How to drill a hole in a rock: A Tutorial

As I talked about in this post, I love to collect rocks and make crafty things with them. Some of you let me know you are interested in how I drill holes in my rocks so here is a photo answer/tutorial for you.

First things first - you will need a small drill such as a Dremel. I use a drill press that Steve's great uncle made. My drill is electric and works great for me though I know some folks prefer battery operated since you use water in the drilling process. Here's a couple of views of my setup:

My drill adjusts up and down along this rod allowing me to get in close to my rock.

This switch increases and decreases the speed of my drill.

Ok, back to what you need to drill a hole in a rock. Besides a drill you need a drill bit. I use a diamond tipped drill bit from Indian Jewelers Supply Co. in Gallup, New Mexico. They have very reasonable prices - last time I ordered my standard diamond tipped Triple Ripple 2.1 MM bit it cost $2.00. You can see the bit in the foreground of this photo.

Other supplies:
-safety goggles (a must to protect your eyes should rock fragments fly!)
-durable dish with cool water (filled so it will just cover your rock; water is essential to keep your bit cool enough!)
-towel to dry your hands as needed
-straight edge such as a straightened-out paperclip
-sharpie for marking drilling location
-tools to tighten your bit if necessary (I need to use my Gerber pliers & channel locks to tighten my chuck (part that holds the bit) tight enough so the bit does not just spin on the rock)
-rock


Here is the procedure I use:

Step 1: Put on safety glasses!

Step 2: Setup drill for drilling. Insert drill bit and tighten chuck. Put water dish with rock under the bit on the press. (Mark rock with sharpie where you want to drill.) Lower the drill to ~1/8-1/4 inch above water. Turn drill speed to low and then drill in.

Step 3: Drill halfway through rock. Hold rock tightly with two fingers and use other hand to move the press up so the rock contacts the bit. Hold very firmly until the bit bites. If you are drilling an uneven rock your bit is likely to jump to the lowest spot so pick a good drilling location and then hold tight! I find if I am drilling an uneven rock I can shim a piece of foam or wadded string under the lower side to bring it more level so I can put the hole where I want.

I turn the speed to about medium to get the hole started and then to medium-high to high depending on the type of rock. I don't really have any hard and fast rules about drill speed. I am sure someone does, but I just tell by the rock dust filtering through my water and how the bit feels on the rock. If you are not seeing any dust (indicating rock being eroded away) adjust your speed. If this does not help and you are using a used bit switch to a new one.

Once my bit bites, which will be in a matter of seconds, I slowly move the press up and down so the bit is coming in and out of the rock ever so slightly. This allows rock fragments to clear the hole and for water to enter it. Some rocks make cloudy water very fast and I need to change the water midway through. Just make sure you can see clearly and you will be set. Also - if I am drilling a particularly hard rock and it is taking a while to get through I will change the water when it starts to warm. Cool water keeps the bit cool.

Continue drilling till you are about halfway through the rock.

Notice the cloudiness from the drilling action next to my finger on the left .

Step 4 - Turn rock over and finish drilling hole from the other side. This step is essential or else you are likely to chip a chunk of your rock away as your bit punches through the other side. The tricky part is to get your two holes to line up! I use a straightened paperclip: I stick it in my drilled hole and eyeball a line through the rock and mark that spot with a sharpie. See photos:

Once you are satisfied with the location to drill, put your rock back in the dish (changing the water if necessary) and repeat Step 3. I have misaligned holes before and it isn't pretty, but you do learn as you practice. :)

Here's a photo of the front of the rock drilled halfway through...


And a photo of the back of the rock getting close to through...

Once you get close to getting all the way through you will notice a couple of things. First, your drilling will feel different. It feels crunchier to me - sometimes you can hear this crunching. When you notice this, hold on securely and go slowly. If you push hard you might chip out the other side, even with pre-drilling, or you might drill through your container or both. Check out the nice hole in my rock in the following pictures.

This rock took about 5-7 minutes to drill through. If this rock was thicker it might take 20 minutes or so because it is quite hard. Rocks such as sandstone, which is very soft, drill very quickly...sometimes in a minute or two.

I hope this tutorial is clear and helpful. It takes time, care and effort to tweak out your equipment and technique. As with any process that uses power tools and hand tools, safety come first - if you don't feel comfortable that you can safely attempt this process, seek help from someone who is more experienced.