There are a couple of different methods I use, depending on how wide
the sides of the channel are. If it’s a fairly narrow strip of metal
and the channel is basically intact, you can file the top of the
channel flat, lay a piece of square wire or strip along the top of
the channel, solder it down, hammer it down a bit and then clean it
up.
If the metal is kind of wide and more or less flat or evenly
rounded, it’s much harder to do and make it look good using the
build-up-on-top method. The better way to do it in this case is to
lower the stones. There are a couple of different approaches to this
strategy. The first (and most time consuming) is to unset the stones,
widen the channel, re-line the channel with strip or wire, file it to
the correct width, polish inside and then reset the stones just like
in a new ring. Another method you can use is to fill the old seats
with solder and set the stones lower. That’s kind of cheating though,
and not a real professional approach for several reasons, but it
works in a pinch. Lasering in new metal is a much better way to do
that and works just fine with yellow gold, not so well with white.
Any porosity in the filled seats can give you fits later on when you
try to finish it.
Setting the stones lower is about the only way to get metal over the
stones if the ring is fairly wide. Keep in mind that if you set the
stones deeper, you have to allow a little more room between the
stones. This is because they move closer together as they get closer
to the bottom of the channel if you were to just drop them straight
down from their original positions. Meaning you will probably have to
lengthen the channel a bit. Make sure the culets won’t be poking out
of the bottom of the ring too. Of course with both build-up methods,
a clean, tight fit of the wire or strip is critical to a nice
finished piece.
If neither of these methods is possible, you may have to replace the
ring.
If you have to cut new seats, cut a seat for each stone, not a
groove. Fit each stone individually, and cut the seats slowly. Cut
and fit, cut and fit, cut and fit until the stone just barely clears,
paying attention to the shape of the seat and pavilion of the stone
and the thickness of the girdle. The better the match of seat and
stone, the better the stone will fit and the easier it is to keep
them level and in the right place. You might find it helpful to use a
divider to mark a line inside the channel where you want the girdles
to end up. For a straight channel with same-sized stones, I start at
the middle of the channel usually by marking the middle of the
channel to place the center stone. When that seat is cut and the
stone is in it (I keep it in place with a little beeswax), I lay the
next stone on the channel and make a mark at it’s center on both
sides of the outside of the channel, allowing enough room for
girdle-to-girdle clearance, cut the seat using the divider line and
marks on the channel to center it and hold that stone in with
beeswax. So on and so on, alternating side to side of the center
stone until I reach the ends of the channel. This is the most
critical and important step in the entire process as this is where
you establish spacing and level of each stone. Take your time here.
It will make the rest of the job a breeze if you do it right. It will
make it a nightmare if you don’t.
Check each stone as you cut the seat for crown height, you want to
have the tables to end up being even with the top of the channel, or
even a little deeper before hammering them in. The smaller the stones
are, the deeper, percentage-wise you want the seat. Ideally, 15
pointers should be about even or just slightly below flush. That will
give you enough metal to hammer and clean up the edge of the channel.
It’s much easier to clean up the channel with more metal than with
less. You may find that some seats will have to be a lot deeper in
the channel than others for the tables to all end up the same height
if the stones aren’t well cut or matched.
You said something about using a copper punch. Try a punch made from
an old bur or a small masonry nail, flattened (but slightly rounded)
on the end with slightly radiused edges, and polished. The shape
should resemble a very slightly used pencil eraser. Put the ring on a
mandrel, put the mandrel in the hole on the front of your bench, and
with the punch just barely touching the metal over the stones, gently
tap the punch with a chasing hammer. Watch the tip of the punch
where it touches the ring, not the hammer or the end of the punch
you’re hitting. Walk the punch along the channel, and go back over it
several times, changing sides of the channel with every reversal of
direction. The idea is to push the metal over the girdles of the
stones gently and evenly, and then straight down. If you took your
time and cut the seats well, the tables of the stones will all be
level and straight. Look at it with light reflected off of the
tables as you roll the ring. You’ll see any variations quite easily.
Do this often during the hammering process and you can correct any
deviations before the stones are locked down, by hammering a little
more on the high side. If you have to, use your copper punch and
chasing hammer to lightly tap on the high side of the stone to push
it down (don’t do this with anything but diamonds though, and be
careful! This is risky business). If it won’t go down with a little
gentle persuasion, you may have to pull it out and re-cut the seat.
It’s almost impossible to correct them after they’re hammered down
tight.
This is also the time to keep an eye on spacing. When you check the
“table rolling”, use your loupe to check spacing. If two stones are
touching, you are almost guaranteed to break one or both if you keep
on hammering. You want the stones to be almost touching, but not
quite. I try to keep the girdles about half the thickness of a piece
of paper apart. If you need to, use an onglette graver to push the
stones to where you want them. Hammer a little more and check spacing
and level again. If they persist in being too close or too far apart,
or won’t stay level when spaced correctly, you may have to recut the
seats. Again, be careful, it’s really easy to chip a girdle with an
onglette, and don’t nick the channel below the girdle. It’ll be there
forever and it’ll show.
If you hold the punch exactly perpendicular to the metal, it won’t
make much of a mark (or move much metal), but if you hold it at a
slight angle, it will make little smiley faced divots, that will
eventually create a shallow groove-like depression parallel to the
channel as you push metal over the stones. Not a problem if you cut
the seats deeply enough in the channel and have plenty of metal, big
problem if you didn’t. Whatever marks you make you will have to
remove or fill later. The flatter the punch the more easily it will
make the half-round divots, but the more easily it will move the
metal in the direction you want to move it.
You may find that to move the metal you have to really whack it,
especially old 10K gold, but start gently and increase the force
slowly and only as much as needed. It’s better to tap it gently a lot
of times than to whack it hard a few times. It’s also easier to see
what you’re doing if you hammer towards you slightly, so turn the
ring around on the mandrel when you change sides. It also works
better to hammer towards the wider end of the mandrel, causing the
ring to almost lock down on the mandrel. It’s a lot more difficult to
channel set going downhill, if you take my meaning.
After all the hammering is done, the tables “roll” perfectly in
reflected light and everything stays tight after a good ultrasonic
and steaming, clean up and polish the inside edge of the channel
before cleaning up the hammer marks on the outside of the ring. I use
a highly polished #40 flat graver and a 000 onglette to clean up the
channel, almost like bright cutting. A quick polish with a mounted
brush and rouge after the graver makes it sparkle. Finish the outside
as normal, but be careful not to round the edge of the channel too
much. Polishing towards the stones from each side (not across the
channel or along it’s length) will help keep the edges crisp.
Good Luck!
Dave Phelps
www.precisionplatinumjewelry.com