Abstract

An improved fastener has a head section and an axially extending shank section. A thread convolution is disposed in a coaxial relationship with the head and shank sections. An improved holding action against rotational and axial movement of the fastener relative to a metal base member is promoted by a plurality of radially extending wedge-shaped compression ramps. The compression ramps are disposed on the head section and slope radially and axially inwardly toward the shank section. The compression ramps are effective to force metal of the base member into an annular groove which circumscribes and undercuts at least a portion of the shank section. The metal which is received in the undercut portion of the groove is effective to hold the fastener against being pushed or pulled axially outwardly from the base member. The compression ramps also force the metal of the base member radially inwardly against corners formed on the shank section of the fastener to hold the fastener against rotation. In addition, the compression ramps are embedded in the base member to further hold the fastener against rotation relative to the base member. The compression ramps are separated by flat arcuate stop surface areas which limit the extent to which the fastener is pressed into the base member.