Abstract: A drill bit is disclosed. The drill bit includes a center member configured to rotate at a first speed and an outer member disposed outside the center member, wherein the outer member is configured to rotate at a second speed. The drill bit also includes a first cutter disposed on the center member and a second cutter disposed on the outer member, wherein the first speed and second speeds are configured to control a resultant side force of the drill bit.

Abstract: An apparatus for drilling a hole in the ground has a hammer drill installed at a bottom of a rod assembled in multi-stages at support structure on the ground. The hammer drill has a pilot hammer drill and a reamer hammer drill coupled to each other through a key structure formed in the vertical direction so as to allow simultaneous rotations and up-and-down movements relative to each other.

Abstract: The invention relates to a rotary drill bit for drilling a borehole in an earth formation, the drill bit comprising a first and a second disc cutter, each disc cutter being arranged to roll along the borehole bottom during rotation of the drill bit and thereby to cut respective first and second substantially circular, radially spaced cuts in the borehole bottom so that a body of rock material is defined between said cuts. The second disc cutter is arranged to cut into the bottom of the borehole at a selected rotational interval of the drill bit behind the first disc cutter and to shear-off said body of rock material in the direction of the first cut. Each disc cutter includes a set of mutually spaced cutting members arranged to create, during a turn of the drill bit, a corresponding set of cut sections of the cut created by the disc cutter, and wherein the cutting members are arranged so that the sets of cut sections created during subsequent drill bit turns are staggered relative to each other.

Abstract: A rock cutting tool with a plurality of independently rotatable cutter units and with a shaft, a sleeve located around the shaft, and at least two rotatable hubs located around the sleeve. At least one cutter unit is located on each of the two rotatable hubs for rotation about an axis of rotation with respect to a rock-face. Bearings between the sleeve and each of the hubs rotatably support the hubs. The bearings comprise at least one cylindrical roller bearing set and at least one ball bearing set for each hub. Each roller bearing set is located substantially entirely under the cutter unit of its associated hub to absorb radial loads, and each ball bearing set is located remotely from the cutter unit of its associated hub to be isolated from radial loads. The shaft has first and second key receiving openings. The key is located on the interior surface of the sleeve.

Abstract: Earth drilling equipment includes a main body tube with jacks to releasably support it within a drilled shaft, or within an erected start up shaft. An outer casing is rotatably mounted within the main body tube, and carries a horizontal base on which are driven wheels, and vertical shafts which have cutting elements. Means within the casing for fluid input and evacuation within the drill area is provided to form a slurry of the fluid and excavated material for withdrawal through the casing. As drilling continues, the main body tube is lowered into the shaft.The cutting elements include plates with cutting edges mounted on individual axles such that the edges are maintained in cutting relation to the area to be drilled.