Motor for coffee grinder

Hi there, this is my first time posting on here and I have (nearly) zero knowledge about motors, but I’m looking for some guidance on a project I’ve started.

I’m trying to convert my current manual coffee burr grinder into an electric/automatic grinder. I recently bought a small electric motor on Amazon (37mm, 6mm shaft, 12V, 60 rpm, 0.02 A no load, using 12V 2A power supply, and a 6mm to 6mm coupler) without much knowledge for the amount of power I would need. This motor actually almost grinds the beans, it just gets stuck too easily. So as to my next solution, I’m currently looking at Pololu’s 37D Metal Gearmotors. They seem to offer much higher torque, amperage, wattage, etc; all the fancy specs that look good. I need something that will grind the beans fairly slow, so maybe the 100:1, 131:1, or 150:1 gear ratio model.

Does anyone have any insight as to whether or not this should work? What are some things I should look out for? Also, if this is a dumb idea, please let me know why. Thanks!

Start by measuring the desired crank RPM and the torque that will be required (and order a motor/gearbox combination that can safely provide at least twice that torque).

You can measure the torque required to operate the grinder using a luggage scale attached to the handle. Here is a handy tutorial on force and torque:


It would be a good start to get a better estimate for how much speed and torque you need from your motor, and you could do so by following the procedures Jim suggested. Then, you can compare them to the specs for our 37D gearmotors in our datasheet for them to see if one might work for your system.

By the way, remember that for our high-ratio versions, the constraining factor will be the instantaneous torques that the gearbox can handle, which is about 10kg•cm.

- Patrick

You can take a look at this AC universal coffee grinder motor:Coffee Grinder AC Universal Motor