To my amazement it did a beautiful job. I fit in the right size
piece of sizing stock turned it to full power and welded all the
way around the seams. It never got too hot to hold in my fingers.
John, this is essentially the same as it's done with a laser, and
the caution for a good weld is similar. You want to be sure your
weld is penetrating deeply enough to go all the way through by the
time you've done it from all sides. If not, you'll have a seam
that's welded at the surface, but cracked (just not welded) in the
center, which might be quite a bit weaker than you realize. One way
it's done with a laser is to fit the insert piece for sizing with a
gap, or litterally a V shaped trough, so the pieces contact only in
the center. Then weld starting in the bottom of that gap, filling it
in from the bottom till you're up to the original surface level.
That way you know you've got a solid piece of metal. And it can then
help, with platinum, to stress relieve the welds. That means quickly
heating the weld (with a small sharp torch flame) to a low red heat
for a moment. Not a full anneal, but enough so the weld isn't
brittle. Platinum is a poor enough heat conductor that you can do
this with even a heat sensative stone in the ring. In fact, to be
sure, hold the top of the ring (and stone) in your fingers while you
do this. Takes just a moment, and the heat won't travel far from the
weld at all. With the PUK welders, your main challenge is welding
properly down in the bottom of that open gap or notch, slightly
harder to do than with a laser. Do a few tests on scrap metal to
see just how deeply the weld actually penetrates (weld a joint from
one side only, and break it again, then examine the broken weld).
That will tell you how much you need to do in this regard to get full
weld penetration. The test results will depend on not just the
power setting, but on the metal type as well, just as with a laser.