Abstract: A method of producing a flat tube T by bending a band-like material M to be worked, wherein the material M to be worked is pre-bent to form a pre-formed groove Md in the material M along the longitudinal center axis thereof. Thereafter, the material M to be worked is gradually moved so that both edge portions of the material M to be worked in the lengthwise direction thereof gradually approach each other with the pre-formed groove Md as a center to form a tubular shape.

Abstract: A method of producing a flat tube T by bending a band-like material M to be worked, wherein the material M to be worked is pre-bent to form a pre-formed groove Md in the material M along the longitudinal center axis thereof. Thereafter, the material M to be worked is gradually moved so that both edge portions of the material M to be worked in the lengthwise direction thereof gradually approach each other with the pre-formed groove Md as a center to form a tubular shape.

Abstract: A gear is manufactured in a half blanking stage, a punching stage and a separating stage. In the half blanking stage, half blanking is performed for a columnar portion of a metal sheet. A part of an outer circumferential surface of the blank is disconnected from the other portion of the sheet, while the other part of the outer circumferential surface of the blank is connected with the other portion of the sheet. In the punching stage, an inner portion of the blank is punched in a punching direction to form teeth on an inner circumferential surface of the blank. In the separating stage, the blank is separated from the other portion of the sheet as a gear toward a separation direction opposite to the punching direction by disconnecting the other part of the outer circumferential surface of the blank from the other portion of the sheet.