First, gluing gemstones (as opposed to pearls) is a risky business
anytime and I hate it but sometimes it has to be done. You usually
cannot use a forced fit on the post due to the possibility of
breaking the stone. You're left with using a quality glue (referred
to in front of customers as "industrial bonding compound") and
applying a minor amount of pressure during the curing process.
Throw out your current epoxy and buy the 1 hr cure Devcon two part
material. Be very sure your mix of equal parts is accurate and mixed
well - and be very careful not to contaminate the supply tubes with
the opposite part. Once you've applied the glue try to apply a little
pressure with, say, a soldering cross lock tweezer. I cover the ends
with a little piece of masking tape which both protects the stone and
gives the tweezer tips some traction on the stone. You may have to
adjust the pressure by bending the arms out a bit.
Once you've appled glue and pressure place beneath a 100w
incandescent bulb and leave for a couple of hours at least. Then
allow the piece to finish curing overnight without disturbing.
Pearls are different to the degree that you can force fit the post -
within reason - and it works even better if you use a square post
that you've twisted completely around a couple of times resulting in
a "corkscrew" post. When correctly done you can actually screw on the
pearl -coupled with the epoxy such a mounting should never come off.
Unfortunately pearls oftentimes come overdrilled re the post at hand
or underdrilled. In cases of underdrilling I re-drill the pearl. This
requires care as it is easy to chip the nacre. I use a a very small
pointed stone mounted on a mandrel and expand the opening of the
hole to accomodate the drill I intend to use. On lesser pearls I'll
hold the pearl in a clamping jig and drill "freehand". For more
valuable pearls I'll use a pearl jig and my mill to make a more
precise hole. Never try to hold the pearl with your fingers while
drilling and, if you're using pearl drills, never try to drill by
hand at all.
In the case of the pearl's hole being too large I'll change the post
if possible or I'll use parallel jaw pliers to squeeze the top half
of the post causing it to widen out in a paddle shape which, while
not as effective as the twisted post, still gives some bite to the
Apply and cure the glue as noted above.