Cabinet knob with facets

Cabinet knob made for threaded inserts (M3-M5)

There is also a version with a slightly raised floor if you don't like flush with the cabinet.

Scale

The model can also be scaled to your desired size. The standard model is 40mm in diameter and about 33.5mm in height. To scale this it's probably best to use the model without any hole for threaded inserts, which is also provided. Then either add the hole manually in the slicer or drill it in afterwards. When you want to drill it make sure to increase the infill denisty in the middle of the model, where the hole shall go. You can also use the provided Prusa Slicer Project, where I already prepared the model with an infill enforcer in the right place (make sure to use the expert settings in Prusa Slicer for this).

Printing

The print should not pose any particular challenge. It's probably best to print this in 0.1mm layer height or even lower to get a nice and round appearence. Scaling the model influences this of course. As I said in the “Scaling” section: When you plan to drill the hole in afterwards make sure to increase the infill density in the middle to 80% or even higher, depending on wether or not you want to use threaded inserts or screw directly into the part. The latter probably requires infill densities of 90% or higher, but I haven't tried that.

With the provided .step file you can also model the hole yourself, create different versions or add stuff to it as you like.
The model is based on this toothbrush stand: https://www.printables.com/de/model/52532-toothbrush-stand-holder/comments/451646#