Expand the subdrilling head

The utility model relates to an expand the subdrilling head, including drilling rod, movable blade and thrustor. The thrustor includes circular chassis, centibar and slip gasket, the coaxial setting of circular chassis, centibar and drilling rod, and the drilling rod lower end is located on circular chassis, and circular chassis diameter is the same with the drilling rod diameter, the drilling rod bottom is equipped with the blind hole, and in the blind hole was located at the centibar top, the centibar bottom was connected with circular chassis, the open end of blind hole is equipped with the stop gear who prevents the centibar upper end to leave the blind hole. On movable blade placed circular chassis in, the centibar setting was kept away from to the cutting edge, thereby movable blade slides in the spout to expansion outside the drilling rod or to the drilling rod internal contraction. The slip gasket is located between blade bottom and the circular chassis, is equipped with the slip medium between slip gasket and the circular chassis. The utility model discloses simple structure, the cost of manufacture is low, uses portably, and the training of workman's without can be operated, effectively improves work efficiency.