Patent ID: 7047617

Claim:
A method of attaching a self-piercing element in a panel supported on a die member, said self-piercing element including a tubular barrel portion having an open free end including a piercing surface and an integral radial flange portion adjacent said tubular barrel portion including an outer surface having a plurality of spaced inwardly concave surfaces, said die member including a panel supporting end face and an annular die cavity in said end face including a central die post having an end surface including a piercing surface spaced below the plane of said end face and said annular die cavity surrounding said central die post, said annular die cavity including a semicircular annular bottom surface and a substantially continuous frustoconical side wall having an included angle of between 5 degrees and 12 degrees extending from said semicircular annular bottom surface to said end face, said method comprising the following steps: supporting a panel on said end face of said die member; driving said open free end of said tubular barrel portion against said panel and said panel against said end surface of said die post; continuing to drive said open free end of said barrel portion against said panel, piercing a slug from said panel between said piercing surfaces of said barrel portion and said end surface of said central die post, forming an opening through said panel, and simultaneously deforming a first portion of said panel adjacent said opening into said annular die cavity against an outer surface of said tubular barrel portion; driving said open free end of said barrel portion against said semicircular annular bottom surface of said annular die cavity, deforming said free open end of said barrel portion radially outwardly and upwardly toward said end face adjacent to but spaced from said side wall, forming a U-shaped end portion of said barrel portion, and deforming a pierced edge of said panel portion into said U-shaped end portion of said barrel portion; and continuously, incrementally deforming a second panel portion in said annular die cavity between said outer surface of said flange portion of said self-piercing element and said side wall of said annular die cavity radially into said inwardly concave surfaces.