This is a proof of concept to print a ball tip (or ball and socket) in one piece.
The default size has clearance of 0.2 mm. It rolls very well for me. Quite a fidget thing.
I have success to print it at 50% size by my Prusa MK3.
IMPORTANT: print it upside down (ball touch the print bed), activate SUPPORT FROM PRINT BED ONLY in your slicer.
Please post your creation if you make applications with it.