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Building an ER collet chuck from scratch for a Myford ML7

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arnoldb:
Following on from my own research, questions asked (and answers received) from another post here, and some other considerations - mostly related to personal finance and the backward location I live in (*), I have decided to build my own ER type collet chuck for my Myford lathe.

This is not the easiest (nor necessarily the best) option, but will provide me with some additional machining skills, personal satisfaction, as well as stress relief, and hopefully, a usable tool as an end result.  If this "quest" adds to anybody else's knowledge, or serves as a spark of inspiration for someone, that would be an incalculable bonus.

I have not yet decided on a specific ER size, but it will either be ER25 or ER32.  I need to see what size collets local suppliers here in Windhoek can get - if they cannot or are not prepared to get collets, or those are too expensive for my budget, I'll make those as well.

So, how can I start on a collet chuck without knowing the sizes ? - well, I will need to machine most of the chuck on my lathe's spindle, so the first step in making the chuck, irrespective of size, would be to machine it's spindle mount in raw stock. Not being an entirely competent machinist yet, I decided the easiest way to accomplish this would be to make a clone of the myford's spindle nose first, and as accurately as I can, to use to test the collet chuck-in-making's mounting.  If you want to propose Ebay, Chronos et al at this point in time for a solution, please refer to (*) above... No offense intended  :(  As a bonus, I'll have a spindle nose adapter for use in other project.

Right, rules of engagement laid: Make a Myford spindle nose adapter.
I used a piece of "suitable" HRS I had available to do this; the metal used is not critical (I think ? :smart: ). This was chucked up (I used my 3 jaw chuck's outside jaws, as one of the inside jaws has a broken inner tooth, and grip would be border-line - or break more teeth):


This lot was _very_ gently faced off without tailstock support to just beyond the bandsaw marks with a very sharp toolbit, then center drilled so I could add tailstock support.
Then I took a "deep" (for me) 30 thou" cross cut with the tool bit set at an angle that would "undercut" the scale and rust - saves effort on sharpening the cutting bit  :D - and immediately cleaned all the swarf from the lathe-ways and slides - the scale works like grinding compound on the lathe's sliding surfaces.

After this some plain turning to get to dimensions - this metal is horrible to get a nice finish on!:


I left the register part 1/2 thou oversize - to work down as needed, as this is the most critical. Then I needed a 55 degree thread cutting bit, which I didn't have, so I just free-hand ground one for my "semi-quick-change toolholder" from 4mm round HSS, checking with a fishtail to get the correct angles:


After grinding, I just moved the bit further back into the holder to minimise overhang.

Then set up the change-wheels on the banjo for 12 tpi for the thread cutting part. Apologies to everyone who knows this, but maybe someone can appreciate the following:  Use a strip of paper while pushing together, and turning, the gears manually to set gear spacing - feed the paper in while turning the gears, and when it passed through, just tighten up the banjo (or gear stud mounting) - And DON'T forget to add a drop of oil to the gear studs/runners and gear teeth!:


Humble pie  :whip: :whip: - I forgot to take photos of the next steps....   :( - well, I simply got busy...
I first turned a groove for thread run-out next to the index ring, and spent many back-and-forths to thread the nose.  Somewhere along the line, I think some dirt got stuck in the Myford's clutch (How do you people do single-point threading without a clutch  :scratch:  :scratch:), causing some creep even when the clutch was disengaged (or should that be engaged??)  Luckily, this was an imperial cut, so, for the first time since I've had my lathe I could use the thread dial indicator and disengage and engage the leadscrew as needed - MUCH easier than doing Metric threads on the old girl  :headbang:

After turning and cleaning up the threads, I tried screwing on my 4 jaw ( :doh: not THAT kind!!), as well as dog-plate carrier. The last went on smoothly, but the 4-jaw refused, so I used engineer's blue (a.k.a. Prussian blue) to check for the problem.  I know my 4-jaw is the tightest on the lathe's own spindle, so if that can fit, everything would be sort of OK.  The blue showed the register was still too big, as I intended, so I used some oil-coated 320 grid sandpaper to get rid of the oversize. - the 4-jaw ended up screwing on with <approximately><exactly>  :lol: the same "feel" as it does on the lathe spindle - that should be good enough for now  :coffee: :


The results of this afternoon's work:

and


 :beer:, Arnold

sbwhart:
Nicely done and shown Arnold :beer:

This link http://www.arceurotrade.co.uk/Catalogue/Collets/ER-Collets-Collet-Chucks leads to a good drawing of ER collets that should halp with the next bit of you project, hope it helps.

