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Making a tension ring, help!


#1

I made a tension ring as an experiment, in 14k gold, and set a
diamond in it. I didn’t have too much trouble with this, but I do know
that I didn’t have enough pressure on the stone, because it came out
eventually :-).

I’ve read on the web that it should be 65+ pounds of pressure, and I
must have had like 5 on it. No wonder.

Anyway, I cast the ring in the normal manner, and am worried that the
metal won’t have enough spring to it in order to put this much
pressure on the stone. What are my options at this point? Banging it
with a hammer?

Thanks,

  • darcy

#2

Hi Darcy, you need to try one of the heat-treatable alloys to
accomplish a good tension. Mike.


#3

Hi Darcy

You’ll probably never be able to obtain the degree of spring
necessary from standard gold alloys. Tension rings are made from
proprietary gold alloys that have ‘spring’, like the tungsten alloy
gold available for money clips or ear wires. Steven Kretchsmer has
worked for years developing the alloys he uses, and as far as I know,
is keeping his alloys a trade secret. I don’t believe spring gold can
be cast, but you could always try… Spring gold develops its memory
after a deep annealing and tempering process, in furnace (s-l-o-w)
cooling from 600 degrees F. I believe, but I’m not extremely sure of
the exact process. If nothing else, you might try using a high nickel
alloy in 18K white gold (aka super-white), that ‘might’ work
(available from AAA Precious Metals, Portland OR) and over-casting a
thin layer of the color gold you desire the finished product to be
(tricky but possible, I’ve done it, but not for the purpose of making
a tension setting).

Jeffrey Everett


#4

Darcy,

AJM Magazine ran an article on tension settings in July, 1996,
(“Putting on the Pressure” p. 44) that should answer your questions.
The long and the short of it: there are two techniques for achieving
this type of pressure, both patented. There are a couple of others
that look like tension settings, but aren’t, and one of these might be
your better bet, since creating a true tension setting is no easy
feat. Niessing GMBH from Germany has a patented technique that
utilizes work hardening the metal, while Steven Kretchmer holds the
U.S. patent for the use of heat-hardenable alloys to achieve the kind
of tension necessary to keep a diamond secure. (Kretchmer also
aggressively defends his patent on this method, so I wouldn’t suggest
making these for resale.) In any case, simply casting your ring won’t
produce a setting with enough tension to keep the stone secure. As far
as I understand it, it just can’t be done. But do check out the July
1996 AJM article, since it may give you some ideas about designs that
will accomplish the look you’re seeking, without infringing on the
patents.

Suzanne


#5

Darcy, To make a tension ring by casting is a bad idea. The precious
metals that we use do not tend to have the spring hardness needed to
hold a gemstone securely. There are 3 basic ways to get the needed
hardness into the ring. The first is to start with a heavy small ring
and forge it to work harden it and create enough spring to hold the
gem. The second is to start with a heavier piece of stock and roll it
down in a rolling mill or draw it down with the use of draw plates.
Then bend the stock into a ring shape. This way you are also work
hardening the metal to create the work hardening. The third method is
to use a heat treaable alloy where after the ring has been made and
before the gem is set you heat treat the ring to create the spring in
the metal. Steve Kretchmer has a patent on this third technique. He
has been challenging other manufactures who use this technique. So do
be careful in making tension rings . There is a large responsibility
in setting expensive gems in mountings. Make sure you test your
designs before you start selling them to the general puplic. best
wishes, Etienne Perret


#6

Darcy, A tension setting is a spring. It is an homogenous band of metal
wrapped around into a ring. Any thin area will give in time. Any
welded or soldered area will tend to give. A lump will tend to cause
the area on either side to to give. This band should be heavy enough
to accept a good deal of abuse. It doesn’t have to spring a lot, just
enough to close back down onto the stone when struck. A cast piece, in
my shy, quiet and humble opinion, will not form a spring of quality
enough to do this job.

The last time that I made a tension setting, I rolled a strip about
8mm wide and 2.5mm thick. I then wrapped the band around into a ring.
I then ground a flat directly onto the opening. I added about 6mm of
thickness to the flat on the opening. From there, I shaped and split
the top again to accept the stone. After cutting what I estimated to
be a good seat for the stone, I slid the ring up a mandrel to open it,
dropped the stone in and slid it back down the mandrel. I may have
needed to use a pair of bow benders to tighten it up. It’s been gone
for over a year now.

Better luck next time.

Bruce


#7

TRY Hover & Strong they sell alloy that is Steven Kretchmer`s. They
also have a list of casters- that use it. Even in platium.- Mitch