You are right about the piece of HSS, it is too thick to go in the tool holder, maybe only by a mm or 2, but that would mean a time on the surface grinder. It might be easier to get a smaller piece (1/2 x 3/4) or nearest metric equivalent.

I have an initial batch of 10 to make, and probably another 10 after that. I would like to get them all the same, so I thought a profile tool would be the easiest. The grinding facility I have is a wet linisher with 100mm x 3 metre belts. That is at a friends workshop, and he is retiring this year, so he isn't worried about the belts.

I have been meaning to make a ball turner for a couple of years now, I have the stock to do it, but not the impetus.