Abstract: A nut in combination with a deformable plastic plug is provided so as to produce a torsional reistance when the nut is screwed onto a similar male thread such as a bolt. The plug comprises an inner core wedge and an outer sleeve which will expand upon insertion of the core. The sleeve is placed into the nut, leaving at least one complete turn of the thread free, and the core is wedged into the sleeve forcing it to deform into the thread.

Abstract: A rock bolt assembly incorporating a friction reducing washer of plastics material between the nut and the plate washer to give an increased tension in the bolt for a given torque.

Abstract: A method of selecting deformed bar for direct rolling of a thread thereon and also a method of threading such deformed bar. The method comprising rolling a preselected thread onto selected deformed bar without machining the bar in preparation. The bar selection is made so that the average cross-sectional area of the bar with the formed thread is substantially equal to that of the unthreaded portions of the bar. The formed thread is of continuous and substantially constant pitch circle. The method is particularly applicable in manufacture of rock bolts and anchor bolts from hot rolled deformed bar.