Does anybody have some recommendations to make re tool geometry for
spherical turning on the lathe? I've found lots of designs for ball
turning attachments on google, but nothing so far that describes rake
and tip angles etc.

I bought an attachment, and it came with a HSS tool - very sharp,
symetrical tip, lots of back rake, lots of end clearance. It sort of
works, but the finish is pretty rough and it has a tendency to dig in a
bit, too.

Any advice appreciated.

Thanks,
Chris