Abstract: A machine attachment of the type having a plurality of swinging blades and a rotor that rotates about a horizontal axis has a cylindrical tubular rotor with stub shafts and bearings at each end for rotation about the horizontal axis, so that the body of the rotor is a single piece, large diameter tubular section having improved structural stiffness and improved flywheel effect. The blade pivot shaft attachments are mounted directly on the external surface of the tubular rotor and inset mounting pockets allow the blades to swing through the rotor interior.

Abstract: A free-swinging cutter element for a timber thinning machine includes a generally stirrup-shaped member having an outer wall and integral side walls. Each half of the member is formed as the frustrum of a triangle so that bevels on the upper and lower surfaces form sharp cutting edges that incline to respective upper and lower points in the center of the outer wall. This construction moves the center of mass further outward toward the outer wall to increase chipping and cutting efficiency, which is further increased by the form of the cutting edges. A single edged cutter having similar overall shape also is provided.