Abstract: A cutter pin for mounting on a mower disc having a keyed radial socket with a curved backstop adjacent thereto, the pin being tapered from shank to tip portion in the vertical plane but with the top portion having substantially the same maximum width as the shank in the horizontal plane to provide a flattened blade-like structure with generally parallel lateral edges. The pin is formed integrally of durable plastic having substantially the characteristics of nylon so that it stands out from the periphery in radially self-supporting position with sufficient stiffness for the cutting of grass as the disc rotates.

Abstract: A cutter disc assembly for a rotary lawn mower in which the disc has a circular central portion and a peripheral portion with a shallow vertical wall in between. Radial openings are provided in the wall in register with radial grooves formed in the underside of the peripheral portion. A plastic pin is in register with each opening, with the shank of the pin occupying the associated groove and with a stiffly resilient tip portion projecting beyond the periphery of the disc into cutting engagement with the grass. Each groove has a curved rear wall against which the pin bends as the projecting tip of the pin strikes an obstruction as well as a curved front wall against which the pin bends upon rebound, the curved walls being of outwardly flaring shape thereby to support the shank of the pin substantially free of concentrated stress. Each groove has, in addition, a bridge or "ceiling" which serves as a guide surface to hold the pin in a downwardly-angled working position and to provide frictional damping.