Assembly method for assembled camshaft and device therefor

A combined cam shaft assembling method comprises the following steps: A, grinding the outer diameter of a steel pipe (2) to specified precision, and machining an inner hole of a cam sheet (1) and a signal disc to specified precision; B, pre-installing the cam sheet (1) and the signal disc onto the steel pipe (2) according to a specified sequence, distance and angle; C, utilizing a tension part (3) to penetrate through the steel pipe (2), ensuring the steel pipe (2) to be expanded, so as to fix the cam sheet (1) and the signal disc onto the steel pipe (2) and reach a specified torque. The method is carried out through a combined cam shaft assembling device. By adopting the tension part (3) to expand the steel pipe (2), the steel pipe (2) and the cam sheet (1) can be rapidly combined, the cam sheet (1) and the signal disc can be clamped onto the steel pipe (2) in a more reliable manner, and the strength of the entire cam shaft is relatively high.