I had to drill 6 holes in porcelain stoneware to install a vertical grab bar in my mother's shower. I was skeptical that these drills would work, but at this price why not give it a try. I first spotted the hairpin with a hairpin detector. Then I sealed the spot with masking tape and carefully marked the spots and checked them several times. Then I used the smallest possible pilot drill. I used a heavy-duty corded drill/driver instead of a cordless drill. I also used it on a standard drill setting rather than an impact drill based on google research. Use LOW/MEDIUM pressure and keep the chisel cool by holding a damp sponge directly under the chisel, which will also catch falling debris. Strong pressure will smash the racquet as other reviews confirm. The drill drilled through the tile with no problems. I then added one of the larger bits that was larger than the stainless steel screws that came with the handrail. No chips or cracks in the tile and I'm awaiting the arrival of the second handrail from Revain. Then I drill these holes. Both used bits appear to have plenty of life left. We recommend!