| 摘要 |
A drill bit 10 has a bit body 12 having a bit face 20 and at least one primary blade 31,32 disposed on the bit face, wherein the at least one primary blade extends into a cone or centre region of the bit face. Further, the bit has a plurality of backup cutter elements 50 mounted on the primary blade in the cone region. The cone backup cutter density of the primary blade is greater than the shoulder backup cutter density of the blade. The drill bit may also have a gage backup cutter density, wherein the cone backup cutter density is greater than the gage backup cutter density. Also disclosed is a drill bit in which the secondary blades begin at the outermost radius of the central cone region. |
