NEMA17 motor to Acme lead screw shaft coupling

I needed a shaft coupling for my 5mm NEMA17 stepper to Acme 3/8" lead screw, and I also needed it to be svelte enough to fit within the motor's standard color width. This is what I came up with.

There are two tightening screws on the collar - M3 x 10mm is a good choice here, and I recommend washers to give better compression. There is also a captive nut and hole for a M3 x 8mm (or 10mm) screw against the stepper's shaft to prevent backlash. Tighten the two side screws first, otherwise the shaft screw will push the coupling off center.

There are two versions of the STL, the original (3/8" lead screw) version shown in the photo, and a 1/4" version as well.