Looking for Geared Stepper with 7mm Shaft

I'm looking for a bipolar DC stepper with a high gear ratio box and a 7mm D-shaft on the output. Output torque requirements are around 25 N-cm. NEMA 17 format would be good. Output rotational rate would only be 2-3 RPM, hence the high gear ratio. StepperOnLine products would be great, but I've not found anything of theirs in a 7-mm shaft. Hanpose has some 7mm devices, but the highest gear ratio of theirs I can find not coming from China is 5.71:1 . Would rather have something up around 20:1 or higher.
I'm new to DC stepper motors, so I'm sure there are suppliers I'm not aware of. I've done a fair amount of searching, and haven't come across anything. Almost certainly these things exist.
Thank you,

Will the common 28BYJ-48 fit the bill? Maybe use a 'coupler' to go from 5mm slotted shaft to 7mm shaft.
Inexpensive and readily available on Amazon with and without ULN2003 driver board. I don't know what their N-cm rating is.


  • Pull in torque: 300 gf.cm

Hmm, so maybe a little low.

These geared motors will do 70 oz-in = 50 N-cm

Sorry. I'm needing a 7-mm D shaft. Thanks for the suggestion.

So get your file out and make it a "D" shaft on the exposed part.

The shaft on the suggested motor is 5 mm. As stated, I need a 7 mm shaft. Motors I've already found are much closer to what I need than the suggested motor. It's a situation which requires a 7 mm D shaft. That's what I have to couple into.

5 mm to 7 mm shaft coupler and a section of 7 mm D shaft.

My situation is not really conducive to the additional length required for such a coupler. Really, I'm an avid DIY'er with good electrical and mechanical skills. I've considered all such optional workarounds and have ruled them out. I'm looking for a DC stepper with a gearbox with a 7 mm D output shaft.

Hmm, it does seem that NEMA17 and 7mm shaft are exclusive.

Digikey doesn't show NEMA17 as being available in 7mm.

Guess you could search at Mouser also.

Yep. I'm coming to the same conclusion. Looks like I'll have to drill out what I need to fit into to fit an 8 mm shaft, which isn't hard to find.

Remember that drills ALWAYS drill holes slightly larger than the drill diameter, so work into the size you need.

I drilled it last night. Slightly smaller drill, then a rat tail file to finish it off to fit nicely. Then I drilled and tapped a hole for a 4-40 set screw that worked well. I'm satisfied.


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