Abstract: A self-piercing riveting system comprising a headless rivet made from steel or a suitable material that provides compressive strength superior to that of the materials to be riveted together and of a height or thickness equal to the sum of the materials to be riveted, the said rivet having flat end surfaces and its body being peripherally concaved between its ends, a die having an opening therethrough of the size and shape of the piercing end of the rivet, and a punch for driving the rivet through the materials to be fastened, the said die and punch each being provided with staking lugs for engaging the margins of the pierced opening through the said materials so as to cause the materials to flow radially against the concaved body of the rivet.