This paper explores the effect of tool wear and surface roughness during the CNC turning of D2 steel by using acoustic emission and force sensors. The values of the forces were measured by using a Kistler 9257B dynamometer while the acoustic emission sensor was fixed upon the tool shank. The machining process was carried out until the flank wear was found to approach the critical value of 0.3mm. Tool wear plays a decisive role in any machining process since it contrarily affects tool life and forces. This has a direct impact on surface quality of the machined surface. Therefore, methods for sensing cutting tool wear are crucial in view of optimum use of cutting tools with effective monitoring system. As the wear increases, the radial forces and the surface roughness were found to shoot up considerably. The acoustic emission was analyzed and parameters were found to increase proportionally with tool wear. © 2017 Elsevier Ltd.