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Abstract. Minimum quantity lubrication (MQL) is a method that uses a very small amount of liquid to reduce friction between cutting tool and work piece during machining. The implementation of MQL machining has become a viable alternative to flood cooling machining and dry machining. The overall performance has been evaluated during meso-scale milling of mild steel using different diameter milling cutters. Experiments have been conducted under two different lubrication condition: dry and MQL with variable cutting parameters. The tool wear and its surface roughness, machined surfaces microstructure and surface roughness were observed for both conditions. It was found from the results that MQL produced better results compared to dry machining. The 0.5 mm tool has been selected as the most optimum tool diameter to be used with the lowest surface roughness as well as the least flank wear generation. For the workpiece, it was observed that the cutting temperature possesses crucial effect on the microstructure and the surface roughness of the machined surface and bigger diameter tool actually resulted in higher surface roughness. The poor conductivity of the cutting tool may be one of reasons behind. IntroductionMinimum quantity lubrication (MQL) has progressively emerged into the area of metal machining and, has already been established as a viable alternative to dry and flood cooling machining. The amount that should be applied in MQL is subjective and depends on the material, process and tools. As a general rule of thumb, MQL uses 5 to 80 ml/hour (0.2 to 2.5 oz./hour) on the tools which has less than 40 mm diameter [1]. Some major advantages of MQL include improved environment, better surface finish, increased tool life, reduced wear and damage at tool tips; reduce health hazards, and overall low costs in various micromachining processes. Machining processes using MQL have been studied for all conventional meso or micro machining processes like micro and meso scale drilling [8]. Implementing MQL in machining process helps to increase the tool life and produce better surface finish. It is also the best remedy for promoting eco-friendly industry due to reduction in waste. In this paper, the performance of mesomilling under MQL has been studied and compared with the same machining experience under dry condition. There have been numerous studies on micro or meso milling using MQL and dry machining. For example, [9] studied the micro-milling using MQL with varying the cutting parameters and analyzed the tool performance and machined surface condition. The tool performance was analyzed by [5] and it showed that MQL increased the tool life by 100 times compared to dry machining. MQL Assisted Meso-scale milling has been studied by [10] and it was shown how that the use of compressed chilly air and nanofluid MQL is effective for improving surface finish and reducing

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