With a 5mm pitch you'll want to operate in a higher RPM range than what is typical of a lot of "high holding torque" cheap chinese stepper motors. Holding torque is a bad metric to size a motor, the motor should be sized to the dynamic application. If the holding torque is insufficient, then you can look at a brake or some other means to stop movement when it is static.
I am not sure this is correct, but I believe this is the same stepper motor you referenced:
http://www.wantmotor.com/WebEditor/U...2594119192.gif
torque falls off fast - now thats at 30V, it should do better at 48V.
Now if your machine was going to do 200in/min rapid cuts - this would put you at the 1000RPM range (1016 to be exact) with a 5mm ball screw.
check out these offerings at automation direct (I don't work for them, I swear).
http://www.automationdirect.com/stat...stepmotors.pdf
At 1000RPM, and 32V, the STP-MTRH-23079, STP-MTRH-34066 and STP-MTRH-34097 are all nearly equal at 100oz-in. The other motor isn't even rated that high.
At 100in/min we're at 508RPM and 32V:
STP-MTRH-23079 = ~162oz-in
STP-MTRH-34066 = ~210oz-in
STP-MTRH-34097 = ~250oz-in
57BYGH115-003 = ~57oz-in
50in/min, 254RPM 32V
STP-MTRH-23079 = ~178oz-in
STP-MTRH-34066 = ~280oz-in
STP-MTRH-34097 = ~400oz-in
57BYGH115-003 = ~177oz-in
It all depends on what RPM you need your torque. I gave you solutions that were a lot more expensive than what you were originally looking at. Sizing should be done off your use cases; what torque will you need at what RPM then size ~30-50% larger for margin.
I've said this in other threads, the increase in stack # of the motor increases the inductance, it's a physical phenomenon as you will end up with more metal mass causing that inductance. This equates to greater low RPM torque and a decrease in high RPM torque. I equate it to a diesel motor vs. a gasoline engine motor with similar horsepower ratings - one will have that torque and hp at a lower rpm, the other at a higher rpm. The power band is what we're interested in for usability.
This spiraled out of control quick, didn't it?
Your 15mm linear guides and screws should be adequate for what you want to do. With the linear guides you will want to mount it to a stout surface - their rigidity is largely dependent on the mounting surface.