Patent ID: 8777532

Claim:
A blind fastener for installation in a workpiece, the fastener comprising a shell; the shell including a core, a head at a head end of the shell, a tail end remote from the head end, and a radially expandable portion between the head end and the tail end; whereby, when the shell is inserted into a suitable aperture in the workpiece and a force is applied to the shell to urge the tail end of the shell towards the workpiece, the reaction force is supported by the head end of the shell, and the radially expandable portion of the shell is thereby caused to deform radially outwards and axially towards the shell head, to form a blind bulb which abuts a blind face of the workpiece and forms a blindside footprint; wherein at least one helical groove is recessed in a cylindrically-shaped external wall of the radially expandable portion of the shell, such that the blindside footprint is formed of at least one lobe; wherein the depth of the at least one helical groove decreases from the head end to the tail end of the shell.