3D Printed 16:1 Nema 17 Gearbox

I designed this gearbox to fit onto a nema 17 stepper motor, whilst also being able to be mounted where a regular nema 17 can be mounted.

This allows you to increase the torque in many applications without redesigning the machine you will be using this on.

It has 3 pairs of 12 tooth gears turning 30 tooth gears, so that gives 3 reductions of 0.4. This results in the gearbox having a ratio of 15.625:1. Meaning that every 15.625 revolutions of the motor, the gearbox shaft will rotate once.


You will need:

  • 3D printed parts - Download STL files here
  • Nema 17 Stepper Motor
  • 2x MR105-ZZ bearings (5x10x4mm)
  • 7x M3 Nut
  • 2x 6mm M3 Screw
  • 2x 10mm M3 Screw
  • 2x 25mm M3 Screw
  • M3 Grub Screw
  • 50mm or longer M5 Bolt with Hex Head
  • 2x M5 Hex Nut
  • CA/Super Glue

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Step 1: DIY 3D Printed 16:1 Nema 17 Gearbox

Clean up 3D printed parts if you used supports or rims. You may need to drill out the holes of the gears depending on your 3D printer setup.

Push one bearing into the back of the housing as shown. Insert the M5 bolt through it.

Push the back of the bolt until it and the bearing are all the way in. The back of the screw should not protrude the frame.

Step 2:

Insert a hex nut into the pinion as shown then screw in the grub screw halfway so that it is captured.

Slide the pinion all the way down the shaft of the stepper motor, then tighten down the grub screw.

Make sure the grub screw is aligned with the flat on the motor shaft if yours has one.

Step 3:

Screw the stepper motor to the housing, only use the 6mm screws in the holes shown for now. We’ll be securing the entire contraption together with the other two holes.

Take one of the intermediate spur gears and push it down the M5 bolt. It needs to spin freely without the bolt moving. It should engage with the pinion.

Do the same with the second intermediate spur gear, this time pushing it onto the motor shaft. It should engage with the previous spur gear. Don’t try spinning the gears now, because of the gearing ratio it will be very hard.

Step 4:

Push an m5 nut into the output pinion gear.

Screw the gear and nut down the bolt until it is in place and engaging with the previous spur gear. Once in place, use a tiny drop of superglue to secure it to the bolt shaft.

Step 5:

Insert hex nuts into the 6 slots on the top housing.

Push the second ball bearing into the top housing.

Step 6:

Slide the top housing onto the gearbox, aligning the shaft of the bolt with the bearing and the motor shaft with the hole.

Screw down one side of the housing using the 10mm M3 screws. Do the other side with the 25mm M3 screws. Screw down the last M5 nut onto the bolt shaft.

Step 7: All Done!

All done! Well done building your gearbox, or reading to the end if you're just browsing. Check out the video at the top of the page for footage of the gearbox running, as well as video instructions.

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    7 Discussions


    8 days ago

    Great guide, definitely going to make one for myself.
    One question though, would it not be a good idea to grease all those gears before sealing up the gearbox?

    2 replies

    Reply 7 days ago

    Thank you! Perhaps, I've never tried that, not sure how the grease would interact with the plastic. I made this for an application where it isn't powered up very often, but in a higher usage situation it might help. Try it out and tell me how you go!


    Reply 20 hours ago

    I would think that white lithium grease would be an ideal lubricant in this situation, as it's non-corrosive and non-reactive with plastics of several kinds.


    Question 9 days ago

    I imagine some materials are better for gears (wearwise). Which material did you use for this?

    2 answers

    Answer 7 days ago

    Definitely, even ABS would be good I think. I used PLA as this print was for a project that doesn't get much use. Worked great!


    Answer 8 days ago

    I have some Ninjatek Armadillo filament that I'm looking forward to using for this project.
    It'll be perfect for these gears, it has great abrasion resistance.