Building a 56mm boring head

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arnoldb

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One of the accessories that's lagging for my mill is a boring head.

I could buy one, but that would not be nearly as much fun as building my own; some of you might have guessed by now from previous projects that I like building my own tools ;D

Once again, Dean's boring head build serves as an inspiration, and I'll also build my unit based on Steve C's (walnotr) plans; changed to meet my requirements - Thanks guys!

Some of the key areas of departure from Steve's plans for me will be:
1. Size - I'll be building at about 150% of the original size. This is for a couple of reasons; I have a bigger mill, so could do with a bigger boring head. The boring bar set I have has 12mm shanks, so the head needs to be bigger to accommodate this.
2. Metric - I prefer to work in metric, so the head's leadscrew will be metric. I've chosen a 0.5mm pitch for it, as it means that for every full turn of the screw, the head will be offset by 0.5mm - and thus take a cut of 1mm in diameter from a workpiece. Also, all screws used will be metric.

The mounting for the boring head had me thinking for a bit as well; initially, I considered fitting it with a 16mm shank to use in the mill's collet chuck, but that is not the best option. So I'll settle for making the shank MT4 to suit my mill's spindle directly - that would be the best long-term solution.

I'll be posting "warts & all" - so some members might be bored with the build; my apologies for that in advance.
And any suggestions and/or questions during the build is welcome!

This is what I have to start off with in terms of materials:
normal_IMG_1557.JPG

A bit of 32mm HRS rod for the MT4 shank, a bit of 60mm cast iron for the body (I might not use this; I'll try and find steel instead), a bit of 60mm steel offcut for the slide/holder, bits of brass for the gib and lead screw retainer, and silver steel for the leadscrew.

As I'm still trying to find some steel for the body rather than use the cast iron, I started off with the shank today. The rod I have is pretty close to the size needed for an MT4 adapter, so there's not a lot of room for removing material, but the surface scale has to go. First I center drilled one side of the 32mm rod as accurately as possible for tailstock support by clamping the stock upright on the drill press - this will become the "thin" end of the taper, as it is not spot-on center. I know the inside jaws of my 3-jaw chuck is pretty accurate at this size, so the end in the chuck would be very close to centered. Here I've turned down some of the scale - as you can see, the bit close to the chuck is more on center:
normal_IMG_1558.JPG

At this point I stopped turning down the scale, as I didn't want the bit close to the chuck turned down any further.

Next I turned a section at the tailstock end down to 24mm - below the minimum that would be needed for the taper:
normal_IMG_1559.JPG


This end will become the "Draw-bar" end of the shank. Once there is a taper in play, workholding becomes difficult, so I decided to finish the draw-bar end completely, including threading it. With a long overhang needing support and working from the end, I brought out the fixed steady. It's one of those accessories that's seldom seen in use, but can be worth its weight in gold when needed. Here I'm setting it up - with the workpiece supported by the tailstock center, it's easy; just push each of the steady "fingers" lightly against the turned flat and tighten up the fingers:
normal_IMG_1560.JPG


A squirt from the oil can to lubricate the steady fingers, and a reduction in speed (I work at a slower turning speed when the steady is in use), and I could drill the end out to 10.2mm for a good depth - about 60mm deep. This is for tapping M12 drawbar thread. Then, with the topslide set over to 30 degrees, I turned a good bit of taper (about 14mm OD at the end) on the end with a boring bar:
normal_IMG_1561.JPG


Next I tapped the thread - I started of with the #1 12mm tap gripped in the tailstock chuck, and threaded in for a bit - this was to make sure the thread is started straight. Then I just opened the chuck, added the T-handle, and continued:
normal_IMG_1562.JPG

The taper tap was followed by the 2nd and 3d taps as well.