Have fun

Stew

arnoldb:
Thanks Stew  :beer:

At last, some more  :dremel:.

I found a supplier in South Africa that is willing to ship me tools for a very reasonable fee to Windhoek.  Stretched my budget, and ordered a set of ER25 collets from them, as well as a closer nut with integral bearing.

Visited the local engineering firm where I can buy odds 'n ends on Monday, and got a nice bit of cast-iron off-cut from the storeman. Showed off the "Fancy" I built to them, and with the storeman and the sales staff (as well as some of their engineers) surprisingly impressed, got a whopping discount  :ddb:.
What I ended up with was this lump of 200mm long 55mm diameter cast iron:


As one end of that had been machined in a lathe before, I marked and center drilled the other end, chucked it up and took off the skin part-way with a deep undercut, as well as faced the end to close to the tailstock support:


I  :smart: overall chuck length would be 60 mm - to allow for the spindle end, length of ER collet needed and about 5mm extra for good luck. Then onto the bandsaw to cut a piece at just over length:


Then mounted the four-jaw chuck, and centered the piece in it as closely as I could. (Twice...   :doh: The first time I forgot to check that I put the faced side into the chuck. Not being any good at gambling, of course I lost the 50/50 odds and the sawed-off face was on the chuck face first time round...) Wish I had more  :med:  :lol:
I used the 4-jaw, as I could get the most grip support from the jaws; the rest of the machining would be mostly without tailstock support.  Then faced off to get the sawed face square and to correct overall length:


As the Myford has a ~16mm spindle bore, I then used progressive drill sizes to drill through up to 16 mm - this is just below the 17mm minimum size needed for the ER25 collet chuck:


Then the CI was further bored out to a depth of 30 mm for the inner diameter for the  1 1/8" x 12 tpi thread, and a home-ground bit used to make a 3mm deep undercut at the maximum depth for thread run-out.  I then ground and honed the other end of the same bit into a 55 degree threading point, and started threading.  Note that the threading bit is turned upside-down, and that I am cutting on the back of the workpiece on infeed, rather than at the front.  This just makes life easier for me  ;) :


And finished thread:


After this, I carefully bored out the register to size, and screwed in the spindle-nose replica I made earlier.  This was a big moment... will things be OK?  Mounted my best dial indicator to test run-out on the spindle replica.   :scratch: - dial indicator must be broken; it doesn't change when I turn the whole lot through a couple of turns - just vibrates slightly  :) - I think that's a good result  :headbang: . Setup to test run-out:


And where I stopped this afternoon:


Tested some more by screwing onto my dividing head - slightly too tight.  A check with engineer's blue shows the register is OK, so the threads are the culprit.  I'll just make a tap to clean out the last bit of tightness later on  :med:.

Now I have to wait for delivery of the collets and closer nut before I can continue; it would be best if I have those for the next steps.

 :beer: Arnold
 :nrocks: :nrocks: :nrocks:

spuddevans:
That's looking mighty good there Arnold :thumbup: :thumbup:

I've been considering whether or not to build a ER32 chuck for my lathe. At the moment I have been using the MT3 chuck from my mill, but I'd rather have a dedicated on for the lathe, especially as it would allow for longer stock to be held through the headstock.

So I'm keenly interested in seeing your build's progress  :dremel:


Tim

Darren:
Very inspiring Arnold, that is coming along nicely... :thumbup:

Good score on the CI..... :clap:

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