The selection principle of stamping diameter of cold stamping die is as follows: when stamping materials with tensile strength of ~50tg/mm, the punch diameter can be equal to the material thickness; When punching materials with tensile strength > 50 ~ 70 TG/mm, the punch diameter is equal to 1.3 times the material thickness; When punching materials with tensile strength > > 70g/mm, the punch diameter is equal to 1.5 times the material thickness. When stamping copper and aluminum materials, the diameter of the punch can be less than the thickness of the plate, which can be 0.8~0.9 times.