Open Column Launch Engine from Kit

[zeeprogrammer]

For holes <=0.5", I normally drill 1/64" undersize, then ream.

Thanks Marv...that was the mistake I made. I drilled to the size called for rather than under. Oh well. I'll wait and see if I have problems. Happily I have more material should it be needed.

Countersink...of course. I knew that...forgot that...will probably forget again.

I will edit my post for others.

 

[mklotz]

The only reason I'm so good at guessing your missteps is that I've made them all myself. ;D

Some other reamer hints:

Run them at about half of drilling speed.

Never turn a reamer backwards in a hole. It will ruin the edges.

Don't run them dry except in brass.

 

[zeeprogrammer]

Thanks for the tips Marv. And I'm happy to know I'm following in your footsteps. ;D

The bearing-port block... woohoo1

About 0.06 shorter than spec but I'm thinking it'll be okay.

The hole dia is .4375 (7/16 or 28/64) so I used a 27/64 drill bit.
Once again I was happy the TP was nearby.
As I was drilling, the bit grabbed and tried to shoot down into the part and gave up a very shrill whine. Luckily I had firm control on the feed handle. If I'd been a smarter puppy I would have had the z-axis travel stop set so that the bit wouldn't have gone into the vise. As it was...it didn't get that far.

Should I have used cutting oil? Should I have started with a smaller bit and worked up? ???

Then it came time to ream. That resulted in this thread...

http://www.homemodelenginemachinist.com/index.php?topic=5187.0

According to the instructions...I went and drilled and tapped the ports. That produced junk in the bearing hole. What to do? ??? I put the part in the vise and carefully reamed it again. What should I have done?

Loosely attached to the base to see what it looks like...

 

[Foozer]

As I was drilling, the bit grabbed and tried to shoot down into the part and gave up a very shrill whine.

Dont feel bad, I just did that very same thing. had that piece of bronze all nice and fitted, a tad to rambunctious with the drill bit and sucked that piece of bronze right out of the part. So sad, So sad. Next piece in progress, coffee break now and I'll step the hole size up bit by bit. That stuff is grabby using regular drill bits.

According to the instructions...I went and drilled and tapped the ports. That produced junk in the bearing hole. What to do? ??? I put the part in the vise and carefully reamed it again. What should I have done?

Chicken or the egg, running the reamer thru by hand to break off the chips, done that many a time, easy with the reamer and you don't blow out the hole

Loosely attached to the base to see what it looks like...

Looking good, can feel your pain with the "Hey the bit wont fit" problem. Spend the time to set it up and something goes haywire. Just part of the adventure. I, not having the experience, just chuckle to myself when the unknown pops up, we learn from it.

 

[DavesWimshurst]

Carl,
A drill ground on the tip like:

can stop the grabbing in brass and bronze. Sometimes just using a hand stone parallel to the length of the drill is enough, especially with small drills. They don't cut as well in steel after this treatment so I have extras set aside just for brass. Just partially locking the feed and clamping the part also works. I sometimes do this on the lathe when I don't want to modify a drill by slightly tightening the ram lock.
Hope this helps.
Dave

 

[zeeprogrammer]

Thanks Foozer. Thanks Dave.

More progress...the rotary valve.

Some of the first advice I got on this forum was to 'sneak up on the part'. There's a lot of good advice on this forum and I suspected this was one ;D and so I did. Turned down to near size (and learning that I can set the dial to zero helped a lot!) then sanding and test fitting...back and forth...back and forth...back and forth...but I got there. Even cooled it down or waited to allow the metal to settle. It fits...but I feel a little binding as I turn the port block. I expect (hope hope hope) that this will clean up after a little bit of running.

The rotary valve. Had some fun parting it off...the lathe stalled, 3 or 4 times, but I got through it. Cleaned it up. Looked good! Then I needed to drill/ream the hole for the set screw. Foo. Busted the tip off the center drill (that's the 2nd time now). Have no idea how to get it out. So I'll pretend it's an oil hole and went to the other side. Center drill (with a bigger center drill), drilled, and tapped. Same problem as before...junk now in the crankshaft hole. Went to the lathe and carefully reamed again. Oh happy day.

A test fit...(well really I just wanted to see what it looks like)...

Now for the sad part to come...and it will come...I still have to cut the two 'watchamacallits' on the valve (two cuts that go part way round the valve). It requires a rotary table and a slitting saw. One boo-boo and it's back to the beginning. (But it will be a little while...I have to get an arbor for the slitting saw and practice a bit before working the valve).

But I am prepared for my propensity to make boo-boos...Have Metal, Will Machine.

 

[two dogs]

Hi Carl,
The "junk" in the center hole is unavoidable. Just re-ream and you're fine. I'm wondering why you've broken 2 center drills now. The material is carbon steel, right? How fast (RPM) are you going and are you using lube? That shouldn't be happening. Let us know and we'll figure out what you can do to avoid that.
I can't believe that they gave you a piece of matl, the length of which equals the finished lengths of BOTH PIECES. If you were to EDM them apart, they'd still be short! Poor planning on their part!
Now, as far as the whachamacallits, if there is a way you can post a drawing (without giving away any of the plan specifics), maybe we can help

Mark

 

[zeeprogrammer]

Hi Mark,

They are the #1 center drills...kinda small. I didn't use lube (at least on this one) until I got to the 2nd step with the drill bit. And...I may have gone too fast. It probably didn't help I was going into steel. I'm not too bothered about it...I see that this has happened to a couple of other members. More experience will help.

