Newbie- More help concerning a stepper

[CaptKidd]

Looks like I'm going to start redesigning my PCB mill. I've acquired a really neat piece of what appears to be an old lathe. I'm guessing it was used in the newspaper industry back when we used letter press instead of offset presses. Probably used to true up press plates or something like that.

Anyway, it's almost a complete gantry. It has a 20 pitch lead screw, probably 5/8 inch diameter, and it really is well built - all steel. Real smooth bearings at each end, so it turns very easily.

Now to the question. It had a chisel mounted on it that would move back and forth across the "gantry" while the object being lathed rotated below it. It was moved by turning the lead screw by hand using a hand wheel on the end of the lead screw. The wheel is about 3 to 3.5 inches. Obviously, this gives it a little more "arm" than just using the lead screw to turn it and contributes to the ease of turning the lead screw. I don't plan on using the hand wheel, but figured it might help in determining what torque I need in a stepper.

Any one have an idea how I might best do this?

Thank for any ideas.