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Development and performance evaluation of self-lubricating drill tools

Drilling is one of the most commonly employed manufacturing processes for any material. However, the frequent tool changes resulting from tool wear limit the efficiency of the process. Unlike in other forms of machining, external lubrication is not very effective in drilling and, hence, the usual strategy is to supply coolants through a hole drilled in the tool, along the axis. However, cutting fluids pose several threats to the environment and workers’ health and there are stringent regulations on their usage and disposal. To address this problem, self-lubricating drill tools were prepared using high-speed steel drill bits in the present work. Channels for the flow of solid lubricant were made in the tools. Further, side channels of various angles (0°, 8°, 15°, 22°, 30°) were cut on the flutes. Solid lubricants were filled in the central supply channels and also in the side micro-channels. The performance of the fabricated self-lubricated tools was assessed while machining AISI 1040 and mild steel. The variation in drilling torque, thrust force, surface roughness and tool wear under dry, wet machining environment, and self-lubricated conditions were studied experimentally. It was observed that by employing self-lubricated drill bits there was an improvement in surface finish of the holes drilled and considerable reduction in tool wear.