Greolt,

I am sorry if I confused you. The threads per inch were part of the calculations for the linear motion.

Now as for the rotary axis. I have a little 3 jaw chuck. that is driven by a pulley on the back side. The pulley is driven by the stepper motor that has a smaller pulley attached to its' shaft. They are connected by a timing belt. The large pulley has a 72 stamped on it, so I am assuming it is a 72:1 ratio. The stepper motor has to turn more revolutions to make the chuck turn 1 revolution. This is where I am having the issue determining what the step number is. I hope this makes this more clear for you.

I guess, like you say, I will have to play around with the numbers and measure the angle of rotation until I come up with what the stepper needs to turn. Thanks for all your help.

Martyondrums