On Jan 1, 12:30*pm, nytrillium wrote:

In all reality, this is not necessary if you are just making a collet
closer. *You can just figure out the root dimension of the 1.238-20
thread (1.19469 *check my math.... ) *"and then cut your ID about .010-.
015 larger"

Scratch that I was thinking pitch diameter not OD..... My brain isnt
functioning today but if you can follow the diagram (make sure you
look at the internal thread diagram, it's the third one) you can
figure out the PD and all the other dimensions you need to know.

-B