A punch is a tool that is forced into a piece of sheet metal in order to shear or deform the material. Punches are available in many shapes and sizes and can be used for a variety of processes. Many punches are cylindrical and the punch diameter determines the size of the hole or pocket being formed. In shearing processes (blanking or punching), the punch has a square edge to shear the material. In forming processes (bending or deep drawing), the punch has an edge radius.