Yeah I was surprised about the length of the piece.

The whachamacallits are two grooves that go around the valve for about 200 degrees and are offset from each other by some angle.

The kit came with decent enough instructions...but they could have been better. Still, with the help of this forum...I'm getting through it.

I'm having loads of fun.

Thanks Mark.

 

[two dogs]

Carl,
I prefer using a 90 deg spot drill over center drills for most things. The tips on center drills can be kinda fragile as you have seen.
This sounds like a kinda involved engine for one that appears simple. Kudos to you for having a good attitude. That last sentance in your last post says it all, "I'm having loads of fun." Keep having fun! :big:

 

[zeeprogrammer]

I really have the feeling that I'm cheating or developing bad habits. Readers will see what I mean but I must press on...time for the crankshaft.

This is the setup to machine the crankshaft. 0.875" down to 0.218....for 2.31" plus enough change for the live center. Tried to be careful in setting things up. Couldn't find a cutter that seemed to fit. Thought about a thread cutter...ended up with a carbide insert at an angle. Checked everything. Had some interference between the tool post and the live center. Took care of that. Locked down the live center, used a carriage stop, and started cutting lightly (0.003").

Had a little smoke (off the part...I quit smoking a year ago). Periodically used some coolant. I just have a spray bottle that puts out a stream. But things never got too hot. Long springy pieces.

Power feed up to near the stop then fed by hand and pulled back. Went pretty well.
Thought I'd up the feed rate...tried taking 0.01. Oops. Got more substantial strands of a goldish color. Quickly had a mass of stuff twirling around. This is what it looked like. The smoother looking strands are the 0.01 cuts...the springy looking ones are 0.003 or 0.004.

Backed off to 0.005 at a time and cleaned out the strands every once in a while. Needed to go from .875 down to .218 for .657. That would require some 65 passes. Took some time but I got there. See the dark spot behind the lathe? My tables are topped with hardboard. They're like a sponge. I don't really mind...they look cool as they are used (and they're replaceable). (In the back is a piece of plexi to keep the stuff that's thrown off the lathe off the wall.)

After much sanding...and trial fitting...the pillow block and rotary valve slip on. woohoo1 A lot of sanding. (I protected the ways with a paper towel when I sanded.) Prior to sanding the crankshaft had a slight taper of less than a couple thou from tail stock to head stock. I'll have to do something about that before I cut another long piece.

Flipped the part around. Had to remove some 1/2 inch or more. That would be a lot of facing. Hacksawed a big chunk then faced and sanded. The OD of the crankshaft didn't need turning down - just sanded it to brighten it.

Now just to see what it looks like so far...

Not finished with the crankshaft yet...needs a flat for the setscrew to hold the rotary valve and a flat, at an angle, for the flywheel. Also need a hole to attach the piston rod.

Pretty happy. Time to relax.

 

[zeeprogrammer]

Hi Mark,

Saw your post while I was putting up my latest adventure.
That's twice I've seen talk about a spot drill. I don't know what it is...so I'll go look. Thanks.

Yeah, the engine's supposed to be the first in a series...I don't think it's as simple as my first engine - the model 2A (from castings). But it came with an instruction booklet...decent...but you have to read it very carefully. An important sentence can be easily missed...and like many things for the beginning machinist...they assume too much. On the up side...I think they presented the instructions, or the design, in a way to introduce a lot of different concepts to the beginner. I'm learning a lot.

One thing I'm getting concerned about...now that I just did a trial fit...is how things are going to line up with the crankshaft. If they don't...I may use paper shims...or loosen the screws and move things around as I tighten. None of which is in the instructions. But we'll see.

Yes this is great fun. I can't express how happy I am to have started it and how great this forum is.

Thanks for reading.

 

[mklotz]

Spotting drill...

http://www.use-enco.com/CGI/INSRIT?PMAKA=SP891-6778

They come in a variety of sizes. For model work, 1/8, 3/16, and 1/4 make a good set.

Get the ones with a 118 deg point grind so a common drill will seat directly into the center hole.

 

[zeeprogrammer]

Thanks for the link Marv.

Any advice on when a spot drill would be used over a center drill?

Or, asked another way...what are the differences in characteristics between the two?

The center drill, as I understand it, is stiffer than a (regular) drill bit and won't wander as much...so it's used to guide the (regular) drill bit. But Mark's point is a good one...the tip is pretty fragile.

Thanks.

 

[mklotz]

A center drill, as the name suggests, is intended for making center holes in a workpiece to be mounted on the lathe, either between centers or in a chuck with tailstock support.

A spotting drill, as the name suggests, is meant for spotting a hole - creating an accurately placed divot to guide the drill and prevent it from wandering when it first touches down.

