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Drilling Agate

I have some flat pieces of Agate that I need to drill holes through.
Does anyone have any tips on how to do this without the Agate

Sara Turnbull
Western Australia

I use a clay, Plastiscine dam to hold a little water. Using a dremel
or similar tool, i use a diamond bit and make sure the piece is on a
solid backing. I also have used brass or aluminum rods and grit to
drill when I did not have a bit to fit.

Use coarse grit to drill with. You can use steel, brass, aluminum or
even wood. Use the same clay dam, put in water and the grit and drill


Hello Sara! One trick that I know and use on any kind of stones is a
diamond-covered bur that is shaped in a very thin cone. To drill a
hole in your agate, just put it in a bowl of water, just beneath the
surface and drill slowly to avoid overheating that usually results in
cracking. This technique is quite a bit slow, so if someone has a
better and faster trick, send me the reply.

Good luck!
Benoit Hamel

Hi Sara, Use a diamond coated bit and lots of water. Go slowly. This
is a highly focused grinding operation, not boring, as with wood or
metal. The water serves to keep things cool, and to flush away debris
resulting from the drilling. It helps to frequently move the bit in
and out to let fresh water in. Don’t let the stone or the bit
overheat. You may want to build a clay “dam” around the area to be
drilled to keep the water pooled where you want it. Diamond bits can
be obtained from most any lapidary or jewelry supplier.

All the best,

Dave Sebaste
Sebaste Studio and
Carolina Artisans’ Gallery
Charlotte, NC (USA)

    I have some flat pieces of Agate that I need to drill holes
through. Does anyone have any tips on how to do this without the
Agate cracking? 

G’day Sara; A diamond drill bit is essential (well, it can be done
without but hey, don’t bother!) Any of the jeweller’s tool suppliers
will have diamond drills and the small ones aren’t expensive. A
drill press makes life easier but it can be done with a Dremel or
other hand electric tool. Use a dish with a bit of scrap plywood in
it, and fill the dish with water; hold your job down on the bit of
ply - which is to avoid drilling partially into the dish when you have
drilled the hole. Start the hole by carefully lying an edge of the
drill in the right place on the work and let it make a start
depression, then go to it! Keep moving the drill up and down, don’t
press down too hard; let the drill do the work Don’t have the drill
rotating at really high speed; it isn’t necessary, and always keep the
drill bit wet. Be careful when you see that you are about to break
through. Smooth off each side of the hole with emery grit and
vaseline on an orange stick in the electric tool, or a tiny roll of
wet/dry paper on the stick. – Cheers,

John Burgess; @John_Burgess2 of Mapua Nelson NZ

Hi Sara,

 I have some flat pieces of Agate that I need to drill holes
through. Does anyone have any tips on how to do this without the
Agate cracking? 

If it were me, I get a diamond core drill of the required size. Core
drills are tube shaped drills that have diamonds either plated or
embeded on/in one end. There are usually a couple of holes in the
side of the tube to allow water to enter & exit. The water cools &
lubricates the bit while drilling. It also flushes the cut rock
particles away.

To drill the holes, you’ll need a drill press & a waterproof pan
large enough to hold the slab that’s being drilled.

Place the core drill in the drill press & the slab in the pan. There
should be enough water in the pan that the slab is covered & the
cutting end of the drill is covered by about 1/4incnh (6mm) of water
while drilling.

Use a drill speed proportionate to the drill size. The smaller the
drill the faster the drill should run. Keep a steady (not to heavy)
pressure on the drill as it cuts. The slab should be held securely to
prevent the drill from grabing it & spining it around. Periodically,
the drill should be raised from the cut to aid in flushing the cut
rock from the hole.

If the hole is small, less than 1/16 inch (2 mm), there are small
solid, plated or sintered diamond bits available that could be used
in a flexshaft or motor tool. If this option is used the slab needs
to be covered in water as above & the drill needs to be removed from
the hole more frequently to flush out the cut rock.


Sara, Not sure what size holes you are drilling. Larger holes can be
a bit more complicated than small ones. Also the thickness of the
Agate is important because, as the hole gets deeper, the ability to
get coolent to the bottom increases. This in turn increases the heat
build up and the potential for cracking.

