It is a kind of screw that can tap the thread without drilling first. Applied on tapping plate is metal or thermo-plastic. The self-tapping screw uses a mold (two thread plates) (male and female) to be installed on the machine when making threads. The thread plate will be driven back and forward by the machine to force the smooth and unthreaded screws to form the threads. Then, strength the hardness by heat treatment, the surface of the screw is plated or painted will delay the corrosion caused by time or environment.