Sounds like you managed the more difficult soldering job: attaching
the 18k bezel to the ss base. Attaching that assembly to the orca
should have been the easier part. I'm assuming that the 'depression'
you're setting the bezel assembly into is flat and mates with the
base of the bezel neatly. If the two pieces don't mate up with a nice
tight fit, soldering is going to be much more difficult!
I'm going to jump on the paste bandwagon here, since this is an
ideal application for paste. Instead of premelting solder in the
depression and then trying to sweat solder the bezel assembly in
place, you would be better off putting a single deposit of silver
solder paste in the depression, putting the bezel assembly in place,
and soldering it together in one step. The trick here will be to use
a minimal amount of solder. If you use too much (whether it is paste
or hard form), you will have a difficult time keeping the bezel
assembly in place.
Because paste already has the proper amount of flux mixed in, you
won't need to add extra flux under the bezel assembly, which will
minimize movement during soldering. Of course, you should still
firecoat the rest of the piece where the solder won't flow, or you'll
spend the afternoon polishing! Rio (since you're already dealing with
them) carries silver paste solder. Their 560 easy solder (order
number 103-093/1....page 43 in the Gems & Findings catalog) would
probably be your best bet.
Oh...a quick tip to help you gauge your heating of the assembly: on
this piece you can also put a small deposit of paste (very small,
just a dot) on the TOP of the ss base of the bezel assembly. If you
heat the assembly evenly--making sure that the orca and the bezel
assembly come to temperature at the same time, you can watch the
small dot of paste on the top of the bezel to help determine when the
paste has melted and flowed. Since you'll be setting a stone, the
small solder stain on the top of the bezel won't affect the visible
finish of your piece.
If you want to stick with hard form solder, I have a few
suggestions. First of all, when you premelt the solder into the
depression, be careful not to overheat the orca. Heat it just enough
to get the solder to melt. Silver solders can be very corrosive on
sterling silver, and if you over heat them a lot, or keep them at
temperature where the solder is molten for an extended period of
time, the solder will begin to dissolve into the sterling silver. Not
only does this affect the sterling, but it can drastically increase
the reflow temperature of the solder. Keep it nice and quick and you
should have no problems of this nature.
When it comes time to attach the bezel assembly, add flux to the
depression. Firecoat the pieces as you normally would. Before adding
the bezel assembly, heat the part gently until all the liquid is
driven off of the flux and you are left with a white crystalline
powder in the depression. Flip over the bezel assembly, apply flux
and gently heat it until it is covered in flux powder. By driving
away the liquid in the fluxes, you'll minimize the dancing bezel
syndrome while heating. The bezel assembly may still try to shift
slightly when the solder reflows, but not nearly as much as it will
want to dance with all that liquid boiling off. When you heat the
pieces to solder them together, make sure that the bezel assembly
comes to soldering temperature before the orca does. You want to heat
the bezel assembly to soldering temperature, and let the assembly
conduct heat to the solder on the orca, melting the solder and
pulling it on to the bezel assembly. If the orca reaches soldering
temperature first, the solder will just try to spread along the
surface of the orca, instead of adhering to the bezel assembly.
Again, you can put a small chip of solder on the top of the bezel
plate to gauge the temperature (make sure you flux it, or it will
just sit there like a lump!)
Hope that helps!