small vs large stepper motor

[lagfish]

Given these two motors, when wired bipolar parallel:
http://www.kelinginc.net/KL23H286-20-08B.pdf
425 oz-in
2.8A
4.17V

http://www.kelinginc.net/KL23H276-30-8B.pdf
282 oz-in
4.2A
1.9V

Does that mean to get the rated torque out of the 282 motor, I would need a driver with a higher current rating than to get the rated torque out of the 425 motor? But to get higher rapids on the 425, I would need a driver with a greater voltage rating?

I think the 282 motor is enough for my application, but I don't want to use it if it would require a bigger driver than the 425.

[ger21]

Yes, you're correct. Holding torque is proportional to current, so you'd need a 4.2amp drive to get full holding torque from the 282oz motor, but only 2.5amps for the 425. Supplying higher voltages keeps the torque from dropping off quickly at higher speeds.

[lagfish]

Then why do some people choose the smaller motor for small milling machines, given that you need a more powerful (expensive) driver to run it, and very fast rapids are not needed in small mills?

[CountZero]

Perhaps they run it Bipolar series instead, and fast rapids are nice even on a small mill.

[Pres]

Has anybody tried/used two smaller steppers per axis?

The thought being it could give more power at higher speed (minimizing the inductance compared to one larger rotor) but still provide similar low speed torque to that of a bigger motor.

Just wondered if this is feasible.
Pres