ER32 Chuck for Unimat M12x1

[carl blum]

Hi Gang:
I found a deal on a set of ER32 collets so I started finding chucks for all my machines. MT4 for my Smithy Granite Lathe was easy as well as a R8 for the mill. Then I found 5-C chuck for the indexer. I even found square and hex holders for grinding. But no one had a M12x1 for the Unimat. I held the other chucks up to the Unimat and it could be a good fit.
I don't like to chase single point threads on the lathe so I try to use "found" threads and stick to tapping holes. The easy way to find the threaded stock and a ER32 nut was to buy a CAT40 - ER32 tool holder on Ebay:

The next step was to remove the CAT40 end. Since it is hardened tool steel, the band saw was not going to work. I used an air driven disk cut-off tool in the tool holder ground the holder in two while I spun it in the lathe. It took a while and made a lot of gritty dust, so clean up the ways after if you do this. I made a bushing to weld into the ER32 chuck so I could bore and tap it for the Unimat.

I put a 3/4" rod in my big lathe and turned a true surface on it. Then I clamped the ER32 chuck on this true surface so when I bored the hole it would run true. I've made all my drill chuck this way for my Unimat with no problems. Once I had it mounted on my Unimat I checked the runout at the collet taper.

It had a bit so I used a lapping stone to correct the runout to less than 0.001"

I'm happy with the result and it has the range to clamp wooden dowels with out jaw marks a three jaw chuck would leave.
Hope this help you with your future projects. Carl.

PS: I have more photos, but I can't get some to load??

[old_toolmaker]

Carl,
Did you measure the T.I.R. of your finished adapter?