A variety of optional bore diameters to solve all size problems Heat Treated M42 HSS Bi-Metal Hole Saw is made of HSS carbon steel and bi-metal steel with sharp edges and high hardness Sturdy and solid The precision of concentricity makes the tooth edge uniform and prolongs the life of the hole Designed to cut with non-binding clean edges, this hole saw cuts smoothly and effortlessly A spring on the drill automatically pushes the disc out of the saw as soon as the hole is drilled APPLICATIONS Suitable for cutting mild steel, stainless steel, cast iron, brass, aluminum, wood, etc , ideal for installing locks, knobs in doors and cabinets, or drilling larger diameter holes in tables, etc , a must-have tool for woodworking decoration Recommendations1 The hole saw may be overheated and damaged or even burnt due to fast rotating friction, we recommend customers to use cutting fluid to keep the hole saw cool during use 2 Keep the drill bit steady when drilling, otherwise the center bit may break due to excessive shaking 3 Start drilling with a slow bit speed, otherwise the center bit may break on the first use 4 The larger the hole saw, the slower the drill bit rotates, which can protect the center bit from being broken