Help with modifying worm gear please

Hello, i’m not familiar with CAD in which was worm gear created. I have NEMA 17 motors with round shaft. Can anyone modify worm gear for round shaft and move screw to the center and insert M3 nut to the plastic. Same way how it is done for example in 3D printer extruder gear.

Thank you very much for help.

Ondra OK1CDJ

That’s one way to the solution, but the flat is important to have. If it were me, I’d try hand filing a flat spot on the shaft first though. You could use vise-grips to LIGHTLY clamp the end of the axle and then file the flat. Then once your flat exists between the pliers and the motor, reposition the pliers and file the end flat too. Or you might try powering the stepper so it holds the shaft steady and then filing the flat. In both cases, just make sure you are positioned so that the metal shavings are falling away from the motor and not down onto the motor.


I’m in the same situation you are in that I don’t have a flat on my motor axles, but to echo @dosman I feel the flat is necessary to provide enough torque so I plan on filing mine down.

That said, I woke up way too early this morning and wanted something to do before work so in an exercise of learning freecad I modified the worm gear to take the notch out. I have not tested this print so it may not work.

(source at modified from )


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I just put a flat on each of my motor axis, quite easily with a dremel and a stone grinding bit. I’d recommend going this route if you have a tool to do it with. Didn’t need to use a vise grip, the axis stayed in place and the dremel did not put too much force on it.

good luck!

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