| dc.description.abstract | Friction drilling utilizes the heat generated from the friction between the tool and the workpiece for machining. This process produces no chip, shortens the time required for hole-making and incurs less tool wear, thus lengthening the service life of the drill.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.In this study, tungsten carbide drills with and without coating were employed to make holes in AISI 304 stainless steel, which is known to have high ductility, low thermal conductivity and great hardness.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 and compare with the traditional HSS twist drill coated TiN and Tungsten carbide drill. The results showed that HSS coated TiN was damaged seriously after two drilling runs and Tungsten carbide was already to create a serious wear of drill edge after three runs. However, the friction drill showed little wear and still can normally drill the AISI304 material after 60 runs. Therefore, the friction drill has a better performance than both the HSS coated TiN and the Tungsten carbide drill. Furthermore, the friction drill avoids serious tool wears, enhances drilled hole quality, and prolongs the tool life more significantly. TiAIN and AlCrN were coated onto the drill surface by physical vapor deposition (PVD). Performance of coated and uncoated cutting tools were examined for drillings made under different spindle speeds. Changes in relationship between drill surface temperature, tool wear and axial thrust force during machining were also explored. Experimental results reveal that lubricating effect of the coating and low thermal conductivity of AlCrN caused AlCrN-coated drill to produce the highest surface temperature but the lowest axial thrust force with the least tool wear. However, the difference in performance between coated and uncoated drills diminished with increase in number of holes drilled. | en_US |