To respond, on one hand, the quick alteration of speed and, on the other, maintenance-free long use, by a method in which a substrate comprises a lightweight holding material and at least its surface portion involved in a folding process comprises a wear-resisting facing.

A folding ram 22 as a part of outside folding-mechanism comprises a substrate 23 comprising a lightweight holding material having a relatively high E-module and low density. The substrate 23 has in its face part, which is involved in a folding process, a plate 24 comprising steel, or a wear-resisting facing for a jacket 26 comprising steel. In the accommodating pocket 7 of a turntable, a substrate 28 has a wear-resisting facing comprising a lightweight holding material and a steel plate and has around a side wall a wear-resisting jacket 29. Thus, the lightweight holding materials of the substrates 23 and 28 of the folding ram 22 and storage pocket 7 allow the high acceleration and deceleration of the folding mechanism and a quick advancing process of the turn table 4 corresponding to them.