Z-Axis Stepper motor torque?

[slow-poke]

Well I now have both X and Y axis steppers installed and running via Mach3. I ran my first G code program to cut an arc for a bracket for the Z axis linear scale I'm adding. Pretty cool, next logical step is to add a stepper to the Z axis. I used NEMA34, 1200 oz-in for the x and Y axis and they seem to work just fine so far.. I will likely use about a 2:1 ratio for the Z stepper. What is a suitable torque rating for the Z-axis stepper?

This thread shows the mill:
http://www.hobby-machinist.com/threads/long-chang-lc-30-cnc-conversion.60990/

Cheers

 

[shooter123456]

1200 is probably massive overkill for the X and Y. For the Z, 600 to 900 should do it.

 

[Wreck™Wreck]

What does the Z axis move? The quill, the column or a knee, most mills that move the column for the Z axis are counter weighted to overcome the weight of the combined parts being moved.

 

[slow-poke]

Just the quill

 

[Wreck™Wreck]

Just the quill

It would depend entirely on what kind of work you expect to do with it, if drilling a good deal of holes it may require more torque to push a drill at a reasonable feed rate, quite possibly more then the X and Y axes.