Claus, L. and Weitzel, S., "Self-Tapping Fasteners for Lightweight Designs," SAE Technical Paper 2014-01-0785, 2014, doi:10.4271/2014-01-0785.
As automotive technology rapidly provides advances in lighter weight designs and materials, the technology to fasten and join them must keep pace. This paper will explore two uniquely different fastening technologies that are being used to address some of today's demanding application challenges in plastics and thin steel and aluminum sheet. These are two areas of application that have historically provided few good options for designers, especially as they attempt to push the envelope with progressive, light weight designs. The first technology is self- tapping screws for plastics that, although not new, are now evolving to enable smaller bosses and shorter thread engagements, and incorporate light weight design options. Although dependent on the demands of the application, these screws can be produced in both steel and, now, lighter weight materials such as aluminum and plastic. The paper will explore how these technologies can be employed by the designer to obtain desired weight reduction initiatives over more conventional threaded fasteners for fastening plastic. The second technology are self-tapping, thermal forming screws that enable fastening of thin metal sheets that normally are unable to safely accommodate a threaded fastener joint because of the minimum sheet thickness. This technology is proving especially useful in automotive body-in-white applications where multiple stacks of aluminum sheet, mixed applications of aluminum and steel, multiple stacks of thin steel, and applications into extruded aluminum or magnesium members, particularly with one-sided access are necessary. This portion of the paper will specifically explore how this technology allows lighter weight aluminum or thinner steel sheets to be used since a robust and secure threaded joint can be formed.