How to Cut a Marble Countertop With an Undermount Sink

Mark a cutting line along the surface of the marble counter top using an oil pencil. Place a strip of clear masking tape over the marked line to prevent scratches on the surface of the marble from the base of the saw as you make your cut.

Place a brace beneath the sink in the cabinet, propping it in place to prevent it from moving as you cut through the marble.

Put on a pair of safety glasses and work gloves to protect yourself from flying marble chips.

Attach a skill saw containing a hose attachment to a guiderail. Clamp a rail onto the counter top slab with the blade of the saw aligned with the drawn cutting line on the marble surface. Attach a hose to a water feed kit, and attach the other end of the hose to the saw’s water intake. Run the second hose from the feed kit into a large bucket filled with water.

Start the water feed, and then switch on the saw. Lower the blade to the surface of the marble and begin cutting through the countertop. Push the saw along the clamped rail to cut through the marble along the marked line.

Release the trigger on the saw when you reach the end of your cutting line. Wait for the saw blade to stop spinning, and then lift it from the marble surface. Unscrew the rail clamps from the edge of the counter, and then remove both rail and saw. Repeat the cutting process for any other cuts you wish to make.

Remove any remnants of the masking tape off the counter top. Wipe off the surface of the counter with a piece of cloth. Sand the edge of the cut with 80-grit sandpaper to level any ridging with the rest of the marble surface. Wipe with the cloth again. Go over the surface a second time with 120-grit sandpaper, removing any scratches left by the 80-grit paper. Wipe with the cloth to complete the cut.