I've got everything done on my ball-turner except for the business end--the holder and bit.
I was thinking of using some drill-rod, old drill-bits, or some round tool-steel for the bits. Struggled with how to hold various sizes yet adjust for center-height w/o making a bunch of holders. Thought I'd drill an angled hole through the holder and clamp the bits with some grub or SHC screws. The angle would allow the height to be adjusted. Sharpening would be as simple as grinding a single angle on the end of the bit--kind of like a tangetial tool.
COC attached. What ye think?