Flux-Gap-Adjustable Jog Wheel — Fidget Toy

18.12.2025: On indefinite break from Printables due to work & family - cannot provide support of any kind at the moment. My apologies & thank you for your understanding.

Introduction

This is a purely mechanical planetary-driven magnetic flux gap adjustment mechanism turned into a fidget toy. Inside the body hides a herringbone planetary gear that translates rotation of the outer adjustment ring into precise linear motion of an internal magnet plate, driven by a lead screw. Turning the ring clockwise or counter-clockwise raises or lowers that plate, smoothly changing the magnetic pull force between the magnets in the plate and a set of opposing magnets in a jog wheel that rests on a bearing.

The result is a highly satisfying, continuously tunable tactile response from the wheel: from completely free-wheeling, to a light “bump”, to a firm magnetic grip that takes quite a bit of force to overcome. Use it as a mechanical curiosity, desk fidget, or demonstration of magnetic force control. I plan to eventually slap a few hall effect sensors and a microcontroller on this thing in order to use it as an encoder wheel for my PC, but I could also imagine this mechanism being used as an adjustable magnetic brake or similar.

Is this a practical design? No, probably not. The same effect could probably be done significantly better and in a smaller package by using a small PWM-controlled electromagnet. But my design doesn't need electronics, and it was a lot of fun to build.

CAD files are available in the Files section (.step & .f3z), should you wish to remix.

BOM

• 15× 5x3mm circular magnet (I used these)

• 1  × 608ZZ ball bearing

• 1  × M3x20mm screw with a head diameter <6.5mm

• 4 × M2 screw, length between 8m and 20mm

• 1  × M3 brass threaded heat-set insert (I used these)

• 1  × CA glue

Printing notes

There's a ready-to-print .3mf for X1C users in the Files section. ~100g of filament, ~5h total print time on my X1C. If you want to set up your print manually:

• Magnet Plate & Jog Wheel:
  In your slicer, place a manual “Pause at Layer Start” on the layer where the holes for the magnets get closed. When the print pauses, insert the magnets (2x per hole for the magnet plate, 1x per hole for the wheel). Then resume. Take care to insert them with the right polarity (the magnet plate should attract the jog wheel).

• Use hole compensation if your magnets won't fit correctly. They should sit in the holes tightly, without being able to move, and flush with the surface.

• All gears should be printed with a .4mm nozzle, .16mm layer height. All other parts can be printed with a larger nozzle and with .2mm layers.

• Use standard supports (build plate only) for the ring gear.

• Supports for the top plate are a bit tricky. I highly recommend using a support filament (like this one) for the interface layer and printing with 0mm gap & tight interface spacing. The shape can theoretically be printed without supports, but I had sub-par results with that. Printing with default supports is also not ideal (rough surface → friction on the jog wheel).

• PLA is fine, PETG is probably better for the gears.

Assembly

1. Apply CA glue to the inside lip of the hole of the sun gear.

2. Insert the M3x20 screw into the sun gear like this:
   

   

    

3. While the glue sets, make sure that the screw stays straight - temporarily threading on a nut can help.

4. Place the ring gear, the planets and the sun gear onto the bottom plate.
   

   

   
   This can take some force. I started with the ring gear, then put in the planets, then forced in the sun.
   The gear assembly should stay in one piece afterwards, and should rotate freely.

5. Remove the gear assembly from the bottom plate and liberally apply a lubricant of your choice to the bottom, the inside of the holes of the planets and the gear teeth. I used silicone oil.

6. Heat-press the threaded insert into the hole of the magnet plate until it sits flush.
   

   

7. Thread the magnet plate onto the sun gear.
   

   

8. Rotate the magnet plate so all four screw holes of the bottom plate are visible.
   

   

9. Insert the four M2 screws into the bottom plate.
   

   

10. Slide on the top plate. One of the pegs has two screw holes - use that one for alignment.
    

    

11. Screw in the M2 screws. Don't overtighten them. The adjustment ring should still rotate freely.

12. Insert the 608ZZ bearing into the top plate. Might take some force.
    

    

13. Put on the jog wheel.
    

    

14. Verify that the jog wheel is running smoothly. Lubricate if required.

15. Turn the adjustment ring to both limits and verify that it's adjusting the magnet force.