In this work, currently used non-biodegradable mineral oil as a cutting fluid during machining is replaced with vegetable oil. In this work, duplex stainless steel is machined (turned) with the vegetable oils like coconut oil and neem oil. As a first step, vegetable oil based oil-in-water nano-emulsions were formulated using non-ionic surfactant (Tween-80) by ultrasonic emulsification method. In the second step, spindle speed, feed rate, depth of cut and type of cutting fluid are varied at three levels and Taguchi L27 machining experiments were performed. Measurement of surface roughness, tool wear and tool temperature were done as an output performance measure. From the results, it is evident that the order of influence for the improvement of tool wear and surface roughness are cutting fluid, feed rate and depth of cut respectively. © 2017 Elsevier Ltd. All rights reserved.