I would like to introduce you to a wonderful site of utilities for the shop:
http://www.myvirtualnetwork.com/mklotz/#shop
Many, many programs that calculate whatever you need to do in the shop. Your answer should be found with the FITS program.
Go up one level and you will find a bunch of math programs as well.
I have also noticed that the KOP CAD models from PTC have incorrect diameters on the motor shafts.