This post and a few others about tac welders prompted me to do a
little experimenting this morning. I had a job in my box that I have
been putting off for a couple of weeks. And to make matters worse it
belongs to my wife. It is a platinum ring set with diamonds and a
very nice tanzanite that she picked out for herself at the Tucson
show several years ago. It needed to be sized from a 5 1/2 to a 6
1/2. I did not want to heat this tanzanite at all and was left with
the thought of running it over to a friend who has a laser welder.
I own a PUK111 welder and have been using it to weld orings and to
tack items together before soldering. I decided to see if it would
size a platinum ring. What did I have to lose? Worst case I would
have my friend laser a new 1/2 shank on it. 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. I put it on a ring mandrel and
tapped it up the last 1/8 of a size and the weld held. It had a tiny
bit of porosity that was easily taken care of with a burnisher.
Sanded and polished, the seam is much less visible than any that I
could have done with and easy platinum solder. This from a machine
that cost me $2695.00 Is that about one tenth of the cost of a
laser welder?
John Wade
Wade Designs
wadedesigns@aol.com
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.
Peter