Yet another ER40 collet chuck for an Atlas

[JPMacG]

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

 

[JPMacG]

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.

 

[Richard White (richardsrelics)]

Is there a link for this project?

 

[wa5cab]

...
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.

 

[JPMacG]

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.

 

[AGCB97]

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

 

[wa5cab]

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.