I made my ring clamp from a 1X2 inch piece of wood. Tapered it on
the bandsaw then cut a wide groove through the middle. The
rectangle shape seems to prevent the ring from slipping better than
a tapered dowel. When the surface gets worn I just cut it again. I
use vice grips with the jaws padded with leather or rubber. You can
adjust the clamping pressure to hold the piece without damaging the
item. I found vice grips with jaws that are about 1.5 inches by 3.
The surface of the jaw plates are smooth making it easier to bond on
padding material. Lee Epperson