Patent ID: 7152297

Claim:
A method of attaching a self-piercing female fastener to a metal panel, said method comprising the following steps: forming a self-piercing female fastener including a central pilot portion having a planar end face, a flange portion on opposed sides of said pilot portion having a panel support face generally parallel to said end face of said pilot portion and a groove in said panel support face of said flange portion having an inner side wall defining an outer face of said pilot portion extending generally perpendicular to said end face of said pilot portion from said end face, a bottom wall including a first bottom wall portion adjacent an outer side wall of said groove generally parallel to said pilot end face, a second bottom wall portion adjacent said pilot portion inclined upwardly from said first bottom wall portion to said outer face of said pilot portion, and said outer side wall of said groove inclined inwardly from adjacent said first bottom wall portion toward said outer face of said pilot portion; supporting a metal panel on a die member having an opening configured to receive said pilot portion and projecting die lips adjacent said opening on opposed sides of said opening, each of said die lips including an end face adjacent said opening extending generally parallel to said end face of said pilot portion and perpendicular to an axis of said opening, a first inclined outer face inclined relative to said end face at an angle of between 20 and 50 degrees and a second inclined face extending from said first inclined face toward a back face of said die member surrounding said die lips; driving said end face of said pilot portion against said panel, piercing an opening through said panel; driving said end face of said projecting lips of said die member against panel portions adjacent said opening through said panel into said groove and against said second bottom wall portion; and said end face and said inclined outer surface of said die lips deforming said panel portions against said second bottom wall portion outwardly against said first bottom wall portion and beneath said outer side wall of said groove, thereby forming a mechanical interlock between said self-piercing female fastener and said panel.