How to drill a hole in a cabochon or slab

by Bruce Frymire Sep 10, 2017 0 comments

Hi, want to know a little something about drilling a hole in a stone cab or slab. Drilling is not all that difficult if you want to try it yourself.   

Supplies needed:  

A glass plate, I use a Pyrex plate.  

A battery operated Dremel drill, which can be purchased at hardware stores.  

You will also  need a pin vice that will fit in the Dremel, it will hold the smaller pin size bits. 

 3/4 mm diamond drill bits, these can can be purchased from or or Harbor Frieght has a complete inexpensive set of bits that start with 1 mm (you will need these).

And of course a cabochon, if you don't have one, on click on Cabochons to see what we have, don't purchase one until you ask us if it can be drilled.  

 My way of drilling:  You are going to drill with the smallest bit and gradually increase the bit to the size of the hole you need (this will prevent you from cracking your cab or slab).

You will be drilling under water to keep the stone cool.  Take the Pyrex plate and add enough water to cover the stone, this needs to be done so the stone keeps cool while drilling.  If the stone is very small, super glue the stone to the pyrex plate before drilling.  You can use acetone later to release the stone.  I have filled the plate with a lot of stones, and drilled them one after another.  The glue holds them securely even under water.

Mark the stone where you want the hole, not to close to the edge.

Start with a small drill bit (3/4 to 1 mm), lightly touch the stone until the hole is started.  Use a little pressure but not enough to bend the shaft of the bit.   Don't drill to fast or force the bit, these small bits can break easily.  If it breaks off in the hole you may not get it back out unless you have a hollow drill bit.

As you drill, move the bit in and out of the hole in order to fill the hole with water (keeps it cool).  Getting it hot, drilling to close to the edge and and using large bits first can cause breakage, also drilling on a fracture line may also cause the stone to break.

After drilling with the 3/4 mm bit you can increase to a larger diamond drill bit.  Use the smallest in the set first.  You are going to gradually increase the hole by using different size drill bits.  As your drilling you can feel the bit stop when it finally touches the glass plate.

Just go slowly and you shouldn't have a problem.

After the hole is finished, use a small ball bit and round out the edges of the hole.

If you glued your stone to the pyrex plate pour a small amount of acetone to cover the stone and let set until the stone is free.  Probably less than an hour.

Safety rules, use eye protectors, don't immerse the Dremel in the water, especially if it's electric  and remember your drilling the stone not your finger. 

Dry your dremel:  Using the dremel around water will cause areas to corrode, dry it after your done.  I use a hair dryer.   I didn't do this and had to replace several dremels because they wouldn't charge.