These hole cutters are used on steel and steel-alloy workpieces for tasks such as cutting knockouts in electrical panels. They can also be used on stainless steel, aluminum, and other soft alloys. Hole cutters have a hollow center and a number of cutting teeth similar to those found on a circular saw blade. They cut holes by removing a section of material while leaving the core whole. This speeds drilling and allows larger holes to be made using a handheld power drill than is possible using a standard drill bit.