How to Drill Holes Through Glass. You can drill a hole of any size through glass if you choose the appropriate drill bit. To drill holes smaller than 1/2 inch, choose a diamond drill bit with a round-end cylinder or use a ball-shaped bit. To drill holes larger than 1/2 inch, choose a diamond core bit. Typically, drilled holes are smooth and won't require any finishing.
Put on your safety glasses to protect your eyes from any shards of glass. You may also want to wear protective gloves.
Place the glass onto a sturdy, flat surface. This will support the glass as your drill into it.
Mark the locations where you will drill your holes. Leave a 1-inch margin around the perimeter of the glass to avoid breakage.
Insert a 1/8- or 3/32-inch diamond bit into the drill. Starting with a diamond drill bit that is smaller than needed will help to keep the glass from cracking as you drill.
Apply lubricant to the drill bit.
Drill halfway through the glass using very light pressure. Start drilling at about 2500 to 5000 RPM, increase the speed very slowly, and apply lubricant as needed.
Turn the glass over carefully.
Drill into the other side of the glass so that the new hole meets the end of the hole your drilled in Step 5. This completes the "pilot" hole.
Increase the size of the diamond drill bit you use gradually until the hole reaches the appropriate size. Continue to drill starting with very light pressure and low RPM and add lubricant as needed.