Effect of Geometry and Process Variations on Fastener Performance

During the last decade, several technological advances have taken place in the construction and fabrication industry in terms of methods, processes and tools which ultimately reduce fabrication time and costs. Fastening of metal plates with bolts and nutes in civil construction of large structures has recently been replaced by self drilling-tapping fasteners. The technique of using a self drilling-tapping fastener not only eliminates use of separate drills and drilling processes, but also eliminates the use of bolts and nuts. In addition, the time to join two plates by a self drilling-tapping fastener is significantly shorter than the time required for joining plates by conventional bolting methods. Although self drilling-tapping fasteners have many advantages, it is equally important that they demonstrate consistent performance in field applications. In this research, performance of self drilling-tapping fasteners is investigated with respect to variations in a) Fastener manufacturing method and b) Fastener length and geometry. Results indicate selection of correct manufacturing method not only results in reduced manufacturing costs, but also improvement in the performance of the fasteners. The significance of geometric features such as drill clearance angle and fastener length on performance, measured in terms of forces and drilling time, is demonstrated. The results are of significant importance in fastener manufacturing industry.