Want to develop an attachment for your kitchenaid, but don't want to do all the engineering to get it to spin? Download this thing and modify to your needs! The Kitchenaid attachment Profile fits Kitchenaid 5 Professional stand mixers and probably a bunch of others. It features an inner dowel with locking rings, allowing it to rotate freely inside the sleeve. The sleeve is secured in place via the kitchenaid itself, like any other attachment. Attach things that rotate to the dowel, and things that don't to the sleeve!
this model is print-in-place; the locking rings means that the dowel cannot physically be printed separately. That means that you'll probably have to print with supports. If you're worried about tolerances, you can increase them in the SCAD file; the default tolerance is 1mm between the dowel and sleeve