I got the bright idea back when Cane Man and I were both trying to make reamers that I needed to make a radius cutter (aka ball cutter). I'm still trying to cut ogives and he's finished his point forming die. Go figure, but here's to you Cane Man.
I couldn't make any of my 3 different tool post holders work to cut an ogive so I decided to make a radius cutter. There were several issues, but one of the main ones was that the pivot point for the compound was short of the center line between the chuck and tail stock. So I made a new base and moved the pivot point closer to the rear of the lathe. Unfortunately, I forgot to figure the extra offset for the ogive. But no problem, I finally figured out I could run the spindle in reverse and put the radius cutter on the back side.
Here are some pics of the radius cutter. It didn't work well, so I decided to try a radius grinder.
Edit: Should have taken more pics but that 4" disc started as a 4X8X.75" block of aluminum. My first attempt at cutting a circle from a square. I cut 8 sides with the band saw and chucked it up in the 4 jaw and had a lot of "interupted" cuts. Also had to bore a 1" hole in the bottom plate and set that up in the 4 jaw but only had 3 jaws holding it, so I clamped it down tight and turned it at 70RPM.