Advanced Machine & Engineering offers the OTT-Jakob power drawbar for toolholding. Designed for power-off clamping in a compact design with minimal rotating mass, the drawbar is said to provide increased spring force while requiring lower tool-release force. According to the company, there is no load on the spindle bearings during tool change.
The cutting tool is held securely in the spindle taper with gripper fingers, which are pulled into the taper with the spring pack of the power drawbar. The pull-in force is multiplied by an intensifying mechanism, and the spring force applied to the clamping sleeve pushes the balls outward. The angle design of the clamping ring and cylinder shoulder increase the spring force by as much as 300 percent, the company says. The cam inside the spindle closes the gripper fingers to securely lock the tool, and according to the company, the tool will not come loose if there is a loss or reduction in hydraulic pressure. The power-off design requires pressure applied to the hydraulic piston and transmitted through the rod to push the clamping sleeve down to unlock the mechanism. After clearing the cam, the gripper fingers open and the face of the holder ejects the tool with a controlled stroke.