When the punching edge is worn, the tensile stress on the material increases, and the tendency of the stamping parts to turn over and twist increases. When turning over, the size of punching holes will become smaller. 2. The strong pressure on the material causes plastic deformation of the material, which will cause the punching size to become larger. When the strong pressure is reduced, the punching size will become smaller. 3. The shape of the edge of the punch blade. If the end is trimmed with a bevel or arc, the punching force is not easy to turn over and twist due to the slower punching force, so the punching size will become larger. When the end of the punch is flat (no bevel or arc), the punching size will be relatively smaller.