For low carbon steel with tensile strength ~50 kg \/mm2, the ratio of punching diameter to the thickness of the metal plate should generally be 1; For steel with tensile strength greater than > 50~70 kg \/mm2, the ratio of punching diameter to the thickness of the metal sheet should be 1.3; For steel with tensile strength > 70 kg \/mm2, the ratio of punching diameter to the thickness of the metal sheet should be 1.5. Only stamping copper, aluminum, zinc and other non-ferrous metal materials, the diameter of the punch can be less than the thickness of the plate.