I then reversed the workpiece on the lathe, and set up the fixed steady on the "clean" bit that was close to the chuck earlier.
This is where a seldom mentioned bit of using fixed steadies comes into play. They are GREAT for getting an accurately center drilled workpiece at a distance away from the chuck. The workpiece is just very lightly chucked initially, and the steady fingers closed a bit at a time, followed by manually turning the chuck through a full revolution after each adjustment. The workpiece was off-center at the steady end completely - by about 1.5mm, but the gradual closing of the fingers and the fact that it's lightly gripped in the chuck causes it to center on its own.
Once all three of the fingers were lightly in contact, the chuck was tightened up a bit more; not too much though; just tight enough to grip the workpiece for center-drilling it. Even if the steady fingers keeps the workpiece slightly off-center, a good center hole is drilled; it will just be a bit over-size ;D:
normal_IMG_1563.JPG


You may be wondering by now why I made all the boo-hah about boring an oversize 30 degree angle on one side of the workpiece and then going through the process of setting up the steady to drill the center hole on the other end...
Well, it all was to get to a point where I could mount the workpiece between centers:
normal_IMG_1565.JPG

Instead of fussing around with binding wire, I just used a cable-tie to tie the drive dog to the catch-plate.

And why did I need it between centers? - well, to turn the taper... I'm fortunate that I have a taper turning attachment (TTA) for my lathe. Setting over the topslide was not an option for an MT4 taper; the topslide does not have enough travel to turn it. And I needed a way to reliably take the workpiece off the lathe to test it in the milling machine spindle for fit. Did I mention that this is the first time I've tried to turn a Morse Taper ?

For the first time since I got my lathe, I'm using the TTA - well for it's intended use anyway; it's a great place to mount a magnetic base for centering jobs in the 4-jaw chuck otherwise :D. My little "Engineering Black Book" gives specifications for MT4 in metric, so I used the specs to calculate that I would need a taper of 5.124 mm for a travel distance of 100mm (I think this is right; the black book is in the shop now!) Well, there's no way I can measure accurately to 1/1000th of a mm, so 1/100 and an eyeball deviation on the DI would have to do. This is the setup I used:
normal_IMG_1566.JPG

The dial indicator is mounted on the TTA link to the cross-slide, as squarely and on center to the workpiece as I could get it by eye :big:, and run over a measured 100mm "clean" bit of the workpiece to get the readings and set the TTA. Not very professional, I know, but I think good enough for "close enough"; it's not going on a space mission.

I started cutting the taper, and after the second cut things looked wrong. The taper was WAAAY too steep!. I had the correct figures, but forgot to halve the diameter while setting the TTA :-[. Fortunately, there was more than enough un-turned stock available to re-set to cut at half the angle. Just more work to get the TTA set.

Things went well from there, and I cut close to size. Then I did a test. First some (too much!) Prussian Blue on the shaft:
normal_IMG_1567.JPG


After a light fit-and-turn in the mill spindle:
normal_IMG_1568.JPG

By no means perfect, but close enough for me. You'll see that the contact area on the larger diameter was closer, meaning that my taper is slightly shallow - but pretty close.

At least the shank sits in the mill on its own with just a light push; pretty much the same as the rest of my mill accessories:
normal_IMG_1569.JPG

I had to use a hammer with the draw-bar to tap it out, so as far as I'm concerned, the fit is a good 'un.

While dismantling the cross-slide to TTA link, I brushed my thumb knuckle across the slot linking the two... The Myford tooling is invariably very well machined and finished with all sharp edges removed, but someone didn't take the sharp edges off that slot... I'll have to now :big: With red stuff leaking from the skinned bit of said knuckle, I called it quits for the day - Not much to show, but some progress none-the-less:
normal_IMG_1570.JPG


Regards, Arnold
 

walnotr

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arnoldb said:
Once again, Dean's boring head build serves as an inspiration, and I'll also build my unit based on Steve C's (walnotr) plans; changed to meet my requirements - Thanks guys!

Looks like a great start. Glad you are able to get some ideas from my little boring head design. Don't you just love making tools to make tools to . . . ? :big: :big:

Steve C.
 

SAM in LA

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Arnold,

Be careful not to leak too much of that red stuff in your shop.

There is nothing boring in regards to your boring head build.

I enjoy your posts and will be following along.

Regards,

SAM
 

ksouers

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Ruh-roh! Arnold is building tools again.

This is gonna be fun.

Sorry to hear you sprung a leak. I really hate burrs, they drive me nuts.
Leaving burrs on tools is just unfathomable, it makes me wonder where else they cut corners.

Anyway, I'm along for the ride. Thanks for driving, Arnold ;D
 

zeeprogrammer

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As usual, an interesting read. Both educational and self-confidence building.
Sorry about the thumb.
 

tel

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Leaving burrs on tools is just unfathomable, it makes me wonder where else they cut corners.

