When replacing a large kitchen sink with a smaller one, or if you just accidentally cut the hole too large, it's no easy job to create a smaller cutout when a larger cutout is already there. To make a sink cutout smaller, you first have to make it larger. A section of the counter top must be removed and an insert must be put in its place. A new, smaller cutout can be cut from the replaced section. Matching material of the original counter top can be used, or you can offset the area with different material, such as butcher block design.
Measure and mark with a pencil and framing square the replacement counter top section. Use a circular saw to cut it to the preferred size. Use it as a pattern for the hole to be cut in the existing counter top. Lay it on top of the existing counter top and mark the edges around it. The area can be several inches or several feet larger than the original hole. Measure carefully to align the section on all sides and with the front of the existing counter top. The left, right, front and back edges of the section must be accessible underneath.
Use a circular saw and jig saw to cut out the section of counter top. The edges will be visible when finished, so the cut must be clean and straight.
Lay the replacement counter top section in the hole and check the fit. Remove the section, apply glue to all four sides and replace it in the hole. The replacement section should be the same thickness as the original counter top. If not, wood spacers will be needed underneath to make the top flush along the edges. Wipe any excess glue off before it dries.
Place wood strips underneath the top along the edges of the replacement area to join the two pieces. Drill holes in the wood strips and partially into the counter top. Use screws to screw through the wood strips and into the counter top to strengthen the top. Place half the screws in the replacement piece and half in the existing top. Do not let the screws extend through the top of the finished counter.
Mark the new, smaller sink cutout area on the replacement section. Now you're ready to cut it out and install a smaller sink.