Investigation of my project is to evaluate the effects of heat treatment process on mechanical properties machinability of material. Material used for this project is Tool steel D3 and CBN insert tool is chosen for performing machining operations on CNC. Comparison of roughness has been done for before and after conventional heat treatment process. Similarly tool wear and chip morphology before and after conventional heat treatment process are also established in detail. Working conditions like cutting speed, depth of cut & feed rate are varied for different values. Mitutoyo surface roughness tester is used for before and after result comparisons. Optimisation is done using Response surface method technique. Resultant machining properties show improvement after heat treatment.