Building a 56mm boring head

[arnoldb]

Thanks Sam - There's not much "outside of the box" though; just applying (or at least trying to apply) some basic machining practices that was in use well over a century ago already - and that somehow seems to be receding into the mists of time.

Stew, Thanks very much mate

Dean, thank you very much ;D Fortunately I'm not an easy fellow to get down if I've set my mind on something - so I do what's needed to get the job done. Instead of moaning and groaning about some extra work to get to the final goal, I simply choose to make it worthwhile and get more fun and experience from the process. From my limited experience, I think at least half of getting a job done successfully is accomplished just by taking a positive attitude Maybe I'm lucky to have more limited access to all the doo-dads thats available at the drop of a brown package in a short time overseas ;D

Lew, thanks for checking in - yes, a quick un-hardened once-off cutter for brass would work

Kind regards, Arnold

 

[njl]

Great job Arnold, I'm really enjoying your approach to getting the job done and I'm learning loads of useful stuff from you, thanks for sharing. I've not tried heat treating to harden metal yet, got the workshop series book on it though, so will definitely give it a try in the not to distant future.

Nick

 

[Blogwitch]

Arnold,

Sorry I haven't commented before.

This is becoming a great post, and you really are coming along very nicely seeing as you had very little experience such a short while ago.

I didn't just comment here to pick you up on a machining oversight, but I will give you a little tip.

When you are machining a fairly large piece as you have been doing, especially round, it is always better if you can machine in the Y axis rather than the X. The material is better supported by the vice jaws in that direction, and won't be tempted to to be knocked over sideways.

Bogs

 

[arnoldb]

Thanks Nick - it's a pleasure to share!

Bogs, Thank you - Your tips are always welcome and very much appreciated, not only by myself, but I'm sure also for anybody else who choose to use them! I'll definitely give the Y-machining direction a go when I do the other part of the boring head and report back

We have a public holiday here in Namibia on Thursday, and I have put in leave for Friday to make a long weekend, so I'm looking forward to a good bit of shop time then

Kind regards, Arnold

 

[zeeprogrammer]

You and your threads are always a motivator for me Arnold.
Thanks.

 

[arnoldb]

Thank you Carl ;D - that makes posting really worthwhile for me!

Today's bit; the boring head base is pretty much finished now.

To mill the slot in the base where the leadscrew and nut will run in, I first drilled out a lot of the excess:

Then milled it out to 10mm; my 10mm slot mill is VERY blunt; it's time to get a new one or build a tool grinder...:

Next I cleaned everything up with a 4mm multi-flute end mill - this one's nice and sharp, so things went really well:

To drill the hole for the leadscrew, I used a small square to set the part up in the vise:

Then I drilled and counter bored the hole as required:

To set the part up to drill the holes for the gib screws and lock screw, I used a thin plate to set it horizontal:

At this point I paused a bit and thought about the future use of the boring head,as well as the sizes and function of the gib screws and locking screw.
Steve's plans call for the gib screws to screw into the gib itself, with clearance holes through the body of the head. Dean made his boring head with threads both in the gib and the boring head. I decided to rather go for threads just in the body, and locating holes in the gib - a more conventional layout. I'll use longish 4mm grub screws (set screws) with a bit of medium strength thread retainer on the threads to prevent them vibrating loose. I was tempted to use screws with lock nuts, but space is at a bit of a premium so I decided against that.
I already have a good idea of how I want to make the leadscrew, and that would entail a modified M5 socket head cap screw for doing the adjusting. This is where thinking of the boring head in-use comes in - ideally, I'd like to use only one size of allen key when in operation, so that means the locking screw must also be an M5 socket head cap screw. One problem though... an M5 SHCS's head is about 9mm in diameter, and I only had 8mm to work with, unless I offset the lock screw. That wouldn't look nice though. There is quite a bit of meat on a 5mm SHCS head, so I decided that I could take one and turn it down enough to fit the 8mm I had available.

