| 摘要 |
A rotary bit which includes a bit body having a tapered, externally threaded neck located at one side of the bit body. The bit body includes three, flat, lateral side faces which extend at 120 DEG to each other and thus lie in planes which would contain sides of an equilateral triangle. Groups of cutter supporting blocks are built-up on the bit body at circumferentially spaced intervals therearound and on the opposite side of the bit body from that from which the tapered neck extends. Each of the cutter supporting blocks defines a generally cylindrical bore for the purpose of slidably and rotatably receiving a cutter element in such bore. The several cutter elements thus mounted in the blocks are arrayed around a centrally located pilot cutter which is mounted on the bit body at a central location and in axial alignment with fluid passageways and ports which extend through the tapered neck and the bit body. |
