You might try painting the stone with several coats of rubber
cement, available from most office supply stores.
A rubber mask is used in the tombstone industry to sheild the
stone when the letters/numbers/ designs are ‘carved’ into the
stone. The rubber absorbs the energy in the blasting media.
I’ve not tried this, but it looks good on paper (bg).
Good luck!
Dave
I have been honing my flush-setting skills (I don’t do a whole lot
of setting), trying out the technique of starting with a
slightly-too-small hole that is enlarged just below the surface with
a hart burr. This is a major improvement for me, but I wonder
whether anyone who is more expert at this can quantify how much
too small the hole should be, ideally.
It also seems to me that the hole can be tighter with a diamond than
for a colored stone-- I am more willing to coerce a diamond through
a tight space. Yes? No?
Thanks!
Noel
Noel if you can get hold of a copy of Blaine Lewis’ video tapes on
setting I would highly recommend it. Blaine has some great bench
tips for flush setting. I especially liked the tip about making a
burnisher out of stainless steel table ware.
Noel,
The way I do my flush setting is this:
Drill out the hole with a drill bit
Use a BUD burr, slightly smaller in diameter at it’s fattest than
the stone to be set and open up the hole
Take the stone to be set and place it in the opening. The girdle of
the stone should sit or rest ever so slightly above or dip into the
opening a tad (you can always open up more but if you drill it to
large, forget it! 
Use a HART burr at this time to cut your seat just below the surface
of the opening.
I use an old bur, snip off the top, file it smooth and polish it to
use as a “pusher”
Put the stone in place, use your “pusher” or whatever to set the
stone. If it does not go in, take the BUD bur and with your hand,
not the foredom, open up the hole, little by little until the stone
"snaps" into place.
This might take a number of practices to get the hang of it.
Hope this helps. E-mail me off line if you need further help
Laurie
if you can get hold of a copy of Blaine Lewis' video tapes on setting I would highly recommend it.
I don’t have the video, but I went and took stone setting from
Blaine a few years ago-- he is terrific, and I learned a lot. But he
didn’t teach us this particular technique-- snapping the stone into
an opening that is slightly too small on the outside, enlarged just
below with a hart bur. It is going pretty well, I just wondered what
the rule of thumb is for how much too small the opening should be.
Noel
Hi Noel,
It also seems to me that the hole can be tighter with a diamond than for a colored stone-- I am more willing to coerce a diamond through a tight space. Yes? No?
No. Or at least, not necessarily. Diamonds are hard, yes, but not
particularly tough so it’s not all that difficult to chip them. I’ve
wrecked one or two trying to force them into a too-small setting and
I don’t advise it!
Beth
The snap-in-place flush stone setting technique is perhaps not as
widely used as the technique of flush setting by burnishing the stone
in place.
This could be due to some disadvantages to the snap in style of
setting:
it isn’t possible to insert and remove the stone prior to the final
setting to insure the seat is cut level or to visually check the
accuracy of the table height. When randomly setting a scattering of
stones on an object this may not matter so much, but in setting a
precise layout or a symmetrical arrangement it is advantageous to be
able to monitor and control these aspects of the process as the seats
are being prepared.
There are many different approaches to flush set a faceted stone. I
prefer to cut the seat as exact as posible to the girdle diameter
using a setting bur. Pressure seat the stone by pressing in place
with a pusher and then burnish the free standing metal down onto the
crown of the gemstone. Burnishing is done by hand and produces a
brightly polished reflector around the stone. When done correctly,
and if the stone and bur size are well matched, it takes only minutes
to set a stone. Some setters use a rotary burnisher in a flex shaft
or a hammer and punch to tighten the metal onto the stone but if the
technique is executed properly neither of these is necessary.
Michael David Sturlin
www.goldcrochet.com
www.michaeldavidsturlin.com
General rule of thumb is to have the opening be about 95% of the
diameter or the stone. It of course depends on the softness of the
metal you are working with, the girdle thickness of the diamond, and
the size of the diamond. The bigger the diamond, the less hard I am
inclined to push on it, especially if it is customers. You can always
go back and tighten it with a hammer handpiece in the case of the
larger stones.
Carol
Hi Orchidland,
For hole size: Using a ball bur just slightly (fractions) larger
than the stone; open the hole so the girdle sits half in and half
above the hole (a bud bur works well too, and you need fewer sizes):
just make sure the hole tapers inward a little. This should be the
ideal size for flush setting rounds (for fancies too, but you have
to cut the seat with saw and files to a slight inward taper. Boy is
that labor intensive). For a stone pusher: You’ll break far fewer
stones if you use brass rod instead of steel! I also shape the back
end of my handy dandy stonesetters brush (a cheap straight-handled
toothbrush) by tapering it down and flattening the end. Even safer
than brass rod but you have to reshape often.
For stones that aren’t diamond cut: I reccommend a lot of practice
and a little prayer (or really well chosen swear words).
Thanks, Hanuman, for the forum,
Bruce Morrison