| 摘要 |
<p>ROTARY DRILLING BITS A rotary drilling drag bit for drilling from the surface deep holes in sub-surface formations e.g. for oil has a body (4) with a diameter of at least 100 mm and having a bore for passage of drilling fluid to its face (3) and rotatable cutting elements (6) having a cutting face comprising an agglomerate of diamond particles so mounted on the body (4) that they are free to rotate in use. The cutting elements are of long life and highly effective in drilling.</p> |
