Question,
We have 10HP HSD spindle, BT30, 10 position ATC. ER-32 collets. I regularly come across great deals on BT30 ER32 collet holders that are too hard to pass up. That said, Ive gotten three now that have a bit different geometry than those that we run in the ATC.

Two different purchases, one for a couple of ER32 collet holders and one for a nice albrecht style chuck, have a slightly different dimensions in the recess that register with the forks on the ATC (the three are smaller in diameter so they flop around in the fork = useless for the ATC). Also, while they are all M12 for the pull stud, the three have a slightly smaller counterbore at the tip of the taper (our ATC holders measure 13mm on the counter bore and the three measure 12.5)

Lastly, the BT30 holders you commonly see out there have the recess for the tool fork machined offset (closer to the collet nut) whereas ours are centered?

Anyone know the callouts or designations for these dimensions? I will continue to pick up these bargain holders for manual changes but would love to be able to keep an eye out for those that would work in the ATC as well.

The one on the left in the image is what we run in the ATC, the one on the right seems to be the standard style you find.

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