| 摘要 |
<p>The bit 10 for a rotary drill includes a cylindrical body 20 having at least two flutes 24 provided therein. The cylindrical body terminates in a cutting end 30. A cylindrical land 22 is defined by a peripheral face of the cylindrical body between adjacent flutes. The cylindrical land includes a margin 23 that is radially elevated relative to a remainder of the cylindrical land. The margin has a width zone that varies 23.1, 23.2 along the length of the cylindrical land. A polycrystalline diamond (PCD) layer may be included in a point of the drill and the wider zone 23.2 of the margin.</p> |
