SERVO FLEX is a metal disk type coupling with high torsional rigidity. It is rigid in the torsional direction, and is flexible in the bending, asymmetrical and axial directions. The plate spring is made by a latest finite element analysis method to achieve an idealized shape. The SFC model is a compact and lightweight model with high-strength aluminum alloy used for the hub material. For the SFS model, carbon steel is used for the body material. The SFM and SFF model developed for use in a main shaft and feed shaft are also available.