ROOF BOLTS FOR USE IN MINES, A METHOD FOR THEIR PRODUCTION AND A METHOD FOR THEIR INSTALLATION

摘要

The invention comprises a roof bolt (2) and nut (10) in screw threaded engagement, said bolt (2) comprising a shaft (4) for insertion in a hole (40 ) drilled in a mine roof and a threaded portion (6) engaged by the nut (10) whereby the bolt (2) may be rotated. The nut (10) is offset with respect to the longitudinal axis of the shaft (4) of the bolt (2) so that when the bolt (2) is rotated by means of the nut (10), the bolt (2) is caused to describe a circle of greater diameter than its own diameter, the amount of said offset being from about 0.015 to about 0.50 inches. Preferably the offset is from about 0.02 to about 0.25 inches. The nut (10) may be releasably locked in screw threaded engagement with the bolt (2) so that the bolt (2) can be rotated by means of the nut (10) and above a selected torque the nut (10) wi ll break out.