Hydraulic chucks is a very broad application of the clamping shank shank such a manner different from the traditional handle system, tighten the bolts just use a pressurized, when the bolt is tightened it will push the piston seal block knife pattern generated within a hydraulic oil pressure, which is evenly transmitted to the steel from the circumferential direction of the expansion sets, swelling wall of the tool is clamped. With this tool clamping system, allows the system runout accuracy and repeatability control 3μm or less. As handle a high fluid pressure in the memory, when the tool is clamped, the built-in structure and the high pressure oil chamber presence of oil greatly increases the structural damping, can effectively prevent the vibration of the tool and the machine spindle. Practical application shows that the use of this clamping system can not only improve the precision and quality, but also the tool life in machining been doubled. In addition, such holder not only has maintenance-free features and dirt capacity, and easy to use and safe clamping of the tool. Because, in the fastening tool, clamping pressure can handle any oil or impurities on lead to the expansion sleeve (processing) of the small groove, so that you can clean up with a clamping surface area, and let dry, eliminating slippage of the torque for the spindle can be well transmitted to the tool.