee for quenching there plough shares after forging, to harden the edges. (Nitriding, but only just!). A modern way is too do the same multi-dip and cook process as case hardening, but using nitrogen fertiliser instead of carbon.

A proprietary tin of case-hardening compound in the UK would be Kasenite.  But I have used ordinary sugar, coal, coke, carbon-arc, leather, etc. with success. The carbon-arc was when I brazed mild-steel brackets onto exhausts, then found the surface to be too hard for ordinary drill bits. After breaking through the surface, the steel beneath was "normal" mild-steel. The leather was old shoes, cut into strips, wrapped around the tools, wired in place, then burnt in a wood fire (red-hot bed of charcoal, not the yellow flames).
Hope there is something of use?
Have fun!
K2


----------



## CFLBob (Sep 26, 2021)

Eccentric said:


> Bob,
> 
> One thing you might want to research is case hardening.  This is where you use a low carbon mild steel and only hardend the surfaces that need it.  I have not made my camshaft yet and I am going to try this.  I will be using this: BROWNELLS SURFACE HARDENING COMPOUND | Brownells
> 
> ...



I'm familiar with case hardening, and Brownells, but have never tried it.   I bought a 3' bar of O-1 steel and I'm going to just try to make it like Brian suggests.  Doing that was actually one of things I told myself I wanted to learn doing this engine. 

I still don't have the stitches out of my finger, but I've been working toward resuming cutting the crankshaft.  I really like the cutter you made with the gap in the middle, and have taken to calling it the Terry Thomas cutter, which may only be meaningful to those of us old enough to remember him as a comedian on '60s TV shows and movies.  (I told my wife and she calls it the Lauren Hutton cutter - same reasoning). 

I'm in the same spot there as the oil-hardening; I know some basics about making cutting tools, but have never done much of it.  Right now, with still less than 10 fully functioning fingers, I'm reluctant to break out the bench grinder and try it.  I have that square tipped cutter in a photo up in post #23, and I think I'm going to try to find a smaller one.  Then I'll try to give it the Terry Thomas gap-osis with a diamond file.

Oh, and K2, thanks for the cool stories.  I have neither donkeys or turnips, but it's fascinating stuff to read.  Makes you wonder how in the heck they discovered these things.


Bob


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## Steamchick (Sep 28, 2021)

Blacksmiths would pee into the quenching tank, to save carrying water from the well... The "donkey pee" could be collected while they were shoeing donkeys and horses - saved it forming smelly puddles on the floor of the smithy! One of the jobs for the "bellows boy". The quenching water became nitrogen rich (Lye) and edges of blades became harder and blades became better able to hold an edge, hence they learned about nitrogen hardening (Nitriding) centuries before they knew of Nitrogen!
Simple if you look at history. (My Dad took us to a lot of museums as kids).
Cheers!
K2


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## Brian Rupnow (Sep 28, 2021)

And just to further screw up Bob's post---Have you ever noticed the bright green roof on the Canadian parliament buildings in Ottawa, in Ontario?  Those bright green roofs were copper sheet. The Royal Canadian Mounted Police were told to save all the urine from their horses, and it was carried up to the top of the parliament buildings and poured on the copper roof, to react with the copper and turn it that spectacular green colour.


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## Ken I (Sep 29, 2021)

During WWII - POW's (like in "The Great Escape") made case hardened wire and bolt cutters from the mild steel corner brackets off their huts by heating and dunking in sugar then allowing it to "soak" in the fire to absorb the carbon.
A "sugar tax" was levied on all rations by the escape committee.


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## SteamChEng (Sep 29, 2021)

Brian Rupnow said:


> And just to further screw up Bob's post---Have you ever noticed the bright green roof on the Canadian parliament buildings in Ottawa, in Ontario?  Those bright green roofs were copper sheet. The Royal Canadian Mounted Police were told to save all the urine from their horses, and it was carried up to the top of the parliament buildings and poured on the copper roof, to react with the copper and turn it that spectacular green colour.


That's a lot cheaper than pouring Budweiser over it!


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## Steamchick (Sep 29, 2021)

They could have allowed the roofers to drink the Budweiser and used their pee.... but probably too watery and very little nitrogenous compound compared to the RCMP horses' pee....
Nitrogenous fertiliser is cheap for nitriding steel... but Bud tastes better!
K2


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## Steamchick (Sep 29, 2021)

Ken I said:


> During WWII - POW's (like in "The Great Escape") made case hardened wire and bolt cutters from the mild steel corner brackets off their huts by heating and dunking in sugar then allowing it to "soak" in the fire to absorb the carbon.
> A "sugar tax" was levied on all rations by the escape committee.


So that's how you escaped!
K2


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## bdolin (Sep 30, 2021)

Brian Rupnow said:


> And just to further screw up Bob's post---Have you ever noticed the bright green roof on the Canadian parliament buildings in Ottawa, in Ontario?  Those bright green roofs were copper sheet. The Royal Canadian Mounted Police were told to save all the urine from their horses, and it was carried up to the top of the parliament buildings and poured on the copper roof, to react with the copper and turn it that spectacular green colour.


They carried the horses up to the roof?!!!


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## ajoeiam (Sep 30, 2021)

Brian Rupnow said:


> And just to further screw up Bob's post---Have you ever noticed the bright green roof on the Canadian parliament buildings in Ottawa, in Ontario?  Those bright green roofs were copper sheet. The Royal Canadian Mounted Police were told to save all the urine from their horses, and it was carried up to the top of the parliament buildings and poured on the copper roof, to react with the copper and turn it that spectacular green colour.



Hmmmmmmmmmm - - - - grin - - - I do believe that your preposition in the third sentence is incorrect. 
You use 'were' - - - - I think that 'are' is much more likely. 
One of the benefits of a 'copper' sheet roof is its great longevity. 
I think it may be one of the longest lived of roofing products with only slate and clay or concrete tiles lasting longer.


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## Steamchick (Oct 2, 2021)

I doubt that modern concrete tiles are so long-lived, unless of "roman" manufacture using the volcanic ash recipe as seen in their long-lived buildings in Rome. The use of aluminium accelerating agents to manufacture modern pre-cast concrete items also accelerates the chemical degradation therein. E.G. Concrete used in tower block building during the 1960s with "fast cure" concrete was destroyed 30 years later because that was the designed life of the concrete. Residents also complained that they could push a finger into the concrete as if it were plasterboard! 
On teracotta ceramics, Roman tiles in the Mediterranean countries are still good up to 2000 years... Victorian tiles in the UK are mostly replaced now as only lasting 100~150 years, my house (Edwardian tiles) only lasted 110 years, Welsh slates have lasted 500 years, Yorkshire sandstone roofing slabs have lasted 1000 years (the weight on roof timbers causes the wood to fail first!).
Cheers!
K2


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## ajoeiam (Oct 2, 2021)

Steamchick said:


> I doubt that modern concrete tiles are so long-lived, unless of "roman" manufacture using the volcanic ash recipe as seen in their long-lived buildings in Rome. The use of aluminium accelerating agents to manufacture modern pre-cast concrete items also accelerates the chemical degradation therein. E.G. Concrete used in tower block building during the 1960s with "fast cure" concrete was destroyed 30 years later because that was the designed life of the concrete. Residents also complained that they could push a finger into the concrete as if it were plasterboard!
> On teracotta ceramics, Roman tiles in the Mediterranean countries are still good up to 2000 years... Victorian tiles in the UK are mostly replaced now as only lasting 100~150 years, my house (Edwardian tiles) only lasted 110 years, Welsh slates have lasted 500 years, Yorkshire sandstone roofing slabs have lasted 1000 years (the weight on roof timbers causes the wood to fail first!).
> Cheers!
> K2


(tongue firmly in cheek - - - - grin!)
AIUI the nails holding the slates in place are the predominant point of failure for such - - yes?

Wonder what the longevity of terracota ceramics would be in my area (can get quite cold and snow is a 'normal' thing for at least 4 months and more likely 5 months of the year?

Guessing that a pretty good balance between longevity and cost for me might be the standing seam metal roofing.
That should get me to a life in the 75 to 100 years (assuming that there is galvanizing AND a good quality paint!) and the cost is not out of this world (like slate).
Slate listed in the US at $4 to 6 per ft2. Found an engineered product out of Ontario that purports to be similar but no costs given.


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## L98fiero (Oct 2, 2021)

ajoeiam said:


> Slate listed in the US at $4 to 6 per ft2. Found an engineered product out of Ontario that purports to be similar but no costs given.


There is a company in Ontario that produces slate tiles as well, and product from the company that produces engineered tile is a "Proprietary formulation of polymers reinforced by natural fibres and elastomers" so I doubt they'd last as long, probably something like the "25 year" asphalt tiles that last 15 years. Of course it depends on how long you expect your house to last, we installed the standing seam steel roofing, it will last longer than either my wife or me and the house too, so that's all I expect out of it. And it wasn't much more than the asphalt shingles.
Getting a bit off topic so that's it for me.


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## Steamchick (Oct 2, 2021)

Sounds interesting...
being late 60s, I only expect to live around another 30 years at most. (Mother is 99 and going on...). So I figured concrete tiles OK for UK use when I re-roofed a couple of years ago. it suits what everyone else is doing round here. But at twice the roof loading, I wonder if the 110 year old roof timbers will hold that long? 
My industrial experience of galvanising: on steel work adjacent to railways (Railway spec.!) and radar installations on top of mountains, plus sea-side marinas, and buildings:
Galvanising generally has deteriorated in corrosive environs in 25 years, so needs over-painting before that. The company I worked for used a thixotropic paint coat, good for 10 years per paint layer. The railways had 1 coat every 10 years (Their accountant decided that!). 
The marina started with 4 layers on top of galvanising, when they built the marina in 1980-ish, and it still looked OK last time I visited?
The mountain-top radar installation had 4 coats on to of galvanising for "40 years without maintenance", which would have meant stopping flights from Heathrow airport while re-painting! 40 years was the perceived lifetime of that radar antenna (in 1978). Technology moves faster though, and despite technical electronic upgrades, I am sure that 40ft geodesic dome has gone by now.









Anyway, galvanising is good, painted galvanising is hugely better and longer lasting. Just pick the best paint, and apply properly. It keeps the moisture and oxygen off the metals - thus minimising the electropotential that actively corrodes the sacrificial zinc in place of the steel. Thus the whole system lasts at least the "sum of the lifetimes" of the coatings. - As used by people who want steelwork to last in the worst conditions.
K2


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## CFLBob (Oct 2, 2021)

Steamchick said:


> I doubt that modern concrete tiles are so long-lived, unless of "roman" manufacture using the volcanic ash recipe as seen in their long-lived buildings in Rome. The use of aluminium accelerating agents to manufacture modern pre-cast concrete items also accelerates the chemical degradation therein. E.G. Concrete used in tower block building during the 1960s with "fast cure" concrete was destroyed 30 years later because that was the designed life of the concrete. Residents also complained that they could push a finger into the concrete as if it were plasterboard!
> On teracotta ceramics, Roman tiles in the Mediterranean countries are still good up to 2000 years... Victorian tiles in the UK are mostly replaced now as only lasting 100~150 years, my house (Edwardian tiles) only lasted 110 years, Welsh slates have lasted 500 years, Yorkshire sandstone roofing slabs have lasted 1000 years (the weight on roof timbers causes the wood to fail first!).
> Cheers!
> K2


There was a good article on Roman concrete on a science press website back in '17





						Why 2,000 Year-Old Roman Concrete Is So Much Better Than What We Produce Today
					

One of the fascinating mysteries of Ancient Rome is the impressive longevity of some of their concrete harbour structures.




					www.sciencealert.com
				




Micrographs and explanations of why Roman concrete actually gets stronger for some years, where as modern concrete pretty much gets weaker after it has fully cured (which can take some time).


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## CFLBob (Oct 3, 2021)

Time for an update on the real meat of this thread, although both concrete and using horse urine to color copper roofs were both interesting sidelines

I had the stitches taken out Friday (October 1) and have been working toward setting up to resume work on the crankshaft since last weekend.  The finger is really ugly but mostly functional.  I'm very likely to have full use of it.

Back in post 39, I mentioned that I was going to round up the parts to make the cutter @Eccentric showed in his post and called it the Terry Thomas cutter. I ordered a couple of 1/4" shaft brazed carbide cutters from MEC, planning to cut the notch.  Out of nowhere, I received an email from a friend of a friend recommending a video by YouTube machinist Joe Pieczynski.  It's a 18 minute video, but he makes a cutting bit like what I was considering except with a wider gap in the middle.  Not a slot but a rounded area.  That video led to this cutting tool.   






It's a little raggedy looking, but not much more ragged looking than Joe P.'s cutter.  The relieved area was made using a Foredom Flex Shaft grinder with a diamond dentist's bit.  The background in this image, by the way, is the gray cast iron bar that's going to become my cylinder.  It's a 2" square bar (almost 2-1/16 on a side) that needs to cut down to 1.750" on a side.

After this, I positioned the cutter in a tool holder so that it was touching the metal at the same machine zero as the other tools I was going to use.  Because it's a 1/4" shank and the cutter is almost exactly 0.250, I relieved the shank on both left and right sides, so that the shank of the cutter absolutely won't touch the side of the bar before the cutter does.  I did that on a benchtop belt sander.  Since it's a 1/4" tall shank in a tool holder set for a 3/8" tool, I put a small piece of 1/8" thick aluminum under it, visible at the very bottom of the picture along the left side of the tool.






I used Joe P's method, using my 3/32 wide parting tool to take deeper cuts in the stock, which makes it look like our typical cylinder heat sinking fins, and then used the cutter I modified to sweep back and forth reducing those fins to the desired constant diameter.  After that it just needed some final size tweaking of both the length and diameter of that round section.  

After a two week interruption, this step is just about finished.  The width is right (0.438) but the diameter is about .0015 over.  @Eccentric showed some grinding stones that he uses, which I don't have as a ready option.  I have sand paper (AlOx paper) in grits that will work and I have needle files.  I've just come in from testing a couple of those and while they're small, they don't get my hands too close to that rotating bar that started the whole delay.  I need to do a look at some of my wife's nail abrasives.  She has some nail buffers with four grades of abrasives and they do produce a very smooth finish on metals.  The ones I can think of are too wide to put in that 7/16" wide slot.  If I need to use sandpaper, I'd prefer a tool to hold strips with than using my fingers.  Maybe I can find something to print on the 3D printer.


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## Steamchick (Oct 3, 2021)

Stick the various grades of abrasive paper onto some hardwood sticks, maybe 1/4" wide. Or, I use mole grips, self locking grips, that have flat jaws, and use the self-Locking feature to set the grip at a suitable pressure on the emery tape. This simulates a tool used to hone real car and truck crankshafts when I was in a workshop in the 1960s.
K2


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## CFLBob (Oct 3, 2021)

Steamchick said:


> Or, I use mole grips, self locking grips, that have flat jaws, and use the self-Locking feature to set the grip at a suitable pressure on the emery tape.



Are those like pliers?  Like Vise Grips?  I have some long nose Vise Grips pliers, as well as a bigger, shorter jaw version of them.


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## Brian Rupnow (Oct 3, 2021)

Popsicle strips and spray on contact cement.


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## Eccentric (Oct 3, 2021)

Your crank is looking good Bob, I am glad your finger will (eventually) be bad to normal, at least functionally. 

I do hold strips of the wet/dry sand paper in strips about the width of the slot to do final polishing.  I use the standard 9" sand paper in increasingly fine grits folded over the journal.  I like to run the lathe in reverse using a spot of oil on the paper. If you are .0015" out I would use a fine file to take off the first thou, then finish with the paper.  I understand if you are leery getting to close to the spinning work piece, a healthy weariness.  When bring the journal down to final dimension use the micrometer across the full width to make sure you are not getting localized low spots.

It is nice to see you back in the workshop.


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## Vietti (Oct 3, 2021)

For wider crank webs I like to get paint stir sticks from the hardware store and make em as wide as the journal.

I stick the wet dry strips on with superglue and then cut the resulting abrasive stick to width.

John


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## Steamchick (Oct 4, 2021)

Hi Bob, yes, "Vice-grips" is a name I have heard. The key is that the over-centre lock gives a fixed and fairly repeatable position for the jaws. If you use simple pliers, the rubbing pressure depends on strength and consistency of your grip. Vice grips simulated the tool I had used where the jaw dimension is controlled by the screw that sets the locked dimension. Do not use a lot of pressure, as the carborundum should do the work with "just enough" pressure. And use oil. You could even use some "journal oversized" jaws made from aluminium, and grinding paste for lapping. Take care to hold the tool perpendicular to the shaft axis, and keep it moving left and right (axially) along the journal to retain parallelism. I'm sure you'll work out what to do.
Just an odd comment that I was taught. The machining is as perfect as it can be, but may not be able to give the required finish. Hand processes of lapping, etc.,  are to reduce the size of cut-marks (tool marks) and "level" the surface, to give a finer surface finish,  not reduce an over-sized journal to size. The whole principle of machining is repeatability. So machining to size becomes a simple and repeatable operation. And "yes", it is faster and easier than hand-work. Which does not decry the accuracy that can be achieved by hand-work, by a skilled operator (not I!).
Hope this is some help? If any expert knows better, I am willing to learn, and improve my processes and knowledge.
Cheers, 
K2


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## William May (Oct 4, 2021)

bdolin said:


> They carried the horses up to the roof?!!!



Certainly NOT! That's TOTALLY ludicrous! And completely insane!!

My understanding is the bought them jet-packs, and taught them to fly, and then told them where to go to deposit their urine. They got an apple as a reward for every successful flight.


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## L98fiero (Oct 4, 2021)

William May said:


> Certainly NOT! That's TOTALLY ludicrous! And completely insane!!
> 
> My understanding is the bought them jet-packs, and taught them to fly, and then told them where to go to deposit their urine. They got an apple as a reward for every successful flight.


AND, the cool part of that is that the Peace Tower was finished in *1927*, Canadians, eh?


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## Sprocket (Oct 4, 2021)

You could try Basil's idea, it won't take off as much as you have left, but it should finish and polish your journals.I dreamed about this last night
Keep your fingers out of the way!
Doug


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## CFLBob (Oct 12, 2021)

I had an adventure trying to get Popsicle sticks last week without ordering them from Amazon or Walmart and wasting a couple of days waiting for them.  Instead, I decided to use my 3D printer and wasted the entire week.  

Starting from the beginning, I needed a G-code file and to get that, I needed a 3D solid  model of a Popsicle stick.  This didn't take long, and I quickly made a  version 1 of what I started calling the Fat Popsicle Stick - because I wanted to put a nice handle on it.   





The dimensions are that it's 5 inches long, the thick part of the handle is 1/2" tall, and the stick portion is 0.4" wide by 1/16" thick. Those numbers were completely PFA.  I mean, I've had Popsicles, just not in the last 40 years or so.  They seemed about that thick.

The first print failed.  I watched it  for the first few minutes and came in to do other stuff during the remaining  hour the print would take.  Just as I was about to go check on it my wife came in to tell me the thin, stick part was off the table.  I  went out to check it out and figure out what to do.  I thought about  putting a spot of glue under that end and pushed on the very end to see if it was flexible  When I did that, the whole thing popped off the print bed.   No choice left but to kill the job.   The good news was that it was about 3/4 done and probably usable.  So I gave it a try and found two problems.  First, it was too wide.  The design was  0.40, but it came out a little wider.  When I wrapped sandpaper on it, it  was too close to the .438 of the journal.  The second problem was that it felt too flimsy.  

Within a few minutes, I had a redesigned "Version 2" stick ready to print.   I doubled the thickness of the stick portion to 1/8" thick.  Stiffness in bending here is proportional to the fourth power of the thickness, so doubling  the thickness should make it 16 times stiffer.  The minor change was to drop the width to 3/8".  
This began some arm wrestling with the printer that still isn't fully resolved, but during the start of this print, I noticed the right front area looked thin, meaning I should re-level the printer bed.  That turned into updating the software in the printer to use some new features I found out about in a video refresher on how to level the bed.   

OK, time to print Rev 2 and very quickly found a problem.  The G-code was having it print the 1/8" thick part but left it the original 1/16" on the back.  Then it went back to print the handle on top of that thinner area and it didn't even attach to it.  A real mess.  I ended up with two parts barely attached to each other.  

So I removed it, started printing again and went into the house for dinner.  After eating I went to check it and found it had printed the bottom half of the 1/8" thick part and then got lost.  The extruder went the width of the stick up in Y and some random offset to the left in X.  Totally FUBAR.  It left me puzzling over which piece of software screwed up or if it was the printer hardware.  There's three possible sources of software errors: the new firmware in the printer, the slicer software that creates the G-code, or it could be that my CAD model had defects I can't see.  

I decided to start everything over from scratch, except for leveling the bed.  I redrew the model and sliced it with the other slicer software I have but isn't the one I regularly use, Cura.  That required me to convert the model to metric in Rhino.  That's not hard, just another step to do, but not having to do that is one reason I switched to the other slicer software, Prusa.  Then I started printing the new G-code.  This one printed fine and was done in an hour.  

If you lost count, I had to print it three times to get one to come out right.  The one that came out in two pieces is usable, I had to cut off the loose filament and glue that one together.






The Fat Popsicle Stick family.  In the back is the Rev. 1 stick that popped off the bed before it was done, but was usable - except for being too wide. It has 220 sand paper glued to it and I actually ran that on the journal for a little while.  The one on the left is a second Rev. 1 that I printed accidentally.  Second from left is the first Rev. 2 that printed in two pieces.  I shaved all the loops of filament off the bottom of the back's top piece and glued it to the bottom.  The odd looking white mess is what came out of the printer losing its X and Y coordinates.   The last one on the right is the finished Rev. 2 stick that printed properly.   

This was Saturday.  On Sunday I went to work on the journal, which I had previously used a needle file on to get down to about .001 over.  I used 220, 400 and 1000 grit.  One end measures 0.3751 with my micrometer, the other end was 0.3752.  

After that aggravation with the printer, I started a thread for help over on the 3D Printers forum and seem to have improved things.   It's not as good as it was before all this started, but it's close.  

Meanwhile, it's on to the rest of the lathe work on the crankshaft, after I make a couple of little tools.


