Abstract: As an article of manufacture, a tapered cutter pin for a rotary mower formed of durable resilient plastic having a shank and terminating at its outer end in a relatively thin but stiffly resilient tip portion, the shank having a head at its inner end for retaining the pin in the disc. With the pin supported cantilever fashion adjacent the head, the bending modulus in the shank is a minimum of 50 in..sup.2 -lb and at the tip is a maximum of 30 in..sup.2 -lb and the initial deflection ranges between 0.5 and 3.0 inches of tip deflection per pound of force. In the preferred embodiment the pin has four evenly spaced flutes extending longitudinally over a portion of its length and of a depth approximately proportioned to the thickness of the pin, the flutes defining between them ribs to produce a cruciform cross section.

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.

Abstract: A safe cutter disc assembly for a rotary lawn mower in which the disc has a circular central portion and an annular outer portion joined by a shallow vertically extending wall having a plurality of radially extending openings. The cutting elements are in the form of cutter pins inserted in the openings, each pin in the preferred embodiment being formed of durable plastic having a head, a relatively stiff shank and a long tapering flexible tip portion, the pins being supported cantilever fashion with respect to the openings. The annular outer portion of the disc closely underlies and protects the relatively stiff shank portions of the pins while the tips of the pins project beyond the periphery of the disc into engagement with the grass, bending back into the projection of the outer portion of the disc upon striking of an obstruction.