The 3C collet has a length of 2 11/16 it has a body diameter of 11/32 and a thread of 0.645-26 RH
See: http://www.shopswarf.orcon.net.nz/collet.html

Jim Benjamin.
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3AT collets:
The 3AT collet was used on the Atlas and I think the Logan lathes. Those lathes had
Morse #3 internal spindle tapers like the South Bend 9 inch lathes so they will fit but
are not original to the South Bend.
Webb Wyman
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