Gearhead landed today, looks great and the parts fit perfectly. Can’t wait to try it out.
It looks nice, but that supposed to get a grip by crushing the filament? It looks like the QU-BD drive pulley all over again.
It’s printing here at our shop beautifully. A bunch of people bought them, so we should hear feedback soon.
Interested to try these! What torque do thee require? I have a Mk8 direct drive gear which works fine with my non-geared stepper, but these look like they have a larger radius. I take it they fit a standard 5mm shaft?
I got mine too. Did you have any resistance sliding the bearings onto the motor shaft?
Yeah, I ordered because I wanted to see if a spring-loaded version would work (since backlash in the gears only becomes an issue when slipping actually starts to happen), but I don’t think these will grip in a spring-loaded configuration without proper teeth.
We have discussed rubber “spring” …, something with a little bit of give.
Teeth that bite ARE proper teeth 
Good luck! Mod to your heart’s content.
Peace
Brook
Can you show us what the bite marks look like? i.e. run a short bit of filament through and photograph the filament?
Diameter where it makes contact is about 8.5mm. They fit well on the few motors I tried them on (5mm shaft). I’ll try to take some pictures of the bite when I get a chance. It makes 4 dimpled tracks, spaced around the circumference of the filament.
Added a picture of the filament bite marks to the album, a mix of ABS, PLA, PET and Nylon. The was run through twice (forward and back) at 3000mm/min. I didn’t use the Printrbot printed parts so the marks will probably be slightly different with the spacing they chose for the gears.
I had a spare kysan 1124090 nema 17 that I’m dry fitting the extruder on, it takes a healthy push to get the bearings to slide onto the motor shaft.
What did you run it on?
I’m using a RigidBot with an E3Dv6. Still getting things dialed in, but it’s working really well so far.