How to Drill in Granite Thresholds

Place the granite threshold in the doorway where you will fasten it. Determine where you want to drill through the center of the granite strip to attach it to your floor. You will need to use at least two screws for an average-sized passageway, and more for larger openings. Measure the space between the spots to ensure they are consistently spaced, around 1 to 2 feet apart. Mark the spots with a pencil once you are happy with the spacing.

Place two 1-inch pieces of masking tape centered over a spot in an "X" shape and repeat with the other spots. The tape will protect the stone from chipping in case the drill slips.

Measure the depth of the granite threshold where you will be drilling through. Place a piece of masking tape on the drill bit to mark the depth of the granite, so you know when the bit is about to break through to the other side. For example, if the threshold is 1 inch thick, wrap the piece of tape around the drill bit 1 inch from its tip.

Place the granite on a wooden work surface in case the granite breaks to prevent damage to your floor.

Drill through the granite in the center of one of the tape "X" marks, holding the drill firmly. Have a second person pour water over the drilling spot to prevent overheating or excessive dust. If it takes more than 10 to 20 seconds to get near the drill's masking tape mark, stop drilling and allow the drill bit to cool for 20 seconds before proceeding. Do not push the drill bit all the way through to the other side of the granite.

Drill for a second or two once you get near the drill bit's masking tape mark. Stop drilling and check the underside for a small mark where just the tip of the drill bit broke through. Repeat until you see the small mark.

Flip the granite over and drill through the hole, using the mark from the drill bit's tip as a guide.

Repeat Steps 5 through 7 for the remaining spots before moving the threshold back to its passageway and attaching it to the floor in your home using screws and a screwdriver.