disk cutter margin to receive rivets or posts 8 39 and 9 39 which serve to attach the later described teeth the apertures 3 39 and 4 39 may be on equal radii of the disk attached to the disk marginal surfaces 1a 39 and 1b 39 are disk abutting right and left hand teeth 11 and 12 respectively having apertures spaced to receive posts 8 39 and 9 39 as the teeth 11 and 12 are mirror images of one another a detailed description of one will suffice the tooth 12 comprises a flat body or plate portion 24 which abuts a side surface 1a 39 of the disc 1 39 the tooth 12 has a single cutter element comprising a reversely curved side wall portion 26 integral with the plate portion 24 and an outer flange portion 28 the side wall portion is laterally offset from the plate portion 24 the amount of offset progressively decreasing from the forward end 30 to the rearward end 32 thereof the flange portion 28 extends from the side wall portion 26 substantially at a right angle to the disc surface 1a 39 across the median plane of the disc the forward ends of the flange portion 28 and the side wall portion 26 are formed with a beveled surface defining a continuous cutting edge 34 the flange portion 28 is inclined downwardly at an angle x of between seven and ten degrees with respect to a perpendicular to a radius r1 of the disc intersecting the forward edge of the flange portion 28 integral with the forward end of the plate portion 26 is a ramp or depth gauge 36 formed by.