Drilling holes in stone

Can someone give me an actual item # from the Rio Grande catalog or
another source for the type of “diamond bit” needed to drill holes in
stone. I have been told it’s easy and to use a diamond bit but so far
have either not gotten the right bit or the right method. Anyone know
the best way to do this?

J. S. Ellington


To drill a small, jewelry-size hole in a stone is one of the most
difficult lapidary procedures.

Picture it this way. Each diamond particle in the drill bit acts as
a plough, scraping a furrow in the stone. Onto the the tip of a large
drill bit you can pack many, large size, diamond particles. With
each rotation they plough for a considerable distance. As the bit
gets smaller the number of diamond particles that can be put on
diminishes drastically. Plus they need to be smaller. They travel
less distance with each rotation. The smaller you get the closer you
approach the limiting condition of a single diamond particle spinning
on its axis doing nothing; the nearer you approach the center the
less material is removed. That is why diamond drill bits are usually
tubes. And again the smaller they get the more fragile they become,
the quicker they break and wear out.

For doing small holes the instrument of choice is the ultrasonic
drill, which is not rotary but percussive, shattering its way through
the stone like a miniature jackhammer. But these cost in the 2,000 $
range, so you need to drill a lot of holes to make one worthwhile.
Still, when you consider the cost of a drill press which you’ll need
to hold tube drills, plus the cost of the bits which you’ll need if
you’re drilling in quantity, the differential diminishes notably.

That being said, for a hole or two a week the rotaries will work,
(always held in a drill press) although I’d be leery of anything
smaller than say 2mm. By about 3 or so mm they begin to work much
better, and at 1/4", no problem.

Alpha Supply has a selection, on page 207 of the catalogue. Caveat:
yes, I have a minor commercial (as well as a friendly) connection
with Alpha.

Hans Durstling
Moncton, Canada

I use small core drills. They are pricey,but used properly they
last. They have the added advantage,by using the outside surface, of
being able to smooth surfaces you can’t get with wheels when prepping
stones for pre -polishing–

Bill from Long Island


Rio item numbers are 349-009 to 349-014 or you could go for a whole
set 349-015, just depends on what size you need. On page 272 along
with these bits are core drills and several other types of stone
drills. I use wax from a toilet ring to build a dam around the drill
site and add a little coolant. Clamp it well in a vice, I use
leather on the vice faces. I find it easier to create a little flat
spot at the point of entry it keeps the bit from walking around. It
takes a little more pressure on the bit than you would think and I
use a drill press.


In the 2006-7 tools catalog, go to page 272. I have never tried
diamond twist drills, but otherwise you can use any of the drills on
the right side of the page of the size you need. I would recommend
that you do not get the value drills, because you’ll use a lot of
them. Sintered is always better. Then on pg. 320, at the bottom,
especially if you’re going to be doing some drilling, get some
tool-cool. Diamond Abrasives: They like all the rpms you can give
them. 50,000 is not too much for a 2mm tool. They must always be
wet, with stone work. And, as with all abrasives, they only cut as
fast as they cut. Be gentle with them, which is to say, firm
pressure. Pushing harder doesn’t cut any faster, it just rips the
diamond off the tool. If you have a high-speed drill press, that
would help. If you need too, or if it’s a shallow hole, you can just
dip the tool frequently, or I used to carve rock crystal in a cool
whip container - flexible sides. Or you can build a dam around the
space out of clay. Then, when you are drilling, since the drill will
load up frequently, you need to pump it - push, pull back, push, pull
back, all the way through. Be aware that drilling a 3mm hole through
1/4" of brazilian agate will probably take 20-30 minutes. It’s not
you, it’s the agate…

I came across this link on the Warmglass Forum

I thought it was helpful.

Tim Blades.

Here is a web tutorial on drilling holes and finishing stone beads :

The author sells diamond tools including drills:



Thank you! It appears to be an excellent site and I’m getting geared
up to use the technique.

Thanks again.


I understand about drilling holes in stone, but I don’t understand
your email. Are you unable to drill these holes? I am not planning to
purchase an ultrasonic drill just to drill two holes. I do have
diamond drills in the shop. I suggested a 1.8mm hole size, but I can
accept a 2.0mm hole. Nothing larger. It would weaken the stone. We
can adapt the tubing size to match your holes. I just happen to have
1.8mm drills and 1.8mm tubing in stock.


Douglas Zaruba
16639 Raven Rock Rd.
Sabillasville, MD 21780
301 241-3494

Here is a web tutorial on drilling holes and finishing stone beads
The author sells diamond tools including drills:

I would like to second this recommendation. There’s no one better
than Danny Lopacki.

Hi Doug,

No I’m not at all saying small holes are impossible, my email was
just a general caution to point out that the smaller the hole the
more difficult it is to drill: that as the diameter goes down the
pain-in-the-butt component goes up, and why this is so.



The original stone is on its way to you. I’m going to be in Panama
until April 15. If you have any questions, I’ll try to get back to
you, but may not be able to reply quickly. If you have a question
that needs a fast answer, please contact Andrew at the gallery:

I know what a pain drilling small holes can be. I had a production
piece that required .8mm holes drilled to a depth of 10mm. Oh yeah!
What was I thinking?


Douglas Zaruba
16639 Raven Rock Rd.
Sabillasville, MD 21780
301 241-3494