Resin anchored rock or mine roof bolt anchor mechanism

A rock and mine roof anchor and bolt assembly of the resin anchored type to be mounted in a bore hole in a mine roof rock formation or the like for strengthening the same, comprising an elongated anchor member of generally cylindrical configuration having a shorter length than the depth of the bore hole in which it is to be fitted and having an uninterrupted upper end surface and a lower permanently interconnected end portion, the anchor member having an elongated axial bore in at least the lower end portion thereof and a constricted diameter threaded entrance throat having female threads and opening through the lower end portion, a bolt having a threaded stem portion having male threads threaded into the female threads of said anchor member and having an enlarged head portion and bearing plate means to be drawn tightly against the face of the rock formation, the anchor member being adapted to be introduced into the bore hole in assembled relation with the bolt after insertion of a destructible cartridge containing quick-setting adhesive resin therein to crush the cartridge and mix and distribute the adhesive material throughout the space outwardly surrounding most of the anchor member and adhesively fixing the anchor member in the bore hole upon hardening of the adhesive material thereabout, said female threads including distorted thread portions providing controlled interference between said female and male threads inducing resistance to rotation of the bolt relative to the anchor member and thereby form a controlled torque thread zone with the threads of the bolt, the bolt being initially assembled in threaded relation with the threaded throat of the anchor member to a position wherein the distorted thread portions of the female threads exert a predetermined restraint to relative rotation of the bolt with respect to the anchor member until a predetermined threshold controlled torque force is exceeded, and said distorted thread portions accommodating further threaded insertion of the bolt into the bore of the anchor member when the anchor member is restrained against rotation by setting of the adhesive resin and torque in excess of the predetermined threshold amount is applied to the bolt.