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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

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. Protection of tip portion of the pin in its bent state is offered by a ledge or radial extension on the disc either above or below the pin and which "wipes by" the obstruction, shielding the pin from abrading action. Upwardly swept radial vanes are provided above the periphery of the disc to generate air currents which agitate the grass as it is being cut and to provide a stream of air to move the clippings through the discharge chute.

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