We use diamond tipped bits from Rocket Supply but they are expensive for a one time use. You can use a regular masonry bit if you keep it wet. You can make a little dam with a modeling clay to hold water around the area you’re drilling. The reservoir you create should be about 1.5″ tall and 4-5″ in diameter with the drill hole in the center. Press it firmly into the granite so that the water doesn’t escape. That will keep your bit cool and allow you to get through the stone. It’s important to go slowly and let the bit work, frequently pulling it out of the hole to cool and remove the debris in the hole.