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## CFLBob (Oct 31, 2021)

I thought I'd wait to update this thread until the crankshaft was finished, which I would have sworn would be a week or more ago but kept eluding me for various reasons.  Most of which come down to learning a lot as I'm going.  This picture is just posing. The counterweights are just sitting on top until I get a couple of screws for those spots.






Today's last operations were to cut the keyway slot on the long side, which required I make a tool to hold that long side the proper distance off the vise bottom and allow me to crank the mill's vise down onto it.  I considered printing the tool but went with machining it out of aluminum.  






I found a piece of slightly under 1/2" aluminum bar in my scrap bin, squared it up and drilled/reamed a hole.  Since the shaft is 0.375, I used a .001-over reamer.  When I cut the unneeded top off, I left it a bit higher than cutting the thing exactly at its midline, and lucked into the shaft snapping into the metal.  






And now for my "oopsie".  While cutting the short side to length, something bound on the lathe slide and then the cutter popped forward.  The very end is boogered up.  For about the last 1/32 or 3/64, the diameter is undersized.






I'm not sure what's next.  I got my cast flywheel in from Martin Models and it needs to be readied, but I still have lots and lots to do.  Plus I need to look at the lathe in terms of some maintenance.   There seemed to be a bit too much play in it, and not just this one cut.


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## Brian Rupnow (Oct 31, 2021)

I'm watching Bob.  It is incredible what you learn from "Doing stuff". It really does become an incredible journey.---Brian


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## Eccentric (Nov 1, 2021)

That is one fine looking crankshaft Bob!  Can you just chamfer the end that got "boogered" and no ones the wiser?


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## CFLBob (Nov 1, 2021)

Eccentric said:


> That is one fine looking crankshaft Bob!  Can you just chamfer the end that got "boogered" and no ones the wiser?



Thanks.  That's better as a question for Brian; I'm trying to understand where that side goes and if simply cutting it off would even matter.


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## Brian Rupnow (Nov 1, 2021)

Bob---Look at your main assembly drawing. If you are asking about the crankshaft end, don't worry---it just hangs out in the air as I show on the drawing.---Brian


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## CFLBob (Nov 18, 2021)

Just an update so that I don't want to fall so low in this category that I have to go into the second page.  

I had been looking at the engine mounting plate for the next thing to work on, after I did some adjustments to my lathe to tighten the gibs and stop the compound rest from wobbling.  It seemed like a fairly straightforward part to make, so I did that. 






There's one spot where I went away from the prints.  The bottom of the plate is relieved like this:






That's a 5/16 radius and depth.  I can see two ways to do that.  One is drilling vertically with a 5/8 drill bit and the other would be cutting those corners with a 5/8 ball end mill.  I don't have either of those tools.      

After a lot of puzzling over how to make this or if I go buy a new cutter, probably too much puzzling, I decided to change both of those to reflect what I actually have, a 1/2" drill bit and the cutout 1/4" deep.   I don't see this as being particularly critical.  There are some screws that go through the small holes, and worst case need to be 1/16" longer.  

My real problem is that I've been following Mayhugh's 300 Ford Inline Six build and between his bead blaster (another tool I don't have) and the way he's painting his parts before they get assembled, they're so pretty that these parts just off the machines just look too raw now.

All that aside, time to pick the next part.  Probably the cylinder.


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## Brian Rupnow (Nov 19, 2021)

Bob--For an internal radius like that, drill thru with a 5/8" drill, (or a 5/8" endmill if you're right on the edge of the material) then bring the saw cuts in tangent to the hole, and presto--A 5/16" radius.---Brian


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## CFLBob (Nov 19, 2021)

Unfortunately, the biggest drill bit I have is 1/2" - except for some spade bits for wood.  

I didn't even think of those spade bits until now.  I've never tried a spade bit on aluminum, but so many other wood cutting tools work on aluminum at the right speeds and feeds that I wonder if it could work.


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## Brian Rupnow (Nov 19, 2021)

I wouldn't use a spade drill. I have a complete set of metal drills ranging from 1/32" diameter up to 1" diameter, by 1/32"s.


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## Nerd1000 (Nov 19, 2021)

CFLBob said:


> Unfortunately, the biggest drill bit I have is 1/2" - except for some spade bits for wood.
> 
> I didn't even think of those spade bits until now.  I've never tried a spade bit on aluminum, but so many other wood cutting tools work on aluminum at the right speeds and feeds that I wonder if it could work.


Spade bits are usually made of relatively soft carbon steel, in many cases they can be sharpened with a file. You might get them to cut aluminium if you keep the speeds low, but I'd expect the sharply pointed pilot and prongs to break down very quickly.

Large diameter Morse taper or reduced shank twist drills can be had rather cheaply from the usual suspects on eBay, Banggood, AliExpress etc and from local suppliers that buy from the same factories in China. They're not going to be the best drills you've ever used, but for this sort of thing they're ok.


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## stanstocker (Nov 20, 2021)

CFLBob said:


> Unfortunately, the biggest drill bit I have is 1/2" - except for some spade bits for wood.
> 
> I didn't even think of those spade bits until now.  I've never tried a spade bit on aluminum, but so many other wood cutting tools work on aluminum at the right speeds and feeds that I wonder if it could work.


Greetings,

I've used spade drills a few times to provide a counterbore for a large washer or the like in aluminum out of desperation to get a job done.  Rather scary, the large edge engagement with the work and the spindly shank flexing, twisting, and bouncing around gives a fairly poor finish and tends to grab.  Sides of the hole were ragged and tapered.  If you think how many times you've had a spade drill snag on break though in softwoods it's MUCH worse with aluminum.  Maybe it would go better with the drill shank cut down to reduce whip and flex and pucker factor.  Even in a heavy drill press or mill it's a pretty sketchy stunt.  Maybe a reduced length 5/8 spade would be stiff enough to at least poke a hole that only needs a huge amount of clean up, seems my efforts were usually in the 1 inch or larger range.

In your application, is there a reason the radius has to be 5/16?  If it's just to eliminate stress risers, most any radius will be fine and look decent.

Cheers,
Stan


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## CFLBob (Nov 20, 2021)

stanstocker said:


> In your application, is there a reason the radius has to be 5/16? If it's just to eliminate stress risers, most any radius will be fine and look decent.



I think it's mostly cosmetic, to make a nicer looking part while also getting some screw heads off of the bottom, but the designer (Brian) is watching the thread and might comment.   Right now it's 1/4" radius and the whole bottom isn't the nicest looking surface I ever machined, but it _is _the bottom and will disappear in use. 


Bob


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## Brian Rupnow (Nov 20, 2021)

Nah, not important. it's just there for "pretty".


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## Eccentric (Nov 20, 2021)

Bob,

Glad to see you back at it.  You said of your lathe,  "after I did some adjustments to my lathe to tighten the gibs and stop the compound rest from wobbling."

One thing you might consider doing is get a piece of steel as the one shown below, drill the four holes so you can mount it to your cross slide in place of your compound, then another hole in the middle and mount your quick change tool post directly to it.  This gives our lathes more rigidity for those tough jobs that really need it.  One way to eliminate the wobble of the compound is to elimiate it!






When I was making my cylinders I also needed a drill bit larger than 1/2" and went on the cheap and bought this:






						Premium 1/2” Shank Silver and Deming Drill Bit, High Speed Steel | 8-Piece Set | 9/16” to 1”: Amazon.com: Tools & Home Improvement
					

Premium 1/2” Shank Silver and Deming Drill Bit, High Speed Steel | 8-Piece Set | 9/16” to 1”: Amazon.com: Tools & Home Improvement



					www.amazon.com
				




It was only $37 bucks and totally NOT worth it. The cutting bit is NOT AT ALL concentric with the shank.  So, be warned, if you do decide to buy some larger bits, get a nice set you will be happy to have for a while.  I relegated my set to a drawer of old wood drill bits and may never use them again.


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## CFLBob (Nov 20, 2021)

Eccentric said:


> Bob,
> 
> Glad to see you back at it.  You said of your lathe,  "after I did some adjustments to my lathe to tighten the gibs and stop the compound rest from wobbling."
> 
> ...



I went looking at just buying a Silver and Deming bit in 5/8 and saw several individual bits that cost more than that set.  Pricey for one drill bit, and not that different from two flute, ball end, 5/8 mills.  I have several drill bit sets, but none go over 1/2" except for those spade bits I was talking about.  My main, go-to set is from 1/16 to 1/2 by 1/64", which is a handy thing to have.  Those are straight shank except for three flats to help chuck jaws grab the bits.

Thanks for the tip on getting rid of the compound, too.  I need to look into making sure I could do that on my Sieg SC4 lathe.


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## CFLBob (Dec 7, 2021)

I'm surprised looking here that my last post was before Thanksgiving.  I would sworn it was last week, Monday or Tuesday.  

After the base, the path I decided to go down is to make the cylinder, connecting rod and piston.  The cylinder is cast iron and pretty much 2-3/8" in length, with the largest remaining metal being 1.750" diameter and a 1.750" on a side square flange.  It looks like this, except for some drill holes I haven't drawn in.  






I had to buy a foot of cast iron bar as rough stock; it's just a bit over 2-1/16" on side, pretty much 2.08".  I cut off a piece about 3-1/4" long on my 4x6 bandsaw and squared that down to 1.875 - that's 7/8 so .062 too big on each side.   That's when I got into a real puzzle about how to proceed.  My original thought was to do everything on my big lathe, the one that just needed adjustments.  

What bothered me is that the intermittent cutting of the rectangular crankshaft blank broke a few cutters and I don't want to do that again.  Most of my cutters are carbide and while I rarely run the RPMs high enough to meet the recommendations for carbide, I would think that would be gentler impacts and speeding up the RPMS would be the wrong way.   So I tried to see a way that I could cut down the pointy corners and turn the square into an octagon.  

I got the idea I could make some Vee blocks to hold one of the points of the square and cut off the opposite corner.  While I have some metal Vee blocks, they're too big for the mill vise, so I thought I'd make some.   It looked like this  






All well and good, except I'd need some taller jaws for the vise.  No problem, I had some scrap 3/8" thick 1018 steel, so I could make them.  But could the piece really take cutting forces with just those sharp corners being grabbed by the vise jaws?  






Yeah, I could mill a small groove where the points hit, but for the first two cuts those jaws are holding the pointy corner, but after you cut those points down they're replaced with flats that are 3/4" wide.   Two sets of jaws?  

I decided the prudent thing to do would be to chamfer the edge of the square block with it held by the flat faces in the vise jaws but I had a stupid and overcut the piece by cutting the entire side, thereby taking off one of the corners of the square flange.   (waving hand like a Jedi in Star Wars) You don't care about the divot from the cutter in the middle.  






So I'm starting over.  Thankfully, I have enough cast iron to spare another 3-1/4" long piece.  I cut this one down to 1.800 on a side, .025 on a side oversize.


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## Brian Rupnow (Dec 7, 2021)

Bob--Glad to see you are still at it. I was beginning to worry. The way I made that cylinder is to first cut a piece of cast iron about 1 1/2" longer than the finished size, stand it on end in my milling machine vice and center drill one end with a center drill until I had a divot on center big enough for a lathe live center to fit. Then I chucked the entire length up in my lathe 3 jaw and supported the outboard end with a tailstock live center. Then I turned everything to finished size, even the portion that is rectangular. Then I put a 15/16" drill in the tailstock chuck and drilled out the center and reamed it to finished size all in the same set-up. I then used my parting off tool to part off the cylinder at the correct overall length. This leaves you with a "stub" of cast iron about 1 1/2" long that you will eventually use on some other build. After it comes off the lathe, the 4 sides of the square part can be band-sawed or milled off, leaving it square.---Brian


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## CFLBob (Dec 7, 2021)

Brian Rupnow said:


> Bob--Glad to see you are still at it. I was beginning to worry. The way I made that cylinder is to first cut a piece of cast iron about 1 1/2" longer than the finished size, stand it on end in my milling machine vice and center drill one end with a center drill until I had a divot on center big enough for a lathe live center to fit. Then I chucked the entire length up in my lathe 3 jaw and supported the outboard end with a tailstock live center. Then I turned everything to finished size, even the portion that is rectangular. Then I put a 15/16" drill in the tailstock chuck and drilled out the center and reamed it to finished size all in the same set-up. I then used my parting off tool to part off the cylinder at the correct overall length. This leaves you with a "stub" of cast iron about 1 1/2" long that you will eventually use on some other build. After it comes off the lathe, the 4 sides of the square part can be band-sawed or milled off, leaving it square.---Brian



No need to worry.  It was the usual mix of other things that need fixing and my tendency to overthink things mixed with Thanksgiving.

I was converging on just going ahead and putting it on the lathe.  Put a dimple in the end with the biggest center drill I've got and use my live center.  I used the live center on the crankshaft, too, turning between centers, but since this is square and not even an inch longer than needed, I was going to put it in my four-jaw get it all centered, then start from the end in the live center and cut the features down to the square side.  Looking at the assembly, it looks like .025 over sized on the square flange won't be a huge deal, just a small lip where it meets the crankcase - as long as the holes are in the right place.


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## CFLBob (Dec 13, 2021)

The start over has been in progress since last Tuesday.  This time I squared the blank to 1.80" on a side (don't recall how different they were, but it was under .005"), and then took it to the lathe to turn it into a cylinder.  

With the sides of the block 1.80" and the desired diameter of the cylinder being 1.750", how much do I remove?   I drew the two shapes up in CAD and it told me that from the tips of the square to the rim of the circle is 0.397".  That's roughly 19 passes cutting .020 (radius) at a time, plus a final cut or two to sneak up on the final size.  Each pass takes about four minutes, which argues that with some clean up time, it should have taken about two hours.  My lathe has power feed, so I can put everything in position for the next cut and engage the gears.  Do "something else" for the majority of the cut and then go stop it at the critical point.  Four minutes is just enough time to not get much "something else" done.

It's starting to look like a cylinder.  







That was yesterday.  By this time I had drilled through my entire blank with a 1/2" bit and then used an end mill in my drill chuck to enlarge that to 9/16".  

While trimming the square bar into the roughly 2.00" long cylinder taking up most of the blank, I noticed the vibration was enough to cause both axes on my lathe to move.  I was able to stop that with a simple fix. 






Blue painter's tape on both dials.  It seemed to work repeatably.  I don't know of any other way to lock those in position.   The entire carriage can be locked in position with a screw I keep an allen wrench in - you can see it just to the right of the crosslide, almost under the compound.  The compound rattles more when at the left end of its travel, so I do this with it at the right end.  The power feed (engaged here - notice the vise jaws are blurred) moves that big handwheel on the bottom left, not the small one on the right that's taped.

Just finished up several passes of my boring bar in the cylinder and it's now at 0.826" ID, on the way to 1.000".


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## Steamchick (Dec 14, 2021)

Hi Brian, noting you probably have a very accurate set-up, gib strips set on the main saddle, and cross slides, but have you mic'd a 3 in long OD cut to check if the bed is truly in alignment with the axis of the headstock? Maybe with a DTI on 0.0001" accuracy, you can confirm if a test bar is good, but under load (with wear and tear?) Maybe it is not quite so parallel? And if you can accurately check the bore, you may find it is tapered? Loads from simple boring bars are the opposite direction on the main traverse to OD cutting. I always find a fraction of a thou taper on my bores from the lathe. Even using an end- milling cutter from the tailstock, so always finish  bore  down the hole on the miller-driller.That way it bores a true cylinder. (Less corrective honing!).
But my lathes were worn, and a thou out of true when cutting, due to bed-way wear....
K2


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## CFLBob (Dec 14, 2021)

K2 - I honestly don't know how to do that.  When I first got the lathe (2014), I put a live center in the tail stock and a dead center in the head stock, then verified they were actually point to point.  That's the only test I've done.  I regularly use a dial indicator to minimize runout in pieces I'm turning, but haven't done

What I get now is wobble in the compound.  I just re-adjusted the gib in it, not even an hour of machine operating time ago, and yesterday, I could grab the compound and feel it move.


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## Eccentric (Dec 14, 2021)

Bob,

Have you seen this for aligning the lathe?  worked for me:


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## Steamchick (Dec 14, 2021)

Hi Bob ( Sorry, Dyslexia called you Brain, or something?)  To control the saddle against cutting torque there is a sort of hook of a running surface beneath the back of the bed slides. The saddle needs to be adjusted to prevent lift at the back - there should be a gib hidden under the back? Frontal down-thrust is taken on the alignment long wedge slide. I suggest using a molybdenum loaded or lithium grease wiped on the bed tracks as the light (7W) lathe oil I find dissapears quickly... especially if you use coolant?
There may be a gib strip on the front of the saddle? (Non-thrust face when the tool is tightened against a workpiece). But my lathe only has the one at the back. Actually, the stability of the saddle on the bed is the pair of "wedges" that the saddle sits on. If the gib beneath the back rail of the bed is correctly set, then there is sliding motion but no lift at the back, which ensures the saddle does not chatter on the wedge on top of the bed.
You say the movement is in the top slide, which is much simpler to set. My technique, is to set the slide mid-travel, adjust the middle screws, then go to either end of travel to adjust the end screws for the gib strip. When set and locked it lasts me years, but I'm not doing more than a few dozen hours lathe work in a year. But lubrication is more frequent, cleaning is after every operation, or when there is a table spoon of swarf. Sometimes after each cut or 2. Swarf is really a killer for precision sliding surfaces.
Enjoy! K2


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## CFLBob (Dec 14, 2021)

Eccentric said:


> Bob,
> 
> Have you seen this for aligning the lathe?  worked for me:




Thanks for the link.  Got busy and haven't watched it yet, but will watch it in the morning.  



Steamchick said:


> Hi Bob ( Sorry, Dyslexia called you Brain, or something?) To control the saddle against cutting torque there is a sort of hook of a running surface beneath the back of the bed slides. The saddle needs to be adjusted to prevent lift at the back - there should be a gib hidden under the back? Frontal down-thrust is taken on the alignment long wedge slide. I suggest using a molybdenum loaded or lithium grease wiped on the bed tracks as the light (7W) lathe oil I find dissapears quickly... especially if you use coolant?
> There may be a gib strip on the front of the saddle? (Non-thrust face when the tool is tightened against a workpiece). But my lathe only has the one at the back. Actually, the stability of the saddle on the bed is the pair of "wedges" that the saddle sits on. If the gib beneath the back rail of the bed is correctly set, then there is sliding motion but no lift at the back, which ensures the saddle does not chatter on the wedge on top of the bed.
> You say the movement is in the top slide, which is much simpler to set. My technique, is to set the slide mid-travel, adjust the middle screws, then go to either end of travel to adjust the end screws for the gib strip. When set and locked it lasts me years, but I'm not doing more than a few dozen hours lathe work in a year. But lubrication is more frequent, cleaning is after every operation, or when there is a table spoon of swarf. Sometimes after each cut or 2. Swarf is really a killer for precision sliding surfaces.



I enlarged my cylinder bore to 0.950 this afternoon, and will use a few more passes for the last of it.  I only measured the ID by using a telescoping ID gauge and it didn't look like it had any taper; at least nothing that showed up on my calipers.  I'll redo that with my micrometer tomorrow, and get a better feel for it.  

I went through the manual trying to find the gibs you mentioned but nothing in the manual seemed obvious.  I'll spend some time looking for that tomorrow.  It's a SIEG lathe like so many others so I'm guessing it's probably built like the 7-by or 8-by lathes that are everywhere.


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## Ghosty (Dec 14, 2021)

Bob,
The Sieg lathe that I had needed the head machined to get it straight, not machined straight from the factory, as it bolts direct on the lathe bed there is no adjustment to get it parallel 
Cheers
Andrew


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## Nerd1000 (Dec 15, 2021)

Steamchick said:


> Hi Bob ( Sorry, Dyslexia called you Brain, or something?)  To control the saddle against cutting torque there is a sort of hook of a running surface beneath the back of the bed slides. The saddle needs to be adjusted to prevent lift at the back - there should be a gib hidden under the back? Frontal down-thrust is taken on the alignment long wedge slide. I suggest using a molybdenum loaded or lithium grease wiped on the bed tracks as the light (7W) lathe oil I find dissapears quickly... especially if you use coolant?
> There may be a gib strip on the front of the saddle? (Non-thrust face when the tool is tightened against a workpiece). But my lathe only has the one at the back. Actually, the stability of the saddle on the bed is the pair of "wedges" that the saddle sits on. If the gib beneath the back rail of the bed is correctly set, then there is sliding motion but no lift at the back, which ensures the saddle does not chatter on the wedge on top of the bed.
> You say the movement is in the top slide, which is much simpler to set. My technique, is to set the slide mid-travel, adjust the middle screws, then go to either end of travel to adjust the end screws for the gib strip. When set and locked it lasts me years, but I'm not doing more than a few dozen hours lathe work in a year. But lubrication is more frequent, cleaning is after every operation, or when there is a table spoon of swarf. Sometimes after each cut or 2. Swarf is really a killer for precision sliding surfaces.
> Enjoy! K2


I disagree on the topic of using grease on the lathe bed. The problem is that even a thin film of grease will attract dirt and swarf that grind down the ways. Ideally you should use way oil, it contains 'tackifiers' that help it stick to the slides and not get washed off. Failing that, for my Atlas milling machine the manufacturer specified SAE 30 motor oil... Which will no doubt have the purists up in arms, but you can't satisfy everyone.

A big help for bed lubrication is a set of felt way wipers, they'll prevent the swarf from getting under the saddle and also act as oil wicks to keep re-oiling the ways as the saddle moves.


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## Steamchick (Dec 15, 2021)

Thanks Nerd1000, I'll take note.. - My lathe has felt wipers as standard, but doesn't specify oil or grease. I agree it is the finest dust does most damage! (I never grind on my lathe for that reason.). I have added a catch-all tray beneath the tool (on the cross-slide - passes beneath the chuck) that keeps most swarf away from the bed anyway.
Ta,
K2


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## Steamchick (Dec 15, 2021)

Just found this...
K2





						Choosing the Best Way Oil, also known as slide oil or way lube.
					

To identify the best way oil or way lube for your machine application, start with a high-quality base oil.



					www.acculube.com
				



.


