TAPPING SCREW, used to connect thin steel and non-ferrous metal plates, its general heat treatment hardness is HRC50 ° - 58 °, it is not necessary to make thread in advance on the fittings, the thread can be formed when tapping. Tapping screw has two functions, locking and tapping. The screw tail is pointed and sharp, the entire screw should have high strength, so that it can drill into the iron plate, generally choose the material of chromium manganese alloy steel, and then heat treatment.