Controlled flow of displaced material in self-pierce fastening

A method of applying a self-piercing fastener to a workpiece comprising the steps of;

• (a) locating a punch in alignment with a setting die, the setting die being formed with a radially inner cavity and a radially outer cavity surrounding the radially inner cavity;
• (b) positioning the workpiece between the punch and the setting die;
• (c) positioning a self-piercing fastener between the workpiece and the punch;
• and
• (d) advancing the punch to drive the fastener into piercing engagement with the workpiece, the fastener thereby displacing material from the workpiece into the setting die wherein the fastener is a semi-tubular fastener having a head and a shank, the shank having a tubular portion engaging the workpiece and the head closing one end of the shank, and wherein, as the fastener penetrates the workpiece the fastener displaces a slug of material with a diameter substantially equal to the diameter of the shank of the fastener, a first part of the displaced material flowing into the radially inner cavity in the setting die and a second part of the displaced material flowing into the radially outer cavity of the setting die.