... or fail to, as they case may be! ;)

Great start Arnold, I'm along for the ride as well.
 

T70MkIII

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Sorry to hear you leaked some Prussian Red.

I'm tossing up making or buying a boring head, so I will be following your project closely. Thanks for sharing with us.
 

arnoldb

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Thanks Steve!
Don't you just love making tools to make tools to . . . ?
- there will be quite a bit more of that associated with this build :big:

Sam, Kevin, Carl, Richard - thanks for the enthusiastic and positive replies ;D

Tel, Rof} You're sharp as ever; Thank you, your comment lifted a bad start to a Monday morning considerably!

Fortunately the thumb is not that bad; less damage than Shrek the Gray causes when he gets in a bad mood ::)

No shop tonight... have to do some chores.

Regards, Arnold
 

BillTodd

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Watching with interest (loved the rotary table thread :)).

Boring only or Bore and facing? Arnold.

Bill
 

walnotr

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The drawings of the original boring head have been uploaded into the download area.

Steve C.
 

bentprop

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Not wanting to hi-jack your thread,Arnold,but there is one thing about boring heads that ,to my way of thinking,limits their usefulness.
Am I correct in thinking that they are "traversed" using the Z axis of a milling machine?
If that is the case,how do you get a smooth bore?Unless you happen to have a powered Z axis,it seems to me the boring head relies on the smoothness of the operators movements.With the weight of the whole mill head,etc.,this would seem a little problematic to me,especially since mine is not exactly super accurate.
Please enlighten me,fellows,and edumacate a dumb dutchman :big:
 

Deanofid

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You're off to a roaring start on another very useful shop tool, Arnold. Pretty soon, you
will be so well equipped you won't have anything to do but build engines! ;)

I hope it's okay that I note something that may be useful; Normally, when you are checking
an external taper for fit using a known internal taper, you would put the prussian blue in the
interior taper, and test your piece. The inside of the taper would be covered with a light coat
of blue on the whole surface, and the clean external tapered piece to be tested will be carefully
inserted into the inside taper. A turn on the piece being tested will tell the tale when it's withdrawn.

For our forum members; Steve Campbell is the fellow who designed the boring head shown on
my website. I just want to be clear that he's the guy who designed it, and provided me with the
prints. Thanks again, Steve.

Dean
 

walnotr

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Deanofid said:
For our forum members; Steve Campbell is the fellow who designed the boring head shown on
my website. I just want to be clear that he's the guy who designed it, and provided me with the
prints. Thanks again, Steve.

Dean

You are welcome Dean (and others). As you will note, the title block on the drawings bares the name "Open Source Tools". It is my way of giving back to the model engineering community at large. I am happy to share anything I have designed, and in the spirit of the now old computer user groups, freely give my designs for non-profit use.

The drawings in the download area have the latest changes to the drawings. I always find something to change when a drawing is revisited. ;D

Steve C.
 

FIXIT

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Arnold
Don't apologise for your 'warts&and all' presentation as it really helps "learners" like me as it's like looking over your shoulder rather going from one thing to another and thinking 'how did he do that !!'
which is obvious to the experienced chaps, so keep it up and thanks.

Steve
 

arnoldb

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Thanks Bill; this one will be for boring only. Though it could be used for facing it will be (hopefully) more of a precision tool and treated as such, I generally use a fly-cutter for facing - though I have considered knocking up a TCMT facing cutter for facing HRS and tougher materials like stainless...

Steve C. - once again thank you for your generous contributions to our hobby :bow:

No problem Hans - thanks for checking in and asking! I'm not sure what mill you have; a boring head is usually used with the quill feed on a mill with the head locked in place - thus no weight from carrying the head. While manual, it just becomes an exercise in feed control; just like a manual feed on a lathe or the mill's X and Y. I don't have power feed on any of my machines (I can do it with the lathe carriage, but it's a pain to set up so I use it very rarely), so I've gotten used to try and do smooth manual feeds. If your mill does not have a separate quill feed, it might be more tricky to use though. Oh, and don't worry, for a Dutchman you appear to be very intelligent! ;) - I've also been called a Dutchman because my native Afrikaans is pretty near Dutch as a language!

