Abstract: A lawnmower blade includes an elongated flat bar having a central aperture for attachment of the flat bar to a rotary drive shaft for rotation of the blade in a predetermined direction in concert with rotation of the rotary drive shaft. The flat bar has a pair of opposite portions, extending in opposite directions from the aperture. A pair of first cutting edges are defined along outer sections of leading sides of the opposite portions of the flat bar and extend substantially perpendicular to the tangential direction of the path of rotation of the blade. A pair of second cutting edges are defined along outer ends of opposite portions of the flat bar and extend angularly outwardly from the outer leading side cutting edges to the outer trailing sides of the flat bar relative to the direction of rotation of the blade. The pair of straight outer leading side cutting edges also can have a plurality of crescent-shaped serrations or sawtooth-shaped serrations formed therein.

Abstract: A lawnmower blade includes a center blade section having an opening for mounting and fastening the blade to the lower end of a mower drive shaft and a pair of opposite outer blade sections containing cutting edges. The outer blade sections are substantially equal in length to one another. Also, the blade includes a pair of assemblies defining yieldable articulating joints attaching one end portion of each outer blade section to one of the opposite end portions of the center blade section such that each outer blade section can both pivot upwardly and rotate backwardly relative to the forward direction of blade rotation and to the respective one opposite end portion of the center blade section so as to yield upon striking an object and thereby prevent damage to the engine crankshaft or the cutting edges.