Abstract: In combination with a workpiece having a bore, a first counterbore, and a second counterbore which is frustoconical and tapers forwardly between the first counterbore and the bore and toward the bore,A. a rivet having an axially extending shank received in the workbore and defining an axis,B. the rivet including a head having an end face, a first section located forwardly of said end face, and a second and forwardly tapered frusto-conical section located forwardly of the first section,C. the first section having an initial undeformed outer surface of a diameter which is less than but about the same as the initial diameter of the first counterbore, the rivet first section being radially deformed to have peripheral engagement with the first counterbore,D. said head end face being substantially flush with the work surface.

Abstract: A metallic rivet is secured to work containing a work bore, the rivet having a head at one side of the work and an axially extending shank extending through the bore, the shank having a terminal protruding at the opposite side of the work. The method includes:A. applying back-up force to the rivet head tending to urge the head toward the work, andB. delivering an impact to the rivet shank terminal in a direction tending to urge said terminal toward said bore, but with sufficient impact velocity as to radially expand and axially shorten the bulk of said terminal, thereby to form an upset engaging said opposite side of the work while the head remains in close adjacency to said one side of the work.

Abstract: A gun for upsetting the shank terminal of a metallic rivet projecting through work is operable after back-up force is applied to the rivet head. An anvil may be employed to form the upset in such manner that the rivet shank in the work bore, and the bore itself, may be controllably expanded.