Re: for the inventors ?
Of course it has been done, and it is amazingly simple, although describing it here may not be so readily
First, imagine a clamshell, its two halves completely open, such that it sits flat on a stone surface. Now
modify your thought of this such that you have instead two strips of spring steel, each bent to form half a
circle, with a rod forming the clamsheel hinge and holding the ends of the two pieces of steel. You
can think of this rod and steel strips as a clam shell, with them starting flat open on the stone surface,
and visualize them chomping down through the stone like a clamshell on something soft. Of course you
can't just do that with stone, it takes diamonds and time. You braze two diamond segments onto the
steel, one at 12 o'clock and the other at 6 o'clock, kind of like diamond buck teeth to the clamshell. Then
you spin the whole thing around in a circle, so the diamond buck teeth trace a circle, lubricated by a water
drip. The spring steel is rigged such that as the buck teeth wear down into their circular path the clam shell
closes. Eventually the teeth meet and out pops the result. In theory you could get results
approximating a half globe, although in reality it tends to be more flattened.
I have not made such a device, because I have not needed it, but I have seen one used.