How to Cut Inside Porcelain Corners in a Shower

Place duct tape over the area that you want to cut. The duct tape helps you focus and also helps prevent the cutting tool from slipping on a slippery porcelain surface. Mark any specific cuts with a pencil for guidance.

Install a carbide-tipped masonry drill bit or a diamond-tipped bit in a drill with a variable-speed trigger. The drill bit cuts through porcelain while the variable-speed trigger prevents the drill from overheating.

Turn down the drill to a low setting. The drill should not operate at more than 100 to 200 rotations per minute. Otherwise, the drill is likely to overheat, especially near porcelain corners, which are often thicker than the rest of the slab.

Dip the drill bit into cutting oil and wipe it down with a rag before using it on the porcelain. This helps keep the bit cool during the drilling.

Apply light pressure to the duct tape with the drill bit and gently squeeze the trigger of the drill to cut holes through the porcelain. Gradually increase pressure as the drill bit starts chewing through the porcelain. Too much pressure too early causes the drill to lock up. Dip the bit back into cutting oil every 15 seconds and wipe it off again to cool it down.

Hold a tile saw with a diamond-tipped blade up to the hole you just created if you need to make a straight cut down the tile and not just a hole through it. The hole makes the cut simpler because the tile has already been broken through. Use the same method of cutting the tile by using light pressure and applying cutting oil to the blade every 15 seconds as you make your cut through the porcelain.