Bi-metal, variable pitch hole saws are for all machinable aluminum, cast iron, PVC, mild, tool and stainless steels as well as nail embedded wood. Depth of cut is 17/8” deep for sewer taps. High-speed tool steel cutting teeth for shock resistance and longer life. The 4/6 variable pitch tooth design reduces vibration and promotes faster and smoother cutting. For steel, use Reed Threadguard cutting oil. Use Bi-metal hole saws to cut cast iron dry and PVC with water.