The post of my sphere became a great discussion about various methods. But I remain unclear on one point. So I wanted to ask this specifically (lifted from my response to Dale's last comment):
"OK. I'm gonna show how dense I can be. I totally get the donut chuck thing and the cutting a groove thing and even the turning between several centers thing. But the hollowing "between cups" bit is not sinking in. It seems to me that to mount the sphere between cups, one cup has got to be right where you are going to want to stick your tool, so to speak. So what am I missing?"