I always wanted to turn a ball on the lathe, and the ears were a great excuse.
Turning a 'Ball' on a lathe is a bit of a process without a spherical tool base. It can be done as I have, but its alot of work. You take step cuts moving the angle and depth at each cut. Then I finished up with a cutting tool whose end I ground with the correct radius. This gives you a rough ball, you then grab your file, and file to the correct shape. This is what it looks like after filling, in person it looks better, the pics make it look very rough and its not.
and finally finish like a normal turned piece.
Quite a bit, the first ear I got right the first time (wow), that took almost 3 hours, the second ear was junk after about 1 hour. But the 3rd ear was fine.
Next will come boring them out for the cross piece and the top part. I plan on milling inserts that will hold the spinner and connect them to a 90 degree gear box, from a dental prophy head.
About $10 in Aluminum, 3 hrs each to turn. Plus about another 5 in smaller parts to finish the cross pieces. Here is a REALLY rough drawing on how I plan to assemble it.