Although tapping has been widely used for thread fabrication, it is often a time consuming process causing a delay on an automated production line. This study investigates the fundamental aspects in vibration-assisted tapping. It addresses two major mechanisms that are responsible for torque reduction during vibration-assisted tapping, i.e., friction torque reduction and material property change at an enhanced strain rate. Theoretical analyses are conducted to account for the effect of vibration on tapping torque reduction, and verified by the tapping experiments with and without vibration assistance. Taps of three different sizes and vibrations of two different wave forms are used in the tapping experiments. The theoretical results are applicable to vibration-assisted tapping and other machining processes.
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