Don’t know if this would work, but suppose you could drill a precise
hole in the titanium, one that would almost allow a piece of 18
karat heavy walled tubing to be set down into it, but so close to a
fit that if you put the tube in the freezer and heating the titanium,
you could slip the tube down in the hole and as the titanium
contracted it would lock the tube in place, with a millimter or so
protruding above the surface of the titanium. Then you’d have a bezel
in which to set your opal. Drill the hole deeper than needed, and put
a spacer in the bottom to lift the opal up to the desired height.
That way, you’d have sufficient contact between hole and tube to keep
it locked in place.
or, for that matter, make a bezel with a bottom on it, solder on a
wire to the bottom, drill a hole the size of the wire through the
titanium, countersinking it where it comes through, and using the
wire protruding from the bottom of the bezel, rivit it in place.
You’d have to put a punch that fit inside the bezel in place to back
up the rivit, sort of as an anvil.
By the way, a pulse welder or laser does a pretty good job of
welding titanium to gold, as long as you’ve got the shielding gas on.
David L. Huffman