Abstract: A hinge joint which connects the back to the remainder of the seat in a motor vehicle has first and second leaves respectively provided with punched internal and spur gears. The internal gear receives the spur gear and at least one of its internal teeth meshes with two neighboring external teeth of the spur gear or vice versa. The rear sides of the internal and external teeth are formed with punched indentations to compensate for shrinkage of the top lands of such teeth as a result of punching. Each indentation resembles the frustum of a pyramid and is designed to effect the flow of material toward the top land of the respective tooth. The two leaves are coupled to each other by a shaft which defines therefor two parallel pivot axes.