Pre-cutting bit is the first cutter to cut the soil body. Pre-cutting bit in the design of the main considerations and other cutting tool combinations work together.Pre-cutting bit is used to first reduce the soil into blocks by coordinating with the cutter during construction,before the cutting of the tools so as to create good cutting conditions. It can increase the fluidity of the cutting soil, reduce the impact load of the cutter, reduce the cutting torque, reduce the wear of the cutter, improve the cutting efficiency.