Hard coatings are well known to improve the performance of cutting tools in machining applications, such as high-speed machining and machining of MMC etc. Unfortunately, the development of cutting tool for high-speed machining of hard and difficult-to-cut material has remain a problem for quality and economy of production. The present work studies the performance of multi layer coated tool in machining of hardened steel ( AISI 4340 steel ) under high speed turning and compared with that of uncoated tool. Also the soft aluminium and soft and abrasive (Al+5% Si) were turned using CNC lathe. The influence of cutting parameters (speed, feed, and depth of cut) on cutting forces, surface finish and tool wear has been analyzed. Under the different cutting conditions, forces were measured both for coated and uncoated tools. For coated tools the forces obtained of resulted in relatively low values. For comparison, uncoated tool was also tested under the similar cutting conditions. The surface roughness of the workpieces were found out using Taylor Hobson (Surtronic 25) Surface Roughness Tester. Tool wear measurements demonstrate the capability of such tools in turning hard materials with reasonable tool life. The wear mechanism at the end of tool life was investigated in detail using scanning electron microscope (SEM). It has also been found that the machining of hard materials at higher speeds and lower feeds is improved by using coated tools as compared to uncoated tools. Turning with coated tool is more economical than the uncoated in terms of energy and power requirements
