Improving Friction Drilling and Joining through Controlled Material Flow

Abstract

Friction drilling is a novel hole-making process that can be performed on thin-walled sheet metals. The friction between a rapid-rotating conical tool and a sheet metal workpiece generates heat to soften and displace the material to form a hole. The bushing is formed in-situ from the workpiece. This experimental study investigated the effects of feed rate and spindle speed on the thrust load curve of friction drilling. Generating a good quality bushing has been a challenge in friction drilling. A counter-bore die was proposed and implemented to eliminate cracks and petal formation. Threads were tapped to demonstrate the improvement of the bushing quality. The present work also evaluated the feasibility of joining sheet metals with friction drilling. It was found that under an appropriate process condition, it is possible to perform friction drilling through two metal sheets to create a weld joint.