To secure a Flush Set stone you only need to burnish the top edge of the metal down onto the stone.
Do not attempt to tighten a flush set stone by hammering on the metal surface, forcing the metal over the stone. This causes a dip in the surface surrounding the stone, resulting in an unsatisfactory appearance. If you use a hammer and punch (or hammer handpiece on your flex-shaft) be certain to hold the punch at a 45 degree angle to the metal surface and tap lightly ONLY on the edge of the metal, until it is worked down over the stone.
How to training videos for Bench Jewelers
See some of the most respected Master Jewelers explain their techniques and tips
on stonesetting, as well as making and repairing jewelry.