In this work a series of test were conducted in order to determine the machinability of tool steels. In these test the effects of tool material, type of coating on the insert (for coated tools) and the cutting parameters that affect the machinability were taken into considerations. The cutting force data used in the analyses were gathered by a tool breakage detection system that detects the variations of the cutting forces measured by a three-dimensional force dynamometer. The workpiece materials used in the experiments are cold work tool steel, AISI O2 (90 MnCrV8); hot work tool steel, AISI H10 (X32CrMo33) and mould steel, AISI improved 420 (X42Cr13). The cutting tools used are HSS tools, uncoated WC and coated TiAlN and TiC + TiCN + TiN inserts (ISO P25). The type of inserts is DNMG 150608. No cutting fluid was used during the turning operations. During the experiments cutting forces, flank wear and surface roughness values were measured throughout the tool life and the machining performance of tool steels were compared. © 2006 Elsevier Ltd. All rights reserved.