What is the M12 part? The drawbar thread?
If so, I'm interested. I'd add a tang instead and use it in my lathe tailstock.
But I'll definitely stand aside if anyone else needs it for their MT3 spindle mill where it will be much more valuable.
For a Morse taper, one does not need a tang. You can just thread in a pin (still need something to provide the knock out). I like having the tang, gives one a feel good that it will drive - however it is not required. I have three lathes - the larger one (15") does not have the tang driving slot - just a smooth tapered/round bore all the way out the back. The knock out is simply the tailstock lead screw. My biggest drill is 1-1/32 and it works fine in the tailstock (I am very fussy about ensuring it is kept clean). A few years ago I set up to drill from the tool post, and that is my preference for drills over about 3/4" - but the first 35 years of owning the lathe I drilled from the tailstock.
Now after that bit of beaking, as a complete hypocrit. I added a tang to a ER32/MT3 collet chuck - there is a socket head cap screw up from the inside that just concealed by the tang. My intent was mainly to use it in the radial arm drill with S&D/Prentice drills, to keep the set up short. Of course it would work fine in the lathe TS. It was a fun little project on the roundtuit list (completed a couple years ago). I have used it exactly zero times, but that has never held me back (if I need it, I've got it).
