This study investigates the effect of work piece hardness, cutting parameter i.e. cutting speed, feed and depth of cut on tool life and surface roughness during turning of AISI-4340 steel. The study has been conducted with two different tools i.e., Carbide and CBN. Response Surface Technique is used to investigate the influence of various machining parameters and work piece characteristics on response factors i.e. tool flank wear and surface roughness. The result of ANOVA and validation of experiments conforms that the developed mathematical model for response excellent fit and predict the values of these response factor close to the experimental values 95% confident interval