I don't know if I'm using the correct terminology for this part or what machines it will fit.  It came with a bunch of other parts that were for a South Bend Heavy 10. The shank measures 3/4" diameter and it is threaded  at the end on both the inside and outside. I do not know if it is a press fir or threaded fit into the holder. The die holding end is designed for dies that are 2-3/4" outer diameter. A set screw on the side secures the die. FEEL FREE TO ASK QUESTIONS AND I WILL DO MY BEST  TO ANSWER. This will need some clean-up work before use. There are various nicks, scratches, and other wear to these collets from age and usage. Please look at the pictures closely as they will show the condition better than I can describe.