Machining characteristic study of friction drilling on AISI 304 stainless steel

A no-chip drilling process was formed by thermal friction principle in which it had the most important features such as no pollution, short machining time, and long tool life. After the friction drilling operation had been conducted, a thin plate (workpiece) was formed into a bush with a thickness of 3 times larger than that of the workpiece. The bush can provide a longer area of contact which can fit a shaft firmly. The bush can also be taped to create an internal screw without welding a nut. The main purpose of this study was to develop a new type of thermal friction drill with a sintered carbide in which it can be grinded and processed to the necessary geometric shape. It then can be applied to drill the Austenite stainless steel (AISI 304). The Taguchi method was applied to explore how the different parameters such as drill shape and friction angle, friction contact area ratio, feed rate, and drilling speed would affect the response parameter. The optimal drilling condition was A, (friction angle= 30 degrees), B, (friction contact area ratio = 50%), C-2 (feed rate = 100 mm/min), D-3 (drilling speed = 90 m/min) and then four drilling confirmatory runs were conducted to obtain an average surface roughness Ra = 0.96 mu m. This Ra value is the smallest one compared with all the Ra values from L-18 arrays. Therefore, the confirmatory experimental runs were verified. After the optimal drilling parameters of friction drilling were obtained, the optimal geometric shape and friction contact area ratio of the friction drill was selected to conduct experiments. The performance of the friction drill was compared with the Tungsten carbide (WC) twist drill. The results showed WC twist drill damaged seriously after three drilling runs. However, the friction drill can normally process the AISI 304 material after 60 runs and only showed little wear of the drill. Therefore, the friction drill has a better performance than WC twist drill. A good quality hole surface which is like a mirror could be obtained. (C) 2007 Elsevier B.V. All rights reserved.