Cutting device for thin metallic plate

A cutting device for cutting a thin metallic plate with a predetermined width, comprising:

• a shearing cutter which is pressed to a predetermined position on a front side of the thin plate to cut the thin plate;
• and
• a contacting member which has a groove facing a cutting position of the shearing cutter and makes contact with a back side of the thin plate,
• wherein the shearing cutter is made of a metal having a higher hardness than the thin plate and has a blade angle of 50 to 90° and is symmetrically shaped with reference to a distal end of the blade in a vertical direction to a pressing direction of the shearing cutter on the thin plate,
• the groove of the contacting member is symmetrically shaped with reference to a center of the groove about the vertical direction;
• an interval between opposing inner walls of the groove is wider at an upper edge of the groove and becomes narrow towards a deepest portion of the groove;
• the inner walls of the groove have curved surfaces each of which has a radius of 15 to 20 times the thickness of the thin plate and is expanded to an inside of the groove, in order to gradually bend the thin plate pressed by the cutter along the curved surface on the groove, thereby causing a material flow in a direction of separating from the cutter on a portion of the thin plate where the cutter cuts in, stretching an uncut side of the thin plate to the edge of the cutter, locally reducing the thickness of a portion of the thin plate where the edge of the cutter faces, and forming a constriction deformed in a concave manner to the edge of the cutter;
• an interval between upper edges of opposing inner walls of the groove is 15 to 30 times a thickness of the thin plate in order to gradually bend the thin plate pressed by the cutter along the curved surface on the inner walls of the groove and to prevent contact of the thin plate with the deepest portion of the groove before being cut, thereby forming the constriction;
• a depth of a deepest portion at the center of the groove is one to three times the thickness of the thin plate in order to prevent contact of the thin plate with the deepest portion of the groove before being cut, thereby forming the constriction, and in order to form the curved surfaces with the curvature radius of 15 to 50 times the thickness of the thin plate.