bb99,
Here's where you start. By the way, I think you are smart to ask that question first rather than getting a couple of motors first, then asking "How can I make them do what I need?'
First, how fast do you want it to go? Second, how many lbs of "push" do you need at that speed? Most people have a good grip on the speed but freeze on the "lbs" part.
If you are a machinist, you probably are familiar with manual machines. Ask yourself how many lbs of force you would apply to the manual crank before you figured you were doing something very wrong.
Example: Say your crank diameter is 4", your leadscrew pitch is 5 TPI and you say "10 lbs is plenty". The lbs of push would be:
Lbs = pi/8 times TPI times in-oz
Rearrainge it to sovle for in-oz of torque.
Leaving that aside, figure how fast you want to (IPM), multiply it by the Lbs af force you want and divide the result by 531. The answer will be in Watts mechanical to do what you need.
If the answer is 100W or less, think steppers. If it's 200W or more, think servos. If it's in between, either will do.
Mariss