Reduce the friction between the flank or secondary flan […]
Reduce the friction between the flank or secondary flank of the tool and the workpiece. However, if the back angle is too large, the strength of the cutting edge will be weakened, and the heat dissipation condition will be deteriorated, resulting in a decrease in tool life. The selection principle is:
a. When finishing, the cutting thickness is thin, the wear mainly occurs on the flank face, and the larger back angle is taken; when roughing, the cutting thickness is large, the load is heavy, and the front and back flank faces wear, taking a small relief angle .
b. Multi-blade carbide cutting tools are thinner and should have a larger relief angle.
c. When the workpiece is poorly rigid (such as a slender shaft or a thin-walled workpiece), a smaller relief angle should be taken to increase the contact area between the flank and the workpiece to reduce or eliminate vibration.
d. The workpiece material is soft and sticky, the work hardening tendency is large, the elastic modulus is small, and the back friction is serious, then the larger back angle is taken; the workpiece material has high hardness and high strength, and the small back angle is taken to ensure the edge strength; However, for the negative rake angle tool for machining hard materials, the back angle should be slightly larger so that the blade can be easily cut into the workpiece; the brittle material is processed, the load is concentrated at the cutting edge, and the smaller back angle is directly lacking.
e. Dimensional carbide tools (such as internal broach, reamer) should take a small back angle to avoid too much tool size change after regrind.
f. For carbide inserts with high feed speed (such as thread turning tools, shovel turning tools, etc.), the choice of the back angle should fully consider the difference between the working back angle and the standard back angle.
g. The back angle of the cutting tool (such as forming cutter, hob, etc.) should be limited by the amount of backing. It should not be too large, but ensure that the back angle of the side edge is not less than 2°....