Heat treated carbon steel, oil resistant, rustproof, high heat resistant, wear resistant, high speed steel teeth for fast and clean cutting, rustproof, durable, sturdy and reusable. Advantages: The teeth have an acute angle of 30 to the right, which is very sharp and can be cut and drilled quickly, which saves energy. The inner wall of the puncher is thick and the quality is good. Easy-to-use design: There are many chip holes to prevent sawdust from clogging during use, and it won't cut at the deepest point. After cutting, there is a small spring on the cut log that will bounce back automatically, which is very convenient to use. How to: The user can achieve a smooth, clean round cut by placing the bit straight in contact with the cutting surface at low speed and letting the saw cut for a while. Wide range of applications: Bi-metal hole saws are the perfect tool for the job. Suitable for cutting wood, plastic, machinable metal, studded wood, plywood, pipe and steel, and can be used for drilling flatbed hand drills, bench drills and other equipment.