Knobs, based on: M3, M4, M5, M6, M8, M10 normal nuts and lock-nuts (they are a bit higher).
After trying them I decided to make two versions of them: a loose fit (the nut can be pressed by hand in the knob) and a tight fit (the nut has to be pressed or hammered in the knob).
The M4 knob is made for the CraftBot buildplate.
I have printed them with Kisslicer, 0.3mm layer height, 5 loops, 2mm skin thickness, 33% infill.
They are designed to be printed without support structure.
The knobs have little "snappers" at the bottom, to prevent the nuts to fall out , after hammering / drive them in the knob.
Scale / adjust the inset parameter of Kisslicer to fit your specific printer needs.