I have a stepper motor (this one). Its shaft is of type "oval" or whatever, so like a circle but with 2 flat sides.

Imagine the motor shaft pointing straight up, in the z-axis. I want a 6-inch rod, or shaft, (honestly doesn't really matter, I just want a rigid metal stick of some sort) to stick out from it. I.e. So that when the motor spins, this rod/shaft is creating a circle in the x-y plane.

I've gathered that what I want is a "coupler", possibly a "flexible coupler" which connects shafts which are NOT parallel.

1) Is there a standard term, or language, for describing my motor's shaft, as well as the coupler which would connect my shaft to a metal rod?

2) Am I even choosing the right things for this task of spinning a rod perpendicular to the shaft's axis?


2 Answers 2


yes, it is called a flexible coupling or flex coupling. they come in a wide variety of designs and sizes. Any engineering supply house (for instance, McMaster-Carr) offers these for sale off-the-shelf.

Your step motor shaft is described as a round shaft with two setscrew flats. the couplings you are interested in are affixed to shafts using setscrews and if the shaft flats are symmetrically opposite one another, you want to specify "2 setscrews at 180 degrees".

Note that some types of flex couplings accomodate radial and/or axial misalignment via springy or rubbery components. these perform poorly when driven by stepper motors because they introduce torsional compliance, which can then resonate off the rotary inertia of your actuator arm and then oscillate uncontrollably when driven by step impulses.

  • $\begingroup$ What about to get a rod to be 90 degrees from the motor shaft? I can find flexible couplings for up to 15 degrees, but I want like a 90 degree elbow joint. $\endgroup$
    – tscizzle
    Commented Jun 24, 2018 at 0:41
  • $\begingroup$ best to do that with a right angle drive. you'll find such offered at the same places. $\endgroup$ Commented Jun 24, 2018 at 2:53

You can get your perpendicular, rotary motion from a miter gear or worm gear drive. Generally, miter for 1:1 ratio, worm for a reduction or heavy load. If your going for an "elbow" go miter, for a "T" or "cross" go worm.


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