Master Cobalt Bi-Metal Hole Saws This premium line of professional quality hole saws features an M3 high-speed steel cutting edge, electron beam welded to a tough steel backer. Caps stand up to abuse and punishment, yet are lighter and easier to use than those of competitors. Positive rake tooth design provides better chip clearance as teeth cut into wood, plastic or any machinable metal. The 1-1/2"" cutting depth cuts easily through 2x4's. A separate arbor is required. --Backer, cutting edge and cap work together to provide faster, longer-lasting cutting action. --Bi-metal design bonds M3 cutting edge to fatigue resistant backer. --Positive rake teeth clear chips better for longer life and easier cutting. --Teeth stay sharper and make smoother cuts.