PURPOSE: To contrive to cut the number of manufacturing processes and to stabilize a dimensional accuracy by dividing a cam constituting a reciprocating mechanism into two bodies.

CONSTITUTION: An assembled cylindrical cam formed by the combination of head cams A6 and B7 respectively having two facing cam groove side faces A1 and B2 is used in a shuttle printer. Both plastic head cams A6 and B7 are manufactured from upper and lower cutting dies arranged in the direction of the arrow so that a grooving work can be superseded accordingly. The press-fit protrusion 1 of the head cam B7 is fitted into the press-fit recess 3 of the head cam A6 and pressed thereinto until the hitting part A4 of the head cam 6 and that B2 of the head cam B7 come into contact with each other, to stabilize the groove width of the cylindrical cam to a constant value. Then, a metal cam shaft 8 is pressed into the head cams A6 and B7.