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Shrinkage in casting...Stone setting


Hi Jim, We do a lot of casting /finishing/stonesetting for our
customers (designers stores etc… ) When we design a model for bezel
setting, say, a 5mm round faceted stone, we will make the opening of
the bezel 5.20 mm with the seat low enough so that the bezel height
is just above the highest point of the stone. When the casting comes
out, most of the stones are set with a bezel setting tool and the fit
is excellent. The problem comes in when the stones are not as
accurate as they should be. In this case, we have in stock some brass
or steel rod that we grind down to 5.10 mm on one end and cut the
rod about 4 inches long. Then, before setting the stone, we tap the
5.10mm end into the setting with a hammer. This will expand the
setting slightly, allowing the slightly oversize stone to fit into the
cavity without using burrs or any grinding process.At this point, we
use the bezel setting tool to tap the bezel over the stone. When we
are done setting, there is no filling, no cleanup and the bezel is
practically polished without having to touch it.We call these tools
setting expanders and make them for every style of stone that we
set.Ovals, square, octagonal are no problem with this method.We use
the same tools to set prong settings, but the stone seat is
prenotched in our casting models.In this case, we use pliers to
tighten the prongs slightly onto the stone, then we use the bezel tool
to (by taping lightly) to do the final tightening of the stone. This
works better and safer than any hand method of setting that most
people use. When setting a cabochon stone, we take a set of bezel
setting tools and grind out the center of the tool deep enough to so
that there is plenty of clearance inside the tool so that the stone
will not be shattered when hamerring the bezel down. After having
built the tools, we mark the tools using a carbide burr with the size
and type of stone (ie. 5.0 /round/cab) so that the tools are easily
identified. On this page of our website, we show these tools being
used . Sorry if the pictures
are not as sharp as they could be… they were done using a 5 year
old video camera through a video capture card. We have not had the
time to redo the pictures with our nikon 950 digital camera which is
much better!!!

A very important thing to remember is that often, we have found that
customers who use dial type calipers to measure their models have
never calibrated their calipers for extreme accuracy and then what
happens is the model openings are then not accurate. We suggest buying
an inexpensive set of digital calipers that measure inch /metric
Item #240-618 @$ 49.75 from the tel: 800-343-3364 are
the ones we use. They are probably available from other suppliers as
well.Round , simple bezel setting tools are also available from them.

Hope this is helpful. Daniel Grandi Tel:
401-461-7803 10 am to 5 pm eastern standard time. We do casting and
finishing in gold, sterling, bronze/brass and pewter for people in the trade.