When drilling with a hand electric drill, the material of the drill should be selected according to the nature and hardness of the material. There are several suggestions: 1. Generally, high-speed steel tool drills are used, which are only suitable for drilling on materials with Rockwell hardness below HRC50, such as the common Q535 steel plate, which is our common drill bit. Good cutting hardness can still be maintained at the working temperature of about 600℃. 5. When the hardness of materials exceeds Rockwell hardness HRC50, such as spring steel and stainless steel. High-cobalt high-speed tool steel drill can be used to drill holes, and its heat resistance is much higher than that of ordinary high-speed steel drill. 3. When the hardness of the material exceeds Rockwell Hardness HRC30, such as heat-treated steel, cemented carbide drill can only be used for drilling, because the red hardness of this cemented carbide drill is incomparable with other materials. Carbide bit means that cemented carbide is only embedded in the cutting part of the bit.