ABSTRACT This investigation focuses on the influence of tool geometry (nose radius) and cutting parameters (cutting speed, feed and depth of cut) on the surface finish obtained in turning of mild Steel. In order to find the effect of tool geometry and cutting parameters on the surface roughness during turning, response surface methodology (RSM) with (3 4 ) full factorial design was used and a prediction model was developed related to average surface roughness (Ra) using experimental data. The results indicated that the tool nose radius was the dominant factor on surface roughness. In addition, a good agreement between the predicted and measured surface roughness was observed. Therefore, the developed model can be effectively used to predict the surface roughness on the machining of mild steel with 95 % confidence interval within ranges of parameter studied