How to Drill Through Granite

Last Updated: September 16, 2021

Granite counters and flooring are popular among homebuilders and homeowners because of the material’s attractiveness and durability. Granite comes in a wide variety of colors and finishes and, despite being somewhat more expensive than most alternatives, it continues to be among the most popular materials in high-end building and remodeling projects. Because of its hardness and relative brittleness, however, granite can be a tricky material to work with: You need special saws to cut granite tiles and industrial-level saws to cut counter-thickness pieces. It also takes special care and tools to drill through granite. The wrong method or drill will likely result in either ruined drill bits or cracked granite. With the right tools and techniques, however, homeowners and do-it-yourselfers can drill through granite like a pro.

Steps

1
Make certain you really, really, really need to drill a hole where you’re thinking about drilling one. Consider other alternatives before you start putting holes in your granite, especially when you’re working with something as expensive as a granite countertop.
2
Determine the ideal hole size your application requires.^{[1]
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3
Mark the area where you plan to drill. For small diameter holes, you can use a small dot. For larger diameter holes, use a template or draw a precise circle that corresponds exactly with the diameter of the hole you’re drilling.^{[2]
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- If you’re concerned that the drill bit will wander, you can clamp a piece of scrap wood with the appropriate sized guide hole over your drilling target.
4
Clamp a piece of stone scrap underneath the area where you will be drilling to prevent chipping on the underside of the granite. For maximum safety and effectiveness, place a clamp on either side of the hole you’re drilling.^{[3]
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5
Install the desired size diamond drill bit into a high-speed drill or angle grinder with a drill bit adapter.^{[4]
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- Make sure the drill bit is specifically designed for drilling through granite and that it can handle the depth of drilling your application requires.
- Diamond core drill bits have a good reputation for drilling through granite with ease; a good one should be able to get through a ¾-inch (1.9 cm) slab in less than a minute.
6
Begin drilling at a steady speed.
- Some drill bit manufacturers recommend using water to cool and lubricate the drill bit while drilling. Others say you won’t need to do that for their bits. Either way, water will serve to reduce the amount of granite dust in the air.
- If you use water, form a dam around the drilling area using plumbers putty.
- If you don’t use water, you can have someone use a shop vac to vacuum the granite dust as you drill.
7
Drill until you’ve gone through the granite target and hit the underlying scrap stone.^{[5]
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8
Cool the drill bit with water in between holes when drilling multiple holes.^{[6]
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Community Q&A

Question

What if it's not possible to clamp any scrap stone under the granite?

Community Answer

It is not necessary. This is just for a more finished look under the sink.
Question

Won't it be better if we start with a C-cut (a segment of the circle to be drilled), then gradually tilt the tool to cover the entire circle? Is the 'rotational movement' you are using necessary once you get a bite? What if the tool is held perfectly vertical and steady at low RPM?

Community Answer

if you tilt the bit, the edge of the hole is parabolic and not circular. "Hole saws" for larger-diameter holes usually have a drill bit in the center that either sets or benefits from a pilot hole, so tilting might be highly problematic with the hole saw. For smaller-diameter holes this is not an issue, but also there's no real advantage to tilting at the beginning of the cut.
Question

Can I file the faucet holes of a granite top? The water faucet is too tight and will not go down all the way. It is an 8-inch faucet, center to center.

Community Answer

Use a rotary rasp. Keep it wet if possible. The rasps come in file, or stone. You will use up at least one rasp per hole.

Warnings

Always wear safety goggles when using a power drill. This caution is especially important when working with high-speed drills and hard materials like granite or marble.

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