A delightfully over-engineered, click-clack alternative to a classic D20.
All parts print as separate pieces—no supports, no glue—and can be taken apart later so you can rescue the bearing and magnets. I used generic PLA with a layer height of 0.16mm and a 0.4mm nozzle, Standard stuff.

Required Hardware

Assembly

1. Load the disk
   • Press the 608 bearing into the center of Disk-Body.
   • Drop 20 magnets into the numbered pockets, all poles facing the same way (left/right).
     Tip: a big helper magnet under the body keeps cubes from hopping out.
2. Seal the disk
   • Align Disk-Cover with the body and twist clockwise—bayonet mount—until it locks, might not click.
3. (Optional) Paint
   • Fill the numbers with acrylic paint (glow-in-the-dark looks amazing). Wipe excess before it dries.
4. Build the platform
   • Slide the two Platform-Walls onto Platform-Base.
   • Snap the Platform-Snaps into the grooves on the inside of the walls (rounded side up).
   • Press a magnet into each Magnet-Cap and screw them into the wall recesses on the outside.
5. Mount the disk
   • Drop the finished disk between the walls so its magnets attract to the wall magnets.
   • Slide the Bolt-Screw through the axle, tighten with Bolt-Cap.

Disassembly: reverse the steps—pop the snaps out first so the walls slide off the base.