The HYDEXTM is the rotary shaft used for separator roll which is consisted a outer-thin-hollow-tube and inner-shaft made of hard steel. And, the outer-tube is expanded by hydraulic pressure between the gap of outer-tube and inner-shaft, and then the separator disks are firmly fixed. The HYDEXTM is suitable to apply thick steel coil slitter line because high hydraulic pressure generates strong force for setting many disks on the shaft.