Composite buckling blind fastener

In a blind fastener comprising (a) a nut with an axial bore therethrough and with a nose at one end and an enlarged head at the other end, (b) a bolt having a stem extending through said nut and having an enlarged head adjacent to said nut nose, and (c) a sleeve on said bolt stem between said nut nose and said bolt head, the improvement which comprises said sleeve having a thick wall section adjacent to said bolt head and a thin wall section adjacent to said nut nose formed by a recess in said section and a collar on said bolt stem between said nut nose and said sleeve which collar has a tensile strength very much less than the tensile strength of said sleeve, said sleeve being adapted upon the setting of said fastener to initially expand its thin wall section over said nut with said collar therebetween, then to have the free end of the thin wall section tapered inwardly toward said nut, and then to have the thin wall section buckle outwardly upon contact with the parts being fastened to form a large bearing surface.