I think everybody has covered all there is about sizing rings
but would like to describe a way of holding the insert of gold or
what ever metal.
When the shank has been cut file a < > in each end of the shank
across it's width, shape the new piece of shank to the new ring
size and with the ring at the size on the sizing stick mark the
length on the shank insert at the points of the v's, cut and file
end to fit ring shank, solder and finish. End pressure of ring
shank keeps everthing in place.
This was shown to me by a top jeweller here in N.Z.. Now I dont
have to worry about the new piece jumpimg out or trying to wire
it in place.
Hope it is of some help to somebody.
Best wishers to all.