How to measure torque of a stepper motor

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How to measure torque of a stepper motor

Postby om_tech_support_JT » Wed Jun 19, 2013 5:41 pm

Q: I'm trying to retrofit an old CNC machine with new motors, drives, and controls. I would like to replace my existing step motors. However, the labels have been worn off and I cannot see the part numbers. Since I cannot find specifications without a part number, I do not know what much torque my motor has. It's making my job difficult. Is there an easy way to determine torque output of a step motor? I would appreciate any help.

A: Yes. There is an easy way to measure torque of a step motor. Torque is how the turning force of a motor is defined, and it's basically force at a distance from the rotational axis. Therefore, you can hang a weight at a distance to estimate your torque. Other methods are also possible - such as using a torque wrench.

For example, if you can mount a 1" long arm on the motor shaft, then mount a 1lb load on the end of the arm (1" away from the motor shaft), and the motor shaft does not deviate from its position, then it means that the motor is producing atleast 1 lb-in of torque. In this example, we are ignoring the torque used up to rotate the arm.

Below is a link that contains good information on exactly how to do it: ... que-rb.htm

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