In the next photo, I'd finished drilling one gib screw hole to 3.3mm (M4 tapping size), as well as the 4.2mm tapping drill and counter bore for the locking screw, and I'm getting ready to start on the second gib screw hole with the largest center drill that would work to start the hole on the angle caused by the rounding on the workpiece:

Then I threaded all the holes, and turned the head down on an M5 SHCS to fit the lock hole; the screw still needs to be shortened, but I'll do that at a later stage. This is where I stopped for today:

Regards, Arnold

 

[Deanofid]

Looking good, Arnold. Thm:
Thanks for the new pics and words!

Dean

 

[arnoldb]

Thanks Dean ;D

Today's little bit... I started work on the sliding part of the head - first off, some mild steel crudely cleaned up to get it nice and square after bandsawing:

I'll bling it up later, as there is still quite a bit of work to do on it.

Then I diverted a bit from the boring head, to make a small pair of matched V-Blocks. There have been many occasions where I needed a V blocks but I never got around to getting/making some. I could have made just one, but a matched pair can be very usable in some set-ups, and it's easy to make. Though not precision ground and all of that, these should help me in a lot of cases:

One of the V blocks was put to use immediately - to hold the workpiece in the mill vise. Two 50mm bearing outer races acts as parallels, and I tried Bogs' tip of milling on the Y axis feed. Worked a treat and I could take a 3mm deep cut with the 14mm mill in one pass. The milling machine didn't complain at all - just took some good sized chips off the workpiece at a good rate of feed ;D:

Both sides milled off the workpiece:

Flipped in the vise, and milled down to cut the dovetails:

I stopped today with one side of the dovetail cut. The cutter barely made it, and is in dire need of some honing - I'll do that tomorrow and finish the dovetail.
A view of where I stopped - in the photo things look like it's not a good match, but that is mostly an illusion caused by generously chamfered edges and some pretty bad clean-up filing on edges on my part :big: - rubbing the two pieces together on the partly-formed dovetail, they slide together much better than I anticipated!:

I had a dash around town this morning to get some supplies - and one thing I forgot was an 8 or 10 mm ball nose mill... Guess I'll have to annoy the engineering supplier tomorrow morning again!

Regards, Arnold

 

[Deanofid]

Things are getting pretty nicely matched up, Arnold. I think you got pretty fair life out of
your shop made dovetail cutter, too. Drill rod seems to take a bit of a beating on an
interrupted cut. Some stone work, and one more cut! It's going well!

Dean

 

[arnoldb]

Thanks Dean - yes; the cuter barely made it, but it was an interesting experience - and its handy to know I can make my own cutters should the need arise . I think I'll order some dovetail cutters from overseas for future projects though...

Things went well today; after I sharpened up the cutter, I finished the last dovetail cut:

Then I milled the pocket where the leadscrew nut will engage:

To get rid of chips from the pocket while milling, I just held the shop vac nozzle to suck up the chips. I wasn't going hell for leather on the cuts, so the chips were cool and could just be sucked up.

On to the gib. I'd miscalculated the size of brass needed for the gib, and the bit in the first photo of this thread was too thin. So I scratched around my stock to find something suitable that would not waste too much material, and settled on some 8mm hex bar to use. This was a blessing in disguise, as the hex bar shape would help when cutting the 60 degree angle needed on the gib ;D
I first milled a flat out of the bar, keeping two "blobs" on the ends:

Then with the brass bar supported on makeshift parallels and with flat ends toward the bottom of the mill vise, I could mill out the angled part of the gib:

I did say "makeshift" - the two V-blocks I made yesterday makes up part of the parallel, and there's an 8mm square HSS toolbit between them and the workpiece!

This is what the gib looked like after milling:

With the "blobs" sawed off and installed on the rest of the bits:

I couldn't test the size of the gib properly after milling - those "blobs" were in the way, and it was _just_ too large initially, so I brought out the trusty files and filed it down to fit closely.

