| 摘要 |
<p>PCT No. PCT/CH87/00155 Sec. 371 Date Jul. 18, 1988 Sec. 102(e) Date Jul. 18, 1988 PCT Filed Nov. 24, 1987 PCT Pub. No. WO88/03849 PCT Pub. Date Jun. 2, 1988.A two-flute drill bit includes two drill webs each provided with a cutting lip. The cutting lips are unequally angularly spaced from each other and the smaller one of two pitch angles included between two cutting lips is preferably 160 DEG . One of the webs has two peripheral margin lands spaced from each other whereby a three-point guidance of the drill bit is obtained.</p> |
