PURPOSE: To reduce unsatisfactory operation such as a jam by carrying mandrels by means of a pair of conveyors, and by adjusting a width of mandrels to a predetermined value during transportation of mandrels through connecting a pair of guide rails to the conveyor.

CONSTITUTION: A mandrel 14 is supported by means of a stabilizing bar, and carried between stations by a link chain conveyor. A cam slot means 40 is disposed between the conveyors, and receives and guides a cam follower 42 fixed to the stabilizing bar supporting the mandrel 14. On the other hand, the mandrel 14 is made of L shaped metallic plate members 14a, 14b attached so as to overlap each other and relatively movable in the right and left directions. The width of the mandrel is adjusted by relatively moving both members 14a, 14b of the mandrel 14 interlocking with the motion of the cam follower 42 cause by the cam slot means 40 during movement between stations caused by the conveyor.