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Setting cabs that are not flat-bottomed

Hello Orchidians one and all,

I’m reasonably proficient at bezel setting flat-bottomed cabs --kind
of a no-brainer after the first few-- but over the years I’ve
acquired a lot of cabs that are not flat-bottomed. In fact they have a
distinctly curved bottom. Oppi Untracht calls them “double-bombe”.
I’ve also seem them called “double cabochon”. Sometimes the curve is
fairly gentle (usually on larger stones) and sometimes it’s quite a
bit more convex.

So the question is, what’s your favorite way to bezel-set these
"double" cabs?

I can think of a few methods --stepped bezel wire OR carve a seat OR
small beads inside as risers OR something soft underneath to conform
to the bottom curve OR shape a wax model to match and then cast-- but
having tried a few a few of these I’m still looking for a good and/or
elegant solution.

Cheers,
Trevor F.
in The City of Light
www.touchmetal.com

So the question is, what's your favorite way to bezel-set these
"double" cabs?

I like to just pop a ring of round wire into the bezel. It doesn’t
need to be soldered down, and will not show even if the cab is
transparent, because the cab acts like a lens.

–Noel

Trevor,

Seems to me Metal Clay is the way to go.

Terrie

Hi Trevor,

I might consider a reverse bezel setting. This would necessitate a
design which uses 1mm (apx.) sheet. Carefully measure the stone’s
girdle 2/3 from the top and pierce and shape an opening for the stone
to fit through to apx 2/3 of the height. The opening should be
beveled to allow for a tight, neat fit from the front. Fabricate a
bezel that is soldered on the back of the sheet and set the stone
from the back.

Donna
Donna Hiebert Design

Hi Trevor,

So the question is, what's your favorite way to bezel-set these
"double" cabs? 

If I’m using a closed-back bezel, I usually grind the back of the
cab till it’s flat!

Beth

An instructor gave me a tip to raise a cab with a piece of old
credit card under it. I’ve seen it done with wood saw dust, but what
about credit card dust. I have no idea if it would work, or what
would happen if you made it soft with a bit of heat and press the cab
into it. If you do heat it, it may never come out, or it could just
pop back out when cold and hard. Who know what they make those things
out of.

Tim…

In my experience deerskin works the best…

Ringman

Dear Beth, one problem with setting any stone whether cabochon or
faceted is providing clearance for the bottom of the stone and
having a properly cut “prong seat” or a properly designed bezel.
Depending on the appearance of the cab and the design and use of the
jewelry, I will generally make the bezel from sheet and then cut out
the back to accommodate the curve of the stone.

Since this might not work with some designs, the previously
mentioned “addition of a ring of metal” inside the bezel is a good
one. This ring provides the actual seat for the stone. Carefully use
a round or bud bur(or similar shape) to put a downward slope to the
metal ring, so it will fit the bottom of the cab. This is cutting
the seat to fit the stone. The ring is placed high enough to support
the stone and prevent the bottom from contacting the base plate if
not cut out leaving the back open. You can use an unsoldered ring of
metal sheet or better still solder a wire loop or sheet metal ring
inside the bezel. Either method will work and provide support for
the stone above the base.

I personally prefer supporting the stone with a curved bottom to
"cutting the stone" to have a flat base, unless the base is totally
wasted and too, too deep.

Thanks for hearing my thoughts on this.
TomDart.