PURPOSE: To ensure a sufficient sliding area, and to increase connecting strength and tensile strength by fitting a protruding section for connection formed at one end of a plate-shaped flat made of a metal into the notch section for linkage of an adjacent flat, plastically deforming the vertical circumferential wall surface of the notch section to the inside, engaging the protruding section for connection under the state, in which the protruding section cannot be moved in the thickness direction, and coupling each flap.

CONSTITUTION: A large number of flaps 1 made of a metal are coupled rotatably in the same plane and an endless chain body 2 is constituted, and cutting edges 4 are fixed on each outer circumferential side and recessed sections 6A, 6B to be driven are formed on each inner circumferential side. Discoid protruding sections 8 for connection are shaped at each rotation front side-face central section and arcuate notch sections 10 for coupling to rear side faces, only one surface sides corresponding to one tapered surfaces 8A of the protruding sections 8 for connection are formed in complementary tapered surfaces 10A in the inner circumferential surfaces of the notch sections 10, the other surface sides are shaped in vertical circumferential wall surfaces 10B, and the opening diameters of the vertical circumferential wall surfaces are made slightly larger than the protruding sections 8 for connection. Arcuate caulking grooves 12 are formed at positions slightly separate from the opening edges of the vertical circumferential wall surfaces 10B, the protruding sections 8 for connection are fitted into the adjacent notch sections 10 for coupling and the vertical circumferential wall surfaces 10B are plastically deformed to the insides, and engaged rotatably under the state in which the wall surfaces 10B cannot be moved in the thickness direction.