Anchor bolt assembly

Claim 1

In an anchor bolt assembly of the type used in mine roofs and the like where the anchor bolt assembly is positioned in a drill hole of a rock formation and in which a quick-setting adhesive secures the assembly to the rock formation, said assembly including an elongated reinforcing rod, an elongated bolt and a coupling internally threaded at each end and connecting the rod and bolt, the improvement comprising a cylindrical plug of a material which is softer than the coupling, said plug extruded into frictional engagement within the internal threads of a bolt end of the coupling bore at substantially an inner end of said threads for engagement by said bolt to permit turning of the entire assembly in a first position and after approximately the application of 100 ft. lbs. of torque, to disengage from its frictional engagement to permit turning of the elongated bolt in a second position, said coupling including a nonthreaded section between the threaded ends, said plug being disengaged from the threads so as to locate in the nonthreaded section in the second position.