Common bathroom tiles are usually made of clay with a hard, glazed finished. Drilling into one can cause the fragile clay to crack, and it is hard to avoid scratching the glaze if the drill bit skips around. Drilling a hole into porcelain tiles can be even more difficult. When drilling porcelain, it may be necessary to stop occasionally and cool the bit with a drop or two of cutting oil.
Place two strips of duct tape in an "X" pattern over the area you want to drill.
Mark the site for the hole on top of the tape, using a pencil.
Insert a new carbide-tipped masonry bit into your power drill if you are drilling ceramic tile. Use a diamond-tipped bit for porcelain tile.
Place the bit on the mark and start the drill. Apply steady but light pressure as you feel the bit eat into the tape and the glazed surface of the tile. Drill at a low speed until the hole is completed.
Reverse directions and withdraw the bit. Remove the tape from the tile.