Then I marked spots on the gib for the retaining screws an lock screw by twirling drills through the various screw-holes in the body, and lightly counter drilled the spots in the drill press; that pretty much finished the gib:

Things needed a triming down and tidying up, so I locked the slide of the head on the body with all of the screws, and mounted the lot on the lathe to turn down:

It was nice to get back to the lathe for a change after all the milling I've been doing for the last couple of days ;D

A little while later after some turning and a bit of elbow grease with strips of oiled emery:

For the tool mounting holes, I started off drilling the holes. I got bored while drilling, so played a bit of "stack the drill swarf" in the process. The swarf lying on the cross slide landed there while drilling - I didn't touch anything!:

That was a 7mm drill - it was followed by an 11.5mm drill, and then a boring bit to open up the hole to 12mm.

Like Dean, I decided on also making just two tool holder holed in the boring head. So with the head offset and locked into place, I prepared for the second hole. That makes a big lump of metal hang off-balance on the lathe, and I had some trepidations... First off, I reduced spindle speed, checked for adequate clearance all-round, and then popped the clutch on the lathe - the old girl did not complain at all, and I could detect no untoward vibration, so things were a go for the next hole:

After drilling and boring the second hole, I decided to call it a day, and here's what things looked like when I stopped:

I think I'm about half-way there ;D

Regards, Arnold

 

[Deanofid]

That looks terrific, Arnold.
I think my favorite part of making one of these was when I got to put both pieces
together and turn down the finished diameter on the OD of the assembled boring head.
It just seemed like the whole thing came together at that point.
It's a really good project, and you're doing great!

Dean

 

[arnoldb]

Thanks Dean ;D - Yes, I'd have to agree with you - putting those pieces together to turn the whole lot down was a serious feel-good moment!

Well, not much done today... Life got in the way of shop time.

First off, drilled the tap size holes for the tool retaining screws:

Then milled the side flanges down more and left adequate meat for running through with a ball nose mill. The extra step I milled out was to make the job for the ball nose mill easier; I'd never used one before, and didn't know what to expect:

On to the ball nose mill; On the first side, I took several light cuts to get down to size, but the mill wanted a very slow feed, so it took a lot of time... I was more bold on the second side, and took the full cut in one go; this worked surprisingly well; I could run at the same feedrate as for the smaller cuts and it took only one pass!

Next up was the feed nut; it was relatively quick to make. First I milled a block of brass to size, then drilled and threaded it to accept the leadscrew. I recently invested in some quality M6x0.5mm taps; they were expensive, but I will find a lot of use for them in making steam fittings in future, so worth the investment. I used the mill spindle to start the tap properly in the hole, and then finished tapping by hand:

The feed nut needs a chamfer on one side to allow one to assemble the boring head - I just ran a countersink past it a couple of times to get the chamfer:

The finished nut:

I really wanted to have the boring head finished this weekend, but alas - not to be, so the rest will remain for next weekend - unless I find some time after work during the week.

Regards, Arnold

 

[walnotr]

It is quite the treat to see so many familiar parts on familiar drawings! You are doing a great job Arnold. :bow:

Steve C.

 

[Deanofid]

... see so many familiar parts on familiar drawings!
Steve C.

:big: :big: :big:
That's funny, Steve.

Again, looking all good and proper, Arnold. Funny about the brass 'nut'. I went by Steve's print
for mine, but couldn't figure out why the heck he had make that odd sloped side on it. That is,
until I went to put it all together!

Dean

 

[arnoldb]

Thanks Steve ;D - Kudos to you though; a great set of plans do make thinks a LOT easier :bow: No catches, I took your measurements, converted them to metric and scaled up, and it just works!

Thanks Dean ;D - I forgot to mention I had a "blonde" moment testing the fit of the nut as well :-[ - I knew why the sloped side was needed, and put it on the nut, but couldn't get the thing together... Turned out, the last time I disassembled the lot, I just slid it apart and let the gib drop out - but I never unscrewed the gib screws to get clearance to make things go together; I spent nearly ten minutes trying to figure out why before I realised :big: :big:

Kind regards, Arnold

 

[Florian]

Hey Arnold

That boring head looks really good.
But i am thinking about one detail for a while now:
Why do you use an incomplete dovetail on one side?
Im not shure about it but i would say the rigidity of the boring head is somehow reduced because on the "square side" (well, the side with the "half" dovetail) the under part of the head can just move downwards with, well, relatively small effort, especially if there is a little play (and if its only just to adjust the boring diameter).
Of course you will tighten it when boring (and after adjusting) But even

I think you also have to think on the fact that the material itself is not absolutely rigid and the head could give in slightly (in the elastic range) and this would really promote chattering.
I guess that is the reason why all the commercial ones have complete dovetails on both side. Because then the under part of the boring head then is well defined in contrary to the solution with one incomplete dovetail on one side...