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## Steamchick (Dec 15, 2021)

Or this - in the UK.








						SLIDEWAY 68 LATHE BED LUBRICATING OIL MACHINE MAINTENANCE RDGTOOLS  | eBay
					

SLIDEWAY 68 LUBRICATING OIL. FOR LUBRICATING BEDS TABLES, MACHINES OR ANYTHING WITH A GROUND SURFACE.



					www.ebay.co.uk
				



Or this...








						Slideway Oil ISO 68 for Horizontal and Vertical Slide Ways British Made   | eBay
					

The quality of machined components depends heavily on the accurate feed and accurate positioning provided by machine tool slideways with slideway oils playing an important role. Good lubrication eliminates chattering and thus ripples on the surface of components caused by stick-slip.



					www.ebay.co.uk
				



K2


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## Steamchick (Dec 15, 2021)

Bob, You could make a GO-NOGO gauge that can check the bore as you get close to size...
K2


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## CFLBob (Dec 15, 2021)

Steamchick said:


> Bob, You could make a GO-NOGO gauge that can check the bore as you get close to size...
> K2



Isn't that what my piston is for?  

Kind of joking, but as I understand it, the usual work flow is to make the cylinder first so that I can fit the piston to the engine.  It doesn't matter if my cylinder is a a few thou oversized or undersized as long as the piston fits it.  It needs to be fairly cylindrical and not tapered.


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## L98fiero (Dec 15, 2021)

Nerd1000 said:


> I disagree on the topic of using grease on the lathe bed. The problem is that even a thin film of grease will attract dirt and swarf that grind down the ways. Ideally you should use way oil, it contains 'tackifiers' that help it stick to the slides and not get washed off. Failing that, for my Atlas milling machine the manufacturer specified SAE 30 motor oil... Which will no doubt have the purists up in arms, but you can't satisfy everyone.
> 
> A big help for bed lubrication is a set of felt way wipers, they'll prevent the swarf from getting under the saddle and also act as oil wicks to keep re-oiling the ways as the saddle moves.


Most machines that recommend other than waylube suggest an ISO VG 32 hydraulic oil, retail it's sold in small quantities as 'jack oil'.


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## minh-thanh (Dec 15, 2021)

Hi CFLBob !


CFLBob said:


> and not tapered.



 When i do the cylinder : a little taper at TDC is no problem.


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## Steamchick (Dec 15, 2021)

The intent for a GO-NO GO GAUGE is to check for taper. IC engines manage taper as they expand more at Hot-Top-of-stroke than at the cooler Bottom of stroke. Steam engines -especially those without rings- benefit from no taper as the temperature is more uniform (steam fed from both ends), hence parallel expansion.
Your IC engine is likely to have a wider top.... but a narrower top is desirable as when hot it becomes nearer to parallel. As this is only identified by lots of tests on a design, for optimum durability, (and  using lots of expensive gauging), and as your model is a one off, I guess you won't bother, however it turns out. 
I can only advise what I know to be best practice. For what 50 years experience is worth....
So you can use a piston as a gauge, not joking!
I can explain more about boring, and tapers, but you'll probably get too bored with the subject and your interest will taper-off.... ( That pun even made me groan!).
I  think?
K2


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## CFLBob (Dec 16, 2021)

Steamchick said:


> Your IC engine is likely to have a wider top.... but a narrower top is desirable as when hot it becomes nearer to parallel. As this is only identified by lots of tests on a design, for optimum durability, (and using lots of expensive gauging), and as your model is a one off, I guess you won't bother, however it turns out.



Because of the way the cylinder is mounted in the lathe, if anything, it's wider at the bottom - which is the farthest from the point where I set the diameter.  That's ideal, because if it expands a little at the top, then it becomes less tapered (or not tapered), and yet it's easier to get the piston started into the cylinder with the slightly wider bottom.  

I find that when it has been a long time since I've measured cylinder inside diameter, and it has been two years since I setup the cylinder in my Webster, I need to practice lots before I get consistent, so I'm not sure exactly what the taper is, but I think it's around .0015 wider at the bottom (far end).   That's one reason I stopped at .050 short of final size - get practiced before I shoot for the real size.


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## awake (Dec 16, 2021)

Bob, you may have already addressed this above, but just in case - as you get close to size, are you taking a spring pass each time?


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## CFLBob (Dec 16, 2021)

awake said:


> Bob, you may have already addressed this above, but just in case - as you get close to size, are you taking a spring pass each time?



I'm still doing rough shaping, .050 short of final size, so I haven't been doing that yet, but I'm with you on that.


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## awake (Dec 16, 2021)




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## Steamchick (Dec 16, 2021)

Hi Bob,
With the "spring" of the boring bar, you may expect it to be constant for the length of the bore... But a few quirky things happen. As the tool engages with the start of the cut, it cuts "full" until it starts to get into the metal, then when the tool is fully engaged it springs back a touch more. On the first cut, this may only be for 0.010" ~0.020" - ish, depending on how wide the cut actually is, when fully engaged. This tiny taper, then exacebates the next cut "start taper", and again, and again,  so you get a bell-mouth or initial taper from the outer-edge narrowing further down the bore. Also, as the cylinder heats up when the cut is traversing down the bore, the last bit of bore is thermally expanded a tiny amount larger than the first bit of the cut. Again, with 20 cuts, this is exacerbated 20 times... so the bottom of the bore - after cooling (normalising) temperature - then returns to a slightly smaller diameter than the top of the bore.  Complicated, but it is the reason that modern production machining floods the parts and cutters with coolant to keep the temperature the same from end-to-end of any cut. - Hence, without any mis-alignment of the lathe, there may be a detectable taper of larger at the top than the bottom of the bore, from these 2 factors...
If you have a larger bottom than top diameter, then that is the natural misalignment of the lathe, and not the dynamics of cutting metal...
Or that's what I remember from 30 ~ 50 odd years ago...
I think a taper of 0.0015" over a 1~2" length is a lot! When I was boiring car blocks in the 1960s (on WW2 machines - well worn) we had less than 0.001" variation of bore top to bottom. In fact I can't rememebr any difference, measured with a clock to 0.001". But when I was honing the bores afterwards, I had to stay withing 0.003" max variation top to middle to bottom... As the hone reached ends only momentarily, but passed the middle on the up and down strokes, we had to double the cut at the bore ends to keep the bore from barrelling: I.E.  bigger in the middle. 
If I made a mistake ( as an apprentice) the boss would take chaarge and "re-parallel" the bore, as he had 40 years practice more than I had! But it didn't happen after I "got the knack".  Incidentally, the Hone was not for sizing the bore, but to remove around half of the peaks of the cut-surface from the boring tool, so instead of the piston and ring surfaces sliding on  a saw-toothed set of "peaks" from machining, they rode on a series of flats, with tiny valleys retaining the oil.  This honing is seen as the cross-hatching of bores, familiar to most engine mechanics. 
The rings have to do a lot of work to retain a seal while adjusting to the bore size with 0.0015" variation, and the piston skirt will flap a bit more at the larger diameter, compared to the smaller... The skirt changes loading at TDC and BDC, or thereabouts, and causes piston slap when you have an extra thou at one end...
Do you have a miller or precision bench mill? If you do, you can set the boring bar to rotate, and the cylinder static, aligned to the axis of the quill. (A dummy bar or Go-NoGo gauge can be used for alignment). Then when you pass the boring bar - for finishing cuts - down the bore, the tool will describe a circle, and the quill traversing will make a true cylinder, compared to the tapered bore you have from the lathe. What you have at the moment, is a part rotating, and the tool is traversing an axis that is mis aligned to the axia of the rotating part, so you are naturally machining a tapered bore, not a cylinder.
When you have a true cylindrical bore, you can set a mandel in the lathe - to a tailstock centre for stability, with the cylinder fitted on the mandrel, and then cut the bottom flange face perpendicular to the bore.
It will all make a better engine.
Have fun!
If any other experts want to teach me better methods, then I am willing to learn more! (I'm not perfect - yet!). Just because I think I am right does not make it true... (That only applies to top politicians!).
Ken


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## Bentwings (Dec 16, 2021)

Nerd1000 said:


> I disagree on the topic of using grease on the lathe bed. The problem is that even a thin film of grease will attract dirt and swarf that grind down the ways. Ideally you should use way oil, it contains 'tackifiers' that help it stick to the slides and not get washed off. Failing that, for my Atlas milling machine the manufacturer specified SAE 30 motor oil... Which will no doubt have the purists up in arms, but you can't satisfy everyone.
> 
> A big help for bed lubrication is a set of felt way wipers, they'll prevent the swarf from getting under the saddle and also act as oil wicks to keep re-oiling the ways as the saddle moves.



I agree, no grease  way oil is fine cleans up easily does the job grease on the lead screws made a mess on our lathe cleaned up. Trying gear lube seems ok  gears like it but it’s stinky and can be a mess if there is too much
Byron


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## Nerd1000 (Dec 17, 2021)

Steamchick said:


> Hi Bob,
> With the "spring" of the boring bar, you may expect it to be constant for the length of the bore... But a few quirky things happen. As the tool engages with the start of the cut, it cuts "full" until it starts to get into the metal, then when the tool is fully engaged it springs back a touch more. On the first cut, this may only be for 0.010" ~0.020" - ish, depending on how wide the cut actually is, when fully engaged. This tiny taper, then exacebates the next cut "start taper", and again, and again,  so you get a bell-mouth or initial taper from the outer-edge narrowing further down the bore. Also, as the cylinder heats up when the cut is traversing down the bore, the last bit of bore is thermally expanded a tiny amount larger than the first bit of the cut. Again, with 20 cuts, this is exacerbated 20 times... so the bottom of the bore - after cooling (normalising) temperature - then returns to a slightly smaller diameter than the top of the bore.  Complicated, but it is the reason that modern production machining floods the parts and cutters with coolant to keep the temperature the same from end-to-end of any cut. - Hence, without any mis-alignment of the lathe, there may be a detectable taper of larger at the top than the bottom of the bore, from these 2 factors...
> If you have a larger bottom than top diameter, then that is the natural misalignment of the lathe, and not the dynamics of cutting metal...
> Or that's what I remember from 30 ~ 50 odd years ago...
> ...


Keep in mind that boring on the mill will only make a true circle if the spindle is trammed to be perfectly parallel to the direction of feed. Tram errors will cause it to cut an elliptical bore.

The lathe will always make a circular bore but as you have noted it may be tapered by various factors, wear in the ways or insufficient levelling of the bed being common culprits alongside tool deflection.


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## Steamchick (Dec 17, 2021)

Hi Nerd, As this relies on long shafts in the quill, precision machined by the manufacturer to be concentric for bearing locations, and the quill sliding surfaces, these quill axis versus rotational axis mis-alignments are very small compared to all the things that will develop a tapered bore from the lathe. It is why industry  uses boring machines for engines that are equivalent to a mill or drill with a rotating Quill passing along an axis that becomes the axis of the bore. (I used boring machines in the 1960s, using 1940s machines. Modern factories - e.g. the ones I saw in 1989 in Japan, etc. - use CNC boring bars of basically the same strategy. - The "CNC bit" checks and measures as it cuts, and resets/replaces tooling automatically - which is what I did manually in the 1960s - after every cut.).
I use an old and worn miller-driller to bore my cylinders, as it is simply better (a more true cylinder) than the lathe. With 0.0001" DTIs (bore gauges) in the 1960s we never managed to see any ovality in the bores, yet with honing (as I was learning the skills of manually traversing the hone in the bore developing cross-hatching) we could develop tapered- , barrel- , and hour-glass-  bores of a few 10ths of a thou. The target was as true a cylinder as we could get axially, as the circularity was not a problem.
However, if you have managed to make elliptical bores doing it that way I am surprised? (Amazed!).
K2


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## Nerd1000 (Dec 17, 2021)

Steamchick said:


> Hi Nerd, As this relies on long shafts in the quill, precision machined by the manufacturer to be concentric for bearing locations, and the quill sliding surfaces, these quill axis versus rotational axis mis-alignments are very small compared to all the things that will develop a tapered bore from the lathe. It is why industry  uses boring machines for engines that are equivalent to a mill or drill with a rotating Quill passing along an axis that becomes the axis of the bore. (I used boring machines in the 1960s, using 1940s machines. Modern factories - e.g. the ones I saw in 1989 in Japan, etc. - use CNC boring bars of basically the same strategy. - The "CNC bit" checks and measures as it cuts, and resets/replaces tooling automatically - which is what I did manually in the 1960s - after every cut.).
> I use an old and worn miller-driller to bore my cylinders, as it is simply better (a more true cylinder) than the lathe. With 0.0001" DTIs (bore gauges) in the 1960s we never managed to see any ovality in the bores, yet with honing (as I was learning the skills of manually traversing the hone in the bore developing cross-hatching) we could develop tapered- , barrel- , and hour-glass-  bores of a few 10ths of a thou. The target was as true a cylinder as we could get axially, as the circularity was not a problem.
> However, if you have managed to make elliptical bores doing it that way I am surprised? (Amazed!).
> K2


My mill hasn't got enough Z travel to bore cylinders (it's an Atlas MFA horizontal mill, there is maybe 4" of Z available depending on setup which leaves very little space for a boring head), so I have no choice but to use the lathe.

I made that remark because a lot of hobby machinists use inexpensive Chinese mills, and some of those machines are notorious for head tramming issues including the head moving after being trammed due to poor manufacturing of the mating surfaces or dubious clamping mechanisms. With such equipment it's probably a good idea to check the tram of the head every time the head is moved. Of course it would take an egregious amount of tram error to make a noticeably oval cylinder, but it's just another thing to watch out for.


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## Steamchick (Dec 17, 2021)

Hi Nerd, Thanks for that - Fair comment! - I do not have that experience of the mills, nor of horizontal mills.
Incidentally, My Dad didn't have a Mill, nor suitable bench drill, so he set the cylinders on the tool post location - with home developed  fixturing - and traversed  the cylinders along the axis of the lathe with boring bar set between chuck and tail-stock centre. It is quite easy to make the boring bar - a 1/8" or 1/4" hole drilled in the middle of a long bar, with locking screw, to hold a tool-bit from round HSS. The bar between chuck and tailstock needs to allow for the length of cylinder each side of the tool, so the tool can pass fully through.
Similarly,  Your 4" Z-travel would allow a bit less than 2" long bore for a cylinder that was around the bar. (4" subtracting the tool bit thickness and maybe another 1/4" for end clearances...). I am sure you could make a small bar for your miller, if you had a cylinder less than 1 3/4" long?  Do you need a sketch? - or can you envisage my idea?
K2


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## Nerd1000 (Dec 17, 2021)

Steamchick said:


> Hi Nerd, Thanks for that - Fair comment! - I do not have that experience of the mills, nor of horizontal mills.
> Incidentally, My Dad didn't have a Mill, nor suitable bench drill, so he set the cylinders on the tool post location - with home developed  fixturing - and traversed  the cylinders along the axis of the lathe with boring bar set between chuck and tail-stock centre. It is quite easy to make the boring bar - a 1/8" or 1/4" hole drilled in the middle of a long bar, with locking screw, to hold a tool-bit from round HSS. The bar between chuck and tailstock needs to allow for the length of cylinder each side of the tool, so the tool can pass fully through.
> Similarly,  Your 4" Z-travel would allow a bit less than 2" long bore for a cylinder that was around the bar. (4" subtracting the tool bit thickness and maybe another 1/4" for end clearances...). I am sure you could make a small bar for your miller, if you had a cylinder less than 1 3/4" long?  Do you need a sketch? - or can you envisage my idea?
> K2


Yes I've considered that. It should even be possible to support the other end of the bar with the overarm, which would of course be ideal for reducing tool deflection issues, similar to your dad's line boring on the lathe. I would need to make a custom Morse taper holder to support the spindle end of the bar without taking up too much space, as a typical collet chuck occupies a fair bit of my limited real estate.


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## Steamchick (Dec 17, 2021)

Cheers Nerd, (Do you have a more "Human" handle?).
You are the expert of your machine. The fun is resolving the tooling issues! Add a picture when you work out a solution! Good for us all to learn!
Cheers!
K2


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## awake (Dec 17, 2021)

Steamchick said:


> Hi Nerd, As this relies on long shafts in the quill, precision machined by the manufacturer to be concentric for bearing locations, and the quill sliding surfaces, these quill axis versus rotational axis mis-alignments are very small compared to all the things that will develop a tapered bore from the lathe. It is why industry  uses boring machines for engines that are equivalent to a mill or drill with a rotating Quill passing along an axis that becomes the axis of the bore. (I used boring machines in the 1960s, using 1940s machines. Modern factories - e.g. the ones I saw in 1989 in Japan, etc. - use CNC boring bars of basically the same strategy. - The "CNC bit" checks and measures as it cuts, and resets/replaces tooling automatically - which is what I did manually in the 1960s - after every cut.).
> I use an old and worn miller-driller to bore my cylinders, as it is simply better (a more true cylinder) than the lathe. With 0.0001" DTIs (bore gauges) in the 1960s we never managed to see any ovality in the bores, yet with honing (as I was learning the skills of manually traversing the hone in the bore developing cross-hatching) we could develop tapered- , barrel- , and hour-glass-  bores of a few 10ths of a thou. The target was as true a cylinder as we could get axially, as the circularity was not a problem.
> However, if you have managed to make elliptical bores doing it that way I am surprised? (Amazed!).
> K2



Is boring an engine done on a mill (or similar machine) due to greater accuracy ... or rather due to the great difficulty of spinning an engine block on a lathe?

I'm thinking the lathe is generally going to be more accurate, but it just isn't suited for some types of boring.


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## Bentwings (Dec 17, 2021)

Nerd1000 said:


> Keep in mind that boring on the mill will only make a true circle if the spindle is trammed to be perfectly parallel to the direction of feed. Tram errors will cause it to cut an elliptical bore.
> 
> The lathe will always make a circular bore but as you have noted it may be tapered by various factors, wear in the ways or insufficient levelling of the bed being common culprits alongside tool deflection.


You already have a good handle in tool dynamics . I’d almost think we came from the same apprentice program.  Midterm in my engineering caree I was introduced to a gentleman that assisted me with tool dynamics using one of my structural analysis programs so I was able to simulate some of thes issues on screen.  With the advent of carbon fiber I think it only a matter of time before someone comes up with ultra stiff tools with bonded carbide or other super hard cut tinging edges weight is not the issue. CF HAS AS MUCH AS 10 times the tensil  of steel so tools could be much stiffer. It would then go to how ridged  is the machine or holder then we will se Star Trek tritanium and even more exotic materials. The ultimat being unobtanium. LOL  BY THEN WE WILL HAVE REPLICATORS SO MACHINE TOOLS WILL BE OBSOLETE .  My mind is drifting sorry I missed caps lock was on.
Byron


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## Steamchick (Dec 17, 2021)

Simply: 
A rotating tool describes a circle. As it progresses along the axis of the quill it makes a "perfect" cylinder.
A static tool and rotating part makes a circle, but the axis of the lathe, is never perfectly true to the bed so the lathe makes a tapered bore, not the desired cylindrical bore. This is because the tool does not run true to the axis of rotation.
K2


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## davidyat (Dec 17, 2021)

*Don't know if this has been said. I have a LeBlond Duel lathe made in 1947. When I moved to Indiana, I just put it on my garage floor. I am no where near any of your talent. No matter what I tried with my lathe, I was always getting that taper of a thou or more over 7 to 8 inches. My mentor asked me, "Did you level the ways when you got to Indiana"? UUHH, no. So I grabbed my Dad's machinists' level and yes, I was out of plumb. Plumbed it and a very small adjustment to my tail stock and things are a million times better.
Grasshopper*


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## CFLBob (Dec 17, 2021)

My lathe is mounted on a pair of accessory cabinets that were intended for it.  

I've noticed that at certain RPMs, it will rattle more, as if the cabinets are going through some sort of resonance.  Above or below that speed range, no rattle or perceptible movement.  I have a shop crane and could conceivably lift the lathe and the cabinets.  Perhaps while getting pushed into place, it went out of level.  Or never was. 

I don't have anything like the precision Starrett level that Blondihacks used in her video of aligning the lathe.


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## Nerd1000 (Dec 17, 2021)

CFLBob said:


> My lathe is mounted on a pair of accessory cabinets that were intended for it.
> 
> I've noticed that at certain RPMs, it will rattle more, as if the cabinets are going through some sort of resonance.  Above or below that speed range, no rattle or perceptible movement.  I have a shop crane and could conceivably lift the lathe and the cabinets.  Perhaps while getting pushed into place, it went out of level.  Or never was.
> 
> I don't have anything like the precision Starrett level that Blondihacks used in her video of aligning the lathe.


Blondiehacks also has a demonstration of alignment by cutting a test bar, which you could follow.

Alternatively it is actually possible to level your lathe using a plumb bob. There are some videos on YouTube that cover the topic, E.g.


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## Brian Rupnow (Dec 17, 2021)

To truly align the tailstock with the rotating head shaft, the best bet is to machine a test bar, supported between centers, driven with a lathe dog. Test bar should be at least 10" long. Machine a section about 1/2"  long at one end, taking note of your cross-feed setting. Move to the other end and machine about 1/2" at exactly the same crossfeed setting. Use a micrometer, not a Vernier caliper to measure the two diameters. If they are both the same, you have perfect alignment. If they are not, then your tailstock is out of alignment.


