Experimental results are presented for the piercing of circular holes in sheet metal using pads of conventional rubber or polyurethane. An empirical equation has been obtained for calculating the required loads and an attempt has been made to interpret this equation in terms of rubber hardness and the work-hardening characteristic of the metal. It is shown that the deformation behaviour of the polyurethane is different from that of the rubber and that it is misleading to treat polyurethane as though it is merely a rubber with a higher Shore hardness.