Maybe its no problem, i can't say it but finally i just wonder why you decided to make an incomplete dovetail on one side...

Anyway, i would always use the boring head that way around that the load points away from complete dovetail. Why? Because then the possible Play on the "flat side" is being eliminated and the under head may buckle a little and the complete dovetail is being pulled downwards because of buckling and so the play is being eliminated by this. If You put the "load" to the other direction, the under part will be pressed against the upper part on the "complete" dovetail and buckling will be promoted because of the lack of the complete dovetail guide on the oder side (the gib will be able to "slide" down).

Florian

 

[arnoldb]

Thanks Florian ;D - I must admit you raised a good point! - I didn't think that far ahead :-[

From the design though, things should lock up adequately for rigidity from my point of view. The "half dovetail" section and it's adjustment and locking screws would be subject to pretty much the same forces as applied to a full dovetail. The entire lock-down force still gets carried by the lock-down screw at the end of the day - I think!

I'm not sure how the up-sizing would affect the boring head - I guess I'll find out in due course. Neither Steve C nor Dean has mentioned any problems while machining with this boring head as-designed - I guess I'll have to just wait and see how it performs scaled up

Kind regards, Arnold

 

[arnoldb]

Finally - the boring head is done ;D Quite a big update, so my apologies if things are a bit slow to load in your browser!

The leadscrew needed making... Steve and Dean used modified cap screws; a perfectly good solution. I didn't as I wanted a 0.5mm pitch lead screw, and M6x0.5 cap screws are unobtainable locally, so I had to do a bit more work than really necessary.
I started off with a bit of 6mm silver steel in the collet chuck on the lathe and parted a 4mm wide groove in it to 4mm diameter. This groove becomes both thread run-out, as well as the groove that the retainer slips into to keep thinks in place when the boring head is assembled, so it was carefully marked off at the appropriate length along the workpiece:

On to threading; I have single-point turned a couple of threads in the last 2 years, but this one was new territory for me. It is by far the finest I have attempted, and there would be definite flex in the workpiece. To make sure I had no unexpected surprises from the drivetrain, I cleaned all the change gears and the lathe's lead screw much more meticulously than I usually do - not that I'm not meticulous with this part normally - today I was just about anal about it. I also dug out the traveling steady I made as one of my earliest projects for the lathe. Last, but by no means least, I spent quite a while honing my HSS threading tool to as sharp a point as it ever had; on this fine thread, only the last 0.25mm (10 thou) of the tip will be used, but the cutting angle must be accurate and sharp there. This is the setup - ready for threading:

Seeing as this thread was for metric, I had to keep the feed nuts engaged and reverse the lathe after each cut, so I wasn't too keen on taking that many passes... First cut was at 7 thou infeed with lots of cutting fluid, then another 3 thou added, and run through again at the same setting to clean up a bit. This is the result at that point:

I was concerned that it looked a bit rough at this point, but a quick run-past with a small wire brush cleaned of the gunk, and the feed nut screwed on easily but without any play or roughness ;D

Then I sawed of the leadscrew-in-making 10mm beyond the parting cut and chucked it in the collet chuck with the sawn-off face pointing out. This was faced off, and drilled and tapped for M4:

An M5 cap screw was then chucked by its "cap" in the collet chuck with the thread sticking out. I turned down the threaded section to 4mm, and re-threaded it to M4:

Some excess length was then sawn off.

