How to Drill Granite? | Bit Type, Speed, And Water Matter Most

Granite is one of the hardest natural stones, and a standard drill bit won’t make a scratch. The reliable method is a diamond core or diamond-tipped bit run in a variable-speed drill with the hammer action switched off. Your success depends on three things: using the correct bit, keeping it cool with water, and starting the hole at an angle. Here is the exact process that gets clean holes through granite countertops, tiles, and slabs.

What You Need For Drilling Granite

Before you start, gather the right equipment. A hammer drill setting will shatter the stone, so a standard variable-speed drill is the base tool. The bit must be diamond-tipped — either a diamond core bit for larger holes or a smaller diamond twist bit for holes under a quarter inch.

The complete setup is straightforward:

• Variable-speed drill with the hammer mode off
• Diamond core or diamond-tipped bit matched to the hole size
• Painter’s tape or duct tape to stop the bit from wandering
• Water supply — a squirt bottle, wet sponge, or a water ring made from plumber’s putty
• Scrap granite piece for practicing first

The type of bit you choose matters more than anything else for a professional finish. Our tested product roundup covers the options that consistently perform well: best drill bits for granite.

Diamond Drill Bit Speed And Technique

Run the drill in rotation mode only and use light, steady pressure. Let the diamond edge do the cutting; pressing hard only generates heat and glazes the bit.

Dynamic Stone Tools’ guidance specifies exact speeds for diamond core bits: use 2000 rpm for bits 0.5 to 0.75 inches in diameter, and 1200 rpm for bits 1.0 to 1.5 inches in diameter. The larger the bit, the slower the drill speed.

Here is the step sequence that produces a clean hole, based on manufacturer instructions:

1. Practice on a scrap piece of granite to test your technique.
2. Place duct tape over the cut area to prevent the bit from sliding.
3. Install the diamond bit in the drill and set the speed per the bit size.
4. Start at a 30° to 60° angle to establish a groove, then lower the drill to 90°.
5. Drill about 3/8 inch deep, then remove the tape.
6. Build a water ring around the hole and keep it filled about 3/8 inch above the surface.
7. Continue drilling with light pressure. The water keeps the bit cool and flushes out stone dust.

You’ll know the hole is progressing correctly when you feel a steady, smooth grinding sensation and the water around the bit turns milky with granite slurry. If you see smoke or the bit glows, stop immediately and add more water. When the bit stops cutting effectively, it can be redressed by drilling through a reconditioning stone, which restores the diamond surface.

Common Mistakes That Ruin Granite Holes

Most failed holes come from a few repeatable errors. Avoiding them is easier than fixing a chipped countertop. Here are the mistakes and the correct approach:

Always clamp the granite to a stable work surface so it cannot move. Wear eye protection to guard against stone chips, and control the fine dust with water or a shop vacuum. If you’re drilling into an installed countertop, place a piece of scrap wood behind the hole to prevent blowout on the underside. Eternal Tools’ practical tutorial on how to drill granite walks through the complete technique with step-by-step photos.

Do You Need To Drill Granite With Water?

Yes for virtually every diamond bit — water prevents the tip from overheating and glazing over. There are a few “dry” diamond bits designed without water, but they are the exception and are usually slower. If you’re drilling overhead or into a vertical surface where water is impractical, use a spray bottle to mist the hole frequently or a wet sponge pressed around the bit. The water keeps polished granite cool enough to prevent thermal cracking and carries the abrasive dust away so the diamond can keep cutting.

FAQs

Can you drill granite with a regular masonry bit?

A standard masonry bit with a carbide tip can scratch granite but will dull quickly and struggle to make meaningful progress. A diamond-tipped or diamond core bit is the reliable choice and pays for itself in time saved.

What speed should I set my drill to for granite?

Match speed to bit diameter. For a 0.5 to 0.75 inch diamond bit, set the drill to 2000 rpm; for a 1.0 to 1.5 inch bit, lower it to 1200 rpm. High speed on a large bit builds heat faster than water can remove it. When in doubt, run one speed lower — slow and steady produces cleaner holes.

How long does it take to drill a hole in granite?

Larger core-bit holes take longer because more surface area must be ground away. Rushing the process with heavy pressure is the most common reason drilling takes even longer.