I drilled a 5/16 hole in my bathroom ceramic tile and it took forever. I walked slowly, I had a spray bottle to keep it wet and I applied a lot of pressure. This took about 20 minutes. I stopped about every 5 to take a break. The next hole I used was the smallest, 1/8th. He penetrated the same tile very quickly. About 45 seconds. I switched the beats to the next larger size and continued at the same pace. At 5/16 diameter, the second hole was completed with no problems, but the drilling was not very smooth. I like to jump a little. Third Hole I'm seeing a dramatic drop in performance at all sizes and I need new bits. I think I'll try diamond because they just don't last. So keep your expectations low and you won't be disappointed.