A bending mechanism for wire or strip material is provided, which is intended in particular for bending back towards the edge longitudinal wires the projecting end portions of crosswires of reinforcement grids for reinforced concrete construction. The mechanism comprises a substantially circular-sectioned cylindrical bending form, and a bending-tool eccentrically mounted on a rotatable tool carrier which can be rotated in either direction about the axis of the bending-form. The bending-form is shiftable along said axis between a working position, in which the end faces of said tool carrier and said bending-form are substantially touching, and a rest position in which said two end faces define between them a gap for the passage of a wire which is to be bent, in particular a crosswire of a reinforcement grid.