The above was a lot of boo-hah just to get to this point:

Next the leadscrew was chucked up in the collet chuck once again and the cap screw thoroughly and forcefully screwed into the leadscrew, effectively completely seizing it up thoroughly. Then I turned the head down to 8mm OD for a distance of 3mm:

Some 3mm brass plate was marked up:

Then sawn off, and drilled with an 8mm hole in the center. From some previous "Fun", I know that my 8mm drill will drill a slightly triangular hole in thin brass plate, and I used that to my advantage in this case. The hole actually ends up JUST below 8mm nominal diameter, so becomes a light press fit on an 8mm round section - I used the tailstock holder which happened to still be sitting in the tailstock to just press the piece of plate over the head of the cap screw:

Then I took the workpiece, clamped it in a toolmaker's vise in the big vise, and silver brazed the plate to the cap screw:

( :-[ Sorry - photo out of focus)

A bit of cleanup in the collet chuck later:

I love the new mill vise; instead of the elaborate setup I needed for making graduations when I built the rotary table, I could just clamp the cross-slide extension I made for the lathe in the vise and mount the dividing head on it:

A simple run-through with the same tool I made for graduating the rotary table, and I had 10 large graduations on the dial:

This was followed by 50 shorter markings. Initially I thought about 100 marks, but 50 is plenty close enough and gives me 0.01mm feed on the leadscrew per mark (0.02mm diameter increment). I can still "guestimate" settings between marks, so this should be plenty accurate enough for my needs:

(I rubbed a dirty oily finger over the marks to make them stand out a bit)

Next up, boring a recess for the dial in the B/H body... This was not a simple task, and it would have been nice to have a boring head to do the job :
Dean did this step on his rotary table, but I could not figure out a way to reliably clamp the boring head to my RT, as its a bit small compared to the B/H... So I ended up on the lathe, with the 4-jaw, and a piece of 6mm silver steel to align things and keep the operation safe. I used the dual-headed turning tool I made earlier in this thread for the boring. A couple of drops of oil on the silver steel held in the tailstock chuck, and pushed ALL the way through and engaging the back end of the B/H where the lead screw would end in, and things were moderately safe and aligned for turning:

Tolerances would be close, so instead of risking smashing the boring head body into the toolpost, I used two layers of masking tape to provide for warning; if the tape got caught, limits would be very close indeed!:

With the lathe at high back-gear speed, I bored out the recess - very gently. This setup was not very rigid, so I erred on the side of caution and safety. After boring out the recess, I used my normal cutting tool make the scale reference mark on the body - a couple of quick traverses with the cross-slide (one too many in fact), and the mark was there (on the body just to the top right of the cutting tool tip in the photo):

One too any, as the mark ended up a bit deep for my personal preference...

Next up, the lead screw retainer - all marked up on some stock:

:-[ I thought I'd taken a photo of the retainer as-finished, but I didn't! I milled it to size and filed roundings on the outside edges, and it slipped in in position. I was a bit over-vigorous on the rounding over though!:

Then I assembled everything, and ran into a minor snag... My 12mm draw bar is a Weeee bit long :-[. I don't have a sufficient length of 12mm threaded rod left for making a new draw bar, so some shopping required after the weekend to make a new one for the boring head:

Besides the draw bar issue, the B/H is completed though not tested ;D:

By no means a perfect job, but I'll settle for this. Operational testing will have to wait till I get a length of all-thread to make a draw bar for it, but I just think it may work ;D
All-in-all, it appears to work as intended; I have very little backlash on adjusting the head, and all adjustments are nice and smooth, so I'll call this one finished.

This was an immensely enjoyable little project with it's own set of challenges and first-for-me operations. ;D

Special thanks go to Steve C and Dean - for sharing so unreservedly from your own experience!

Thank you also to all who followed along and especially those who contributed to this little quest :bow:

Kind regards, Arnold

 

[ozzie46]

Well done as usual Arnold. Both project and postings. Thm: Thm: Thm:

Ron

 

[Deanofid]

By no means a perfect job, but I'll settle for this.

Wow, I would not feel like I was settling for anything with this tool, Arnold.
It looks smashingly good! I'll bet you are really going to enjoy having one, and when
someone is over to your humble shop, and asks where you bought that boring head,
they're not going to believe you when you tell them.

Really Well Done!!

Dean