I was only able to drill a hole in 0.25" porcelain stoneware with a drill bit. The chisels are hollow, with very thin walls the entire length. I spent about 15 minutes drilling a hole, being careful to avoid the Keep speed low and cool the bit.The bit collapsed when I reached the thickness of the tile.I'm glad I only had to drill one hole with these bits, all the other holes were in the joints.