The CNC milling machine has the characteristics of high speed and high efficiency. Compared with the traditional milling machining, the CNC milling machine has higher requirements for the cutting tools. The rigidity, strength, durability and installation and adjustment methods of the milling tools will directly affect the cutting work. Efficiency; the tool's own precision, dimensional stability will directly affect the workpiece's machining accuracy and surface processing quality, reasonable selection of cutting tools is also an important part of the NC machining process. 1. Selection of hole cutting tools 1) The numerical control machine tool hole processing generally does not have the drilling model, because of the drill bit rigidity and the cutting condition difference, selects the drill diameter D to satisfy the L/D ≤5 (L is the drilling depth) condition. 2) Use a center drill to locate the hole before drilling to ensure the accuracy of hole machining. 3) Reamer can use floating reamer, and the front hole of reaming hole should be chamfered. 4) For countersinking, symmetrical multi-edged boring heads should be used for cutting to balance radial forces and reduce boring vibration. 5) Try to choose thicker and shorter arbors to reduce cutting vibration. 2. Milling tool selection 1) Mounting without regrind The milling cutters with indexable cemented carbide inserts are mainly used for milling flat surfaces. The diameter of the milling cutters is selected smaller during roughing, and the diameter of the milling cutters is selected larger during fine milling, when the machining allowance is large and more When the amount is not uniform, the tool diameter is selected to be smaller, otherwise it will cause the workpiece machining quality to be affected by the depth of the knife. 2) When machining workpieces with three-dimensional curved surfaces or variable-angled contours, ball-end milling cutters, ring-type milling cutters, drum-type milling cutters, conical milling cutters, and disk-shaped milling cutters are often used. 3) High-speed steel end mills are used for machining bosses and grooves. If the machining allowance is small and surface roughness requirements are high, faceted cutters with cubic boron nitride inserts or ceramic inserts may be used. 4) For rough machining of rough surfaces or holes, hard milling with a carbide insert can be used for strong cutting. 5) For the groove with high machining accuracy, the end mill with a smaller diameter than the groove can be used to mill the middle part of the groove first, and then use the tool radius compensation function to mill both sides of the groove.