# Yet another ER40 collet chuck for an Atlas



## JPMacG (Feb 20, 2019)

Just completed an ER40 collet chuck for my Craftsman (Atlas) 12-inch lathe.  I followed the excellent drawing by Ronald Crowell, Harold Hall's website, and the many YouTube tutorials.  This was a real nice learning experience with a variety of operations... boring a precise diameter, internal thread relief, internal threading, external metric threading, boring a taper, and the order of operations was important.  I'm getting a TIR of about 0.0005 on a .500 pin gauge. I think this  is okay, considering that I am using an economy collet and chuck, and I'm nowhere near the proper nut torque.   The repeatability of installation on the spindle is good - that is, I can measure TIR, take the collet off the spindle, put it back on and get very close to the same TIR.


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## wa5cab (Feb 20, 2019)

That looks quite good.  Did you cut the internal taper with the compound set around or with a taper attachment?From your third from last photo, it looks like probably the former.


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## JPMacG (Feb 20, 2019)

Thanks Robert.  I cut the taper with the compound.  To get the angle I installed a collet on a mandrel and adjusted the compound rotation to get a constant indication on a dial indicator as it traveled the length of the collet.


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## wa5cab (Feb 20, 2019)

OK.  That's what I thought that the photo showing a dial indicator and ER collet on a mandrel probably meant.


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## WesPete66 (Feb 21, 2019)

Did you purchase the collet nut? and, was it a metric thread (or are they available with inch threads)?


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## JPMacG (Feb 21, 2019)

Yes, I purchased the collet nut.  It was about $12 from Shars.  It is metric - M50-1.5mm.   

I did not see any for sale with inch threads but people do make their own.  The standard nut design has an eccentric ring and groove that helps to extract the collet from the chuck.  I think the ring and groove would be difficult to cut.  They could be left out and the collet could be knocked out through the spindle with a brass bar.  Then the nut would be straightforward.


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## wa5cab (Feb 22, 2019)

ER collets were "invented" in Europe and are a metric based system.  Although it would be possible for someone to make the compression nut with a UNF or UNEF thread, I seriously doubt that anyone ever would.


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## T Bredehoft (Feb 22, 2019)

Sixteen pitch thread, sloppy, will fit.


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## wa5cab (Feb 23, 2019)

As I seem to recall, the required pitch is M1.5.  If it is, any Atlas built 6"  with the standard set of gears that were supplied with the machines new can cut M1.5 accurate to within at least 3 decimal places.  The same is true of change gear 9", 10" or 12".  Owners of a 10" or 12" equipped with a QCGB will need to purchase a 44T and a 52T gear and follow the instructions given in a file in Downloads.


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## Ambit (Feb 23, 2019)

Wow, the way you are cross drilling using that boring bar holder is such a smart idea. Can you provide a little more information on what that setup looks like? I have never seen it before!


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## JPMacG (Feb 23, 2019)

Thanks Ambit.  I made the drill fixture following Ulma Doctor's thread here on Hobby-Machinist.  The bearings and 12L14 steel came from McMaster Carr.  McMaster also carries stubby drill bits to fit the fixture.  The fixture has come in handy on several projects.








						Shop Made Axa Toolpost Cross Drilling Fixture
					

Cross Drilling Fixture from an AXA Boring Tool Holder! i had an idea to make a cross drilling fixture for my shenwai 1236 lathes' AXA clone toolpost.     i machined the shaft from 3/8" 12L14 hex shaft and single point threaded the drill chuck end to 3/8-24 to accept an old but new Jacobs short...




					www.hobby-machinist.com


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## JPMacG (Feb 23, 2019)

wa5cab said:


> As I seem to recall, the required pitch is M1.5.  If it is, any Atlas built 6"  with the standard set of gears that were supplied with the machines new can cut M1.5 accurate to within at least 3 decimal places.  The same is true of change gear 9", 10" or 12".  Owners of a 10" or 12" equipped with a QCGB will need to purchase a 44T and a 52T gear and follow the instructions given in a file in Downloads.



To get the metric thread I followed Atlas Bulletin No. 6818, "Metric Thread Cutting Gears for Atlas Quick Change Lathes."  It is available here on Hobby-Machinist in the downloads section (thank you Robert!).   Only a 52-tooth gear was needed.  I found one at the Cabin Fever Expo last year for a few dollars.  Atlas gears also show up on Ebay.

If I understand correctly, metric gears produced on an imperial lathe are just an approximation to the metric pitch.  There will always be a small error.  But the error is so small that for practical purposes it does not matter.


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## Richard White (richardsrelics) (Mar 21, 2019)

Is there a link for this project?


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## wa5cab (Mar 21, 2019)

JPMacG said:


> ...
> If I understand correctly, metric gears produced on an imperial lathe are just an approximation to the metric pitch.  There will always be a small error.  But the error is so small that for practical purposes it does not matter.



That is correct.  So long as you use a gear setup out of any of the published lists,  The result thread would not be good enough for making a metric lead screw.  But so long as the mating metric thread is going to have no more than around 10 threads engaged and was make with normal clearances or allowances, it will fit.  For example, when making a collet chuck for ER collets to use on an Atlas lathe or mill, it is SOP to purchase the compression nut and to cut the male threads with one of the approximations.


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## JPMacG (Mar 22, 2019)

Richard White (richardsrelics) said:


> Is there a link for this project?



There are several YouTube videos that describe making ER collet chucks for Atlas lathes.  ER32 and ER40 are popular sizes.  The best drawing that I found is by Ronald Crowell.   There is a downloadable PDF on the Atlas-Craftsman section of Groups.io.   Here is the link, but you may need to register to view it:  https://groups.io/g/atlas-craftsman/topic/er_40_collet_chuck_body/28743158?p=,,,20,0,0,0::recentpostdate/sticky,,,20,2,0,28743158

I am hesitant to attach the PDF here because it is copyrighted.  Maybe Robert (our moderator) will add it to the downloads section on Hobby-Machinist.


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## AGCB97 (Mar 22, 2019)

When I made mine I bought a metric nut but cut out the threads and recut what was available on my lathe.


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## wa5cab (Mar 25, 2019)

All Atlas lathes can be set up to cut M1.5 threads.  You might need to acquire one gear that isn't in the standard set, but that is preferable to boring out the existing M1.5 threads as the nut remaining wall would be marginal.

According to information on the drawing, it carries a regular copyright, although he did not put a year in the declaration.  The copy in the A-C Groups Files area on groups.io was actually uploaded by the copyright owner, so it's safe there.  If I have what's still a good email address, I'll ask him if it is OK to put it in Downloads here.


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