Thanks Dean :) - you should see my "tools to build" list though... And of course its OK - all contributions are welcome! Thank you; I've filed your notes on checking a taper for future use :)

Steve (Fixit) - Thank you - that means a lot. And please feel free to ask questions if you want to; I'm happy to try and answer any questions if I can, and I'm sure more experienced members will add in if/where it is necessary (just like Dean did earlier). I'm pretty much still a beginner as well, and there are new experiences for me in each of my builds.

Had a bit in the shop after work today...

First off, an action photo for a change - nothing special in that, except if you look closely, you'll see some smoke coming off from the cut, as I'm pushing the lathe a bit to get some material removed quickly - this is on 20 thou in-feed and a good rate of cross-feed, so the water from the infrequently sprayed water soluble oil evaporates, and the oil left starts to smoke. I made a couple of cuts to get the end of the workpiece down to 24 mm for threading:
normal_IMG_1572.JPG

Why did I include this photo? Well, for the simple reason that working like this will heat up the workpiece, and it will expand in length due to the heat. It is important to stop after every couple of cuts like this when turning, and loosen the tailstock slightly and re-set it. If you don't do this, the workpiece lengthening could end up pushing your centers so hard into their tapers that you'll have a heck of a time to get them out, or even worse, you could end up damaging the lathe bearings.

As further machining on the 24mm section would entail threading - and as a result a future problem with workholding - I stopped, and transferred the arbor to the mill to mill spanner flats on the section between the taper and the section to be threaded:
normal_IMG_1573.JPG

(Aside - I've been "bugged" by a certain member about using the new mill vise :big: - so there! - it works great!; Thanks Wagner!)

Back to the lathe with the workpiece, and I turned down more of the end to 22.4mm, and added a parting cut to the same diameter. The turned down section is a cheat to easily see when I'm at the correct depth of cut when threading, and the parting groove is for thread run-out while threading. Lazy rotter that I am, I'm going to thread the arbor and boring head to 16TPI - thats pretty darn close to a 1.6mm pitch. Now, I know I have stated that I normally work in metric, but as this is a one-off, I'm taking liberties; it's easier to single-point thread in imperial with my lathe - I get to use the thread indicator instead of having to reverse it all the time to get back to the start :big:. This is where I stopped this evening:
normal_IMG_1574.JPG


I'll cut the thread when I'm feeling fresh and can finish it in one session; I love single-point threading, but it does take some attention ;D

Regards, Arnold
 

Wagner1975

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Whoo hooo ..... I'm looking over your shoulder aswell .... can't get enough of this tooling business! :big:
Glad to see the vice being usefull .... still glad my little mill didn't topple over when I tried it out! :hDe: Fits nicely on your machine though! ;D

Regards
Wagner
 

arnoldb

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Thanks Wagner ;D - the vise appears to be the ideal size for me Thm:.

Well, I haven't been in the shop again, so no further progress. At least I managed to find another bit of 60mm x 250mm long BMS to use instead of the cast iron for the head today ;D

Regards, Arnold
 

njl

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Great thread Arnold, I'm enjoying watching your progress. I also have a boring head on the to do list.

Nick
 

arnoldb

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Thank you Nick :)

At least I got a bit done today. Not much though, but at least some progress.

First off, turning the threads on the arbor. The last threads I turned on my lathe was for the rotary table chuck adapter - that was 12 TPI. So setting up the lathe change wheels for 16 TPI was easy; I just had to change one gear ;D. My lathe's leadscrew is 8 tpi, and I had a 40-idler-60 tooth set mounted for the 12 tpi; I just replaced the 40 tooth gear with a 30 tooth. The lathe's screwcutting chart specifies a 20-idler-40 set, but as long as the ratios are the same just about any combination can be used to give a 1:2 headstock to leadscrew reduction - as long as it fits on the banjo. I always use a strip of typing paper tightly rolled in between the gears to set the tooth clearance:
normal_IMG_1584.JPG

Oh yes, don't forget a drop of oil on the gear teeth and their bushes. I'm not sure if plastic gears need lubrication, but metal gear wheels do.