But first things first. Clean one side of the agate and a piece of
reasonably thick piece of glass (or flat piece of junk stone) a bit
larger than the piece to be drilled. Using dopping wax, warm the
agate and make a sandwich of the two. Be sure there is very good
contact, especially in the area where the hole will be drilled. The
reason for doing this, is to preclude the little chip from coming out
when the drill breaks through the agate…the drill cannot tell it is
through the agate and just keeps on drillin.

Now with some play dough or molding clay, build a little circular dam
around where the hole will be drilled. Fill this with water.

It is best to use a small drill press to insure consistant pressure
and that the drill is going straight into the hole. If one is not
available, use a Dremel or Foredom but be very very careful to enter
the hold at 90 Deg and do not let it wobble or it will chip the stone.
Gently place the right size diamond drill against the stone until it
begins to abrade an indentation. Continue to gently press the drill
into the hole lifting it every few seconds to allow the water to cool
the hole and to remove swarf. Continue this process until the hole is
through the agate, clean up and place the sandwich into the freezer
for a few minutes. The agate should separate from the glass. Clean
up with alcohol.

If you can, use hollow (core) diamond drills. If you have a lot of
drilling to do, you should purchase a water collar for your drill
press (check with Diamond Pacific for this). This allows you to hook
up a water hose and force coolent down through the center of the drill
to cool and clean the hole.

Good luck and cheers from Don at The Charles Belle Studio in SOFL
where simple elegance IS fine jewelry!

Saw this ad in the classifieds at Bob’s Rock Shop

Ad number: 5433 Posted: 5/1/1 13:4:16 UT Sonic Drilling I can drill
1mm,1.5mm,2mm,or 2.5mm holes in stones up to 3/4 inch thick. I can
also enlarge pilot holes in beads. Sandy Klepel email:
Stones by Sandy

Those classifieds are a gold mine if you’re into lapidary!

All the best,

All, The main thing to remember when you are grinding a stone is that
you are not cutting. You are grinding. Grinding requires a lubricant
and a means to remove ground away material. I have made many holes
in rocks by using copper rod, a drill, and silicon carbide grit or
diamond grinding bits. You must control the speed of the rod so that
the grit or diamond has time to be carried into contact with the rock
to be drilled. Harder steel rods work better than copper because
they resist being ground by the grinding action, but copper was what
I had available. With loose grinding material you must build a dam
of some kind to keep the grit and lubricant near the hole. The dam
must have an exit for the grinding sludge to flow out of. With
diamond tools I still build a dam, but do not worry about the sludge.
I used modeling clay for the dams when I was putting holes in rocks.
To put a hole in a thin slab of rock I would place the slab between
two layers of hard board with a hole drilled through them slightly
larger than the hole I need in the rock. Next I would build a dam
around the top hole. Then I would grind the hole in the rock using
the hole in the board as a guide. Go slow and lubricate well. You
still will lose a few, but that is the best way I know.

Gerry Galarneau

After reading all the posts about drilling, I find I have some
important things to add. I did an article about this for Lapidary
Journal a few years ago.

First, your drilling process will improve a great deal if you add a
soluble oil to the water. There is a brand called Tool Cool that
works well. This will also save your bit.

Second, when you first start, the bit will cut well. When it begins
to slow down, as it will, it is because the diamonds have been worn.
If you’re using smaller bits in the mm range, sharpen the diamonds and
clean the bit by running the tip of the bit over a grinding wheel,
preferably aluminum oxide while the bit is under water.

I use an old glass soap dish to hold the piece of stone in which also
has the oil and water, about 1/2 and 1/2. You should be able to tell
whether you’re drilling throught the stone by a swirl of dust that
comes out of thie hole. If there is no swirl, try sharpening. Also,
once you’re finished drilling, the solution can be left to separate
and reuse.

If you sharpen and it still doesn’t cut, use a fresh bit.

Finally, don’t be tempted to turn the piece over and try meeting the
holes from the other side. It won’t work.

Good luck. the drilling takes much longer than you expect,
especially when \you think you ought to be through by now.