High strength blind bolt with uniform high clamp over an extended grip

Abstract

A high strength, high clamp blind bolt for fastening structural workpieces, which blind bolt has a core pin with a blind side head and a plurality of locking grooves or threads, a high stand-off collar adapted to be swaged into the locking grooves or a nut adapted to be threaded onto the pin threads, a compression frangible main sleeve structure and an expandable, short fixed length blind side sleeve structure; the blind bolt is set by a relative axial force applied to the pin which forces the short blind sleeve structure against the main sleeve structure causing the blind side sleeve to expand and form a blind side structural load bearing blind head; the relative axial force can be applied by pulling in a swage configuration or by torque in a threaded configuration; the core pin head acts on the main sleeve structure to cause a frangible portion to shear and reduce the main sleeve structure length after which the blind head engages the blind side of the workpieces; the high stand-off collar is then swaged into the pin lockgrooves or the nut is threaded further onto the core pin with none of the clamp load developed being shared by the collapsed main sleeve structure resulting in a fastener having a high, uniform workpiece clamp load, a high, uniform tensile strength, and a fixed, short back side protrusion over a wide grip range.