Leadscrew or Acme for Al. Router

[js530]

I am building an aluminum framed CNC router, mainly for injection molds, PCB's, and some MDF stuff, but I have yet to decide on leadscrew or acme threaded rod. I have two 12" lengths of lead screw (salvaged from some semi conducter equipment) with antibacklash nuts, but I'm afraid they will be too short. 8-10" of travel is too small. 20" of X travel with 12" of Y and Z travel is fine. Will 1/2" 10 tpi acme threaded rod be stiff enough for milling aluminum? I have three identical steppers, 24 volts at .1 amps 1.8 degrees/step, but I also have two larger (nearly twice as big) steppers with unknown ratings. I only have two, and getting a third would be nearly impossible. Should I use the three identical steppers or use the two big ones for XY and a smaller for Z?

[joecnc2006]

I think the 0.1a will not move anything, what did it come from?

you usually want a stepper motor with low volts and high amps. maybe i'm mistaken?? Anyone?

[js530]

It was new old stock, some IBM part.

[DieGuy]

Yep low volts and high amps and then drive them at 10-20 the voltage rating if the windings are rated that high.

A better questions to ask, if you are milling aluminum for molds are:
1) what kind of tolerances need to be maintained?
2) what are you going to use for a cutting spindle? And what kind of runout does it have under load?
3) how much torque does it take to move the Amce screw with no load and the lash tightened up?