(1) For processing materials with large plasticity or elasticity, large back angle is adopted to reduce friction between back cutter faces; For processing high strength and high hardness workpieces, small back angle shall be taken to ensure the edge strength; The finishing cutting force is small. In order to reduce friction and improve the quality of the machined surface, a larger rear angle can be used;

(2) During rough machining, the cutting force is large. To ensure the strength of the cutting edge, a smaller back angle can be used; The finishing cutting force is small. In order to reduce friction and improve the quality of the machined surface, a smaller rear angle can be used;

(3) The back angle of high speed steel tool can be 2~3 degrees larger than that of tungsten steel tool;

(4) When the radial wear of the milling cutter will affect the machining accuracy, for example, the diameter of the peripheral tooth of the keyway milling cutter will decrease after the wear, which will directly affect the width of the keyway. The back angle should be appropriately reduced (generally 8 degrees).

(5) The friction between the back of the milling cutter teeth and the workpiece is the direction of re cutting speed, and the cutting thickness is smaller than that of general turning, so the wear mainly occurs on the back cutter face. Therefore, appropriately increasing the back angle of the milling cutter can reduce the wear.