I needed some gears, https://youtu.be/Rld1ZAs6YxA shows them running. Seem to fit reasonably well. Included the OpenScad file with settings from GregFrost's thing.
Printed at .2mm layer height, 10% infill (final one I'll do thicker). One axis is designed for a 30mm hex shaft. The other is a 6mm shaft from something like a 37D motor.
The motor gear has a 3mm set screw hole that would need tapped to use.
There are two different sets: 13:43 and 15:37, I'm not sure what gear ratio I'll need for BB-8 :)
The shaft of the little gear printed a tad too small, but I expect you guys to adjust the fittings to fit your project.
These are intended for my Lego BB-8 flywheel drive, we'll see how that goes.
I printed with rafts 'cause I'm having some trouble with warping. I used 4 shells to try to have strong teeth. Which makes infill pretty pointless, though the middle of the big gear has some, won't cost much more to have higher infill if you use 4 shells.
1st attempt used a more normal 2 shells, which seemed fine. Probably depends on your application.