a saw tooth , of which a number are removably mounted on a tree - felling saw head , includes a body portion having a lead cutter and a trailing primary cutter separated by a throat . the combined lead cutters function to cut a narrow side wall kerf on each side of a larger principal kerf together with corresponding inside corners of the larger kerf . the remainder of the larger kerf is then cut out by the following primary cutters , forming a square cut end . as the cut progresses , the combined primary cutters separate the longitudinal fibers of the tree at the square cut end without double cutting the fibers , thereby improving cutting efficiency and reducing energy requirements in felling a tree .