The spec sheet of a stepper motor will list an inductance value on them, usually in mH (milliHenry).

There’s a lot of stepper motor theory (https://www.geckodrive.com/support/step-motor-basics.html is a great read, Section 4 covers inductance) as to how inductance relates to operating voltage but it boils down to the operating voltage is setting an RPM limit of useable torque while the stepper is turning.

The lower the inductance, in general, the flatter the torque curve at low RPMs meaning you maintain more torque and don’t get power output limited.

Does this REALLY matter on the Xcarve? I think it does but the math says maybe not.

1500 mm/min (~60ipm) is an RPM of 37.5:

(40 mm/step) / (1600 steps/rev) = 0.025 rev/mm

0.025 rev/mm * 1500 mm/min = 37.5 rev/min

Looking at 2 torque curves (3.6mH inductance vs 5.4 mH inductance), realizing one is 24V and half step, the other is 1/8th microstep at 48V, looking at around 100 RPM (still over 2x higher)

3.6 mH @ 24V 1/8 microstep is about 138 oz-in (half the graph value)

5.4 mH @ 24V 1/2 microstep is about 155 oz-in

Now microstepping is at play. 1/8 microstepping has less incremental torque than 1/2 microstep so you could say the 3.6 mH value at 100RPM will be higher and probably on-par with the other motor.

Much higher RPM values makes the difference much larger.

All that being said, I did some tests awhile back (Z Axis Acceleration Tuning) and found that 2 similar motors (269 oz-in and 270 oz-in) when used on my linear Z had a 15 ipm difference in their max rate value.

What does it all mean? Essentially get what you want and is cheaper because at our speeds, it doesn’t really matter. I’m just an engineer that likes the theory and for $3 more per motor got the lower inductance one.