Tool life and surface roughness, not only affects product quality and power consumption but also has a significant influence on productivity. This cause economical loses like spoiling of work piece or lessening of surface quality as well as product quality. Objective of this research paper is to investigate optimum spindle speed wrt surface roughness and tool life. Tunsten Carbide cutting inserts coated with PVD technique are used in conventional turning process on mild steel. Minimum surface roughness is observed on 1000 RPM keeping feed rate and depth of cut as constant. Maximum theoratical tool life is calculated on the basis of Taylor's tool life equation, which is subjected to minimum spindle speed 300 RPM. It is clear from the experimental results that increasing cutting speed resulted in decreasing tool life due to increasing temperature by metal to metal frictional contact. Increasing temperature damaged tool nose radius and ultimately cause low surface finish.

Maximum surface finish is corresponding to increasing spindle speed. High surface roughness achieves at low speed keeping depth of cut 0.2 mm and feed rate as constant 0.10 mm/rev throughout the experimentation. Experimental results reveal that surface roughness is directly proportional, while tool life is inversally proportional to the spindle speed.