Cutting seats in Prongs

When cutting seats in prongs I use a setting burr the size of the
stone or slightly smaller and cut all the seats at once. These are
the burrs with a normal pavilion shape on the bottom and vertical
sides. I rarely use a burr that is significantly smaller than the
radius of the girdle where it meets the prong. These seats are
easily modified to suit deep bellied stones with bud or ball burs.
With thick girdle stones I will usually use a bud bur. Shaping seats
can be done with many different tools. Specialized setting burs,
ball or bud burs, files, gravers, drill bits, separating discs,
sanding discs, pretty much anything that will cut metal can be used.
The more flexible your mind the more options become available. Look
at your stone from all different angles, look at you tools without
prejudice and try to relax! Also, if a prong seems reluctant to move
the way you think/wish it should, often trimming the outside of the
prong above the girdle can help facilitate progress.

Hope everyone has/had a peaceful harmonious Thanksgiving!

Spike Cornelius
Portland, Or.
RC ArtMetal

This is in response to Judy’s post regarding her frustration cutting
seats in prongs while stone setting. When I first started, I had a
tremendous problem getting the “run around” when cutting seats in
prongs. Since I didn’t have the time or the temperment to mess
around with this rather simple task, I came up with a jig that I
still use today when cutting seats in prongs that have the potential
to give me a problem. What I did was take a chunk of white plastic
cutting board measuring 10mm x 25mm x 8mm thick and trim the end as
follows. I clamp the piece in my bench vise, I use a Benchmate, and
then cut a “V” groove in the top of the plastic block just deep
enough to fit a prong. I then bevel the edges of the block at about
45 degrees to provide relief for the rest of the mounting. Then I
just place the prong to be cut into the groove and cut the seat,
making sure to hold the prong firmly in the groove. If the bur does
happen to “grab” it merely runs out into the plastic and no harm
done. Using this safety device you can become more familiar with how
to cut your seats without worrying about the cutter grabbing. If
you’d like a picture of this fixture send me an e-mail, to remind me
when I get to the shop, and I’ll send you one. Good luck and have
fun !


call me late in replying to this very late posting…:>( but now that
the jewellery season is FINALLY over I can get back with my own
observations on SETTING STONES. cutting bearings in claws…what is a
bearing cut? glad you all asked me in unison! a friend said to me a
bearing cut is just that, it is a cut in a claw that “bears the
weight” of a stone, or in other words the stones sits “on” this seat.
got it?

If any of you folks have a stone that is larger than the available
claw setting. Do not pry open the 4 claw setting, you will definitely
stress the gold and cause some breakage with the setting process. I
will VERY GENTLY with the aid of a tip of a larger round bur (with
the head removed) open the 4 claws uniformly and equally. There will
be times in your setting life you must tell the claws to “open wide &
say ahh”. The end result is that the claws must hold the stone and
have the claws actually cover the girdle. Along with this you the
jeweller and setter must allow for polishing and customer wear and
tear, hence, a little more metal MUST be over the girdle. Lets not
forget the “77B”, or cup burring process.I would at this point round
off the claw tips but holding the bur at slightly backward position
maybe at a 33 degree back angle. No sharp edges must be felt to your
fingers. If there are any, then smooth out the rough edges with a
sharp pointed pumice wheel of #180 grit. Make sure with this process
with your “baby finger”, claws should be as smooth as a babies tush,
as I call it…:slight_smile: If there are any sharp edges, the polishing wheel
will snap back the claw and you will loose the stone while being
polished!!! Now you don’t want this do you??..:>)

All of the stone claws should be holding the stone securely, “table”
should be horizontal and the claws near as a vertical position, when
completed. Enjoy setting!

Gerry, the Cyber-Setter !