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## Steamchick (Dec 18, 2021)

The "out-of-level" sydrome twists the bed and misaligns the saddle as it moves away from the headstock, as well as misaligning the tailstock - that is all the centre drilling, boring and long OD machining "knackered", and because the saddle is at any unknown position away from the headstock, the cross-feed - so all facing is knackered as well! - 
In other words, the whole lathe becomes a lot less accurate (and ALL your work with it!) than the manufacturer made it. 
So aligning the lathe MOUNTING correctly is SUPER IMPORTANT!
Pressed steel cabinets are not as stiff as triangulated steel frames. The more solid the mount, the better you will maintain the lathe in whatever alignment it has. Brian's check above is used in the factory to check the lathe before shipping, and the makers use strong pallets to minimise any changes during shipping, but you need to set the support frame mounting points true before mounting the lathe. Usually, a car jack, or levers, can lift one end at a time to permit insertion of appropriate shims - after you have determined any misalignment in the lathe bed mounting.
K2


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## Steamchick (Dec 18, 2021)

A fair explanation here:

K2


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## Steamchick (Dec 18, 2021)

I have used a fine tapered burr (comes to a point) that I use for setting a centre when drilling gas jets down to 0.25mm (~0.010"). With the test bar, set at the headstock, faced and a centre marked, I then extend it to the longest length from the chuck and see where the point in the tailstock lies against the tiny mark in the centre of the test bar. Very quickly you can see the misalignment between head and tail of the lathe caused by twist.
Check yours, then follow corrective procedures as per the videos...
Or if you have a really good test bar (stiff enough it doesn't deflect under its own weight? - And without any bend!) you can pop a DTI in the tool post and watch the pointer change as you traverse along the test bar, on the side, and on the top.
Then reset the lathe as per the videos, and recheck with the DTI on the test bar....
K2


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## CFLBob (Dec 19, 2021)

I think my problem is more fundamental.  I can't measure worth a flip.  

I just took 20 measurements of the inside diameter of both ends of the bore.  There's some sort of taper there, wider at the bottom of the cylinder (lathe chuck end) than the other end, but my measurements are all over.   The outer measurements run from .9491 to .9510.  The bottom end runs from .9514 to .9550.  I did five sets of a few measurements and the variation is mostly between the sets.

I'm using a micrometer and a telescoping ID gauge.  

Anybody have any favorite videos for this?  Websites?


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## Steamchick (Dec 19, 2021)

CFLBob said:


> I think my problem is more fundamental.  I can't measure worth a flip.
> 
> I just took 20 measurements of the inside diameter of both ends of the bore.  There's some sort of taper there, wider at the bottom of the cylinder (lathe chuck end) than the other end, but my measurements are all over.   The outer measurements run from .9491 to .9510.  The bottom end runs from .9514 to .9550.  I did five sets of a few measurements and the variation is mostly between the sets.
> 
> ...


Or you can do some statistics, and use the average for each measurement point. Normally I would measure each point at least 3 times - using internal calipers to micrometer, because that is how I was taught 50 years ago. But I now double check using  an ID gauge as well. But easy to make a stepped checking gauge - 1/4" bands at 0.001" increasing diameter sarod the dimension you are checkingl, and you can more easily what fits and what doesn't. Do not use a tapered gauge, it will only tell you the size at the outer edge of the bore.
Cheers, 
K2


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## CFLBob (Dec 19, 2021)

Steamchick said:


> Or you can do some statistics, and use the average for each measurement point. Normally I would measure each point at least 3 times - using internal calipers to micrometer, because that is how I was taught 50 years ago. But I now double check using  an ID gauge as well. But easy to make a stepped checking gauge - 1/4" bands at 0.001" increasing diameter sarod the dimension you are checkingl, and you can more easily what fits and what doesn't. Do not use a tapered gauge, it will only tell you the size at the outer edge of the bore.
> Cheers,
> K2



Statistics is practically my middle name, but I'm not comfortable using them here.  Let me show you why.  Two batches of ID measurements at the non-chuck end of the cylinder

Test 1
0.9510
0.9510
0.9508
0.9509

Test 2
0.9497
0.9499
0.9495
0.9499

Those are two different populations.  The averages for each group are 0.9509 (#1) and 0.9498, with a standard deviation of .0001 for the first group and twice that for the second.  Sure those two averages are only 1.1 thou apart, but in standard deviations, they're more than 3 sigma different.  If I combined all of those readings into one average, the std deviation would get bigger.  

The chuck end is worse.  When I figure the std. dev. for the chuck end vs. this end, it's about 2 to 3 times greater.  Because of that, the tapers I measure vary more.  

What I think I need to do is get more precise settings of the telescoping gauge.  I'm not doing as well when it's down the bore as I am when the telescoping gauge is right there at the end.  

Since the bore is obviously close to 0.950 and my target is 1.000, I can take off another .040 and then repeat all this.  I just don't like the spread in values test to test.  Also, this design calls for a Vyton piston ring instead of cast iron.  I tend to believe that makes the real application a bit more forgiving.


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## Richard Hed (Dec 20, 2021)

CFLBob said:


> I think my problem is more fundamental.  I can't measure worth a flip.
> 
> I just took 20 measurements of the inside diameter of both ends of the bore.  There's some sort of taper there, wider at the bottom of the cylinder (lathe chuck end) than the other end, but my measurements are all over.   The outer measurements run from .9491 to .9510.  The bottom end runs from .9514 to .9550.  I did five sets of a few measurements and the variation is mostly between the sets.
> 
> ...


How did you cut it?  Did you use a reamer?  I never completely trust those telescoping ID gauges.  They require the use of two tools, each tool representing another layer of error.  Do you have any direct reading micrometers for inside?  Since you still have a way to go, why not cut out .030 and then ream it?


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## Steamchick (Dec 20, 2021)

If you have a side lever DTI, you may be able to arrange it as a clock comparitor to the micrometer, by adding a stem behind the ball-ended contact lever. I'll try and do something today and show you a picture.
K2


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## Steamchick (Dec 20, 2021)

Bob, I just produced this "quick check" that you can do on your lathe to give you a clue as to how accurate it is... (Mine is aligned well enough, but the chuck has some distortion  - probably strained from some mis-haps that I have had...).
Maybe this quick check can help you decide what to do with the lathe, I.E. show you where the taper is being generated?
K2


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## CFLBob (Dec 20, 2021)

Richard Hed said:


> How did you cut it?  Did you use a reamer?  I never completely trust those telescoping ID gauges.  They require the use of two tools, each tool representing another layer of error.  Do you have any direct reading micrometers for inside?  Since you still have a way to go, why not cut out .030 and then ream it?



I cut it with a boring bar that has a carbide insert.  It cuts at a relatively small point; I mean the contact in the telescoping gauge has to be 10 times the width of the cutting point so it's not like one measurement is in a valley and the next measurement is on a peak.  They're all over a fairly wide swath.    







I don't have any sort of inside micrometer.   I don't have a reamer that's 1" diameter.  

In terms of buying a tool like a 1" reamer, or a different micrometer, that's possible, but this is a one-off engine.  If my bore ends up .987, but otherwise good, I just make my piston a little smaller.   It's not like the 1000th piston I make has to fit the 10,000th engine block that someone else makes.  



Steamchick said:


> Bob, I just produced this "quick check" that you can do on your lathe to give you a clue as to how accurate it is... (Mine is aligned well enough, but the chuck has some distortion - probably strained from some mis-haps that I have had...).
> Maybe this quick check can help you decide what to do with the lathe, I.E. show you where the taper is being generated?
> K2



Thanks for that.  I'm in the awkward stage of having a carefully set up part in my four jaw chuck and I think the chances of getting everything back exactly where it was (if I take out my work and switch to a round bar, swapping out the chuck or not) are just about zero.  Which means I start over.  Now if I screw this up badly enough, I may end up starting over again anyway,  but I'd rather not risk it.   

I figure I'll limp along on this cylinder and try to finish it, then spend some time checking the lathe.  

The thing that bothers me is not getting as consistent readings deep in the cylinder as toward the end in that picture.  The fact that there's a little taper doesn't bother me anywhere near as much as not being able to tell you how much taper there is.  The fact that the cylinder is smallest at the top, where it's going to get the most thermal expansion is better than being the other way around.  Some measurements tell me the taper is .001" and some tell me .003.  If I look at the averages of every measurement I took, I can see that one or two sets end up moving the average the most.


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## werowance (Dec 20, 2021)

Bob, for what its worth,  i also use a telescoping bore gauge and then my mics to measure.  i also use a very similar boring tool.  and i always have similar measurements of the cylinders i have made on the engines that i have made that run just fine. (which is not a whole lot of engines but a few)

one thing i do is make a lap and use either diamond paste or the last 2 engines i started using clover with silcon carbide suspended in what smells like regular old grease.  i start with 600 grit and move on up to 1500 grit.

i then run the piston in usually with the 1500 grit but some times i have to back down to 1000 an then back up to the 1500 in order to get it thru.

hope that this information can help you in some way or other.


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## Richard Hed (Dec 20, 2021)

CFLBob said:


> I cut it with a boring bar that has a carbide insert.  It cuts at a relatively small point; I mean the contact in the telescoping gauge has to be 10 times the width of the cutting point so it's not like one measurement is in a valley and the next measurement is on a peak.  They're all over a fairly wide swath.
> 
> View attachment 132035
> 
> ...


What speed are you cutting at?  and what feed?  If you speed up your cutting speed and slow down the feed, you might get better readings.  Also, reverse your feed once your reach the end cut.  This is all before you reach within, say .015" of finish.  otherwords, take a light cut, reverse feed without changing the setting, then check the bore.  If necessary (being very careful not to disturb the setting) take a spring cut.  Make sure your carbide bit is clean and new and sharp before doing any of this final business.  What kind of lathe do you have.  Me thimpfks you told us once, but I doesn't remember.  Is it a light machine,?  Medium sized?  If you have a light machine, you just might have to live with it.  One of the fellows on this forum said something about one end of a cylinder is best being .001 smaller than the other end anyway.  It made sense what he was saying, but I forget who and exactly what he was saying.

There is a method of making your own reamer.  Do you just happen to havve a piece of 1" drill rod?  YOu live in Florida, no?  As for myself, I bought a 1" reamer from Shars as I need a 1" just often enough to get a cheapo.

Naturally, I am not there to observe your measurements, and I'm sure yhou are being careful to remove the telescoping guage properly, but how about re-viewing Quinn's video on that?

In the mean time, I thimpfks I would order a cheapo (but still quality enough) inside micrometer from Shars or some other cheapo chinese company.  I have two, one from .2 to 1.2, nd the other from something like .6 to 2.6".  I consider them invaluable.


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## Steamchick (Dec 20, 2021)

Hi Bob, I just tried a quick demo of the idea for using a side-lever DTI for a comparitor against the micrometer. Easier to show pictures...:
The internal calipers I use, with a large diameter thumb wheel for very fine feel. I find these much better than bore gauges for less than 1" bore.




Another alternative to your bore gauge:
A side-lever DTI with a scriber held on the back with a rubber band. - If properly fixed, and adjustable, this could serve as a bore gauge comparitor for use against the micrometer.






The next picture shows how you would set the micrometer to the size to be measured, then set the DTI Bore gauge to zero aganst the mic.




Then it can be used as a comparitor to measurethew undersize or oversize of the bore. = becomes a direct reading bore gauge!
While I have only shown the scriber affixed with a rubber band, there is no adjustment of the gauge to various dimensions. If you made a small clamp-on fixed point that was adjustable with a screw, and locknut, then you would have a more secure but versatile measuring gauge. - This DTI measures to 0.0001" per division, so you can even use it for honing to size, where you may only be removing a fraction of a thou per pass of the hone.
But I would recommend you try and reset the lathe to be closer to a parallel bore before you finish boring the cylinder, anyway.
Cheers!
K2


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## trackmaggot (Dec 20, 2021)

What level of confidence do you have in your tools? Has the mic been calibrated, are it's anvils true, has it been dropped, is the back sprung? You might also look at doing a Gage R&R (just for fun) to see if you can identify where the variations might be coming from during the measurements.


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## Steamchick (Dec 20, 2021)

I have some telescopic bore gauges, - cheap stuff - with poor ends on the telescoping measuring ends. Possibly that is causing the variation? - Which is why I prefer the internal calipers. I think I am more consistent transferring bore size to mic.
Bob, can you show us a picture of your bore gauge?
K2


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## CFLBob (Dec 20, 2021)

This thread got very busy as the day went by.  

@werowance Yes, it does help.  I think people who tend to say, "meh ... close enough" all the time don't take on machining as hobby, and I can see I might be over analyzing this condition.  



trackmaggot said:


> What level of confidence do you have in your tools? Has the mic been calibrated, are it's anvils true, has it been dropped, is the back sprung? You might also look at doing a Gage R&R (just for fun) to see if you can identify where the variations might be coming from during the measurements.



The micrometer is new and seems decent.  The anvils are good; never been dropped and everything seems to do what it's supposed to.  It's midway in price between Shars and Mitutoyo.  I had a Shars that died at its first battery change.  About a year old?  Certainly less than two years old.  
https://smile.amazon.com/gp/product/B075K2DJPB/ref=ppx_yo_dt_b_asin_title_o05_s02?ie=UTF8&psc=1 

The telescopic gauge is marked as Starrett and came in a box marked Starrett, bought used from eBay.  I have a set that's not as good quality, but when this size broke, (3/4" to 1" -  I think) I picked up this Starrett.  

The Gage R&R studies I've been involved with were all electronics testing and I wouldn't know what to do here.

This would be a good place to post this picture: 






The Telescopic gauge we're talking about.  Note how the shaft is a few degrees above perpendicular to the head.  That's the only thing I know that isn't as good as I'd like to see it. 

My technique is to lay this on the side of the cylinder so that the head is on top of the last circular flange, then grab the knurled part of the handle with a pair of long needle-nosed pliers (it's just left of the non-knurled part on the end).   Then I put it in place in the cylinder still holding it in the pliers, with the pliers flush with the end of the cylinder, and unscrew the clamp holding the movable pin in place.   Jiggle it a bit and then tighten down the screw to hold the position - all the while trying to preserve that angle so that the measuring head is perpendicular to the walls of the cylinder.  



Steamchick said:


> Easier to show pictures...:
> The internal calipers I use, with a large diameter thumb wheel for very fine feel. I find these much better than bore gauges for less than 1" bore.



I might have a pair of calipers like that around here.  Sounds odd, but I know I've had them before.  The other trick, the dial indicator with a pointed scriber is interesting, but I don't think I have anything like that pointed scriber.



Richard Hed said:


> What speed are you cutting at? and what feed? If you speed up your cutting speed and slow down the feed, you might get better readings. Also, reverse your feed once your reach the end cut. This is all before you reach within, say .015" of finish. otherwords, take a light cut, reverse feed without changing the setting, then check the bore. If necessary (being very careful not to disturb the setting) take a spring cut. Make sure your carbide bit is clean and new and sharp before doing any of this final business. What kind of lathe do you have. Me thimpfks you told us once, but I doesn't remember. Is it a light machine,? Medium sized? If you have a light machine, you just might have to live with it. One of the fellows on this forum said something about one end of a cylinder is best being .001 smaller than the other end anyway. It made sense what he was saying, but I forget who and exactly what he was saying.



My lathe is a SIEG SC4, from Little Machine Shop, their LMS3540.  These are 8.5 by 20" so not quite a 9x20 lathe.  The spindle motor is 1.3 HP (1000 Watts).  I've been taking .020 radius off per pass (.040 diameter), running 300 RPMs.  The lathe has power feed, which is coupled to the turning RPMs.  It feeds at about .002" per revolution.

What I've been doing is similar to what you describe, not not exactly.  I power feed until the boring bar is just about as far as it will go into the cylinder, remove power feed and advance the tool the last .025 to .050.  Then instead of reversing the motor and reversing the power feed, I manually turn the handwheel on the cross slide until the the cutter comes back out of the cylinder.  Going forward, it takes about 5-1/2 minutes to cut an entire pass.  I've never timed myself doing this, but I think it's more like one to two minutes to take that spring pass taking the boring bar back out.


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## Richard Hed (Dec 20, 2021)

CFLBob said:


> This thread got very busy as the day went by.
> 
> @werowance Yes, it does help.  I think people who tend to say, "meh ... close enough" all the time don't take on machining as hobby, and I can see I might be over analyzing this condition.
> 
> ...




I think (Oh dang, I misspelled that!) that your cutting speed is too low, especially for a finish cut.  What speed do yuou have that is next highest?  Do you have a lower feed rate?  What do you mean by "I manually turn the handwheel on the cross slide until the the cutter comes back out of the cylinder".  This does not sound right.  I thimpfks yuo mean something else.  Do you mean the handwheel on the carraige?  On the way back out, can you see what size of flakes you are getting?  You've recently checkt that all the slides are tight?  Maybe you could try tightening the gibs so that the slides are immobile whe yu make a cut.

Also, I am not clear on how you do your tele gauge.  You mean, you wiggle it before withdrawing it?  Utub peeps do it different.  First, they have the gauge perpendicular to gravity.  they may wiggle it before tightening it to center it in the cylinder, but then they push the handle down only (or up) without any other wiggling.  this gets a single sample with no wiggling.  Notice that they tighten the handle, THEN push down, this is an important movement.  withdraw carefully, measure.

What about a piece of 1" drill rod?  not any, huh?


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## Steamchick (Dec 20, 2021)

Hi Bob, on the side-lever DTI.... I just used a scriber from a small marking block I have. Actually, it is just a piece of sharpened silver steel with a bend. What this set-up really needs for use as a bore gauge, is a bracket holding a bar, with a threaded hole, then a screw with a small ball end through the threaded hole and locknut, forming an anvil opposite to the ball on the lever of the DTI. BUT, all that is irrelevant to your current measurements...
Your bore gauge, while having been made by Starrett, and appearing to be OK, may be the culprit. It looks skew... as you are aware. My opinion -  as more experienced machinists may have better opinions - is that the skew end of the bore gauge means you cannot get a repeatedly perpendicular diameter of the bore. Also, the ends of the bore gauge need to be a smaller radius than the bore , so you get a contact on the exact centre of each end of the gauge. When the gauge is true and perpendicular to the handle, the tight spot at true diameter of the bore will mean the handle is it the centre of the open end of the bore. Because it is skew, you cannot repeatedly get the gauge end truly perpendicular to the axis of the bore, so may get some readings that are larger than the true diameter.
But there may be another explanation?
K2


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## CFLBob (Dec 20, 2021)

Easy one first, no 1" drill rod.  

On withdrawing the cutter: obligatory picture of the lathe:





When power feed is engaged, the handles on the compound (7) and the cross slide (5) do not get touched.  I taped those in position to keep them from loosening themselves back when cutting the points off the square bar and I could see the knobs moving.  I move the carriage to the right by using that big black wheel on the bottom left of the carriage.   Just left of where number 11 points.  Yes, I can see the size of the flakes bouncing out of the bore when I make that cut, there are fewer and smaller flakes than when cutting into the bore the first time.

I can adjust the motor speed in 10 RPM increments from 100 to 2000 RPM.  I don't think I've ever had it at the top end. 

I'm focusing on the gauge because of the reasons you talk about.  When I'm measuring the end farthest from the chuck, the gauge is right where I can see it best and touch it.  I consistently get the lowest deviation on that end.  I consistently get 3 to 4 x that deviation when measuring the end closest to the chuck.


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## Richard Hed (Dec 20, 2021)

I've been wanting to try that method of making your own reamer for a long time.  I just don't need any reamers.


CFLBob said:


> Easy one first, no 1" drill rod.
> 
> On withdrawing the cutter: obligatory picture of the lathe:
> 
> ...


What control do hyo have on the feed?  I thimpfks I would turn that speed up to 6-800 rpms on this cut.  Have you tried that yet?  Might be miraculous.


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## Nerd1000 (Dec 20, 2021)

Richard Hed said:


> I've been wanting to try that method of making your own reamer for a long time.  I just don't need any reamers.
> 
> What control do hyo have on the feed?  I thimpfks I would turn that speed up to 6-800 rpms on this cut.  Have you tried that yet?  Might be miraculous.


I agree with this, carbide tooling likes to run fast. The speed and feed calculator I use suggests 1200 rpm for this cut, but it does seem to assume you're using a big industrial CNC so a reduction to 800 might be sensible.


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## Steamchick (Dec 21, 2021)

ALIGN THE LATHE. I bet it has a twist. The U-tube explanations are pretty simple. Unless it is set "True", Speed and feed won't fix a taper. The lathe probably needs a shim under one of the feet at the tailstock end? (My guess = the back one?).
On Measurement, use internal callipers to develop your skill, as they have rounded points, not large curves on the ends. And you can "feel" much better.... " with small movements, "left-right", Up-Down".


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## Ken I (Dec 21, 2021)

Bob, This is the way I use a telescopic gauge :-
Insert it deliberately skew and very lightly nip it up - then tilt it into alignment (going to be a bit more difficult with your "bent" gauge) - the telescope will collapse - when you feel it is a good fit - tighten more solidly.
Re-check the fit in the bore - a very light interference - tilt to remove and check it with a micrometer.
Repeat several times at the same spot to "calibrate" yourself.
Regards, Ken


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## Steamchick (Dec 21, 2021)

Bob, You are trying to attain the perfect diameter with the gauge, when perpendicular to the axis of the bore. Your "skew" handle does not enable you to judge the "perpendicular to the axis of the bore". The difficulty I find with a bore gauge like that is finding the tightest when rotating the gauge in the bore (true diameter), but at the same time the "loosest" fit when rocking the handle to engage longitudinally in the bore (now perpendicular to the axis of the bore). The curved points (contacts with the bore) and thumb wheel (for fine adjustment) of the internal calliper teach you the "right spot" - in my experience. Then repeated in the jaws of the micrometer, to repeat the "feel",  Practice on a KNOWN bore till you get the right measurements... That's what I was taught, and thousands of apprentices can't have been taught any differently?
K2


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## Ken I (Dec 21, 2021)

Bob - slightly off topic - but you did say that statistics was your middle name.
I once visited Fichtel & Sachs and queried a Vickers microhardness check which they had placed on a report as 1052.1 - I said that such accuracy wasn't possible.
Turns out I was wrong - they calibrated each and every one of their inspectors against known standard samples - so they had a statistical offset and error range for each inspector.
By having 5 persons taking a reading they could then statistically masturbate the data into a more precise answer.
Trust the Germans to be so precise as to "calibrate" their people.
Hence my comment - and K2's valuable suggestion to  calibrate yourself against a known standard.
Regards, Ken
Edit-P.S. as a reference use a ball-bearing of the same I.D. they're generally pretty accurate.


