| 摘要 |
<p>A cutting edge 24 is divided into a center area 28 including a V-shaped apex portion, a pair of intermediate areas 29 on the outer sides thereof, and a pair of side areas 30 on the farther outer sides thereof. The center area 28 has first teeth with the highest tooth height and second teeth with a smaller tooth height, the first teeth being situated at the apex portion and the second teeth being situated between the first teeth at a prescribed spacing around them as the center. A first straight line connecting the tips of the first teeth, a second straight line connecting the tips of the second teeth and a third straight line connecting the bases of the first teeth and second teeth are parallel, the second straight line being located between the first straight line and third straight line. The tips of the intermediate teeth of the intermediate area 29 are located on the second straight line or between the second straight line and third straight line. The tips of the side teeth of the side area 30 are located on the second straight line or between the first straight line and second straight line.</p> |
