To prevent the tiles from splitting when laying "nylon" dowels, you must have in the concrete drill box, "round iron" ends of about 7 to 10 cm long and of every usual drilling diameter.: 6, 8, 10.
After piercing the tiles, place your ankle and push it into its hole, then with the round iron of the same diameter push the back of the enamelled part of the tile, so by screwing in, the screw will have room and will not burst the enamelling.
To start a hole in wall tile, using a "tungsten" scribe, point the front hole with the aid of the latter and a small hammer, the impact is sufficient to blow up a pellet of enamel and because of this, the drill can turn without slipping.
Then drill without percussion until the drill is not in the biscuit (unglazed part).Suggest a tip for this theme