A study has been made on the relation between the distribution of cementite (Fe3C) and the wear of tool in high carbon chromium bearing steels. Two kinds of materials with different state of cementite were prepared by utilizing the thermo-calc program. The particle size and content of cementite in these materials were controlled by heat-treatment. In the first stage, machinability was estimated by using the materials of three kinds with a different particle diameter of cementite. In the second of the experiment, the influence of interparticle distance of cementite on the tool life was evaluated using the cutting tool of TiC and SiC. The amounts of tool wear were increased with increasing particle size and the areal ratio of cemented carbide. The amounts of tool wear were also increased as the interparticle distance became short. The tool life of TiC tool was longer than that of SiC tool in cutting the same chemical composition of materials. Surface roughness (Rmax) of the material was influenced by the particle diameter and interparticle distance of cementite. An experimental equation was proposed to estimated the tool life from interparticle distance of the precipitated particle.
