Abstract: A fastener mandrel has formed on one end a spherically curved shoulder and an elliptically shaped head adjoining the shoulder. In setting the fastener in a workpiece, the shoulder enlarges the end of a tubular rivet and clamps workpieces together in combination with a preformed head on the other end of the rivet. The mandrel head deforms the rivet tail into an elliptical shape that partially encloses the mandrel head to provide good stem retention. A plurality of annular ribs on the mandrel stem are drawn into a reduced diameter section of the rivet head end when the rivet is set, thereby providing additional stem retention.

Abstract: An elongated stem extends through a bore in a sleeve having a preformed head at one end. The sleeve extends through aligned holes in one or more workpieces to be fastened together. Pulling the stem through the sleeve causes an enlarged tail on the stem to be drawn into the end of the sleeve opposite the preformed head. The sleeve thus expands, forming a blind head. The workpieces are sandwiched between the preformed head and the blind head. To prevent the stem from sliding out of the sleeve, a locking collar is provided within the sleeve bore. The collar is slideable from a first position spaced from the preformed head to a second position within the preformed head. The collar is engaged by a shoulder on the stem and is moved from the first position to the second position as the stem is pulled through the sleeve. When in the second position, the collar is prevented from further movement, and is deformed as the stem continues to advance.