During a machining process such as milling, often the prediction of tool life is associated with the cutting parameter used. AISI P20 is pre-hardened high tensile tool steel which possessed high hardness is commonly known as mold steels. Due to the high tool wear rate compared with other workpiece material, it is hard to be machined. Tungsten carbide tool inserts was used in the experiment to observe the suitability of the tool used and to find the optimum cutting parameter to delay the critical failure from occuring. This research is done based on the help of Response Surface Method (RSM) that is an experimental statistical analysis to generate combinations of parameters.