On the processed, all tools are all preserved in the knife library, and the corresponding tool change operation is performed by the selection knife of the CNC program and the tooling instruction. Use the corresponding standard shank for the machine tool system specification so that the CNC machining tool can be quickly and accurately mounted to the machine spindle or return to the knife library. The programmer should be able to understand the structure size, adjustment method, and adjustment range of the tool holder used to ensure the radial and axial dimensions of the tool when programming, and arrange the order of the tool reasonably. 1. Factors affecting CNC tool selection When choosing the type and specification of the tool, it mainly considers the following factors: (1) Production properties Here, the production property refers to the batch size of the parts, mainly considering the effects of tool selection. For example, in a large number of production, special tools may be costly, and when single or small batches are produced, choose a standard tool more suitable for some. (2) Machine Type The effect of CNC machine tools used in this process pair selected tool type (drill, car blade or milling cutter). Under the conditions that can ensure the rigidity of the workpiece system and the tool system, high productivity tools, such as high-speed cutting, and large feed pulses. (3) CNC machining plan Different CNC machining programs can use different types of tools. For example, the machining of the aperture can be drilled with a drill and a reagent, or a drill and a boring knife can be processed.