Blind rivet having counterbored sleeve head of double-angle configuration

Claim 1

In a blind rivet of the type having a mandrel, and a sleeve and a locking collar both slidingly surrounding said mandrel, said mandrel having a circumferential locking groove to receive said locking collar upon installation of said rivet, said sleeve having a cylindrical body of uniform internal diameter and a head at one end facing said locking collar, said rivet being adapted for installation by a non-shifting pulling head, the improvement wherein the head of said sleeve is double counterbored to form adjacent inner and outer conical surfaces interior of said head, said outer conical surface extending inwardly from the exterior annular edge at which said counterbore intersects the exterior surface of said sleeve head to a smooth junction with said inner conical surface, said inner conical surface, extending inwardly from said junction to the inner annular edge at which said inner counterbore intersects the interior surface of said cylindrical body, said outer conical surface defining a relatively shallow locking collar entry resistance angle, the inner conical surface defining a relatively steeper angle for guiding insertion of said locking collar into the locking groove of said mandrel, said double counterbore being of continuously increasing diameter between said inner and said exterior annular edges.