M42 Bi-Metal Hole Saw For Use in Most Materials: Wood, Plastic, Aluminum, Brass, Cast Iron, & Stainless Steel. Variable Pitch Design (4-6 Teeth/Inch) Reduces Labor & Tool Costs By Cutting 45% Faster & Lasting Longer than Straight 6 Pitch Saws. Better Chip Clearance, Less Heat Build-Up, Lower Feed Pressure & Smooth Cuts. Bi-Metal Hole Saws Combine the Toughness & Shock Resistance of an Alloy with the Cutting Ability of High Speed Steel.