Holey Stones, Or: So You Want to Drill a Hole in a Rock

So you've got a pretty stone and you want to hang it on a necklace, but alas it has no hole for a cord or jump-ring from which to hang.

What do?

Follow along and I'll show you.

Time: Varies. Depends on hardness and thickness of stone, and abrasiveness of burrs (read: new burrs fast, old burrs slow).

Skill: Some

Caution: Basic power tool precautions. Tie long hair back, don't wear super loose clothing that can get tangled around a burr spinning at several thousand RPM, and wear safety glasses/goggles.

Step 1: Tools & Materials

Need

• The stone(s) you want to drill a hole in.
• Dremel, Foredom or similar rotary tool, preferably with a flex-shaft attachment (can be done without the flex-shaft, but will be much easier with).
• Diamond engraving burrs (or coring bits, but they make holes much larger than I wanted, and also I would have had to special order them)
• Container deep enough for the stone being drilled, but not so deep you can't comfortably hold the stone in place. I used an old Philadelphia cream cheese container.
• Piece of craft foam, or leather or other thick, tough fabric.
• Contact cement, or any other adhesive that can glue foam/fabric to plastic, and won't dissolve in water.
• Water, either right from the faucet or in a bottle
• Safety glasses

Recommended

• Towel
• Permanent marker
• Ear protection

Optional

• Flashlight
• Another larger container
• Dust mask

Step 2: Water Tray Preparation

"What do I even need this for? Can't I just start drilling through the rocks as-is?"

Well, yes, you could, but that would a) take a lot longer, b) get a lot hotter, and c) shorten the life of the burrs. The water bath acts as both lubricant and heat-sink, keeping the burrs from getting gunked up, and pulling the heat out of the stone so no burning of fingers happens. Yes, the friction of burr against stone can heat things up that much. (Have I drilled holes in rocks without using water? You bet I have. Not doing it that way ever again if I can avoid it.)

Trim the piece of craft foam (or whatever you're using) to size if need be, place it in the container and mark off where you want it to sit. Follow the directions for the adhesive you're using to glue it down. The foam or leather will help hold the stone in place while it's being drilled, and add an extra layer of protection to keep the burr from punching through the container once it breaks through the back of the stone, though unless you chose a very thin-walled container or you're super-aggressive with your drilling, that isn't likely to happen with or without the foam.

Step 3: Stone Preparation

Grab the stone you want to drill, and mark where you want the hole. Why mark the hole? Because refraction. And waves. The vibrations from the rotating burr often makes some really neat interference patterns on the surface of the water, and that coupled with the way water refracts light means that once the stone is under water it can be finicky getting the burr properly lined up. Marking the position of the hole provides a target to aim for.

Or don't mark anything and just jump right in, refraction be damned, if that's how you roll.

Step 4: Choose Your Weapon

Select a burr. The narrower cylindrical or tapered ones are what I prefer. Coring bits are another option, but they're too big for what I'm usually working on. Secure the chosen burr in the Dremel chuck.

I have a bunch of carabiner clips suspended from my workshop's ceiling, which I'll clip the Dremel to when I'm working. Having it hanging freely makes it much easier to use and control, since the extra weight of the flex-shaft isn't pulling on the hand-piece.

Step 5: Fill 'Er Up

Spread the towel over your workspace. Not required, but recommended. At least a little bit of water will probably end up splashing outside of the container at some point, plus it's convenient to be able to just wipe your hands right on the table.

Place the container on the towel, place the stone in the container, and fill the container with enough water to completely submerge the stone.

Step 6: Engraving GO

Grab the Dremel and let's go.

The water traps all the rock dust so I don't always bother with a dust mask, but if you want to wear one, go ahead.

Starting with the burr almost vertical makes it much more prone to slipping out of position as there is no pilot hole yet. It's much easier to begin at a shallow angle to engrave a little pit, and raise to vertical once the hole is deep enough to keep the burr from wandering.

Once the burr is vertical, move it in very small circles (watch the video for a better visual on what I mean), and pretty much just keep on doing that. Some other how-tos on drilling stones I've seen suggest pulsing it up and down, but those were all for coring bits instead of engraving burrs, and in my own experiments I've found that a slight rotational wiggle does a faster job.

Pause every now and then to check the bore depth so you have some idea of how soon the burr will punch through the other side. Pressing too hard at the end could make it chip out the back, and/or punch through the bottom of the container, so back off a little on the pressure when you think you're getting close. There might be a very slight change in the sound or feel of the drill right before it breaks through.

The stone I drilled through for this is an opaque piece of black jasper, but if you've got a more translucent stone, you can check your progress from the reverse by shining a bright light through the stone. I have a small LED flashlight that does a good job at this, though sometimes just an overhead light will do if the stone is very translucent or the hole far enough through. Marking where the hole is and then drilling from the reverse to meet in the middle is a good way to prevent chip-out.

Step 7: Touch-Up and Finishing

It's difficult to completely avoid all chipping, so once the hole is completely drilled I lightly chamfer the edges with a round burr. This cleans up any existing chips and prevents future ones.

Rinse off and dry the stone. Now it's ready to string on a necklace, either by adding a jump-ring or threading a cord right through the hole.

Enjoy your new shiny.