| 摘要 |
<p>1432546 Twist drills OSBORN-MUSHET TOOLS Ltd 5 July 1973 [21 July 1972] 34325/72 Heading B3C A twist drill comprises first and second lands 12, 14, Figs. 2, 4, lands 12 being either relieved by chamfering up to point 20, which is further away from the chisel edge 22 than the point 24 on lands 14, or alternatively are relieved so that the diameter at the end of lands 12 is less than that of lands 14, Fig. 8, so that each second land 14 is radially proud of its associated first land 12. The roots of the drill flutes (10), Fig. 6 (not shown), are formed, so as to fracture the swarf. In a further modification a flute (28), Fig. 9 (not shown), is provided in front of each second land. There may be two or more second lands to each first land.</p> |
