How to Drill Through a Knockout on a Granite Kitchen Sink

Measure the center of the knockouts on the bottom of the sink flange with a tape measure. Transfer the measurements to the top of the sink flange. Many manufacturers place a dot sticker on the top of the flange to indicate the center of the knockout. Move the dot sticker as necessary to mark the center of the hole.

Place the granite sink on a pair of saw horses. The front and back of the sink flange should rest on the top of the saw horses. Position the packing box or cardboard under the bottom of the sink to help support the bottom of the sink.

Install a diamond-tipped hole saw that is the same diameter as the knockout circumference into your drill. Diamond-tipped hole saws will not dull as quickly as a standard hole saw.

Ask your helper to standby with the water-filled spray bottle. Set the spray nozzle to “stream” instead of “spray.”

Place the tip of the drill bit in the center of the hole saw over the center mark of the knockout hole on the top of the sink flange. Begin drilling until the hole saw begins to touch the granite surface.

Lift the drill out of the hole and ask your helper to stream water into the hole. This cleans out the hole as well as cools the granite.

Begin drilling again, applying light pressure at a medium speed. Ask your helper to stream water directly onto the hole while you drill. This keeps the bit cool while drilling. Make sure the water reaches down to the very tip of the drill to ensure adequate cooling.

Continue drilling until you feel the knockout plug release from the rest of the sink. Pull the drill out of the hole. Clean the area with water, and file the inside edge of the hole lightly with a fine file to remove any burrs.