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## Steamchick (Dec 21, 2021)

25 years setting standards in Quality has rubbed off on me then. We calibrated all our inspectors against each other and international other plants and Companies. Most suppliers had calibrated inspectors as well. We checked data and regular test results during audits, and I only ever found 1 plant (Bosch = German) that was rubbish! Never Italians, French, Spanish, etc. - they always told the truth! The Germans wanted to sack the poor sod, I said we would sack the as a supplier with that sort of attitude, so the MD agreed "re-training" and "re-calibration" was the answer - for the inspector, his supervisor and the Quality Manager! Zeig! ...
re: my valuable suggestions - please re-train me when I get it wrong!
re: "use a ball-bearing of the same I.D.  " - use a bore from a ball race as a calibration bore as well...
K2


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## Richard Hed (Dec 21, 2021)

Steamchick said:


> 25 years setting standards in Quality has rubbed off on me then. We calibrated all our inspectors against each other and international other plants and Companies. Most suppliers had calibrated inspectors as well. We checked data and regular test results during audits, and I only ever found 1 plant (Bosch = German) that was rubbish! Never Italians, French, Spanish, etc. - they always told the truth! The Germans wanted to sack the poor sod, I said we would sack the as a supplier with that sort of attitude, so the MD agreed "re-training" and "re-calibration" was the answer - for the inspector, his supervisor and the Quality Manager! Zeig! ...
> re: my valuable suggestions - please re-train me when I get it wrong!
> re: "use a ball-bearing of the same I.D.  " - use a bore from a ball race as a calibration bore as well...
> K2


I don't quite get this.


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## Steamchick (Dec 21, 2021)

Calibrating inspectors against standards, and across companies, makes all the products the same - irrespective of the plant. 
The Germans didn't like that idea, if a guy met the standards - OK. if not they sacked him. They believed they were the best - but were not - according to their own results compared to others!
Manufacturing guys have to make 99.997% of stuff right. Inspectors equally have to find 99.997% of faults in products. So during a shift, they would be fed "known" faults at random and had to be 100% OK on finding them. E.G. during visual inspection of dye penetrant crack detection of forged parts.. It worked and the warranty failures dropped to Zero.
C'est la Guerre..
K2


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## ajoeiam (Dec 21, 2021)

CFLBob said:


> Statistics is practically my middle name, but I'm not comfortable using them here.  Let me show you why.  Two batches of ID measurements at the non-chuck end of the cylinder.
> 
> snip
> 
> Since the bore is obviously close to 0.950 and my target is 1.000, I can take off another .040 and then repeat all this.  I just don't like the spread in values test to test.  Also, this design calls for a Vyton piston ring instead of cast iron.  I tend to believe that makes the real application a bit more forgiving.


Hmmmm - - - - you're overthinking this - - - agonizing over tiny amounts of stuff that  -- - - - well - - - at this point - - - just don't matter. 

Rough cut to -0.050" of desired size. 
Usually this roughing is done in 0.100 to 0.200" dia cuts (radius of 0.050 to 0.100" have done up to 0.200" radius but that's on more stable machines!!). 
Get a quick measurement +/- 0.001 is quite good enough!!!!!!! 
Now you are finish cutting - - - may need to change your tool - - - - I did (roughing and finishing are 2 different steps!!). 
Do one light cut - - - say of 1/2 the dia left to cut (0.010" is maybe too light but not more than 0.025" radius). 
Now is when you measure the crap out of the piece. 
If you have a taper - - - note it. 
Mark out what you're going to do (mark on the lathe bed for boring every 0.001" change or on the piece for turning). 
Cut leaving 0.001" of material doing the cut as planned!!! 
Now you have some fun sanding (or using a flap wheel on an air die grinder). 

Doing this my worst project had the lathe giving me 16 thou change and I was within tenths at 0.002" too big. 
Should have shot for 0.001" too big - - - there was a pile of sanding. 
Bearing fit over 14" was the result with -0.0002 to -0.0004" on final size - - - just what the boss wanted.


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## ajoeiam (Dec 21, 2021)

Richard Hed said:


> How did you cut it?  Did you use a reamer?  I never completely trust those telescoping ID gauges.  They require the use of two tools, each tool representing another layer of error.  Do you have any direct reading micrometers for inside?  Since you still have a way to go, why not cut out .030 and then ream it?



I don't trust reamers!!!!!!!!!!!!! I've even had one cut a thou under size - - - over being more common. 
It is possible to trust telescoping gauges - - - - but only with regular use. 
Developing the feel first takes practice and to maintain the skill also takes practice. 
So practice makes perfect. 
Direct reading mics are fine if your bore is short - - - if the bore is say 3.50" rough and 8" deep your direct reading mics - - - - well they're nice ornaments. 
You can buy yourself a dial bore gauge - - - - but if you're only doing occasional work - - - - they're not worth the $$$$$$$ and they ain't cheap!!!


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## Richard Hed (Dec 21, 2021)

ajoeiam said:


> I don't trust reamers!!!!!!!!!!!!! I've even had one cut a thou under size - - - over being more common.
> It is possible to trust telescoping gauges - - - - but only with regular use.
> Developing the feel first takes practice and to maintain the skill also takes practice.
> So practice makes perfect.
> ...


Yes, you are rite.  however, it's better to be a single thou under than a thou over or maybe even worse, two thou under.  Course you might try a second reamer.  I read that a brand new reamer often is half a thou OVER but eventually gets down to the correct size, so a used reamer may be better than a new one.  Such is life.


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## minh-thanh (Dec 21, 2021)

HI CFLBob !
Now what is the error between cylinder diameter measurement positions ?


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## CFLBob (Dec 22, 2021)

minh-thanh said:


> HI CFLBob !
> Now what is the error between cylinder diameter measurement positions ?



Most accurate answer: I don't know.  

I had chores to do yesterday and didn't work on it, but here's every measurement.


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## minh-thanh (Dec 22, 2021)

Hi !
I don't understand :" 2" deep in Cyl "
Is your cylinder 2" longer and you measure at 2" ?


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## CFLBob (Dec 22, 2021)

Sorry, Minh Thanh

The cylinder is going to be 2-3/8" long when it's finished.  

The column that says outer end is where the cylinder head sits, the very top of travel.  

The 2" deep in cylinder isn't really 2".  It's more like 1.6" to 1.7" mostly because my telescoping gauge won't reach all the way in.   The piston has a 1" stroke and is 0.96" long so it's around where the bottom of the piston ends up at the bottom of its stroke.   

I wanted to measure top to bottom of the piston stroke, but my telescoping gauge isn't long enough.


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## minh-thanh (Dec 23, 2021)

Hi !
Have you checked the vibration of the chuck?
Maybe the bearing is worn, what bearing does the chuck shaft use ?


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## CFLBob (Dec 23, 2021)

minh-thanh said:


> Hi !
> Have you checked the vibration of the chuck?
> Maybe the bearing is worn, what bearing does the chuck shaft use ?



The holiday preparations here have overtaken the work in the shop and I haven't spent a minute on it since the original post.  

I can see or feel no looseness in the bearings, although I haven't tried to measure it.  My lathe is turning six years old in January, so it's not that old and gets light use.   I'm not saying the bearing can't be bad, just that I think the problem is coming from me, not the lathe.


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## Richard Hed (Dec 23, 2021)

CFLBob said:


> The holiday preparations here have overtaken the work in the shop and I haven't spent a minute on it since the original post.
> 
> I can see or feel no looseness in the bearings, although I haven't tried to measure it.  My lathe is turning six years old in January, so it's not that old and gets light use.   I'm not saying the bearing can't be bad, just that I think the problem is coming from me, not the lathe.


THis begs the question:  did you check the levelness yet?


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## CFLBob (Dec 23, 2021)

Richard Hed said:


> THis begs the question:  did you check the levelness yet?



Same answer: "The holiday preparations here have overtaken the work in the shop and I haven't spent a minute on it since the original post. "


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## minh-thanh (Dec 23, 2021)

CFLBob said:


> I think the problem is coming from me, not the lathe.


 There are many mechanical causes, sometimes it's the way we do it, anyway, there's no rush, I think you'll find the cause.


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## awake (Dec 23, 2021)

CFLBob said:


> My technique is to lay this on the side of the cylinder so that the head is on top of the last circular flange, then grab the knurled part of the handle with a pair of long needle-nosed pliers (it's just left of the non-knurled part on the end).   Then I put it in place in the cylinder still holding it in the pliers, with the pliers flush with the end of the cylinder, and unscrew the clamp holding the movable pin in place.   Jiggle it a bit and then tighten down the screw to hold the position - all the while trying to preserve that angle so that the measuring head is perpendicular to the walls of the cylinder.



Bob, you are using the wrong technique, and will definitely get variations in your readings. Ken I's technique below is correct - you deliberately "cock" the gauge off square and let the ends contact the cylinder walls. Tighten the clamp, then tilt the gauge through square and beyond, and remove it. The clamp mechanism allows the fingers to be compressed as this happens, but does not allow them to spring back out.



Ken I said:


> Bob, This is the way I use a telescopic gauge :-
> Insert it deliberately skew and very lightly nip it up - then tilt it into alignment (going to be a bit more difficult with your "bent" gauge) - the telescope will collapse - when you feel it is a good fit - tighten more solidly.
> Re-check the fit in the bore - a very light interference - tilt to remove and check it with a micrometer.
> Repeat several times at the same spot to "calibrate" yourself.
> Regards, Ken


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## CFLBob (Dec 23, 2021)

awake said:


> Bob, you are using the wrong technique, and will definitely get variations in your readings. Ken I's technique below is correct - you deliberately "cock" the gauge off square and let the ends contact the cylinder walls. Tighten the clamp, then tilt the gauge through square and beyond, and remove it. The clamp mechanism allows the fingers to be compressed as this happens, but does not allow them to spring back out.



Thanks, Andy,

Crossing my fingers that I get a couple of hours tomorrow to go back out to work on this.  I'm all but sure I'll have time on Christmas day.  


Bob


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## CFLBob (Dec 30, 2021)

Steamchick said:


> Hi Bob, I just tried a quick demo of the idea for using a side-lever DTI for a comparitor against the micrometer. Easier to show pictures...:
> The internal calipers I use, with a large diameter thumb wheel for very fine feel. I find these much better than bore gauges for less than 1" bore.
> View attachment 132038
> 
> ...



K2 

After messing around with my telescoping gauge a bit more, I figured it was time to get a replacement.  I could get another used Starrett gauge or an internal caliper like you showed (except I'm guessing you made that knob yourself).  I found a used Starrett internal caliper on eBay, and got it yesterday.

This is going to be a whole new learning curve.  While it seems easier to put in the center and find the diameter rather than some other distance, when I adjust my micrometer ratchet, it closes the jaws and wipes out the measurement.   I've always heard to use the ratchet knob to prevent that, but I don't see how that's going to work.  

More study.


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## Nerd1000 (Dec 31, 2021)

CFLBob said:


> K2
> 
> After messing around with my telescoping gauge a bit more, I figured it was time to get a replacement.  I could get another used Starrett gauge or an internal caliper like you showed (except I'm guessing you made that knob yourself).  I found a used Starrett internal caliper on eBay, and got it yesterday.
> 
> ...


I've always had that problem with my telescopic gauges. As a result I don't use the ratchet, instead I had to develop a 'feel' for the pressure on the gauge so as to measure repeatably. If you collapse the caliper even slightly you should perceive a sort of 'mushiness' in the feeling of twisting the micrometer.


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## Steamchick (Dec 31, 2021)

Nerds described it well. The caliper is a comparitor, not a measure. Set the micrometer to the size you think that you have machined the hole. Compare the feel of the caliper in the hole and the micrometer.  It too tight or too slack in the micrometer, reset by a couple of thou. Try the comparitive feel again... repeat until you have a setting of the micrometer that  matches the feel of the bore, when comparing them with the caliper. Just touching both means you have the size of the bore. You'll soon get a setting on the micrometer that exactly matches the feel of the bore.
K2


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## CFLBob (Dec 31, 2021)

Nerd1000 said:


> I've always had that problem with my telescopic gauges. As a result I don't use the ratchet, instead I had to develop a 'feel' for the pressure on the gauge so as to measure repeatably. If you collapse the caliper even slightly you should perceive a sort of 'mushiness' in the feeling of twisting the micrometer.



While doing my previous experiments, on one of the sets of measurements I ran into the problem of the micrometer making the gauge smaller. Tightening the screw that keeps the gauge from moving fixed it.

I think.

What if my whole problem with excessive variation in the numbers I got is actually from the micrometer squeezing the movable piston in the gauge?


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## CFLBob (Dec 31, 2021)

Steamchick said:


> Nerds described it well. The caliper is a comparitor, not a measure. Set the micrometer to the size you think that you have machined the hole. Compare the feel of the caliper in the hole and the micrometer.  It too tight or too slack in the micrometer, reset by a couple of thou. Try the comparitive feel again... repeat until you have a setting of the micrometer that  matches the feel of the bore, when comparing them with the caliper. Just touching both means you have the size of the bore. You'll soon get a setting on the micrometer that exactly matches the feel of the bore.
> K2



This is completely different from the way I've been doing things and I'm not quite sure I have enough hands to do this.  Do you set the mic and then set the lock to keep it from moving?  Do you hold the mic in a stand?


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## Steamchick (Dec 31, 2021)

Hi Bob,
Maybe you haven't been shown the simple way to hold a mic and use it.... - Fundamanetal training for MECHANICAL apprentices... but Electrical/electronic apprentices have a differnt agenda.

Hold the mic in your LEFT hand, using the last 2 fingers (your ring finger and pinkie) wrapped over the saddle of the mic.
Make sure the barrel is pointing AWAY from you, and the barrel will readily fit between your thumb and forefinger for adjustment. (You can feel better than the clicks oif the ratchet button! - and anyway you are SETTING the mic to a specific dimension with NOTHING between the jaws.).
You should be able to easily see the scale with a slight twist of the wrist/forearm and with a little practice this becomes second nature. - But when I was 14, with small hands, I found this quite difficult with anything bigger than a 3" mic.. the 10" mic definitely needed 2 hands!
Now set the mic to size. Then stop twiddling the mic. It will keep that size without using the lock as you won't be twiddling the barrel when comparing the caliper to the mic. Take the comparitor/caliper/Bore gauge/test piece, or whatever, in your right hand, and carefully insert between the jaws of the mic. You will now appeciate that while we mechanical oiks have a reputation with girls for having 8 hands when in the back row of the cinema, you are only using 2 of those hands. - One to manipulate the mic to size, the other to manipulate the gauge between the mic jaws.

It fits perfectly? Same feel as in the bore? - Great ! - That is sized.
It was a sloppy fit... Oh well, just more boring work to be done. Remove the caliper(etc.) and close the mic by a couple of thou. Check the caliper again. Eventually you will have enough practice so you get consistent readings.
It was a tight fit? OOPS! the gauge is telling you the bore is bigger than the size you set on the Mic. Just be sure and re-check the gauge in the bore...
Of course, when you are measuring a part directly, the same hold on the mic will permit you to adjust the mic carefully onto the part - often held in the other hand - when you may choose to use the ratchet knob to twiddle the mic. 
Any sinistral mechanics will note I am talking about the conventional mic held in the left hand, and will be aware that you can do the same with the right hand, but ensuring the barrel is pointing to the front and a bit to the right... I have never had a "left-handed Micrometer"...
Hope you enjoy this bit of learning, and are able to follow my crazy instructions!
Cheers!
K2


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## bluejets (Dec 31, 2021)

Used many brands and the only one that passes is the Moore & Wright.
Just did a one way bearing recess for the starter driver on the four cylinder.......perfect fit.
Seems it may have a rather fine thread in the shank which "pinches" the barrel under the slightest tension.
Usually give them a slight nip extra after withdrawing.
Naturally use vertical if measuring a bore in the lathe.


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## CFLBob (Dec 31, 2021)

bluejets said:


> Used many brands and the only one that passes is the Moore & Wright.



Sorry, bluejets, but one brand of which: the caliper or micrometer?  I've never heard of them before, but I see they make both things.


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## Sprocket (Dec 31, 2021)

I learned to hold the micrometer in the RIGHT hand, (I'm one of your sinistral mechanics) so the reading is toward you without the "slight twist of the wrist/forearm". Or is this only with the T gauge? Mics were made for right handers, why try to use it lefty?
Doug


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## Brian Rupnow (Dec 31, 2021)

I am right handed and I always hold the micrometer in my right hand. I close it on whatever I am measuring (Which I am generally holding in my left hand). My micrometer has a lock lever on the side which I engage, then turn the micrometer so I can see what the reading is. I have learned from experience that Vernier calipers are used to get a general idea of what a dimension is, but if it's anything critical, use the micrometer.


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## ShopShoe (Jan 1, 2022)

RE: Using telescope gauges...

I like Abom79's video on how he uses the guages and micrometers. I've increased my accuracy by following his lead:



--ShopShoe


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## xpylonracer (Jan 2, 2022)

Steamchick said:


> Nerds described it well. The caliper is a comparitor, not a measure. Set the micrometer to the size you think that you have machined the hole. Compare the feel of the caliper in the hole and the micrometer.  It too tight or too slack in the micrometer, reset by a couple of thou. Try the comparitive feel again... repeat until you have a setting of the micrometer that  matches the feel of the bore, when comparing them with the caliper. Just touching both means you have the size of the bore. You'll soon get a setting on the micrometer that exactly matches the feel of the bore.
> K2


.
It's find it's never so easy to get the same feel as the surfaces being gauged are so different, turned bore and polished flat anvils of the mic.
Like most I always do a 2nd check.
I have a mix of Moore & Wright and Mitutoyo gauges and as you would expect both have a silky smooth movement.

xpylonracer


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## Steamchick (Jan 2, 2022)

Doug, 
I use the micrometer (or gauge) in the left hand and introduce the calliper (comparator) with my right, as I am not sinistral, and use my right hand for the delicate setting and feel of the calliper in the bore I am checking. To hole the mic in my right hand, would mean I was changing hands for the feel of the calliper in the "gauge". - Not good for repeatability.
As you are sinistral, I assume you use the bore gauge with your left hand, in both the bore and the micrometer. Not changing hands between bore and gauge is key to repeatability. 
Irish quality control is "to be sure, to be sure" - but I Check-3-times, then put the tools down, and pick-up and check again. You quickly become accustomed to the operation and your measuring repeatability and accuracy stabilises quickly.
The major point here is that you do NOT adjust the micrometer onto the comparator (calliper or bore gauge, etc.) but set the micrometer and gauge the comparator with the fixed gap. That way you do not adjust the comparator during the check in the gauge. Screwing a mic onto a comparator will most certainly be risky for repeatability of your measurement, as that is a different contact loading to the feel you have when using the comparator in the bore, and likely to move the comparator.
I was taught by guys who machined parts for Rolls Royce Merlin engines during WW2... They were sticklers for precision and repeatability, as every engine was flown - and used to its extreme limits. Also, they had equipment that was about as accurate as most home workshops, not modern high precision CNC mass production with lazer and air gauging, temperature controlled clean measuring rooms, etc. I can only advise what I know to work for me... But many contributors have a lifetime of expertise to beat mine, so any other advice?
In the "home workshop" there are many gauges, some very high precision, like ball bearings, who's races have very precise bores and ODs - e.g. a 1" bore ball race makes a pretty good gauge for final finish checking of the comparator when making a 1" bore steam cylinder... I also use the shanks of milling cutters as "gauge standards" for ODs, and as gauges in small bores that need to be precise. (e.g. shaft bushes). I wonder, how often do many home workshop machinists check the accuracy of their micrometers and verniers? - Important when making thousands of parts, but maybe annually would be a good idea in the home workshop? - I usually do a "start of shift" check when I get a mic out of the box, and verniers get frequent zero checks. (I have mechanical verniers, not digital with "set zero" buttons. Too easy to measure something that has been inadvertently reset to a non-zero point!).
Enjoy!
K2


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## ajoeiam (Jan 2, 2022)

xpylonracer said:


> .
> It's find it's never so easy to get the same feel as the surfaces being gauged are so different, turned bore and polished flat anvils of the mic.
> Like most I always do a 2nd check.
> I have a mix of Moore & Wright and Mitutoyo gauges and as you would expect both have a silky smooth movement.
> ...



If you can find some - - - - you might want to try some TESA mics. They're even nicer than the Mitutoyo (haven't worked with any M & Ws).


----------



## xpylonracer (Jan 2, 2022)

ajoeiam said:


> If you can find some - - - - you might want to try some TESA mics. They're even nicer than the Mitutoyo (haven't worked with any M & Ws).


Hi aj
Nothing wrong with Mitutoyo mics, silky smooth operating adjustment, as I said you are comparing the feel of a turned part and polished carbide mic anvils, all you can do is check at least once to be sure of the reading.
I also use dial calipers in bores, especially useful to check parallelism of the bore. 





xpylonracer


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## Steamchick (Jan 3, 2022)

Xpyl... 
Excellent! The bore gauges I am familiar with are a DTI at the end of a long stem, with the mechanism of a "button" that reads via levers to the DTI opposite an anvil - that can be replaced with a longer one for larger bores: AKA: 








						Dial Bore Gauge High Accuracy Indicator Inner Diameter Measuring Tool 50mm-160mm  | eBay
					

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					www.ebay.co.uk
				



And here's one for  sub 1" sizes...








						Dial Bore Gauge Indicator Set Diameter Measuring 50-160mm 35-50mm 18-35mm 0.01mm  | eBay
					

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K2


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## Steamchick (Jan 3, 2022)

Thanks for the prompt lads, I have just decided to buy this...








						18-35mm Metric Dial Bore Gauge Cylinder Internal Measuring Mill Lathe Workshop  | eBay
					

Find many great new & used options and get the best deals for 18-35mm Metric Dial Bore Gauge Cylinder Internal Measuring Mill Lathe Workshop at the best online prices at eBay! Free delivery for many products.



					www.ebay.co.uk
				



I selected this as the description seemed to contain a better range of anvils, etc. for setting the gauge to various bore sizes. May be it's just the description, but it seemed the better kit of parts to me. And I reckon if the DTI is "not the best", I have a good one that will probably fit anyway. For conversion Metric to IMperial, I just change mics. The Zero will always be at the size I want, irrespective of the size of the "divisions" to get there. I'm happy with all dimensions anyway. 
Has anyone had to work in Korean Inches? - They are 1/10th of a Foot! Their version on Metric! - Confusing when a Korean book tells you a size in feet and Inches... - A Lesson for NASA there!
I'm making a couple of steam powered water pumps, so this will help do the "boring stuff" with tools I haven't handled in a while. - I'll cross-check with my callipers and mic anyway, but it's really nice to see a dial gauge instead of just relying on "feel"! The DTI may be just a factor more precise..? (But "Feeling the bore" can be fun as well)...
K2


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## xpylonracer (Jan 3, 2022)

Steamchick said:


> Xpyl...
> Excellent! The bore gauges I am familiar with are a DTI at the end of a long stem, with the mechanism of a "button" that reads via levers to the DTI opposite an anvil - that can be replaced with a longer one for larger bores: AKA:
> .
> Here's a few more gauges that I use most of the time.
> ...


