PLATE MATERIAL BENDING METHOD AND PLATE MATERIAL BENDING MACHINE

PROBLEM TO BE SOLVED: To provide a plate material bending method and a plate material bending machine capable of carrying out bending work equivalent to the three point bending work of air bending work using a punch and a die in a press brake.SOLUTION: A plate material bending method is used to carry out bending work by a plate material bending machine provided with a top die 3 and a bottom die 5 which sandwich a plate-like work-piece W from the top and bottom and a bending die 7 provided vertically movably for bending the projected portion WP of the work-piece W projected from the tip edges 3A and 5A of the top die 3 and the bottom die 5 up and down. The bending work is carried out by retaining the tip edge 3A of the top die 3 from the tip edge 5A of the bottom die 5 in a projected state when bending the projected portion WP of the work-piece W in the upper direction and by retaining the tip edge 5A of the bottom die 5 from the tip edge 3A of the top die 3 in the projected state when bending the projected portion WP of the work-piece W in the lower direction.