For stone setting in rings, I use the "Inside Ring Mandrel". Its
very secure and rigid in use, which makes it ideal for hammering.
Great tool, I use the version designed for use in an engraver’s
block and I love it. One word of caution, however. It uses a split
collet and a tapered expansion screw to apply outward pressure on the
ring to hold it from the inside with friction. It is possible to
damage a ring with this tool, similar to the damage caused by using a
ring stretcher. If you put too much pressure to the expansion screw
in an attempt to keep it from turning, it can stretch the ring. If
the ring is delicate or has thin portions around stones or solder
joints in thin parts of the shank and so forth, you can easily rip it
wide open with a single twist of the allen wrench. It can generate a
lot more force than might be apparent to the casual observer.
If you find yourself with a ring that you might be uncomfortable
putting on a mandrel and trying to stretch a little with a leather
mallet, or if the thought of someone putting it on a ring stretcher
to ease it up a quarter size makes you break out in a cold sweat, it
is probably delicate enough to warrant caution when tightening the
In any case, be aware of where the split in the collet is and index
the ring and collet so that the split is at the thickest / strongest
part of the ring, not under a stone seat or at a sizing joint or
other comparatively weak spot. The split is where the stretching
effect is greatest and the tighter the screw is, the greater the
It is also wise to orient the ring so that any sideways or rotating
pressure is applied to the ring in the direction of tightening the
screw. Hammering or pushing in the direction the screw would turn to
unscrew can cause the ring to be released suddenly and without
warning, especially if the ring is delicate and therefore not
tightened down past just snug.
The GRS Inside Ring Mandrel is a wonderful holding tool. I bring
these limitations up not to scare anyone or down-grade this very
useful tool, just to point out to potential users the potholes in the
road that I found the hard way.