or notch the flow of sawdust may not be efficiently channelled away from the cutting surface of the tooth as can be seen in fig2 through 6 replaceable cutter tooth 10 has a concave top surface 12 a front surface 14 a rear surface 16 a bottom surface 18 and opposite side surfaces 20 and 20 a respectively a top cutting edge 22 is formed at the intersection of top surface 12 and front surface 14 when viewed in side profile as illustrated in fig5 the intersection of top surface 12 and front surface 14 forms an acute angle u03b1 as a result of surface 12 sloping rearwardly and slightly downwardly with respect to cutting edge 22 bottom surface 18 and front surface 14 intersect generally at right angles side surfaces 20 and 20 a converge slightly toward bottom surface 18 and may in alternative embodiments converge slightly toward rear surface 16 front surface 14 is arcuately concave with a first radius r 1 of one inch in the embodiments of fig2 7 radius r 1 is smaller as described below in the embodiments of fig1 16 in the prior art re sharpening of face 14 is usually accomplished by hand using a diamond abrasive wheel 24 wheel 24 may have various diameters for example to form a radius r 2 of one inch wheel 24 is two inches in diameter difficulty has been experienced when field sharpening prior art teeth such as seen in fig1 since the amount of pressure required to be applied by hand for effective sharpening.