Super hard wear resistant high speed steel (tooth area) laser welded to a flexible spring steel backing material. Benefit matrix II high speed steel retains tooth hardness at high temperatures for metal cutting applications. Bi-metal construction allows the blade to flex and absorb impact without breaking while cutting nail embedded wood. Hole saws are constructed with 3/16 inch thick steel backs on 1-1/2 inch diameter and larger. Smaller diameters have backs thicker than 3/16 inch thick backs eliminate the need for driving plates and prevent drive pin holes from elongating. 4/6 teeth with 8% cobalt multiple tooth design with varying tooth sets and gullet depths. Deeper gullets provide more efficient chip clearance with less heat build-up. Requires lower feed pressure-ideal for higher rpm drills. Bi-metal hole saws are high production tools designed for cutting all machinable materials, including steel, aluminium, copper, brass, sheet metal, stainless steel, wood or plastics. Heavy-duty 3/16 inch thick steel back. 1-1/2 inch cutting depth. Faster, more aggressive cutting plus. Heat resistant cobalt. Less vibration for smoother cuts. Shatter resistant. High alloy steel body construction for longer life. High speed steel teeth electron beam welded to a steel body.