[/QUOTE]


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## CFLBob (Jan 3, 2022)

For unknown reasons the forum "Watching" this thread stopped emailing me that posts were coming in and the last update I saw was my own post last Friday night.  I didn't even notice the thread in my daily "Yesterday's Forum Activity" activity emails and it should have been there.  

I can't say I'm "done", just getting a feel for the new instrument (calipers).  I enlarged the bore to 0.995 (by calculation) and I'm getting a feel for things.  

A few things that need to be done outside the shop have bubbled to the top of my list, so I'm probably going to be here for a while.


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## Steamchick (Jan 3, 2022)

Xpylon.. I have most of the gauges and comparitor you have, and have now ordered the DTI gauge, as I didn't realise before that I can afford one! They used to cost an arm and part of a leg.... as the DTI was built-in, not detachable like these modern ones. I last used one at work 30 years ago, but used one regularly when I was a lad. It will be nice to have one to use when boring my cylinders now.
But whatever comparitor is used, it needs to be carefully compared to a set gauge, whether an outside mic, ring gauge, or other .... The technique of making the comparison is the skill that doesn't come in a box. That's the bit where we should help Bob, and anyone else.
Thanks for the pictures of all your kit. Far more than I need. I guess you have the test bars and gauges for calibrating them as well.
Cheers,
K2


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## CFLBob (Jan 3, 2022)

There was one scene in that Abom79 video that ShopShoe posted that made watching the video 100% worthwhile.  He was showing how he checks the fit of the telescoping gauge in his micrometer.  The trick was it sticks on its own, but the tiniest touch makes it fall out.  That's at the 11:53 time mark.  A minute or two on either side to that time mark is the meat of it.


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## Brian Rupnow (Jan 3, 2022)

Bob--I use telescoping gauges all the time to measure the inside of things I am turning, and measure the results with my micrometer. I generally take three readings and then average them. Readings will be directly affected by how much you paid for the telescoping gauges. I always have some cold rolled round stock kicking around my shop. If I do get a taper inside a cylinder I chuck up the round stock (1" in this case) in my lathe chuck, dab some 600 grit aluminum oxide paste on it, then turn the lathe on relatively low speed and hold the cylinder in my hand, working it back and forth about 2" overall on the round stock. That will quickly take out any taper. You can feel the tight spots working themselves away while you're doing it. Just make sure that if it sticks, don't fight it---let it go. You don't want to get wound up in your lathe. If it does stick tight, take it over to your press and press the round stock out.


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## xpylonracer (Jan 4, 2022)

_Thanks for the pictures of all your kit. Far more than I need. I guess you have the test bars and gauges for calibrating them as well.
Cheers,
K2
._
Hi Steamchick
I don't have any setting rings so have to rely on a mic to set the bore gauges.
I do have some gauge blocks, bought the imperial set from a firm closing down sale in the UK and the metric set from a Russian dealer when visiting Czechoslovakia in 1984 at we now call a _car boot sale_ , it was at an airfield where I was competing in a model plane pylon racing contest, about 50 cars where goods were displayed. The exchange rate was excellent at that time and from memory I paid £15 for the metric set.

xpylonracer
.


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## Steamchick (Jan 4, 2022)

Hi Xpylon, I guess you use the gauge blocks on your surface plate to set heights and set sine bars. If you have any ball or roller races in your spares bins, then you have some gauges... as these are ground to sub-thou tolerances. Easy to look up in the maker's table for bearing sizes. External mics should come with a gauge bar in the kit. But you can use your gauge sets. Internal mics need a gauge, or calibrated mic. ALL my second-hand mics were out of calibration... but make good consistent comparitors, so gauges are most useful. When I was a teenager in the machine shop I was taught to check the mic against the gauge (zero) every time I took it from the box for use. Also with every mic with interchangeable anvil it must be confirmed to the gauge after every anvil change. As I had small hands then, I had the smaller boring jobs as I could get my hands with internal mic down the bore. But even internal mics were always confirmed against external mics when close to finished size. And when possible, Go/No go gauges were used. Often these were made before boring commenced: 0.001" oversize, Size, 0.001", 0.002", 0.003" undersize in 1/2" sections on the end of a test bar - and with tapers and shoulders if appropriate.
For finish Honing, Brian describes a method that is good. Remember, honing is to improve the surface finish of a bore (by taking the peaks off the machinning marks), and eliminate tiny irregularities from the machined bore. It is not a recommended practice to remove quantities of metal if the bore is badly made. The hone will follow the "average axis" of the peaks, not the true axis from machining. So excessive honing can misalign or distort a bore (even microns will lead to excessive wear in use). Think of this... 0.001" ovality or taper from "bad" honing means you need 0.001" wear of high spots before you "run-in" the piston to get a good bore (circular and cylindrical). That is more than 1/3rd of the lifetime of most engines!
Cheers,
K2


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## ajoeiam (Jan 4, 2022)

xpylonracer said:


> Hi aj
> Nothing wrong with Mitutoyo mics, silky smooth operating adjustment, as I said you are comparing the feel of a turned part and polished carbide mic anvils, all you can do is check at least once to be sure of the reading.
> I also use dial calipers in bores, especially useful to check parallelism of the bore.
> 
> xpylonracer



wasn't trying to imply anything negative. 
IMO there is even better than Mitutoyo and its that absolute top end Swiss tooling. 
(Haven't run into others at that level but bet there would be a few more though.)


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## xpylonracer (Jan 4, 2022)

aj

No offence taken as I am aware that Tesa are excellent measuring devices.

xpylonracer


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## CFLBob (Jan 14, 2022)

I got a break between the other things I have to work on, so I got back to the cylinder using the method in that Abom79 video that ShopShoe posted.   It dramatically improved my measurement repeatability.  I even used my existing telescoping gauge for this, concentrating on the feel and tightening the barrel until it would hold the gauge until a light touch made it fall out of the mic.

Within the last couple of weeks, I had brought the cylinder to just under the 1.000 it's supposed to be.  This time, in two sets of four measurements at both ends of the cylinder, my repeatability is .0001 to .0002".  

The top (outer) end of the cylinder is 0.9962 and the measurement deep in the cylinder was 0.9976.  Yesterday, I decided to press on and finished machining the outline of the cylinder, and cut it off to length.   All that's left is eight holes to drill with four to tap.  I'll do that using the mill as a precision drill press.

It's time to make the piston to match.   First, with the cylinder off the lathe, I can look at some of the leveling questions and other things that have come up.

Footnote:  chances are Florida is opposite from where you are if you work in the shop all winter.  Around here, I work in the shop all summer to stay out of the sun.  If I have anything that needs to be done to the house, the first question is "can it wait til winter?"  As a result, every year I have a backlog of projects that start with "when it cools off, I need to..."  I was doing the biggest project from about New Year's Eve until Tuesday, and now have just a couple left.  One will be "a couple" of days and the other one day.


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## Steamchick (Jan 14, 2022)

Well done Bob,
Learning the various skills is a big part of the fun of this hobby.
K2


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## CFLBob (Jan 23, 2022)

It's time to declare the piston is ready to be put aside so that I can get the piston and conn rod ready for their role in this.   






The inside of the cylinder hasn't been lapped, and I'm pretty sure that's something I should do.  That will open the cylinder up a little, so it's probably best to do that first, although it can always be used to open it up some more.   

One of the things I wanted to do was to verify the numbers for inside diameter that I talked about in the last post.  It took me a long time to get numbers I was comfortable with and I wanted to cross check on the completed cylinder.  With the cylinder parted off the blank, I get the big advantage that I can now use the telescopic gauge exactly the same way on both ends because I don't have to work from just the one end.  Now I can just turn the cylinder around and test from either end. 

The numbers I got testing today matched the previous numbers.  

I found earlier this week that while I thought I'd ordered the #5-40 screws that hold the head onto the cylinder, I actually hadn't.  I need to order some hardware and the piston ring this engine specifies (a Vyton polymer ring).


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## Steamchick (Jan 24, 2022)

Hi Bob,
Just going back a bit, to clarify some odd points:

Post #126. I had a small boring bar much like this, but it wasn't good for the smallest bore, as the bottom corner of the tool bit was touching the bore before the proper top cutting edge. So I made my own stuff so I could grind away the underside to a smaller radius than the smallest bore the tool could be used in. (I smashed the carbide tool with a hammer, then brazed a suitable shaped piece onto an old boring bar and ground it afresh with a carborundum stone, before I found out about the new diamond "stones".).
Post#102 and a few following discussion points: I have recently been boring a cylinder - using my cheap and nasty mill-drill. A perfect bore - as far as I can measure... See pickies attached. Bore is perpendicular to one end face - as I sat it on parallels while setting the vice. The other face and bore were machined in the same setting. (locked bed). I think this is self-explanatory? Oh, it also shows I don't just write "boring" stuff, but practice a little boring, myself. The calliper was set to "just touching" and measured in a micrometer pre-set to the size I expected, then +0.001" and -0.001" settings until I got "exactly" the same touching feel. If you "screw" the micrometer onto the comparator, you cannot simulate that "feel". It is the "comparator" hand that has the feel, not the measuring gauge. Callipers just happen to be my preferred "comparator".
On Lapping the bore - see my comments back around post #104-ish (or wherever) about honing: You are ONLY going to take off the machining peaks, not the whole machining marks, otherwise you risk losing all the PRECISION MACHINING of the shape of the bore. If the V-shaped valleys are (say ) 10 microns deep, you only want to remove "Max" 5 microns. Lapping/honing is NOT the right way to get size of fit, except within the scope of the surface finish from machining. Take out 0.001" with a hone and you'll have to make a new piston - to avoid the noisy, damaging piston slap.
Enjoy,










Ken


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## Brian Rupnow (Jan 24, 2022)

Bob--the cylinder looks good. Try and make the o.d. of the piston so that it is a light press thru fit into the cylinder. You should be able to press the piston all the way thru the cylinder bore with your  fingers, but if you stand the cylinder on end, the cylinder shouldn't free-fall thru the bore.


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## Brian Rupnow (Apr 24, 2022)

Bob--anything going on with this build?--you haven't posted for a while.---Brian


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## CFLBob (Apr 24, 2022)

Aside from some "life interrupts us sometimes" stuff, I've mostly been wrestling with software for my CNC parts, both CAD and CAM.  I've been meaning to post on it, but I'm working on the piston conn rod.  I still haven't finished one, but I'm getting incrementally closer.  

I had a couple of page thread under the software and programming section called, "Can We Talk About CAM Programs?"


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## CFLBob (Apr 30, 2022)

While I'm not done with the conn rod, I completed my first experimental piece - which my system turned into scrap very early in the process - but while it isn't possible to complete this, it actually came out fairly well. 

As I mentioned in the previous post, several of us have had a lot of discussion of the issues I had with my CAM program. A lot of the story - as it happened - is there.

So let me bring this thread up to date. 

What I had started out wanting to do was to duplicate the approach I saw @Mayhugh1 use to make his tiny, two-sided parts in his Ford 300 build, which is to machine one side of the part about half the thickness off the blank, fill the area just machined away with epoxy, flip the part (while maintaining the machine's zero) and then machine away the rest of the excess material on the second side.   My approach was to do a rough and a fine pass - so two passes on each side.  The rough pass was going to leave margin around the final geometry, using a technique called waterline cutting which is largely cutting away the excess material around the part.  I elected to do a fine pass in a completely wrong approach, and it led to a butt-ugly result (which is a comparison that's offensive to butts everywhere).  I fixed it by doing a different type of machining strategy.  Details over on the CAM discussion. 

Once the second side was finished, I baked it in a toaster oven at 250 for two hours. It fell apart perfectly.






Those yellow chunks in the front left are the epoxy, and the leftover, machined metal is in the back.  The first side machined is facing you.

As I say, the dimensions I've checked are all within a reasonable tolerance of the intended size (.005" or less), and while a long way from done, if not for the machine screw-up on the first pass, it would be usable.  The machine screw up is visible here.






The machine screw up happened in a way I've never had my system screw up before, but in the bottom of the square area on the right, you can see that it's pretty short on the front (first pass side). 

From the second side, it looks like this: 






It's about .075 extra cut away along that one edge. 

I've done one (and only one) conn rod, before and that was for my Webster.  For fun, here's the two rods alongside each other.  Webster in white.






I did the Webster's in a completely different way, using a larger end mill and cutting the contour of the part and then relieving around the circles in G-code I wrote manually.  I put the cutter near the left circular feature so that the end mill was leaving the final shape, and then cut a circle around the center of that feature.  Then I moved the cutter to the larger feature on the right and repeated the approach.   As a bonus, it cut the area between them to the right depth.  The tool paths looked like this






The trick with this rod is that the raised area that looks circular on the big end isn't circular.  It's two pieces separated by the thickness of my slitting saw (.047") and then filled in solid.  It's still possible to do this sort of tool path with that distortion, I just need to cut two semicircles separated by that distance.  I'd post a picture like this but on this scale, with each of the smaller squares 1/4", the .047" straight line segment isn't visible. 

So that's where I am right now.  If I sound a bit undecided on how to approach making the real part, that's because I am.  I'm not sure if I'm going to do the epoxy trick again, or screw the conn rod blank onto a fixture before I attack it.


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## Steamchick (May 1, 2022)

Hi Bob, Is it Aluminium? Is there adequate material that you can rescue this with a file? - or are all the edges "sized" - but misplaced? (I think that is what you are showing in the zoomed picture of the big-end).
I like the technique, but not having CNC would have to make the mistakes manually in my shop (not difficult... I do it often for fun of rectifying later!). I am sure you are having fun whichever process you choose.
But with CNC, I would have simply machined the part from a solid billet... the finished bores being done after the big-end had been split, machined and joined by the big-end bolts. But perhaps that is too easy and less entertaining?
(The 1" long steel rods I made for a Stuart SUN engine were made from solid. Not a perfect pair, but work fine and are not visible so I don't care too much!).
Good post!
K2


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## CFLBob (May 1, 2022)

Steamchick said:


> Hi Bob, Is it Aluminium? Is there adequate material that you can rescue this with a file? - or are all the edges "sized" - but misplaced? (I think that is what you are showing in the zoomed picture of the big-end).
> I like the technique, but not having CNC would have to make the mistakes manually in my shop (not difficult... I do it often for fun of rectifying later!). I am sure you are having fun whichever process you choose.
> But with CNC, I would have simply machined the part from a solid billet... the finished bores being done after the big-end had been split, machined and joined by the big-end bolts. But perhaps that is too easy and less entertaining?
> (The 1" long steel rods I made for a Stuart SUN engine were made from solid. Not a perfect pair, but work fine and are not visible so I don't care too much!).
> ...



Yes, it's aluminum.  The top and bottom are a little offset, but mostly have a burr that has been hard to remove with a deburring tool or a mild file.  The missing area was from when my system had what seemed to be a power glitch and then resumed cutting improperly.  It cut in an area it wasn't supposed to cut.

It looks to me like it might even be usable because the area that had too much cut off doesn't seem to do anything.  Let me grab a pic:





The red rectangle is about what's missing (not from my CAD program, just MS Paint).  It's very close to the hole that needs to be threaded, but I'm not sure if it breaches the screw hole. 

This part: "But with CNC, I would have simply machined the part from a solid billet... the finished bores being done after the big-end had been split, machined and joined by the big-end bolts. But perhaps that is too easy and less entertaining?" is exactly what I'm doing.   I drill and tap the two holes for #5-40 SHCS before I cut off the end of the rod.  When I put it together after that with the screws, I drill and ream the big hole.


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## Steamchick (May 1, 2022)

Good stuff!
Well done on tackling this the difficult way by making your own castings.
K2


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## awake (May 2, 2022)

Ehh, no problem. Just TIG weld back the missing bit,* file or recut, and off you go.

*Of course, my own aluminum TIG welding skill is not up to this task, but since I'm speaking for you, I feel comfortable advocating this approach ... !


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## CFLBob (May 2, 2022)

awake said:


> Ehh, no problem. Just TIG weld back the missing bit,* file or recut, and off you go.
> 
> *Of course, my own aluminum TIG welding skill is not up to this task, but since I'm speaking for you, I feel comfortable advocating this approach ... !



And since I don't even own the simplest kind of welder, let alone TIG, it's ... academic.  

I looked at this part for hours yesterday.  Yes, it might well actually be usable.  Yes, it's going into an engine where it will never be seen so "ugly is OK."  I just know I can do better, so I'm going to do that.


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## Brian Rupnow (May 2, 2022)

There is no shame in using ugly parts, as long as the ugly doesn't interfere with the way the part functions. However, it is vitally important that the ugly doesn't show. If the ugly shows, then regardless of how well the part functions, at least 137 forum readers will step up and offer helpful advice on how to do it right, suggest that you remake the piece, or denigrate your skills as a machinist and suggest that you should take up basket weaving or dog washing as a hobby.


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## awake (May 2, 2022)

CFLBob said:


> And since I don't even own the simplest kind of welder, let alone TIG, it's ... academic.
> 
> I looked at this part for hours yesterday.  Yes, it might well actually be usable.  Yes, it's going into an engine where it will never be seen so "ugly is OK."  I just know I can do better, so I'm going to do that.


Oh, I'm with you on this - it sounds like this was as much or more of a learning opportunity than it was anticipated to be a final part. I've done some of those (though only manual - no CNC available), and once in a while the experiment is usable ... but always a learning experience!


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## CFLBob (May 2, 2022)

Brian Rupnow said:


> ... suggest that you should take up basket weaving or dog washing as a hobby.



I never thought of dog washing.  My fall back on "I'm going to start a less demanding hobby" was always stamp collecting.  There are only two steps:
Buy stamp.
Paste in book.  

Neither can be done to even .001" 

Dog washing sounds easier, although probably messier.  Probably depends on the dog.


----------



## Eccentric (May 2, 2022)

My vote is to chock it up to the learning experience and make another one.  Like I tell my wife, the garbage man could make three engines for every one I do.


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## Steamchick (May 2, 2022)

I have an "impatient" approach. Make it go, put it on show, talk about it with those folk who wish they could make "beautiful " models, but too shy to try. More join the Club that way. And I respect the perfectionists, just don't try and sing in the same choir, even if I do read the same hymn sheets.
I'm human and fallible, and not too shy to show it. All my models end up working, but I can't say any are pretty, at the show standard of stuff displayed here. That's (my) life!
K2


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## Richard Hed (May 3, 2022)

CFLBob said:


> I never thought of dog washing.  My fall back on "I'm going to start a less demanding hobby" was always stamp collecting.  There are only two steps:
> Buy stamp.
> Paste in book.
> 
> ...


Just so you know, I am a stamp collector as well as machining, welder, all round King of Fools (KoF) plus a foo other things too.


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## Steamchick (May 3, 2022)

Hi Richard, despite other aberrations, you have managed a few decent models though.? And your wit must come from years of practice!
K2


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## CFLBob (May 3, 2022)

Richard Hed said:


> Just so you know, I am a stamp collector as well as machining, welder, all round King of Fools (KoF) plus a foo other things too.



Having been a ham radio operator since 1976, I have a desk drawer full of mostly foreign stamps I've kept.  I'm just unorganized about it.  No albums.


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## minh-thanh (May 3, 2022)

Hi CFLBob!


CFLBob said:


> I looked at this part for hours yesterday.  Yes, it might well actually be usable.  Yes, it's going into an engine where it will never be seen so "ugly is OK."  I just know I can do better, so I'm going to do that.


 
Maybe, just grind and it will be beautiful again
If you do not like , make a new one
  Personal: I like every part of the engine to be beautiful
But often I can't do it, just accept it


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## CFLBob (May 3, 2022)

Second attempt about to get underway.  I need to call the center of that left hand screw X=0.500 and Y=1.000 to use files I've already created.  I think it's currently those coordinates, but I'll triple check that.







I'm going to rough around the part with a bigger end mill and a contour cut farther offset from the outline to leave a larger margin around the part.  Not sure what - maybe 1/8" instead of 1/32.  I'd like to eliminate cutting slots but that's easier at the wide end than at the narrow part of the rod.


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## Eccentric (May 3, 2022)

Go Bob Go......  

One thing I do to insure the hold down screws are in the exact center, is to drill the holes with the CNC mill set to 0,0, then tap them in the vice.    It is a little akward, but insures the center of the conrod holes are exactly where your CNC program thinks they are in both the X and Y axis.


I have a good feeling about this one.


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## CFLBob (May 3, 2022)

Eccentric said:


> Go Bob Go......
> 
> One thing I do to insure the hold down screws are in the exact center, is to drill the holes with the CNC mill set to 0,0, then tap them in the vice.    It is a little akward, but insures the center of the conrod holes are exactly where your CNC program thinks they are in both the X and Y axis.
> 
> ...



The first operation went as smooth as can be. 






This was done with a 3/8 dia. carbide, 4-flute EM.  My intent was to make it big and wide enough to get rid of all of the rest of the rough - and it did.  I did the first two passes with compressed air coolant and cutting oil in the slot, then added the Fogbuster mist for the last two passes. 

This left a 1/8" margin over the part design.  I only checked one detail, the diameter of the small boss on the left and got 0.252 difference between CAD design and metal - 0.126 on each side.

My plan was to do the circular bosses and thin out the rod between the two big areas, but while my G-code checker (GWizard Editor from CNCCookbook) told me the code was fine, Mach3 barfed at it.  In the worst way; the window that tells you what the problem is was too short for the full message.  The code is the way I did two semicircles separated by 0.050. 

