I do a lot of glass work of all kinds. Since I recently acquired a kiln, I have started branching out in some of the work that I do, and some of it has even worked out ok! But I know from experience that drilling into glass isn't always the easiest thing to do, and I did learn a lot by trial and error. I personally don't like to have a lot of the "error" part, nor can I afford it..... So I thought I would share my way of drilling into glass that seems to give me good results almost every time. It really isn't too hard, but then if you don't do it right, it can seem impossible!

Step 1: What You Will Need:

There are few things you will need to have to get a good clean hole drilled into your glass. Glass can not only be very durable, but it can also be very susceptible to the changes in temperature that occur when a friction (such as a drill bit) is applied to it.
So first off find the glass you want to drill. You can drill in almost any glass there is, but some glass is a little more difficult just because it is harder to keep a steady stream of water applied to the surface friction point.

SO gather up some glass.... or even a mirror if you want. This is a great way to add elements into a mirror such as placing your faucets "through" the vanity mirror when they are back mounted, or even adding lighting sconces on top of a mirror and the wires going through it. Just a note on drilling through mirrored glass, make sure you start on the coated side. You are less likely to knock off the coating or have a "blow out" chipping away more of the mirror surface than you would like to lose if you do this. There are mixtures sold through stained glass supply companies that help to keep the mirrored surface in tact, but they are really more expensive than I want to pay, so I just try to be a little more careful.

Step 2: A Drill or Rotary Tool, and the Bits

A good drill or rotary tool is a must. I prefer to use my "Faux" dremel rotary tool since it has a flex shaft attachment that makes it lighter than using a standard drill. You can use a standard electric drill as well, just be sure you can hold it steady on the glass.
Diamond drill bits are the only thing I ever use when drilling glass. There might be some other product out there that will do the job, but I have never found one. If you have, please let me know. I can imagine that somewhere there are drill bits tipped with corundum, but those would be way out of my price league! Harbor Freight and many of the Home Improvement stores carry these drill bits at a very reasonable cost.

Step 3: A Water Source to Keep the Glass Temperature From Fluctuating

You will need a small bowl of water for small pieces, but if you want to drill something larger that cannot fit into a bowl, you can always stream the water over the drill bit while drilling. Keep in mind that water and electricity DO NOT MIX, so take precautions to keep the water from entering the drill or getting onto plugs and sockets.
And always ALWAYS wear eye protection when drilling glass. Even if the glass does not break while it is being drilled, small particles from the hole being drilled out can get into your eyes.

Step 4: Get Ready, Get Set.... Drill!!!

But start slowly.... if the glass has no texture, or if it has a rounded edge such as these glass cabochons, there will be a strong tendency for the drill bit to skip. Skipping will not only scratch the glass, but it can chip off the edged of the piece if it goes too far.
Place the bit where you want the hole drilled, and start out slowly so that a "dimple" or small indentions is formed, this helps keep the bit in the right place.

Step 5: Be Steady... Be Patient.... and Let the Drill Do the Work...

This is probably one of the hardest parts for me, I have never been good at letting the drill (or the saw, or the lawn mower, etc.) do the work for me. I want to hurry it up and push down thinking that will increase the speed. Instead it just makes it more likely for for glass to break from the pressure being applied.
Just keep the drill as steady as possible, and eventually it will get through to the other side. You will know when it does because of the "give" you feel from it going through. I have never used the drill press to drill glass, although I am sure it can be done. I want to be able to feel how much pressure I am actually putting on the glass while drilling.

Step 6: The Drilled Hole....

There it is, a nice round hole drilled into a piece of glass so that it can be used for jewelry, or really whatever you want to use it for.
.............That is all you have to do now, find something to do with you glass piece.

Step 7: Now Just Keep on Drilling.... If You Want To!

I try to drill more than a few pieces at a time, just to save on cleaning up my work area. If you want, thread a jump ring through the hole and you can hang it from just about anything you want.
I find drilling the holes much easier than trying to keep an open hole during the firing process of the kiln. Also, it usually makes a cleaner hole, and I can decide where I want to place it by looking at what the glass did while fusing.
If you decide to try this, I wish you luck and hope you have fun doing it!