Hardened steels, like AISI H13 and D2 extensively as the hot working tools, dies and moulds due to their high hardness and heat resistant properties. However the same properties are responsible for poor machinabilty of these materials. The challenges in machining of these materials in hardened state called for many research works. This book introduces induction heating as a new online heating technique to improve machinability hardened steel AISI H13. The research work considered the influence of heating parameter - temperature; and cutting parameters - cutting speed, feed and axial depth of cut on machinability parameters - surface roughness, tool life and chatter/vibration. Two different cutting tool materials, namely, TiAlN coated carbide and PCBN were used in the experimental work. Response Surface Methodology (RSM) was used to design the experiments and develop empirical mathematical models of the response parameters - tool life and surface roughness in terms of the chosen heating and machining variable parameters. Heat assisted mchining was found to have an advantage over conventional hard machining of the given hardented steel in terms of all the response parameters.