How to drill holes in sea shells or sea glass

Time for a bit of non-photography craft now. I spent some time last night drilling a collection of shells and sea glass to make hanging decorations, and I had to search around a fair bit looking for instructions, so I’m going to lay out how I did it to help other people in the same situation. Before I start let’s just get this out of the way:

Warning! Drilling stuff is dangerous! If you accidentally drill a hole in your hand/get shell in your eye/inhale silica dust/lose your hearing using these instructions, I am not responsible!

Tools

You’ll need some sort of rotary tool. I used a Dremel, but there are many other brands which I’m sure would work just as well.

The choice of bit is far more important. You want a diamond wheel point bit – this is basically a shaft with a sphere on the end which is covered in tiny diamonds. The diamonds are hard enough to cut through the glass and shell. They come in various sizes; the 4.4mm one is the best one for this job – it makes a nice-sized hole for threading onto twine, etc. but more importantly, it’s the only one where the cutting bit is smaller than the shaft:

This is important, because it means that once you’ve drilled your hole, it doesn’t matter if you accidentally keep pushing and push the shaft through the hole you have just made. In contrast, if you use one of the smaller bits, the shaft will not fit through the hole, and if you don’t stop as soon as the hole has been drilled, the conical bit of the shaft will crash into the edges of the hole and probably make a mess.

The 4.4mm diamond bit has a 2.4mm collet, which I think is not the one that you get when you buy a Dremel. So you’ll need to buy the right sized collet as well. Might as well get the set, they’re cheap.

To replace the collet that’s currently in the Dremel with the right-sized one, just unscrew the chuck all the way and the collet will drop out. You’ll also want a shallow container, since the actual cutting needs to be done under water to stop the shell and drill from overheating. A shallow plastic food tray will do the trick.

Ear and eye protection would also be a good idea. You probably got a pair of safety goggles when you bought your roatary tool, so there’s no excuse for not wearing them. Also, you won’t believe how loud this tiny drill gets when you’re cutting your way through a thick shell or piece of glass. It’s like a dentist’s drill but much louder. So wear earmuffs if you’ve got them. If you have a dust mask, use it too. There shouldn’t be a much of an issue with dust for this particular job, as all the cutting will be done under water, but it’s a good habit to have.

Technique

Take your shell or bit of glass and figure out where you’re going to drill your hole. Hold it at the bottom of your shallow container and figure out where the water level needs to be. This is the only tricky part of this job; you have to get the water level so that the bit of the shell you’re drilling is completely covered, but making sure that the drill itself doesn’t go in the water.

You want the water to come about half way up the shaft of the drill bit. If you have a bunch of shells to drill, you can put a bit of tile or spare shell underneath smaller shells to raise them up – that way you won’t be topping up or emptying the water every 30 seconds.

Once you have the water level correct, start drilling. Figure out how you are going to hold the shell steady in such a way that you don’t drill into your hand. Because the speed of the drill is so high, there isn’t much torque, but there’s still enough to spin the shell around if you don’t steady it. Be sure to start the drill before it’s touching the surface of the shell – if you start it when the bit is in contact with the shell it will just skid off. Use the slowest setting and don’t apply very much force – let the drill bit do the work.

You’ll be able to feel once the drill bit has broken through. Turn off the drill and wait for it to come to a stop before lifting the shell off the shaft. If you just pull the drill out while it’s still spinning, the cutting bit will nick the edges of the hole and make a mess.

If you have a very delicate shell with multiple layers, the underneath of the hole might be messy. The trick to drilling a nice neat hole in shells like this is to drill until the hole has just broken through the back side, then turn the shell over and widen the hole by drilling from the other side. This technique is very time-consuming, as you have to keep stopping to check the depth of the hole, so only use it if you have to.

Remember to change the cooling water when it gets too cloudy to see. You don’t want to be plunging your drill into the murky depths only to find out that you’ve drilled through the bottom of your container, or your table. Also, if you have a bit batch of shells to drill, you might want to stop every few minutes and let the drill cool down.

That’s pretty much it – if you have questions, just leave them in the comments.