| 摘要 |
<p>A diamond drag bit has cylindrical polycrystalline diamond faced inserts with a convex cutting surface, the insert being imbedded in the cutting face of a drag bit. The inserts are of the type in which a polycrystalline diamond layer is adhered to a cemented tungsten carbide substrate to form a composite, and the composite is bonded to a support stud or cylinder. The diamond surface has a convex curvature radius optimized to the extent that the best shear action on the earthen formation is achieved. The convex curvature has a radius in the range of from five to six times the radius of the cylindrical substrate. The resultant positive and negative side rake angles assure that each insert remains free of detritus, presenting a clean cutting edge to the formation. <IMAGE></p> |
