Abstract: The prepared T15K6 carbide tips are activated by neutron irradiation in atomic pile, hence the radioisotope Co60 is generated and its gamma ray is utilized as the tracer. Geiger-Muller counter system is used to measure the activity of the resulting chips upon which the tool wear products adhere. And the instantaneous tool wear rate is determined by the activity data. Using the medium carbon steel No.45 as the material to be turned, the authors have studied the influence of cutting time, cutting speed and feed upon the wear of carbide tips. It is found that during the early “running-in” period the tool wear is notable serious (fig. 4 and 7). And the higher the cutting speed or the larger the feed will result in the shorter the running-in period, although this effect of cutting speed is more prominent than that of feed. The tool-life-index m or n in such well-known relationships can be quickly and accurately found out by means of radioisotope method (fig. 6 and 9).The machinability of several materials has been compared under the exactly same cutting conditions. The largest tool wear rate is obtained when the low carbon steel No.CT3 is machined; the medium wear rate belongs to the medium carbon steel No.45; and the smallest wear rate is obtained when the steel No 415 is machined (table 4). The authors believe, this is due to the higher plasticity of the steel CT. 3 that makes the tool wear rate larger. During cutting of steel NO.415, the portion of tool wear products adhered to the work piece surface is relatively higher. This indicates that here the frictional condition between the tool nose and the No.415 work piece surface is more serious. Since the radioisotope method can only determine the weight or volume of the tool wear, while the tool wear geometry (which is important for tool regrinding practice) can only be determined by conventional microscope method. Hence, obviously, taking advantage of the combination of these two methods will lead to a complete, innermost and exact understanding of the tool wear characteristics.