| 摘要 |
<p>An elongated drill bit (20) has a shank (22) at one end and a working end (24) at the other. A flute portion (26) is between the working end (24) and the shank (22). The flute portion (26) is continuous with the shank (22) and the working end (24) and is generally unitarily formed with them. The flute portion (26) has at least one flute (30) with a helix angle between approximately 30° and 35°. The working end (24) has a pilot tip (36) with a cutting portion (34). A tapered web (94) is formed in the flute portion (26), a thickness (K) of the web (94) at the tip of the working end (24) is about 9% to 15% of the nominal diameter (D).</p> |
