So the hole saw shank is round on one side instead of flat. By using a rounded shank, the drill slips when drilling. I bought this hole saw to drill 4 holes in a granite/composite sink. The bit gets very hot, so be sure to use water. In addition, the chrome coating on the bit came off immediately. If you only need to drill a few holes, this is for you as a homeowner. The holes he cut were very good with no torn edges. Stay away from it like a pro as it is easy to use.