How to Cut Quartz Countertop for Undermount Sink

Installing an undermount sink in a quartz countertop can seem daunting, but with the right tools and techniques, it can be done successfully. Here is a comprehensive guide on how to cut a quartz countertop for an undermount sink installation.

Selecting the Right Tools

Cutting quartz requires specialty tools to get clean edges and avoid cracking or chipping. Here are the essential tools you’ll need:

  • Diamond-grit hole saw or core drill – creates sink cutout hole
  • Jigsaw with diamond-grit blade – cuts straight edges
  • Router with diamond-grit bits – smooths and polishes cut edges
  • Respirator and eye protection – quartz dust is extremely harmful

Avoid using a circular saw, as this can crack the quartz. Stick to tools designed specifically for cutting engineered stone. Investing in quality tools will give the best results.

Measuring and Marking the Sink Cutout

Accurate measurements are critical to get a perfect cutout for your undermount sink. Follow these steps:

  • Set the sink in place on the countertop to find the ideal positioning. Make sure it clears the cabinet front and walls.
  • Trace the outline of the sink with a permanent marker.also mark the faucet holes if drilling them out.
  • Measure the sink specs to mark the correct cutout size. Account for any overhang or rim.
  • Use painter’s tape to mark cutting lines, allowing an extra 1/16″ gap for adjustments.
  • Use a straightedge and square to ensure cut lines are perfectly straight.

Double check all measurements before cutting to avoid expensive mistakes!

Cutting the Sink Hole

With measurements set, it’s time to cut the hole. This is done in stages:

1. Drill Inside Corners

  • Use a diamond hole saw to drill relief holes at the inside corners of the cutout. This prevents cracking.
  • Drill slowly at low speed to avoid overheating and damaging the quartz.
  • Make holes just larger than the jigsaw blade width (1/2″ to 5/8″).

2. Cut Outline with a Jigsaw

  • Equip the jigsaw with a diamond-grit quartz blade and set low speed.
  • Keep the jigsaw base completely flat to the countertop so the cut stays level.
  • Cut just outside the traced sink outline following the tape edge.
  • Make relief cuts at corners to turn the blade. Go slowly for best control.

3. Smooth Edges with Router

  • Use a router with diamond polishing bits to refine the cutout edges.
  • Work incrementally with successively smoother bits from coarse to fine.
  • Rout both the top and bottom edges for a polished finish.
  • Carefully trim to your line for a perfect opening.
  • Ease and round over the top inside edges slightly.

Go slow and be cautious to avoid chipping at the last stage. The patience will pay off in the end.

Installing the Sink

After cutting, dry fit the sink to ensure it slides in cleanly. Use silicone adhesive to attach the sink according to manufacturer instructions.

Finally, make sure to use a quartz composite cleaner to remove all dust from cutting. Let adhesive fully cure before using the sink. Proper planning and careful cutting will result in a gorgeous undermount installation that flawlessly matches your countertop. With the right precautions, cutting quartz for an undermount sink is very achievable.

FAQs About Cutting Quartz Countertops for Undermount Sinks

Can I cut the sink opening myself or do I need a pro?

With the right tools and patience, an experienced DIYer can cut their own quartz countertop and achieve nice results. However, the high cost of quartz means mistakes can be costly. Hiring a professional fabricator is advisable if you are unsure.

What blade is best for cutting a quartz countertop?

Always use a diamond-grit cutting blade specifically designed for quartz. Diamond abrasives are very hard to withstand cutting quartz without wearing down. Don’t use a wood, tile, or metal cutting blade.

What’s the best way to get a clean cut in my quartz?

Cut very slowly and steadily while following your cut lines precisely. Also using a router with diamond polishing bits will refine the edges for a clean smooth cut. Rushing the cut will likely chip or crack the quartz.

Should I seal the cut quartz edges after installing the sink?

Sealing is not necessary but can add extra protection. Use a clear quartz sealant made for engineered stone around the cutout edges. Avoid silicone-based caulk which can stain.

How can I prevent cracking when I cut the hole for my sink?

Always drill relief holes at inside corners before cutting to prevent stress cracks. Follow the sink outline as closely as possible without over-cutting. Rapid temperature changes can also risk cracks, so avoid exposing cut quartz to extremes.


Installing an undermount sink in quartz countertops adds a seamless, stylish look. With careful planning, the right tools, patience, and proper technique, you can create a perfect custom cutout. Be sure to use specialized diamond blades and bits, move slowly, and double check all measurements. Relief holes are key for preventing cracks at corners. Smoothing with a router and polishing edges will complete the professional look. While an ambitious DIY project, installing an undermount sink in quartz is certainly achievable for a determined homeowner. Just allow plenty of time and care when undertaking the precision cutting.