The first thing I noticed about my new MakerFarm prusa i3 was that the NEMA 17 extruder stepper motor was getting very hot. So I ordered a 40mm x 40mm heatsink and 40mm x 40mm x 10mm 12V fan from Amazon.com. When I attempted to install the heatsink and fan I realized I needed much longer machine screws. They needed to be 25mm longer then the stock NEMA 17 screw. So I started looking for m3 75mm screws. McMaster Carr only went up to 60mm, Fastenal did not carry them either. The only place I could find the proper length screw was a German R/C car site that looked a little out dated. I could not believe the screws were so hard to find. One day I was telling my father this dilemma and said “why don’t you just make them from threaded rod?”. Damn good idea Dad!
I ordered a m3 threaded rod from McMaster Carr. Threaded on some nuts then cut it into 72mm lengths.
Then I threaded 2 of the rods into the extruder stepper motor. A nut was used to tighten up against the motor.
Now with the studs extended I put on some heatsink compound then slid on the heatsink and fan a washer and lock nut.
You may notice I went heatsink crazy and added some passive heatsinks to the three exposed sides of the stepper. All I can say is that my extruder stepper runs nice and cool now.