For most drilling operations, the preferred tool is the spotting drill. It's short, therefore stiff, and lacks the delicate tip of the center drill. Also, with the 118 deg tip, the divot perfectly matches the shape of the drill so the drill isn't cutting only on the edge of the guide hole when it touches down - a possible source of drill chipping with harder materials. That said, I've used a center drill to locate plenty of holes. It's not oh-my-god wrong but, as you discovered, tip breakage can be a problem.

Also, there are situations where I find a center drill easier to work with. For instance, if I'm tapping a 1/16" rod for a 00-90 thread, I find a #00 center drill is easier to use than a spotting drill.

One tip: If you use center drills in lieu of spotting drills, change them out for new ones on a regular basis before the tip fatigues. Since doing this, I've had much less problem with broken tips. Maybe my "fatigue" idea is personal black magic, but it works for me. It could be that the older ones are dull and I don't know it. I'm not going to try to sharpen a 1/8 diameter center drill. They're cheap enough to be regarded as disposable.

 

[AlanHaisley]

Alan,
I sighted them too. Your question implies I should have dialed to the others? Assuming so, I thought, why bother then with the other scribe lines? Perhaps as a way of verifying that I dialed accurately?

If you think in terms of datum points, the first point, which you sighted in, can become the control for all other points on that face. The advantage to dialing after the first point is to make the others all accurately (within the precision of your mill table movements) located. If the first were off a bit, due to parallax or other error causer, at all of the points would be jointly consistent.

However, if you sight them in, on each point there is a possibility of a position error totally uncorrellated with the positions of all the other points.

Mark-up can serve as a check. In my case, there is a good chance of miscounting how many times the dial revolved. ??? Knowing the needed measure, and having markup lines, if I am off by a revolution on the dial I can easily see it. So, I just take the dial on around and then set to the specified graduation.

Alan

 

[zeeprogrammer]

Also, with the 118 deg tip, the divot perfectly matches the shape of the drill so the drill isn't cutting only on the edge of the guide hole when it touches down - a possible source of drill chipping with harder materials.

Thanks Marv. The drill chipping? Or a ragged edge on the hole?

In my case, there is a good chance of miscounting how many times the dial revolved.
Alan

Thanks Alan. In my case...a better than good chance. But I'm getting better and more comfortable using the dials...now that I figured out how to zero them. :big:

Thanks all.

 

[zeeprogrammer]

I've been having some adventures as I work towards making the cylinder. Cutting the side required grinding a lathe cutting tool. Here's a link to the thread where I posed my question. Pay no attention to the various suggestions regarding personal lubricants.

http://www.homemodelenginemachinist.com/index.php?topic=5206.0

So after some (not a lot...but some) success at grinding...I started the process of making the cylinder hole. Need 9/16". Center drilled...started with a small drill bit...and worked up to the 1/2"...my biggest drill bit. Whipped out the boring bar. Going to bore within 0.005 to 0.002 of the required diameter of 9/16". Once I do that...then I can ream to size. Uh...wait a minute...I don't have a 9/16 reamer. Nooooooooo! Another tool is needed!!!

Well here's where I am for now...

Do I remove the part (I haven't bored yet)...or leave it until I get the reamer? I think I'm okay. I have 1/16 to go yet.

Got some purchasing to do. Still need two dies, a slitting saw, an arbor for the slitting saw, and a 9/16 reamer. Wondering when it ends...knowing it never does. May as well get some more personal lubricant too.

What a great hobby.

 

[vlmarshall]

Can you leave the part in the chuck until you get a reamer? If it were me, I'd pull it out unless I could get a reamer tomorrow.
Meanwhile, use your lathe (and grinder) to make a D-drill/reamer, a slitting saw arbor, and the two dies you need! ;D
Nice thread, I was actually wondering how you were doing today while I was at work. I've got a lot of respect for you guys learning on your own.

 

[Foozer]

I
So after some (not a lot...but some) success at grinding...I started the process of making the cylinder hole. Need 9/16". Center drilled...started with a small drill bit...and worked up to the 1/2"...my biggest drill bit. Whipped out the boring bar. Going to bore within 0.005 to 0.002 of the required diameter of 9/16". Once I do that...then I can ream to size. Uh...wait a minute...I don't have a 9/16 reamer. Nooooooooo! Another tool is needed!!!


What a great hobby.

You can just sneak up on the final bore size. Last couple of passes cutting just squeak <0.001 should get you a nice clean and round hole. Match the piston to fit.

 

[zeeprogrammer]

Can you leave the part in the chuck until you get a reamer? If it were me, I'd pull it out unless I could get a reamer tomorrow.
Meanwhile, use your lathe (and grinder) to make a D-drill/reamer, a slitting saw arbor, and the two dies you need! ;D
Nice thread, I was actually wondering how you were doing today while I was at work. I've got a lot of respect for you guys learning on your own.

Thanks 'vlmarshall'. Thanks very much.

I'm going to leave the part in the chuck until I can't stand waiting for the parts anymore. That should be in about an hour or so. ;D