Faced with the need to join aluminum to aluminum and aluminum to steel, automakers have been forced to find alternatives to the tried-and-true spot welding technology they had been using for decades to join all-steel assemblies. Flow drill screws are one such alternative.
A flow drill screw is a self-piercing and extruding fastener for joining sheet metal. Combining the properties of friction drilling and thread forming, the screw acts as both a fastener and a drilling-and-tapping tool. It penetrates the sheets, extrudes a short boss, forms its own threads, and applies clamping force.