Abstract: A wood-chipping machine (FIG. 1) has a plurality of cutters carried by a flywheel which is rotated to move the cutters across a throat through which material to be chipped is fed, and in which each cutter is substantially frust-conical and hence circular and a plurality of such cutters form a blade at a generally radial location of the flywheel. These facilitate blade replacement in the event of wear eg by adjusting the worn cutter angularly.