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Drilling hole in boulder opal

Don Rogers instructions for drilling seem very good. A couple of
things I’d add. First and most important, if the matrix is soft when
you start drilling, give it up. The stone is too soft and it will
not wear well. That means if the drilling goes at all quickly, like a
millimeter a minute, the matrix is too soft.

Second. I’m assuming you’re using a small flexible drill bit, so
when you’re starting, in order to make the pilot hole, let only a
small amount of the drill bit show, just so you keep the collet above
the water line. That will keep it more rigid and easier to direct.
But when the collet hits the water it will spray all over the place
so be careful. As you move further into the stone, extend the bit out
a little at a time and it will bend less. Also, for faster easier
drilling, add some water soluble oil to the water, like Tool Cool. It
will really enhance the drilling. It will also prevent you’re having
to use the up and down motion so much to clear debris.

Third. The break out. You can very much reduce breakout on the
back by reducing pressure when you get near. It can be deceptive how
long it will take and the closer you get to going through, often the
more pressure you’ll use becasue you’re sick of drilling. So measure
it when you get close. Stick the drill bit into the hole and hold
your thumb nail up to the hole. Then, remove the drill bit and hold
the exposed end up to the side of the stone to get an idea of how
close you are. The reason is that you can reduce the pressure
somewhat when you get closer to going through and this will reduce
breakout at the back of the stone. Also, the amount of breakout you
have can usually be evened out with a ball shaped diamond burr.

Finally, instead of a jump ring, I suggest a wire bail. One of the
posts was right, in order to use a jump ring, you will need a much
larger hole than you’d probably want.

The bail can be made easily with either silver or gold. Just make
sure you have the wire partially annealed so that when you close the
bail, it will close easily.

Drilling is actually much easier and surer than many think. I’ve
experimented with it a great deal and it’s gotten like old hat.

Good luck.
Derek Levin