Hydraulic clamp for drilling machine

The utility model discloses a hydraulic clamping device used with a turning machine, which comprises a three-claw clamping chuck. The three-claw clamping chuck comprises a sliding seat, a chuck body and a chuck holder and further comprises a transmission mechanism which consists of a toothed rack, a gear wheel, a hydraulic cylinder, a piston rod and a transmission shaft, wherein the toothed rack is engaged with the gear wheel, the gear wheel is fixedly connected with the transmission shaft as a whole, one end of the transmission shaft is fixedly connected with a flange disk fixed at the bottom of the chuck body via a bearing and the other end thereof is fixedly connected with the bottom of the chuck body via a bearing, and one end of the toothed rack is fixedly connected with the piston rod. Three connecting rods are distributed uniformly and axially on the bottom of the chuck body in a way that one end of each connecting rod is movably connected with the gear wheel as a whole and the other end thereof is movably connected with the sliding seat as a whole. With the structure, the hydraulic clamping device has the advantages of simple operation, easy use, automatic and accurate positioning and high production efficiency.