The bulk of the code was the way I did the bosses on my Webster's conn rod.


----------



## CFLBob (May 4, 2022)

I found the silly error in my Gcode for the circular bosses.  I left off the negative sign on J= number on the circles that needed it. 

G91.1
G01  X0.907 Y1.000 Z0.125 F25
G01  Z-0.031 F6.5  
G03  X0.907 I-0.406 F12
G01  X2.437 Y 1.00 
G01  X2.437 Y0.502
G01  X2.937 
G02  X2.937 Y1.503 I0.00 J0.500
G01  X2.987
G02  X2.987 Y0.503 I0.00 *J-0.500*
G01  X2.937

After verifying the outlines still seemed correct in my GWizard Editor and then air cutting above the part, it was on to the real deal. 






Now I have a puzzle.  The bosses need to be cut on the far side, too, and the body of the part is still oversized by 1/8" in all directions (1/4" overall).  

It seems to me I should cut the body to final size first, then flip it over and re-run this code to cut the bosses on that side.  The only drawback is that the final contour cut requires me to change cutters, which may require me to change the holder.  This file used a 3/8" EM, while the fine contour needs a 1/4" EM - the inside radius where the boss on the left meets the rod is 1/8".  

If I flip it and then cut the bosses, I use this EM and then change to the smaller one.   

It's two tool changes vs. one.  Not a big deal, since we're not planning production of a million of these and every second counts.

Any inputs?  Anybody see anything I'm missing?


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## CFLBob (May 6, 2022)

The machining of the part proceeds with the milling done.  It will be a precise drill press for the next operation and then drive a slitting saw blade. 






To answer my own last question, I did the final contour first in the position shown on the previous post - that required a tool change from a 3/8 EM to a 1/4" EM.  Then I flipped the part, changed back to the 3/8" EM and cut the circular features.  After that was finished, I removed the #8 screw (on the left) and then finished that hole, which is reamed to 0.188. 

In my mind, this result is much better than the previous approach. 

Still to do is to use the CNC mill as a precise drill press.  Twice.  I need to drill and tap the holes for the screws that hold the cap on.  Then I use it to hold the slitting saw so I can cut off the cap with the slitting saw.  Finally, I'll attach the cap with the screws I just made holes for, and turn the mill back into a drill press to drill and ream the big end to 0.375.


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## Steamchick (May 6, 2022)

All sounds logical and straight forward. Enjoy!

I am in the middle of making the valve chest innards for the steam pump I am making. Lots of milling and drilling... The secondary valve works with air, now making a the primary... must try and do some photos...
K2


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## Eccentric (May 6, 2022)

Bob,

It is looking really good.  What is your concern with changing end mills?  The X and Y should remain dead on and the Z height needs to be changed to account for any difference in height between the two end mills.  I will machine with the first size end mill, then bring the end mill down and touch off on the top of the vise, record the Z value displayed on the DRO.  Load the second end mill, again drop down and touch off Z at the same spot on the vise, set the Z value to the one recorded.  Then machine with the next tool path.

Greg


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## CFLBob (May 6, 2022)

Eccentric said:


> Bob,
> 
> It is looking really good.  What is your concern with changing end mills?  The X and Y should remain dead on and the Z height needs to be changed to account for any difference in height between the two end mills.  I will machine with the first size end mill, then bring the end mill down and touch off on the top of the vise, record the Z value displayed on the DRO.  Load the second end mill, again drop down and touch off Z at the same spot on the vise, set the Z value to the one recorded.  Then machine with the next tool path.
> 
> Greg



Greg, 

That's what I do.  Basically, any time I change the setup, I get concerned.  Work holding is everything.  I haven't adjusted the Y axis setting in the mill since I started working on version 1.  A full month?  I have reset X with an edge finder when I turned the first one over, and then again with this one.  Tedious but I trust it to under 1 thou.  

Yesterday, after I cut the circular areas and I switched to the 1/4" dia. EM, I made a mistake that I spotted soon enough to not damage anything.  I went to the flat area between the raised bosses and set the Z to 0.000.  Only it's not.  It's -0.062.  I noticed doing the fine contour pass (taking off 1/8" all the way around the part) that the heights looked wrong.  That's when it hit me what I did.  Stopped Mach3, reset that zero to what it should be, stripped the last pass around the part out as a file and ran the last pass by itself.  

It wasn't a big deal, it just would have cut the tooling piece deeper than I want.


Bob


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## Eccentric (May 6, 2022)

CFLBob said:


> Greg,
> 
> That's what I do.  Basically, any time I change the setup, I get concerned.  Work holding is everything.  I haven't adjusted the Y axis setting in the mill since I started working on version 1.  A full month?  I have reset X with an edge finder when I turned the first one over, and then again with this one.  Tedious but I trust it to under 1 thou.
> 
> ...



Yep,  I have done the same thing (actually ruined a part that way),  that is why I touch off the vise, write the z height down, instead of touching off on the part again.  Because I might have machined off the top!

But watch those minus signs, I set a Z height one time and forgot the minus sign, and the Z axis took a rapid move dive into my part.  Scared the bejesus out of me.

You are doing all the right things.


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## Steamchick (May 7, 2022)

Hi Bob, I like what you are doing!
My "memory" (Datum zero) is the chalk mark on the rotating scale... (NON-"Electronic Digital" living). Works every time for me... Just slacken the lock screw, rotate the scale and set at the chalk-marked division. May be of use to those with MANUAL tools? I agree with deciding whether to "zero" from part or machine datum. I always use "part" to avoid moving the part from its alignment with the previous tool axis (Worn feed-screws mean the settings and measurements are only repeatable from one direction anyway). 
A point to note. NO machine is perfect. So correctly dimensioned parts won't be "random" dimensions strewn all over the drawing (Draughtsmans' normal practice), but ALL set from the appropriate datum (rarely seen on "Amateur" plans and especially CAD!). The process should always be (Or so I was taught in the days of worn WW2 machines!): 

Set the part to machine the part datum (Face and location sides or centre/hole). 
PLUS any Datum precise machinings required before changing settings. (Mark datum faces, and annotate the drawing!).
Plus any "non-datum " based shapes accessible in this setting. 
"Turn over" to set ON the datum face, and up to datums that were machined in the first setting. 
Machine all the previously  inaccessible bits to the datums. Then finish by machining all the other non-datum specific shapes. 
Remember that the designer didn't think like a machinist, so don't always blindly follow his dimensions.  (That was one of the most important rules I learned _as a designer_!). When making all my jobs I find I have to re-calculate some dimensions to DATUM. And if you don't do it right before you start machining, you'll end up making lots of "trapezium lozenges"! (Speaks a voice of experience). And my miller is a known fraction of a degree off true... in each of the dimensions (degrees of freedom)! But by working to datums, the finished job always works OK. Remember the OLD rule, "right first time every time!" - and  Irish Quality Assurance (Based on the Navy's "CHECK, CHECK, CHECK!"): "To be sure, to be sure!".
Now _Please _teach me where I am wrong, because I have forgotten stuff, and don't want to write something that the "less knowledgeable" will take as gospel - and then get it wrong!
(Now I must go and "do as I said", not "what I did"...! - I am only human, after all.).
Cheers!
K2


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## CFLBob (May 7, 2022)

My problem is that since I have no actual training at all in how to do any of this means I pretty much only learn from my mistakes.   

To that point, if my drawings don't show a datum point, how do I pick one?  Come to think of it, I might have done that on this part.  As I worked on the drawing after importing it from Brian's .pdf, the small screw hole (in the left boss) ended up centered on (0.500, 1.000) so all the tool paths I had generated were based on that coordinate system.  To use those files, I had to fixture the part with the hole there.

What I did when I made this version 2 of the part was use the center of the small hole as my reference for X and Y.  I have a center finder that has a point one end, and that seemed best for using in a hole because tiny amounts of being off center seem easy to see.


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## CFLBob (May 7, 2022)

As of this evening, the conn rod is finally done.  






I had transferred the rod off that fixture to drill the holes for the cap screws on the big end and cut the cap end off.  Then I had to re-transfer it back onto that fixture to dill and ream the big hole on the right.  I think I reset zeroes three times today.

One little gotcha is that the plans call out #5-40 screws.  I would have sworn that I bought those but searching the shop turned up nothing.  I don't a drawer in my box for #5 and they weren't with the other screws I bought in preparation, so either I put them "someplace safe" (_really_ safe) and they'll turn up now that I'm not looking for them or I never ordered them.  I thought about just using 4-40 but went up to 6-32.  Still fits and may even be a touch stronger.  

In this view you can easily see how much better this came out than version 1.






Another part to go in the "Done" box.  It's almost a month ago that I got started on version 1 of this, which led to my CAM discussion.  I don't know how many parts are left to do, and I don't really want to know.  If I make one part per month I'll be working on this engine for years.  When I started the cylinder (in December!) I figured the next parts would be the matching piston because it gets sized to the cylinder, which means I need this connecting rod and the wrist pin.  Those are lathe parts so the adventures in CNC milling are over for the moment.


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## Steamchick (May 8, 2022)

Keep going Bob, I will chuck-in ideas as I think of them, but you have made what seems to be a very good con-rod!
- Just odd ideas (from what I remember from when I worked on Engine design years ago!):
The con-rod-bolts. What material are they? They "look OK", but as an engineer, that is where I always see a big "CAUTION" sign! The tensile strength of the con-rod bolts are severely stressed, and fatigued, so need to be a VERY robust design (usually) to cope with the stresses and resist fatigue. Typically, the endurance limit is less than half the tensile strength of a bolt (the single cycle failure point). EVERY corner of the bolts is usually radiused with quite a large radius, unlike simple "bought" bolts. Never having design the bolts, I cannot advise much, but on car engines it is common for the bolts to be 120ton steel, often forgings, heat treated, and very complex shapes. At 2000rpm (a pretty slow model?) the rods perform 120,000 cycles in 1 hour of running, or 1 million cycles in little more than 8 hours running. Of course a car engine/industrial engine can be expected to perform thousands of hours running, and typically up to 6000rpm or more. (Motorcycle engine s easily double that). So lifetimes are designed for hundreds of millions of cycles.... for reliability. Can you get some high tensile hex. socket cap screws with solid shanks through the most part of the rod? (I can only see the heads, not shanks, of your bolts) - preferably installed in "sized" holes (reamed?). (I guess you have done so?). And another idea... the washers under the bolt heads are normally precision ground so they do not create a skew face for the bolt heads to sit upon. The stress raiser of even the tiniest "out-of-square" between the axis of the bolt and the face under the bolt-head can dramatically reduce the life of con-rod bolts, and is OFTEN a cause of failure of the bolt-heads. (Ask guys that race engines!). Many engine makers specify replacing big-end bolts with brand-new parts EVERY time that the rod-end is dismantled, and re-assembled. It is that critical. Models mostly survive because they have very short running periods, at slow speeds, and low loads. Except aero-engines.
I guess there will be some simple maths somewhere on the web to determine bolt sizes against your design? I'll have a look when I get some time. (DIY at the Daughter's house today!). AND often the threads are special rolled threads, as machined threads are simply too prone to early life failure at the "pre-engineered cracks" in machined thread roots. Nuts also need to be as good as the bolts.
Bolted Joint_R1.doc (live.com) - may be of interest/relevance?
Also, based on root diameter of thread, the #6 x 40 is about 13% "stronger" in tension than the comparable  #5 x 40. (88% of tensile stress), because of the increased thread root area... Bolts threads should be as "perfect" as you can get them, lubricated and torqued accurately to the pre-load so they are never slack in the dynamic loading on the rod. (allowing of the coldest start-up - differential expansion). Best Way to Improve Fatigue Resistance of a Bolted Joint - Nord-Lock Group may be of interest?
Well done so far with the rod! I'm sure your expertise (and CAD-CAM) has set datums that work, (as otherwise you would have a lot of scrap!).
Most interesting from my chair.
Thanks for posting your process and thinking for making the rod.
K2


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## CFLBob (May 8, 2022)

Steamchick said:


> Keep going Bob, I will chuck-in ideas as I think of them, but you have made what seems to be a very good con-rod!
> - Just odd ideas (from what I remember from when I worked on Engine design years ago!):
> The con-rod-bolts. What material are they? They "look OK", but as an engineer, that is where I always see a big "CAUTION" sign! The tensile strength of the con-rod bolts are severely stressed, and fatigued, so need to be a VERY robust design (usually) to cope with the stresses and resist fatigue. Typically, the endurance limit is less than half the tensile strength of a bolt (the single cycle failure point). EVERY corner of the bolts is usually radiused with quite a large radius, unlike simple "bought" bolts. Never having design the bolts, I cannot advise much, but on car engines it is common for the bolts to be 120ton steel, often forgings, heat treated, and very complex shapes. At 2000rpm (a pretty slow model?) the rods perform 120,000 cycles in 1 hour of running, or 1 million cycles in little more than 8 hours running. Of course a car engine/industrial engine can be expected to perform thousands of hours running, and typically up to 6000rpm or more. (Motorcycle engine s easily double that). So lifetimes are designed for hundreds of millions of cycles.... for reliability. Can you get some high tensile hex. socket cap screws with solid shanks through the most part of the rod? (I can only see the heads, not shanks, of your bolts) - preferably installed in "sized" holes (reamed?). (I guess you have done so?). And another idea... the washers under the bolt heads are normally precision ground so they do not create a skew face for the bolt heads to sit upon. The stress raiser of even the tiniest "out-of-square" between the axis of the bolt and the face under the bolt-head can dramatically reduce the life of con-rod bolts, and is OFTEN a cause of failure of the bolt-heads. (Ask guys that race engines!). Many engine makers specify replacing big-end bolts with brand-new parts EVERY time that the rod-end is dismantled, and re-assembled. It is that critical. Models mostly survive because they have very short running periods, at slow speeds, and low loads. Except aero-engines.
> I guess there will be some simple maths somewhere on the web to determine bolt sizes against your design? I'll have a look when I get some time. (DIY at the Daughter's house today!). AND often the threads are special rolled threads, as machined threads are simply too prone to early life failure at the "pre-engineered cracks" in machined thread roots. Nuts also need to be as good as the bolts.
> ...



They're the _best_ kind of screws: chosen for size from from a junk box full of random screws!  

More seriously, they seem to be stainless, but are likely to be made for a different purpose than holding a conn rod together. Probably 18-8 or 304 stainless. The extent of the information I have on what to use is one note: "D & T FOR #5-40 SHCS". These don't have a longer shoulder, and are threaded all the way to the cap (or around 1 thread before the cap).

The introduction of the reality for the screws in this application for high performance engines is interesting engineering.  I think that a 1" bore, 1" stroke engine (pi/4 or 0.785 cubic inches) that will run for a few minutes in its life and get put on a shelf isn't likely to ruin them.


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## minh-thanh (May 8, 2022)

Bob !  
 Con-rod  is nice .
Steamchick 
I think bolts are good enough,


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## Steamchick (May 8, 2022)

Just a point of Engineering, as this site is about free comment on that subject: the stress raiser of the root of the thread is at least 3. To machine this away (with a large radius at the ends) so you have a smooth, unblemished surface of the bolt through the solid part of the rod will eliminate the stress raiser in this region. All you need is to take of 0.001 in below the root diameter of the thread to make the bolts at least 3 times stronger. The tool radius should be at least the depth of thread. That is Engineering. Your choice if you want to just make something or do "the Engineering".
I am sure you'll be torquing the nuts core try on final assembly, so the bolts will be appropriately pre-stressed, so they can take the fatigue of the oscillating loads within the big-end. Just help them resist fatigue by using the best steel, and design practice.
It is the old adage, "spoil the ship for a ha'porth o' tar"...
Just my opinion....
I'll not debate it further.
K2


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## CFLBob (May 8, 2022)

Steamchick said:


> Just a point of Engineering, as this site is about free comment on that subject: the stress raiser of the root of the thread is at least 3. To machine this away (with a large radius at the ends) so you have a smooth, unblemished surface of the bolt through the solid part of the rod will eliminate the stress raiser in this region. All you need is to take of 0.001 in below the root diameter of the thread to make the bolts at least 3 times stronger. The tool radius should be at least the depth of thread. That is Engineering. Your choice if you want to just make something or do "the Engineering".
> I am sure you'lloyds be torquing the nuts core try on final assembly, so the bolts will be appropriately pre-stressed, so they can take the fatigue of the oscillating loads within the big-end. Just help them resist fatigue by using the best steel, and design practice.
> It is the old adage, "spoil the ship for a ha'porth o' tar"...
> Just my opinion....
> ...



I hope you don't think I was debating, ridiculing or doing anything less than studying what you said.  

You and I don't know each other, and to make matters worse, there's that quote about Americans and Brits being two people divided by a common language so that anything we say may be understood in an unintended way - especially typed text with no voice inflections.  

For future reference, or for anyone like to come across this, there's only one person on this planet I make fun of and that's me.  

When I build something to someone else's plans, I strive to live by that famous MIL SPEC, MIL-TFP-41C  "Make It Like The F***ing Plans For Once."


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## Steamchick (May 9, 2022)

Hi Bob, I'm sorry, I wasn't taking offence at what you are doing. I appreciate you have (previously) stated that you are basically an Electronics Engineer, but enjoying making models (exemplary work I might add! - I am learning from you as much as anything!). Therefore you are asking for comment, feedback and advice about what you are doing.  As such I am offering my "mechanical Engineering" expertise - for what it is worth.(Only 50 years in this...). But I am not the expert on everything, although I have worked with more than a few and learned some of the questions and pitfalls of Engineering life.  I apologise as seeming to be a "tactless old what's-it sometimes", but (Based on a lifetime of "I told you so" experiences) sometimes over-react to many people who just say "I think it is OK" without offering their reasoning. Often they are correct, but just as often they didn't look at the problem I (or others) have queried, and then make errors of judgment as a result. I am just trying to be sure that wherever you got your design from, you are sure that the bolt design is adequate for your application. In am not a metallurgist.  But - to put my message simply:
Con-rod Big-end bolts are usually designed by the original designer to be strong enough, and stressed to be fatigue resistant for the application to have some long durability.
If you use a different material, size or whatever, then it only seems reasonable (to me, anyway). that some simple correlation is conducted to see if the proposed alternative is adequate to the original design.
Whether or not you are the original designer, you have made the rods for bolts with 13% more CSA for tensile stress - which in itself reduces the stress accordingly, but also have selected a bolt with what I think is a lower strength than what I GUESS the original designer may have chosen? So if the resulting stress on the bolt is relatively higher (in relevant terms) compared to the strength of the material, then you are at risk of reducing the lifetime before failure (due to fatigue).
N.B. Off the web: 18-8 stainless is typically 0.2% proof stress >205 MPa. Here's a table of strength of parts (not as complete as to include your parts):





but it shows that "Stainless" is only about 1/4 of the strength of "Alloy" steel screws. As the specification you have is so vague (#5-40 SHCS), I would have certainly gone for the "best available" material, rather something unknown, for this application.
It is "not hard" to do some checks: (I, or others, can do them for you or check what you have done if you wish). All one needs is the actual details of the original con-rod big-end bolt design versus your selected alternative. The internet has all the "text book stuff" to make this relatively easy to do.
I just found this...
Connecting Rod Bolts Calculation with VDI 2230 standards (excelcalcs.com)
But I haven't downloaded it yet (pointless unless I have all the data to input anyway!).
Just for some "Odd" background: having worked on engines since the 1960s, through to the 1990s, I have only ever experienced the "nuisance" of manufacturers' instructions to change the con-rod bolts for NEW parts every time the big-end is assembled. (The exception being any engine that had not run, and had not been fully torqued). There is a table in the link that shows the various methods ("Qualities") of tightening, and the "factor" to use in the calculation spreadsheet. This may give you some appreciation of how highly critical the industry consider the design and installation of the big-end bolt.
Recent experience (within this website) has had 2 threads discussing strength of crankshafts (because of failures at VERY early life), so I am advising "what I know" so maybe you will not experience a running failure within minutes of first start-up - or ever.
Sorry, if my English is a bit blunt: I reiterate that "good Engineering" is necessary on some components, and I am trying to advise you to "check, check, check". It will help avert any failure.
My best wishes for a successful model, I do think you are presenting some excellent work.
K2


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## Steamchick (May 9, 2022)

Hi again Bob,
Sorry to be a nuisance, but I just had to re-check everything I could on this one... (Worrying "Does my brain in" sometimes!) I.E. the meaning of "D & T FOR #5-40 SHCS". I reckon "D & T" means "Drill and Tap"?: 
And I just looked up "SHCS" - (I had guessed it referred to "High Strength Carbon Steel" - but guessing is not right, so I checked.).
It actually means "Socket Head Cap Screw" - which _I GUESS_ would likely mean "regular Alloy steel" - Not "Stainless".
You may note from the table that for:

a #5 screw in Alloy steel has a yield strength of 1290psi.
a #6 screw in Stainless has a yield strength of 363psi.
I.E. from which I conclude your stainless screws are likely to fail, as they are only about 1/4 of the strength of the Specified parts. (here I must assume that the fatigue strength of the alloy steel is not exceeding 75% of the yield strength, but that the stress loading from the running engine may be as high as 70% of the yield strength (= 903psi: because I don't know any better! And is a lot more than the yield strength of the larger Stainless screw) - But that is only my interpretation of the problem, and justification for being a nuisance to you. And it does depend on the pre-load on the bolts, quality of parallelism of the end flat surfaces (Flippin' excellent I think from what I can see of your work!), washers under nuts, etc... including the "actual stress oscillation loading" of the bolts from the con-rod when running.
Also, I GUESS that the fatigue resistance of Alloy steel is better that stainless, compounded with the larger root diameter of the "40" thread compared to a UNC... or whatever, so the specified bolts may be stronger than my guess? And this is then compromised by the smaller root diameter of the "40" thread versus the UNC of the table... so too much "guess work" here!
Make of this what you will... this is only my advice with the best of intentions.
(These problems awaken brain stuff I haven't used in years... but please tell me to "go away" if I am too interfering.).
Best wishes for a successful model,
K2


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## minh-thanh (May 9, 2022)

K2 !



