NC tools can be divided into conventional tools and modular tools two categories. Modular cutting tools are the direction of development. The main advantages of developing modular cutting tools are: reducing tool change downtime, increasing production and processing time; speeding up tool change and installation time, improving the economy of small batch production; improving the standardization and rationalization of cutting tools; To improve the level of tool management and flexible processing, to expand the utilization rate of tools, to give full play to the performance of tools, to effectively eliminate the interruption of tool measurement, can be pre-adjusted outside the line. In fact, due to the development of modular cutting tools, CNC tools have formed three systems, namely turning tool system, drilling tool system and boring-milling tool system.