Die set for securing a self-attaching element

Abstract

A die set for attaching a self-attaching fastener having an annular barrel portion to a panel. The die set includes a driving member and a die member having a concave annular die cavity which is generally hemispherical in cross-section and which surrounds a center die post which projects from the bottom surface of the die cavity. The die post includes a conical side surface, adajcent the top face, which is inclined outwardly from the axis of the post. The top face of the die post preferably includes an annular top surface, adjacent the conical side surface, which defines a piercing edge, and a conical top surface, adjacent the axis of the post. The driving surface aligns the barrel portion of the self-attaching element with the center post of the die cavity and drives the free end of the annular barrel portion into engagement with the panel and through the opening in the panel to first engage the conical side surface of the post. The conical side surface accurately aligns the fastener on the post, begins outward radial deformation of the post and prevents collapse of the barrel portion during installation. The free end of the barrel portion is then received against the hemispherical bottom surface of the die cavity, deforming the free end of the barrel portion radially outwardly in a U-shaped configuration and the panel portion adjacent the panel opening is driven into the U-shaped barrel portion, forming a secure mechanical interlock.