1. During machinability study in hard turning. It is observed that, the tool life for multilayer TiN coated carbide insert is higher, i.e. about 19 min, 8 min for multilayer ZrCN insert and less than 1 min for uncoated carbide respectively under extreme cutting conditions of hard turning of AISI 4340 steel (47 ฑ 1 HRC). The uncoated carbide insert fails by chipping that leads to catastrophic failure due to higher thrust force noticed in hard turning at extreme parametric range selected.