Fidget knob with soft spring

Update: I added a “loose tolerance” version, if the original is too tight, which adjusts several measurements. This also changes the square hole into a rectangle, so the tabs must be aligned in step 2.

This fidget knob feels like an encoder knob, like the volume control of modern stereos, where there is no end, and soft “detents” you can feel. For me, this prints in about an hour and 10 minutes at 0.2 mm layer height.

To assemble:

1. Place the shaft of the round wheel in the hole of the housing, so that the square hole is facing the inside of the housing.
2. Align the tabs of the “wavy” inside wheel with the tabs inside the square hole.
3. Press the wavy wheel's tabs into the square hole until it clicks.
4. Place the spring in the slot in the left side of the housing, shown in the third photo.
5. Align the back so that the short tab is above the spring, and slide the 3 tabs into the housing. The back should fit all the way in and will be flush with the walls of the housing.

Friction of the layer lines keeps the back cover in place. The spring could be glued in if desired, but I don't think it is necessary.

This was mainly a project to re-learn CAD, and to get used to working with tolerances of 3D printers.

I only have one printer, so let me know if tolerances are too tight or too loose on yours. The walls can likely be tweaked in your slicer to adjust the fit, if needed. I used PLA, but it should work with any stiff filament.

I might make another version with some decorative slots, and/or reducing some friction or a tighter spring, if I find time.

Note: I printed most of the parts with concentric lines, but did print the housing with diagonal lines, since the rounded corners don't come out as well with concentric lines (at least when using Cura).