Abstract
BT toolshank, which is widely used in machining centers, is generally clamped with the force from Belleville-spring directly acted on a pull-stud. Since such clamping mechanism has a very long forceflow loop from a nose of spindle to a belleville-spring mechanism near end of spindle, it is said that the static stiffness of the tool holding system becomes lower and then the durability to chatter becomes worse. In this study, the new clamping mechanism for BT toolshank is proposed to become the forceflow loop shorter and enable to magnify clamping-force with wedge mechanism. From the FEM analysis of the clamping characteristics of proposed mechanism, it is found that the force-flow loop inclamping is restricted within the limited area, which only includes the small clamping wedge, pullstud, toolshank and spindle-end, and much shortened compared with conventional mechanisms. Furthermore, due to the design improvement for preventing the wedge inclination in clamping, the magnification ratio of clamping force becomes higher and is enabled to keep over 2.5 times even in spindle speed of 30,000 min.
