| 摘要 |
A raise drill for enlarging a pilot hole into a larger diameter hole by disintegrating the earth formations surrounding the pilot hole is disclosed. The raise drill includes a main bit body having a plurality of cutters mounted thereon. The bit body is detachably secured to the drive stem to permit removal and replacement of the stem. The removable drive stem allows the raise bit to be transported through small drifts and helps extend the useful life of the raise bit. The drive stem extends through a central opening in the raise bit body and includes an upwardly facing shoulder for engaging the margin of the bit body about the opening. The drive stem further includes a plurality of tapered flat surfaces located about the periphery of the bottom end thereof. A plurality of bolted wedge blocks, attachable to the main bit body are provided to engage the tapered flat surfaces of the drive stem in order to urge the shoulder of the drive stem into locking engagement with the main bit body. |
