Friends, Don't Print This. It's Crap - It will only serve to disappoint and anger you. Really, it doesn't work. -schlem May, 2014 This thing was made with Tinkercad. Improved Ball Bearings with 9 ball bearings 24mm OD / 6mm ID as designed. Should scale fine up or down. I think. Based on the first 8-ball Ball Bearings cartridge I designed, I packed another bearing in the races to better support the structure. Who knows how this gizmacchi will print, but the design has bearings precisely dimensioned (5mm) to fit the races. I don't know yet how round these balls will print, but they will likely need to be broken from races before they will rotate. This is not a precision bearing, this is proof of concept, but a high precision 3D printer might actually produce a usable low-speed, low-load bearing. +++ I have further improved this design by using a shape script for the spherical bearings, that creates smaller facets and then laboriously and precisely positioning the bearings in the race, so that there is absolutely minimal contact between bearings and races. +++ When you print it out, let me know how it came out - Thanks, schlemI had a couple of these printed up by Shapeways, and as a bearing, they are terrible. The precision of the printing process used is such that the bearings are fused to the inner and outer races. If you could break them free (and I haven't), they would be a lumpy, dumpy bearing that would soon self-destruct. I think a better plan of action is to print the inner and outer races, adjusting for the precision of your printer, and use off the shelf round things for bearings (BBs, pellets, airsoft, etc). Keep me posted, Thingmakers.