Method of manufacturing a fastener such as a bolt, rivet, or the like

Claim 1

In a method of manufacturing a fastener such as a bolt, rivet, or the like, the steps of cold forming one end region of an elongated shank into a head of frustoconical configuration having a circular cross section throughout its length and having at one end of saId shank a free circular end surface of minimum area and between the ends of said shank an opposed end of maximum cross-sectional area greater than the cross-sectional area of the shank so as to define a shoulder projecting outwardly from the shank, inserting said frustoconical head into an opening defined by an inner peripheral region of a flange blank, with the latter opening being large enough to receive said end surface of minimum diameter but too small to receive the opposed end of said frustoconical head and with said opening having a non-circular configuration according to which the edge which defines said opening engages said frustoconical head at circumferentially spaced portions thereof with the edge portions of the opening which engage said frustoconical head being composed of straight edge portions, so that said flange blank engages said frustoconical head between the opposed ends thereof, and then finish cold forming said frustoconical head while axially compressing the latter and flowing the material thereof around said inner peripheral region of said flange blank which defines said opening thereof onto and againt opposed faces of said flange blank and into the spaces between those portions of the edge which defines said opening which initially engage the exterior surface of frustoconical head, so as to integrate the flange blank with said shank while uniting the flange blank and shank not only by the pressure of the flowing material of the frustoconical head against the opposed faces of the flange blank to prevent relative axial movement between the flange blank and shank but also by the material of the frustoconical head which flows into the spaces of the opening between the edge regions thereof which initially engage the frustoconical head for providing in the opening of the flange blank a configuration of the shank which is of a non-circular configuration matching the non-circular configuration of the opening of the flange blank to prevent rotary movement between the flange blank and shank.