My kid loves things that spin and refrigerator magnets. So when I saw her play with the gear magnet toys at the museum I knew we had to have some.
It is simply a set of customizable gears that you can press a 608 bearing and magnet into. The magnet was selected because it is the perfect size to press into the bearing, though I do recommend using a dab of glue to keep it permanent because tolerances can make some looser than others.
The gears also have 4 optional locating pins that allow you to stack them to make a gear train! (FYI Doing this makes them hurt to step on!)
Get your bearings here: http://amzn.to/2ziLeex
Get your magnets here: http://amzn.to/2yJhsTn
Also note that I lowered the pressure angle in the model from what I used to help reduce the gear separation forces. My gears range from 15 to 25 teeth but the magnets are strong enough that you could do more.
Printed in ABS and PLA successfully. I liked ABS better because I didn't end up with lots of sharp edges this being a kids toy and all. I made one using flexible filament and it was a total failure and I don't recommend it.
3 perimeters all sides minimum. Supports are recommended for the section where the bearing presses in.