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73 double bit is installed at the bottom of the drill pipe, the top of the bit is inlaid with alloy, easy to drill the drill pipe, the barrel of the bit is equipped with two nozzles on both sides, the diameter of the nozzle is 1.6~3.0mm earlier, around the nozzle is equipped with annular gas nozzle, ensure the coaxial injection of slurry. For some soft geological structures to the end, no need to replace the drill, can be slowly lift rotary jet, improve work efficiency.