Use the Milwaukee 4 in. Bi-Metal Hole Saw to cut holes in a variety of materials. The steel hole saw can drill almost 2 in. D. Milwaukee Ice Hardened products utilize a proprietary cryogenic hardening process that improves upon traditional heat treat processes. Unlike surface coatings that wear away, cryogenics harden to the core by minimizing soft metal (austenite) and creating more hard metal (Marten site). The result is a product that is more consistently hard throughout, resulting in life up to 50% longer than the competition.