I'm not going to buy one soon, but if I did:
Could I put a tool holder on a rotary table and use it for turning
spheres and spherical sections? Or is your average rotary table not
designed for such abuse?
In conjunction with a lathe? Unless it's really tiny or your lathe is
bigger than most home shops have, the table height is going to be a
problem with clearing the work. The principle is correct, just the
means chosen isn't probably going to do the job. I suppose you could
set it vertically on a mill table, chuck up your work somehow in the
spindle and proceed that way. Far easier to make/buy a radius rig
There's any number of variations on the theme, it's a perennial
project in the hobbiest mags, all would be cheaper and faster than a
rotary table for ball and radius turning.
You can make spheres and spherical cavities by using a flycutter or
boring head on a mill, with the workpiece held in a chuck mounted to a
tilted rotary table.
That's how I made the little spherical lamphouses. The collimator
retaining collars pressed on to short necks left on the spheres.
This technique is documented in Guy Lautard's next Bedside Reader
(TMBR4) if he ever publishes it. Email me if you'd like a copy of my
article and promise not to distribute it further. It is copyrighted
One other trick is with a dividing head, which can be easily
adjusted to angles other than horizontal or vertical. Mount a chuck on
it, clamp the workpiece in the chuck, set it at an angle (45 degrees or
so, depending on the needed diameter of the stem from the ball), put a
boring head in the mill's spindle, with the tool bit oriented to cut on
the inside instead of the outside, and then lower the spindle until the
dividing head is cutting a circle in the angled stock. Then start
cranking the dividing head. You may need to do multiple passes,
starting with the dividing head cutting too high, and slowly working
down to the proper height. I've seen this used to make the ball handle
for a bolt-action rifle being modified to accept a 'scope.