I need to enlarge the cutout in my tile counter to accomodate a new cooktop. The countertop is hard ceramic tile on cement board on plywood. The cutout is now 34x18 1/2 and it I need 33 7/8x19 1/8 for the new cooktop. All the cooktops we've considered need over 19" in width.
I plan on getting a 7" dry diamond blade for my circular saw and I may need a diamond cup blade for my grinder to finish in the corners.
Sure that will work. Build a plastic room around you and go for it. Or you could Wetsaw the ceramic and then cut the rest with a circular saw. Or you could pop out the ceramic carefully. If you had extra tiles I would say you could take the tiles out around the existing hole then cut the wood and then put new tiles in. Probably could come up with options if I think about it. Got to Go!
If you use the circular saw, cover the tile to protect in from scratches from the saw's plate. Have a helper hold a shop vac close to the exhaust.
Personnaly I would use a grinder for the whole job of the tile and cement board and a jigsaw for the wood.