Strong manual knob for Mk8 extruder (Ender3 etc)

You will need an old extruder gear with a clamping screw. (A worn out one is fine, a new one would work too.) As long as the bore is 5mm and the diameter is 11mm.

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Note: This will only work if your NEMA 17 extruder motor has a “D” shaped shaft that is longer than it needs to be. Many new machines are cheaping out and using a shorter round shaft with a heat pressed gear. On these new cheap motors the gear will wear out long before the motor, so you may as well get one of the old style ones with a replaceable gear.

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You may need some heat to press the gear into the knob, but this will help the teeth cut grooves making it stronger.

This was designed for my Ender 3, but should work on most machines with a Mk8 extruder and NEMA 17 stepper motors.  Your mileage may vary.