On Thu, 5 Apr 2012 12:52:28 -0400, "Jim Wilkins"
wrote:


"Stanley Schaefer" wrote
Classic method(besides Ed's), is to use a collet with a stop in the
lathe and a pivoting tool rest. This last can be just a bar with a
pivot held by some means on the compound rest up to an elaborate gear
driven C-shaped holder in a half-gimble.
Stan

I chucked the top half of the compound in the 3-jaw and marked the
center of rotation, which for my lathe is on the top slide close to
the tee slot with the compound fully back. I can turn a small convex
radius by swiveling the compound, with a bit in a lantern holder.

jsw

Why not just rotate the non locked compound as your ball turning
apparatus? Use a collet in the spidle, use the tool mounted to the
compond to stop the rod, clamp the collet and rotate the compound rest
90 degrees clockwise to generate the hemispherical surface (you need
to set the tool bit back of the center of rotation of the compound by
the rdius of the rod and exactly on center height).Clear as mud?