US Patent 7018313 Sprocket with wear limit indication

In a sprocket for use with a roller chain, a wear limit marker, having a different color from that of the base material of the sprocket, is provided on side surface of a sprocket tooth adjacent to a keyway. The wear limit marker is disposed on an imaginary line extending in the direction of the pressure angle, and is located in a hole or groove provided in a side surface of the sprocket tooth. The marker makes it possible to determine easily and reliably whether or not wear at the location at which wear of a sprocket tooth proceeds most rapidly is within a predetermined limit, and the location of the marker makes it possible to evaluate wear conditions even when the sprocket is installed in a machine.