Abstract: A drill bit is disclosed for drilling large diameter shafts. The drill bit comprises a main bit body having a plurality of cutter assemblies rotatively mounted on the lower side thereof. The cutters contact and disintegrate the earth formations at the bottom of the shaft, thereby creating rock chips. The cutters are strategically located along arcuate paths and extending generally from the bit gage or periphery to the center of the bit. An arcuate channel is formed by the bit body to house the cutters and to provide a high velocity flow path for drilling fluid which engulfs all the cutters and flushes the rock chips away during operation of the bit. Drilling fluid containing rock chips enters the drillstring at the center of the bit body and is then pumped up and out of the shaft being drilled.

Abstract: A raise drill is disclosed for enlarging a pilot hole into a large diameter hole by disintegrating the earth formations surrounding the pilot hole. The raise drill includes a bit body having a plurality of roller cutters mounted thereon. The bit body is detachable secured to a drive stem to permit removal and replacement of the stem. A shock absorbing element is interconnected between the drive stem and the bit body to enable the bit body to be flexibly mounted on the drive stem. A central yoke is provided to extend around the drive stem and interconnect the saddles of the two innermost cutters. The central yoke functions to distribute the loading of the inboard cutters. The central yoke can also function as a housing for a packing element.

Abstract: A large diameter drill bit is disclosed that is capable of drilling various size bores. In the preferred embodiment, the drill functions as a raise bit for enlarging a pilot hole into a larger diameter hole by disintegrating the earth formations surrounding the pilot hole. In the primary stage, the raise bit includes a primary body supporting a plurality of yokes positioned at various radial locations thereon. A frusto-conical cutter is rotatively mounted on each yoke for contacting and disintegrating the above-mentioned earth formations, with the outermost cutters forming the gage row. For the second stage, in which larger diameter holes are to be drilled, a plurality of ear assemblies are provided for attachment to the primary body at circumferential locations between the outermost primary cutters. Each ear assembly comprises a unitary support frame having a yoke and cutter mounted thereon. A vertically oriented roller stabilizer is also mounted on each support frame.

Abstract: 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.

Abstract: A raise drill having a central drive stem to which a surrounding cutter mounting frame is attached, the cutter mounting frame supporting a plurality of rotary cutter units. One or more inboard cutter units each include a shaft and a rotary cutter journaled for rotation on the shaft. One end of the shaft is inserted in a bore extending into the side of the stem. A yoke member receives the outer end of the shaft. The yoke member is supported by a mounting block secured to the frame. The mounting block has first and second intersecting planar surfaces, the first surface extending substantially parallel to the axis of the bore and the second surface extending in an obtuse angle to the first surface facing the stem. The yoke member has a first surface which slidably engages the first surface of the mounting member, and a second surface spaced from the second surface of the mounting member, allowing axial movement of the cutter shaft into and out of the bore.