After making this, I realized how old I am. Apparently anyone under the age of 35 has no clue what a 45 adapter is.
I was looking to make a variation on the popular tri-hand spinner that was slightly smaller and I thought the 45 adapter would work perfectly. The bearing is a standard skateboard bearing (I found Bones Reds to be the smoothest and fastest). The three machine screws around the outside are 1/4-20 x 3/8 that I tapped in, however, a simple nut and bold will work as well.
The bearing can be pressed in with an arbor press or a pair of channel-locks. I suggest printing this solid to avoid flexing or breaking when pressing in the bearing.
I tried many materials and the heavier the material, the better it spins. To date it is a tie between PLA Bronze and PLA Copper.