Drywall Mechanical Anti Loosening Glue Screws

It is widely known that screw fasteners loosen sooner or later, even so-called Anti-loosening Screw fasteners available in the market do not prevent loosening, as reported in an earlier paper. The purpose of this paper is to present the development of a real anti-loosening screw fastener that has a strong resistance against loosening without sacrificing any of the advantageous features of conventional screw fasteners. Before introducing the development, the mechanism of the loosening process of screw fasteners is investigated. It is shown that the loosening of screw fasteners is caused by two factors. One is relative slip between the bolt and nut screw threads, the slip causing torsion in the bolt. The other is relative slip between the bearing surface of the bolt or nut and the surface of the fastened material, the slip causing slackening of the torsion. The prevention of loosening should be possible if either one of these causes is eliminated. Aiming at eliminating the first cause, the torsion, a new screw named `The Step-Lock Bolt' (SLB) is developed. The developed bolt has eight steps in which the lead angle degree is nil at the circumference of the thread. The efficacy in preventing the initiation and progress of loosening is examined by applying a force cyclically at right angles to the center line of a bolt. The results show that whilst a conventional fastener lost the fastening force within 1000 cycles, the developed SLB does not lose the fastening force until over 30 000 cycles. It may thus be concluded that the SLB is a practical means of preventing screw fastener loosening.