A die assembly having a guide rod that includes a lower rod which is fixedly placed on a stripper plate which guides a punch for engagement with a lower die and an upper rod which is placed removably on the stripper plate for engagement with an upper die. When punching a material for punching, the upper rod is removed from the stripper plate so as to put the upper plate and the stripper plate in a disconnected state, i.e., so that the stripper plate is made free to move backwards and forwards relative to the lower die by the lower rod. When the material for punching is not punched, the upper rod is attached to the stripper plate so as to put the upper die and the stripper plate in a connected state by the upper rod, so that the stripper plate is held on to the upper die.