Steamchick said:


> sometimes over-react to many people who just say "I think it is OK" without offering their reasoning.


 
Yes . that's me:  a guy who can only say: " It's fine "
  Maybe I'm not too bothered about complicated calculations or actually   I don't know or have forgotten most of them..



Steamchick said:


> I am just trying to be sure that wherever you got your design from, you are sure that the bolt design is adequate for your application.


  It's the design of *Brian Rupnow .*


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## CFLBob (May 9, 2022)

Steamchick said:


> Hi again Bob,
> Sorry to be a nuisance, but I just had to re-check everything I could on this one... (Worrying "Does my brain in" sometimes!) I.E. the meaning of "D & T FOR #5-40 SHCS". I reckon "D & T" means "Drill and Tap"?:
> And I just looked up "SHCS" - (I had guessed it referred to "High Strength Carbon Steel" - but guessing is not right, so I checked.).
> It actually means "Socket Head Cap Screw" - which _I GUESS_ would likely mean "regular Alloy steel" - Not "Stainless".
> ...



I was dimly aware that stainless has a lower yield strength than "alloy" steel, although I'd guess in both cases the question is "which alloy?"  Likewise, I'm aware that hex bolts come in different strengths and quality standards, shown by marks on the head of the bolt.  If I had gone to buy screws, I probably would have bought "alloy black finished steel SHCS" like these: 




__





						Socket cap, Alloy steel black oxide finish - Bolt Depot
					






					www.boltdepot.com
				



not that I know what that alloy is either.  After spending a month on one part, I wanted to be done so I used what I had.  I can pick up those screws at any time.  

The engineering question is whether 3.5x better yield strength matters.  It's such a big difference that I'd guess it would, but I have no idea what the loads are.  Maybe a much smaller screw, like #0-80 would be strong enough.  Since we come from very different fields, I can't offer an example for comparison, but I think any designer has had a manager ask/tell them to cut cost and that always comes down to "how strong does it have to be?"  What's the cost/benefit ratio?  

I live in an area where stainless is practically a necessity - I've been told our oceanfront gets the saltiest air in North America.  You can walk around houses and know which side gets the sea breezes just by noting how corroded the metal around windows is.  That's why around half of my hardware bin is stainless.  

Strangely, I actually wrote this reply almost nine hours ago and forgot to hit the "Post Reply" button as life interrupted, which it sometimes does, with a larger than normal bunch of chores and distractions.


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## Brian Rupnow (May 9, 2022)

Bob--All I have ever used for rod bolts are "over the counter" black oxide finished socket head capscrews from a local company. I don't really know what grade of steel they are, but I don't think it is anything special.---Brian


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## Steamchick (May 10, 2022)

Bob, Brian, I don't know what is "standard" from US shops, but in the UK we can get "unknown grade" steel bolts over the counter, - which are probably 80 ton steel, not the 100 or 120 ton alloy steel of "reputable specified parts". but who knows what comes from the more Eastern countries? possibly even Mild steel (40 ton?). But the "Stainless" in one manufacturer's table is quoted as much worse (akin to 30 ton steel?), so I should change to a "better" bolt if I were making this engine. Failures are such a nuisance!. Is the crankcase closed and oily? - Which would tend to keep Mr. Rusty at bay...
K2


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## CFLBob (May 10, 2022)

If I'm seeing this properly, yes, it's a wet a crankcase and the bottom of the piston splashes through on every revolution.


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## Steamchick (May 10, 2022)

Hi Bob, That's what I was guessing, so "proper" steel bolts will be better than Stainless, I think?
In Electronic terms, if the design showed 3A resistors or diodes, you may try 1A, but at the risk that something would blow. You would tell me to use the proper parts..... I reckon?
Vheers, 
K2


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## Brian Rupnow (May 10, 2022)

I just spoke with the people I buy my socket head capscrews from. A standard hex head bolt is grade 2 or grade 5. A socket head capscrew is grade 12.9.---Brian


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## CFLBob (May 10, 2022)

Brian Rupnow said:


> I just spoke with the people I buy my socket head capscrews from. A standard hex head bolt is grade 2 or grade 5. A socket head capscrew is grade 12.9.---Brian



An answer on Quora says, "12.9 grade steel means that a component manufactured form this grade of steel has 12X100 N/mm^2 tensile strength and 9 is a multiplier means 90% of 1200 = 1080 N/mm^2 is the yield strength of the grade. "  








						What is the meaning of 12.9 in "steel grade 12.9"?
					

Answer (1 of 3): I bet you will get your answer in the above pic.




					www.quora.com
				




McMaster-Carr says that translates to 170,000 PSI.  "Alloy Steel Thread-Locking Socket Head Screws. With a tensile strength of 170, 000 psi, these alloy steel screws are among the strongest we carry. They are stronger than *Grade* 8 steel screws and are nearly two and a half times stronger than stainless steel thread-locking screws. They have a thread locker to prevent loosening from vibration. "


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## Steamchick (May 11, 2022)

Hi Bob,
I'm glad you checked. If I had been wrong, well, it's happened before. 
 But there is nothing like doing the check yourself, "to be sure to be sure" - as the Irish are oft to quote.
If Brian is using grade 12.9 bolts, then that's the top grade (Alloy steel) on the table I sent in post #224.
So:

Brian's 12.9 grade #5 x 40 bolts have a yield strength of  1345lbs (UNRF thread?).
Your #6 x 32 (UNRC?) Stainless bolts (Grade "3.5"?) only manage 363 lbs Yield strength. = 27% of the strength of Brian's design.
Minh Thanh: I am not sure of your comment saying that you think the Stainless bolts are OK? (Post #226). Do you have some better information than I have been studying? (I am not perfect, nor always right, so if you can teach us something then that is a good thing).

Sorry if I made my feedback  a bit too complicated? - I do prattle-on a bit...
K2


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## minh-thanh (May 11, 2022)

Steamchick said:


> Minh Thanh: I am not sure of your comment saying that you think the Stainless bolts are OK? (Post #226). Do you have some better information than I have been studying? (I am not perfect, nor always right, so if you can teach us something then that is a good thing).
> 
> Sorry if I made my feedback  a bit too complicated? - I do prattle-on a bit...
> K2


 

Sorry, I don't have any research to prove it.
  Perhaps relying on experience is not a good way either...
Maybe I'm wrong, but with that engine, if it runs for a long time maybe one or more parts will be damaged or worn out...before those bolts break.
  Still inference based on experience and nothing to prove.
  Maybe I should limit the my comments based on my little experience.
Teach someone: I don't think I have enough experience, knowledge, expertise, .... to be able to teach someone .


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## werowance (May 11, 2022)

sorry to barge in on your build Bob,  but on the discussion of tensile strength of bolts and shcs's.  i guess limit what im asking to just bolts for discussion,  but i recall being told once when i was installing a hitch on my truck DO NOT USE grade 8 bolts or higher to use grade (i believe it was) 5 bolts.  they described the reasoning for this was something to the effect that a grade 5 would stretch before sheering or snapping vs a grade 8 would just shear off.  even though grade 8 was considered harder and stronger.  so in my mind i related that to knife making where a rock hard blade will shatter vs a blade that has been tempered or drawn to a light straw and maybe even down to a light purple on the spine to soften up the non cutting part so it wouldnt crack.   so with all that said (and im hoping steamchick and or anyone else) can throw in some teaching wisdom on when to consider using a softer bolt vs a harder one.  maybe a "how do you know when you should use a grade 5 vs grade 8" aside from the obvious answer of "because the plans said so" but what if you dont have plans or the original bolt to go by and have to do a best guess.


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## CFLBob (May 11, 2022)

werowance said:


> sorry to barge in on your build Bob,  but on the discussion of tensile strength of bolts and shcs's.  i guess limit what im asking to just bolts for discussion,  but i recall being told once when i was installing a hitch on my truck DO NOT USE grade 8 bolts or higher to use grade (i believe it was) 5 bolts.  they described the reasoning for this was something to the effect that a grade 5 would stretch before sheering or snapping vs a grade 8 would just shear off.  even though grade 8 was considered harder and stronger.  so in my mind i related that to knife making where a rock hard blade will shatter vs a blade that has been tempered or drawn to a light straw and maybe even down to a light purple on the spine to soften up the non cutting part so it wouldnt crack.   so with all that said (and im hoping steamchick and or anyone else) can throw in some teaching wisdom on when to consider using a softer bolt vs a harder one.  maybe a "how do you know when you should use a grade 5 vs grade 8" aside from the obvious answer of "because the plans said so" but what if you dont have plans or the original bolt to go by and have to do a best guess.



I think that's an excellent point.  All metals are treated with various combinations of heating physical treatment.  That's one reason for the image we all have in our minds of the guy pounding on red hot metal with a hammer.  "Hammer forged" is harder.   Unlike most guys in my line of work, I took a class in materials science as an undergrad.  A vivid demonstration I'll never forget was in cold working.  The lab instructor put a sample of some metal into a tester to test hardness.  This one dropped a known weight metal ball from an exact height onto the test piece to measure the height it would bounce back to.  

The vivid part was he repeated that drop, with nothing changed about the test piece.  It bounced higher the second time - I mean so much obviously higher there was no need to look at photographs to compare them - showing that first drop work hardened the metal.  

I think I recall the only metal that doesn't tend to get more brittle or break more easily when it gets hardened is cartridge brass.  

I wouldn't be at all surprised if grade 5 stretched a bit more before snapping than grade 8.


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## awake (May 11, 2022)

CFLBob said:


> When I build something to someone else's plans, I strive to live by that famous MIL SPEC, MIL-TFP-41C  "Make It Like The F***ing Plans For Once."



Whereas, when working up my own design, I tend to use the TLAR spec: "That Looks About Right."


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## minh-thanh (May 12, 2022)

CFLBob said:


> When I build something to someone else's plans, I strive to live by that famous MIL SPEC, MIL-TFP-41*C*  "Make It Like The F***ing Plans For Once."


 Hi Bob !
  What does the "C" at the end mean ?


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## ajoeiam (May 12, 2022)

CFLBob said:


> snip
> 
> I wouldn't be at all surprised if grade 5 stretched a bit more before snapping than grade 8.



Exactly!
Then Gr 10 and 12
Then look at L9 hardware - - - tough like Gr 10 but stretches more (think for use of equipment frames). 

The whys and whens can consume a lot of time. 
I do tend to do the monkey see monkey do routine (looking at what has been specd and then doing similar.


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## CFLBob (May 12, 2022)

minh-thanh said:


> Hi Bob !
> What does the "C" at the end mean ?



The number 1 and the C get pronounced as "once".


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## Steamchick (May 12, 2022)

Hi guys: I appreciate the application of the correct /best material for the job is required.
But (from what I remember being taught in the Engine Design office in Japan in the late 80s...) the big-end bolts are among the most highly stressed bolts in the engine, at Max engine speed, when the throttle is closed rapidly. They are designed to withstand the maximum stresses incurred, for a fatigue life of many millions of cycles. Therefore, in "production" engines, they always tend to be the highest grade steels, and tempered appropriately, to achieve the required lifetime and NEVER fail. Although, incorrect servicing, re-use of bolts, engine tuning (even caused accidentally by poor fuel and pinking, crashing tha car, etc.), can cause failures. But these are very rare and almost are all well outside the Warranty period. Warranty data can show show "no failures" year on year. (I read it for a couple of engines).
To have a "lower strength bolt" than required by the design, that "stretches before it fails", has actually failed by stretching, before it breaks. - And the higher stresses of a slack big-end from a stretched bolt will very rapidly cause it to fatigue and fail. (In engine testing we recorded every big-end bolt length before and after the longest durability tests on the dynamometer. Both off-the engine and as installed in the big-end assembly.).
But that is my "experience-based knowledge" and opinion.
So to re-iterate the "make it to the design" comment, if Brian R made his engine with 12.9 bolts, then those are the basis for anyone else making their own "copy". (Until proven that "lower grade" bolts are adequate..). Or course, most of this is immaterial to the model maker who's models are simply shiny ornaments, (Yes, I have a "display" model too.). But if my advice was that Brian has over-engineered the bolts, I would have justified that to you all by calculations at least, if I hadn't made the engine and tested it. (Which I have not). And yes, I assumed his bolts would be a "high grade" of steel.
What I have been presenting in the calculations, is an example of how the Designer thinks, before any metal is even ordered, never mind machined, built or tested. MANY problems are never seen down-stream of the design office, because the calculations say they won't work.
As a contributor to this website-of-"knowledge and best practice", I present my best knowledge, and recognise an expert will either confirm or correct me. - Hence I try to justify my opinions - sometimes with simple calculations. Therefore I always try and be considerate of every proposal, or counter-idea, because that way we can discuss it and all learn from what we agree is the right solution.
Minh Thanh has suggested he shouldn't chuck-in his ideas because they may be from insufficient experience (posts 226 & 235). But I think he should question us/me, as I am certainly not expert in many things that are discussed here. (And he makes things that work (His diesel engine) - and is not ashamed when they don't (his broken crankshaft), as he asks us for help.). And the learning from others is a great joy to me (so Thankyou ALL).
On the specific application of the "best" grade of steel bolts for these big-ends, I have put my ideas forward, but do remind you that I have not done the calculations of the loads on the big-ends, but have compared how different bolts can withstand stresses generally, so have only considered that "usual practice" (in industry) is for the high grade of steel bolts that Brian has selected.
I hope this makes sense?
K2


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## CFLBob (Jun 9, 2022)

This is hard to explain easily, but I've spent the last two weeks getting piston rings for this.   Now I have a question for anyone bothering to keep up with this. 

Brian suggests somewhere that this is a Vyton piston ring.  I searched for these at McMaster-Carr and a couple of sources I can't remember (it has been about month) and while I could find Vyton I couldn't answer the question, "which blend of Vyton do you want?"  I eventually went to the reliable source of cast iron rings, Otto Gas Engine Works (Dave Reed) and ordered three rings, assuming I needed one ring.  I ordered the rings to the drawing width, 1.000" dia. by .093 wide.  

My question is: should change over to two rings because of using cast iron instead of Vyton?   

This is what the drawing looks like:







As you can see, there's one ring groove 0.170 edge to edge from the end of the piston.  If I add a second ring, how much space should there be between them?

There's not enough room to put a second ring farther down (right) on the piston if it's spaced the width of the slot (.093") away from the existing ring.  I did a quick sketch in CAD to check the room.  






That construction line dropping down to the wrist pin hole shows that it cuts .020" off the wrist pin hole.  I suppose I could just make the pin shorter so that it doesn't hit the piston rings.

I have no idea if the spacing should be the same as the ring width or if something smaller, like 1/16 or .050 is acceptable or even better.  Or if I should shrink the 0.170 from the top down and move both rings and spacer to the left.


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## minh-thanh (Jun 9, 2022)

Hi !
If you use a cast iron ring , one ring is not a problem .
Some of my engines have pistons without rings and they still  run, so don't worry too much about a ring or two.
 If you want two rings, a distance of about 1.5 - 1.8 is fine


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## Brian Rupnow (Jun 9, 2022)

Bob--the piston you made is only for Viton  o-rings. If you plan on using cast iron rings, then your piston should look like this. Cast iron rings can be a real bear to get them to seal. Viton o-rings are a much easier method of sealing the piston. Since you have already ordered your cast iron rings, then you will have to make a new piston that looks like this.----Brian


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## CFLBob (Jun 9, 2022)

minh-thanh said:


> Hi !
> If you use a cast iron ring , one ring is not a problem .
> Some of my engines have pistons without rings and they still  run, so don't worry too much about a ring or two.
> If you want two rings, a distance of about 1.5 - 1.8 is fine



Thanks.  I have one piston with no rings (compressed air wobbler), one with two rings (Webster) and now this.  

Brian,


Brian Rupnow said:


> the piston you made is only for Viton o-rings.



I haven't actually done this part of it, yet.  I wasn't going to cut the groove until I had the ring in my hands.  Every other feature is machined already, the oval and circular counterbores, and all.  

I had sent you an email three weeks ago asking for more details on the Viton and your source.   I figured you were on vacation somewhere else. 


Bob


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## Brian Rupnow (Jun 9, 2022)

Sorry Bob--I never seen that email. I just talked to Hercules O-rings here in Barrie, and the o-rings are brown in color and have a 75 durometer hardness. They sell for 60 cents each, and you only need one o-ring on the cylinder.


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## CFLBob (Jun 9, 2022)

Brian Rupnow said:


> Sorry Bob--I never seen that email. I just talked to Hercules O-rings here in Barrie, and the o-rings are brown in color and have a 75 durometer hardness. They sell for 60 cents each, and you only need one o-ring on the cylinder.



Brian,  


A little searching shows these at Grainger.  Hercules OEM only listed Viton ETP in their options that I found.  Does this look right?  







The only advantage to Grainger is that they're less than six miles from me.   OTOH, it's a BIG difference from 60 cents each to two for $14.


Bob


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## L98fiero (Jun 9, 2022)

Double post


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## L98fiero (Jun 9, 2022)

L98fiero said:


> Or you could buy 50 of part #5267T83 for $19.26 from McMaster-Carr


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## Steamchick (Jun 10, 2022)

I like Brian's drawing of the piston with 2 cast iron rings.
For anyone interested - my understanding from working on "Industrial" jobs with pistons, iron, steel, PTFE, Labyrynth, O-ring, etc. :-
Viton is an incredible  material - copes with high temperature (see manufacturers' specs), low friction, oil resistant, etc. The key to Brian's success (IMHO) is the radial clearance and precision sizing of the bore and ring groove. The generates adequate contact pressure to commence sealing, so gas pressure increases the seal- pressure. But not too much pressure to wipe-off lubrication from the bore. Follow Brian's design exactly within tolerance. But at higher ring speeds Viton will fail due to heat - From friction, and piston, and cylinder wall. But in these engines Brian has success, so should be OK.
Cast iron rings. Advantages  - higher temperature resistance, more durable (no long term material degradation), "tangential load" tolerant, I.E. variability in the "spring" pressure of the ring in the bore affects friction, sealing, etc, but engines are very tolerant of this up to a max when the oil-film breaks down. An advantage is the conduction of heat from the hot piston to the cooler cylinder wall. Necessary on full sized engines at moderate to high loads.
Steel rings: Generally, a lower tan load is set on these than for cast iron. 2 zones: the continuous ring curve, and the ends of the rings. Tan load changes in the last 30 degrees towards the ring ends, so cast iron rings must wear in the bore (running-in, lapping, etc.) to develop the lower tan load towards the point so the ring Shap is a more perfect circle when in the bore.  The steel rings are made with a deformed circular shspe, so when installed they exactly fit the bore with a uniform tan load. So no running- in is necessary from new. Steels are selected and nitrided for a very hard and durable surface, so last much longer than cast iron. They are usually much narrower, with a curved outer diameter face for tangential contact on the bore. = lower friction overall, better lubrication, etc.
Enough for now, (flat battery!) unless someone wants to understand Labyrynth seals, PTFE, etc.?
K2


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## CFLBob (Jun 10, 2022)

L98fiero said:


> Or you could buy 50 of part #5267T83 for $19.26 from McMaster-Carr



One of my problems was that McMaster offers several of Viton's formulas but they don't specify them by the letter/number designation that Viton uses.  I wasn't sure I'd be getting the right ones.


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## Brian Rupnow (Jun 10, 2022)

The rings should be 1" outside diameter with a nominal cross section of 1/16". (It actually measures 0.070" in cross section.)


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## Eccentric (Jun 17, 2022)

Good start on the crank, This what i use 








						Lathe Dog Set | Lathe Dogs for Sale | LittleMachineShop
					

This set comes with 5 lathe dogs suitable for material of up to 1.5"and includes driver pins for lathes with either an 80 or 100 mm spindle flange. Order today.




					littlemachineshop.com


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## CFLBob (Jun 17, 2022)

Eccentric said:


> Good start on the crank, This what i use
> 
> 
> 
> ...



That's what I used.  Well, I just bought a couple of the parts of the set since I've had the lathe eight years and haven't needed one yet.


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## CFLBob (Oct 20, 2022)

Is thing still on?  Tap... Tap...  

To make a long story short, I'm going to not say much, but it has been a rough year for me.  It started with my cat having some issues that have had him on medication every day since last March, and going to the vet every few weeks.  Then it was my turn for some medical issues around the time of the last posts, and I'm in a waiting queue for a "minor" surgery in the next few weeks.  Add in relatively minor damage from hurricane/tropical storm Ian that really decimated southwest Florida then went west of me there have been distinctly unpleasant things keeping me out of the shop.  

However, since life has more or less stabilized, I was able to finish adding the piston ring grooves last talked about and I'm refreshing myself on what I was doing and what is planned.  

The hurricane damage is going to involve some almost construction-level work that I'll need my machine tools for (repairing my ham radio tower) and some delays there, too.  I won't be able to do anything strenuous after the surgery, so I have no idea how long things will remain unsettled.


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## ajoeiam (Oct 20, 2022)

CFLBob said:


> Is thing still on?  Tap... Tap...
> 
> To make a long story short, I'm going to not say much, but it has been a rough year for me.  It started with my cat having some issues that have had him on medication every day since last March, and going to the vet every few weeks.  Then it was my turn for some medical issues around the time of the last posts, and I'm in a waiting queue for a "minor" surgery in the next few weeks.  Add in relatively minor damage from hurricane/tropical storm Ian that really decimated southwest Florida then went west of me there have been distinctly unpleasant things keeping me out of the shop.
> 
> ...


Sounds like serious no fun. 
Hopefully you heal fairly quickly and you're soon back in the shop.


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## Steamchick (Oct 20, 2022)

Stick with your priorities Bob, then you'll get back to some level of normality sooner. My friend is in Jupiter, so I appreciate what Ian did to you all... 
We appreciate what you add to the forum, when you can.
Catch you later.
K2


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## Brian Rupnow (Oct 20, 2022)

Good on you Bob. I was going to ask about your progress, but some things are better not asked on a public forum. I have had other people start to build my projects and realize they were in over their head and gave up. I think of you every day when I come downstairs and turn on my computer. Best of luck to you---Onward and Upward!!---Brian


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## stevehuckss396 (Oct 20, 2022)

Sorry to hear, but I'm glad things have stabilized.


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