Made fully functional bearings made out of PLA and some 3.5mm steal BB gun balls.
I guess plastic BB gun balls will also work for this.
There is two sizes of the bearing that uses either 3.5mm or 4.3mm balls.
And for each size I have one with less tighter tolerances for really rigid PLA and one with tight tolerances for more elastic PLA.
This is due to when squeezing in the balls the more rigid PLA could crack.
Check out how well they spinn: https://youtu.be/64NqtiytOHI
Print without supports, 0.1mm layer height and random Z seam for optimal results.
(I used both generic PLA for the rigid version and eSun PLA+ for the elastic version).
Recommended items needed:
11x steal BB gun balls
1x small polygrip or similar
(Optional) tiny amount of grease
Tip if you want updates or modifications