Yes, Don't do it. This type of setting needs to re-hardened
after it has been sized. It's my understanding that the stone is
under about 10,000PSI of pressure and requires special equipment to
harden the ring. I have ALWAYS sent these rings back to the
manufacturer for sizing, as well as 'Cabana' and 'Bagley and
Hotchkiss' Opal inlay rings.
I’ll second that, especially with tension sets from Steve Kretchmer,
who of course is the only U.S. manufacturer who’s got the patents and
copyrights (not to mention the metalurgical expertise) to make them
properly. One correction though. With well done tension sets, there
is only a little actual pressure on the stone. Just enough to hold it
firmly in position. What you’re referring to is the types of forces
(and I don’t recall the exact numbers) that are resisting the removal
of the stone. Unlike a prong, which can be bent back by only a little
bit of pressure against a hard point or surface or tool, the tension
sets are held over a much wider area of the girdle, and the entire
setting must be sprung away from the stone to actually remove it.
Since the whole point of such settings is that the metal is highly
conditioned to a spring condition, slight deflections that might, in
unusual situations, spring the setting apart a bit, don’t hurt since
the setting instantly springs right back to it’s original position due
to it’s being engineered as a compression spring. It does not need to
actually exert much force on the gem. It only needs to maintain it’s
own shape, or if sprung apart, return to that shape. Then the stone
can only be lost if the ring is sprung so far apart as to allow the
stone to escape all in the one event. THAT takes a lot of force.
When they’re made, after heat treating, it can take heavy duty vices
and vice grip pliers and similar tools that really don’t look
appropriate around fine jewelry to spring the setting apart far enough
to insert the stone in the already cut seat. Once release, the
setting then springs in again, and the stone is secure unless someone
exerts similar forces on the ring again, or some jeweler is foolish
enough to try and size the darn thing.
As a general rule, when selling tension sets, be sure you’ve got the
size right the first time, and make sure the customer is aware that
sizing these things is NOT routine or practical. Some of Steves
designs pretty much require remaking the ring in order to size it…
And he understandably does not just give that service away for free.
Properly sizing those that CAN be sized still requires the use of
fairly high tech equipment, and then some very careful and precise
heat treatments to restore the hardness and spring of the setting.
Leave this to the folks who made the ring, and fully understand the
alloy they’ve used.
And if by chance, you’ve got a U.S. made tension set ring that is NOT
a Steve Kretchmer piece, then do yourself a favor and still don’t go
near the thing. Most likely, it’s a knock off of the design, but made
in an alloy that does not have sufficient hardness and spring to allow
it to properly function. Should you attempt to size it, then WHEN the
stone loosens (which it eventually would have done anyway) then YOU’LL
be caught in the crossfire. Even if it’s properly made, it like as
not violates Steves patents and copyrights. If it’s from Germany, on
the other hand, then maybe it’s ethically OK. But still, size it at
your own peril. If you can determine the alloy, and it’s required
heat treating cycles, then, if you can properly fuse/weld the sizing
job (usually needs a laser or heliarc, at least for the platinum ones)
so as to create a seamless job (don’t use solder, and don’t thin it
out. It needs the thickness) you’ll still need to have removed the
stone first, sized it, heat treated it again, and then will have to
wrestle the stone back into the mounting.