Holding torque of SO Pro stepper motors

Hey folks, I am curious to know about the holding torque of SO Pro stepper motors. Can anyone please help me?

I don’t know about the motors themselves but testing on the machine as scientifically as I can, I got 19 lbs in X, 42 lbs in Y, and 52 lbs in Z.

Tests were done by jogging the machine axis so that it pulled on the most accurate fish scale I could find on Amazon (for a reasonable price) while it was anchored to the bed. This was an average of 10 pulls on each axis.


That’s consistent with the approx 18lbs force from previous measurements on the Shapeoko 3, are these the same motors?

The holding in Y is variable on the SO3 dependent upon the X position as the force distribution across the Y axes varies as you move side to side.


I believe they are the same specs as the SO3, but have longer shafts to accommodate the wider belts/pulley.

I should also note that I tested the X and Y axis on the center of travel to get what amounts to an average.

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In the center of the axis what you get is the sum of the two Y axis stepper holding torques, as you move towards the X=0 and X=MAX you tend toward one motor’s worth of holding torque.

It’s also worth noting though that the holding torque of the stepper is not really a useful number in determining cutting forces the machine can support as

  • The cutting forces are dynamic, not static and the interaction of the frequency of the cutting forces with the inertia of the machine components generally dominates
  • The holding torque is a static measurement on the stepper and generally cutting forces only exist when the stepper is moving, as the stepper speed increases the achievable torque decreases rapidly

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