Setting up for threading - I'm going to cut 60 degree threads, so my 60 degree external thread cutting tip, and a guage plate to make sure it is set up squarely:
normal_IMG_1585.JPG


Then a light pass - just a thou (0.02mm) deep - turning the chuck by hand. I always do this check; sometimes there are surprises in store, and this was one of those times! :
normal_IMG_1586.JPG

If you look carefully, you'll see that the toolbit touches the shoulder on the left of the thread run-out groove. That shoulder is important in this specific arbor application, and must not be damaged - so I can't cut the thread with this toolbit.

scratch.gif How now brown cow ? I dug through my toolbits, and found a bit that I ground quite a while ago for situations like these. The toolbit has a tiny 60 degree tip and when I ground it, it was exactly for the purpose of threading up to a shoulder. Here it is mounted and showing the clearance:
normal_IMG_1587.JPG

Just adequate - so no need to grind a new cutter ;D

As the first cut was very light, I set the tip to approximate the first test cut - and did another manual test - you can see the second groove from the second test:
normal_IMG_1588.JPG

When starting a thread, this is adequate - and no need to get it any closer. Picking up a part-way cut thread (for example when your cutting tips break while threading) requires much better accuracy and a good "feel" for your lathe though!

This is a relatively fine thread to cut - I did just three passes to get it down to "size", but something was looking wrong... When I did the last pass on what was supposed to be "size", the crests on the threads were still slightly flat, and not sharp as they should have been! I knew I used a 60 degree tip for cutting, so that was right. Some measurements, and I found that the section towards the tailstock that I thought I had turned down to the required 22.4mm (to cheat at finding thread depth) was in fact still 22.6 mm in diameter. So much for cheating :big: So I went back to the end of the stock, and dialed in another 4 thou (0.1mm ~= 4 thou) and did two passes at that setting - the first to "cut", and the second to "clean". This is what I ended up with:
normal_IMG_1589.JPG

By no means the best set of threads I have done, but in this case "it will do"

On to the band saw to get rid of the excess - with a bit of scrap to support the end as squarely as possible:
normal_IMG_1590.JPG


To finish off the threaded end, (I could just have left it as sawn off, but that's just not good enough) I chucked the arbor in the 3-jaw on the short piece of parallel section that I made at the end of the taper. If I was a reckless kind of person, I could just have faced the end off, but there was simply too much overhang. The fixed steady literally takes less than a minute to set up and support the overhang, so I did - and then faced off the end:
normal_IMG_1591.JPG

As you can see, the steady fingers slightly overlaps the spanner flats I milled in the arbor - thats not a big issue, as most of the fingers are carrying on a completely round bit of the arbor.

Facing a threaded section leaves a VERY sharp section of "half thread" at the start - I just used a needle file to file it down flat about 1/3rd of the way around. One thing I'm not entirely sure of is the treatment of this section of the start of a thread - there might be a better way to handle it.
The finished arbor:
normal_IMG_1592.JPG


Next up, a bit of steel to start on the "base" of the boring head:
normal_IMG_1593.JPG


I chucked that up and tried to face the yellow painted bit off, but promptly ruined the tip of my favorite HSS cutting bit on it. I tried a carbide tipped tool next, and while it cut it, there were some decidedly hard sections on there - it actually deflected the carbide tip tool visibly! - so there was a very hard section on that face. The face in question appears to be sheared, so it could be work hardened. Turning along the length of the piece, it became apparent that that was the case - the rest turned down nicely - so I sliced off the end on the band saw. If you look carefully, you'll see where I tried to machine the face and the hard section started by the ridge at 2 o' clock:
normal_IMG_1594.JPG


With that lot out of the way, it was a simple matter to mount in the lathe and true up the band sawed bit:
normal_IMG_1595.JPG


Then flipped in the chuck, center drilled to get tailstock support, and a 15mm wide step turned on. I didn't bother to measure the depth - just to "taste" :big: :
normal_IMG_1596.JPG


Then I drilled out the bit with a 4mm drill to 20mm deep, then a 10mm drill with the lathe at lowest non-backgear speed. For the 16mm drill in the next photo I changed to highest back gear speed:
normal_IMG_1598.JPG


That was followed by a 19mm drill, and I stopped for today:
normal_IMG_1599.JPG


Regards, Arnold
 

Deanofid

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By no means the best set of threads I have done, but in this case "it will do"

Shoot, your threads look good to me, Arnold. The finished piece looks good, too!
The color on the large lump you turned down later in the post looks suspiciously like
Caterpillar Yellow. Maybe it was a big pin, and had been hammered on one end, making
it hard.
You got it whipped, whatever it was.

Thanks for the new post,

Dean
 
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