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Exact gear ratio for Micro Metal Gearmotors


I’m designing a mini CNC and need to know the exact gear ratio for these Gearmotors. Do the Micro Metal Gearmotors 10:1 and 5:1 have this exact ratios or are them approximate?

I’ve taken apart a 10:1 model gearbox from the motor and taken a picture of the motor pinion and then examining the photo I counted 13 teeth, but the gearbox itself is pressure assembled and I’m afraid of spoiling it if I try to disassemble it in order to apply the same procedure for counting the number of teeth.

Does someboby know the number of teeth of the different gears/pinions in the gearboxes or the global exact ratios?

Thank you very much for your answer!




The gear ratio for our 5:1 micro metal gearmotor is exactly 5.13:1, and our 10:1 gearmotor is exactly (259/26):1.



Goes without saying, don’t forget that gears have backlash when you’re designing your system. I hope it goes well, as non stepper motor CNC systems are pretty innovative and interesting.


Are the exact ratios for the other micro metal gear motors available?



We can probably get you those numbers. Are there specific gearboxes you are interested in?

- Ben


I’m interested in the 30:1 and 298:1 motors presently, or a full chart if there is one.


Hi, Clyde.

I looked into it some more, and it turns out that the exact numbers we had corresponded to older versions of the gearboxes from a different supplier. To get those numbers for our current micro metal gearmotors, we will have to physically take each gearbox apart and count all the teeth. We’ll post back here when we have those counts.

- Ben


The exact gear ratio for the 298:1 micro metal gear motor is:

(25/12) × (34/9) × (37/10) × (35/13) × (38/10) : 1 (or approximately 297.9238:1)

and the exact gear ratio for the 30:1 micro metal gear motor is:

(31/16) × (33/14) × (35/13) × (34/14) : 1 (or approximately 29.8609:1)

- Grant


The decimal values look good. I think there might be a typo in the 298:1 fractions since they don’t equal 297.9238:1, but the 30:1 being (31/16) × (33/14) × (35/13) × (34/14) looks right.
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You are right, Clyde; sorry about that. I edited Grant’s post to fix the typos (one of the /10s should have been /13), and I think the two calculations were mislabeled.

- Ben