The last comment in your first post implies the plan might be to try and use the stepper motor as a means to measure torque?

Stepper motors that I can easily test (i.e. they're not attached to a machine) are:
3.0Nm Nema 24, 4.2A/phase (parallel), one from Zapp
1.0Nm Nema 23, 1.4A/phase (parallel), Astrosyn MY103H702.. Quite high (10mH) phase inductance which might actually be useful here.
12.2Nm Nema 34, 6.2A/phase, SY85STH156-6204B

Plan:
- Hold stepper motor shaft in lathe chuck, clamp motor to saddle.
- Lathe induction motor controlled via VFD/gearbox, so can easily set various speeds.
- Got an upto 50V, 20A lab PSU which is plenty...
- Can get (more) exact motor speed from oscilloscope.

Which motor (or motors) would you prefer me to test?
Do you just want the open circuit voltage waveform of the non-powered coil, or the voltage under load (i.e. with a resistor attached)?