ATTACHE BORGNE AUTO-BLOQUANTE

In a blind fastener (20) of the kind comprising a tubular nut (22) having shank (28) with a head (30) at one end and a tapered nose (32) at the other end, a headed bolt (24) threadedly engaged in the bore (34) of the nut (22), and an expansible sleeve (26) which, by rotating the bolt (24), can be forced on to the nose (32) to form a blind head, a section of the shank (28) of the nut (22) is formed with a single protuberance (42) which protrudes resiliently into the bore (34) sufficiently to interfere with and restrain rotation of the bolt in the nut, and thus render the fastener self-locking. The shank (28) may have more than one section provided with a single such protuberance (42), the effect of several protuberances being additive. Each protuberance (42) lies entirely within a minor sector of its section of the shank, and presents either a flat or a curved threaded surface traversed by the thread (38). Protuberances may be in different sectors if spaced longitudinally of the shank. Each protuberance is formed by impressing a minor zone of the external surface of the thank with a punch (74) while supporting a diametrically opposite zone in a nest (70) shaped so as to substantially preserve the cylindrical shape of the shank in the remaining major sector. A cap (16) is used in cooperation with the nest (70) to define an angled cavity (79) to restrain deformation and axial bending of the shank (28) during the impressing by the punch (74).