Abstract: A drill bit and method in which polycrystalline diamond cutters mounted on a bit crown cut formation chips akin to the manner in which a grater cuts cheese. Chips in impermeable or plastic formations are extruded by the cutters into cavities internal to the bit via slots adjacent each cutter. Drilling fluid circulates internally of the bit from the drill string and into the annulus above that portion of the bit bearing cutters. In one embodiment, the portion of the bit body upon which the crown is formed is made of an elastomer which is pressurized into sealing engagement with the bottom of the borehole thereby further sealing freshly cut formation from drilling fluid.

Abstract: A rotary drill bit comprises a bit body carrying a plurality of primary preform cutting elements defining a primary cutting profile. The bit includes means to apply a lateral imbalance force to the bit as it rotates, and a portion of the outer periphery of the bit body includes a low friction bearing surface so located as to transmit the lateral force to the formation. There are associated with some of the primary cutting elements respective secondary elements spaced inwardly of the cutting profile defined by the primary cutting elements, but the portion of the periphery of the bit body where the bearing surface is located is substantially free of such secondary elements. The arrangement enhances the anti-whirl characteristics of the bit.

Abstract: A rotary drill bit comprises a bit body having a shank for connection to a drill string and a passage for supplying drilling fluid to the face of the bit, which carries a plurality of polycrystalline diamond preform cutting elements. The cutting elements are mounted on a single radially extending blade so that the bit is imbalanced and a resultant sideways force is applied to the bit as it rotates during drilling. The gauge of the bit body is provided with a low friction bearing pad which extends rearwardly of the blade and transmits the resultant sideways force to the sides of the bore hole. Since the bearing pad is low friction, it slides around the surface of the formation and any tendency for bit whirl to be initiated is reduced.

Abstract: A subterranean drill bit operable with a rotational drive source is provided for drilling in subterranean earthen materials to create a borehole having a borehole wall. The drill bit comprises a drill bit body having a base portion, a gauge portion and a face portion disposed about a bit axis. A plurality of diamond cutting elements are fixedly disposed on and project from the face portion and are spaced from one another. The cutting elements are disposed for causing a net radial imbalance force during the drilling along a net radial imbalance force vector substantially perpendicular to the bit axis. A substantially continuous cutter devoid region is disposed on the gauge portion about the force point, and a bearing support is disposed in the cutter devoid region about the force point for substantially continuously contacting the borehole wall during the drilling.

Abstract: A rotary drill bit comprises a bit body having a shank for connection to a drill string and a passage for supplying drilling fluid to the face of the bit, which carries a plurality of polycrystalline diamond preform cutting elements. In order to reduce bit whirl, the cutting elements are so disposed as to apply a resultant lateral force to the bit as it rotates during drilling, and the gauge of the bit body is provided with low friction bearing means to transmit said resultant force to the sides of the borehole. Each low friction bearing means includes a roller mounted on the bit body for rotation about an axis parallel to the axis of rotation of the bit, each roller being so disposed that its periphery bears on the formation as the bit rotates.

Abstract: A rotary drill bit comprises a bit body having a shank for connection to a drill string and a passage for supplying drilling fluid to the face of the bit, which carries a plurality of polycrystalline diamond preform cutting elements. In order to reduce bit whirl, the cutting elements are so disposed as to apply a resultant lateral imbalance force to the bit as it rotates during drilling and the gauge of the bit body is provided with low friction bearing pads to transmit said resultant lateral force to the sides of the borehole. Each low friction bearing pad includes an outwardly facing cavity which is connected to the passage by a choked conduit so that, in use, drilling fluid under pressure is delivered to the cavity, which thereby acts as a low friction hydrostatic bearing surface.

Abstract: An imbalance compensated drill bit is disclosed that takes advantage of undesired and destructive imbalance forces to prevent bit whirl. Methods of designing and making such imbalance compensated drill bits are disclosed whereby a drill bit body has at least one cutting zone with a plurality of cutting elements extending therefrom and at least one bearing zone. The bearing zone has a relatively smooth surface and is located at a position where the net imbalance force (from the cutting elements) is directed towards. When the drill bit is rotated, the imbalance force presses the bearing zone against the borehole wall, and the bearing zone slips along the wall, thereby preventing the center of rotation to shift and create the destructive whirling motion.

Abstract: A device for forming an elongated hole in the ground, comprising a hollow, flexible conduit, a head (2') which is connected to one end of the conduit and which is fitted with at least one nozzle (5') through which fluid passing along the conduit under pressure is delivered in such a direction and under such pressure that when the head is not in rotation, the head will form a hole of curved configuration and such that when the head rotates about its longitudinal axis and the conduit is moved forwards in the hole-forming direction the head will form a substantially straight hole, the end of the head facing towards the hole-forming direction being provided with a surface which is positioned obliquely to the longitudinal axis of the head and which assists the head in forming a curved hole.

Abstract: A drill bit for producing an undercut. The drill bit includes a shaft and a cutting edge that is disposed asymmetrically radially beyond the shaft in a front end portion of the drill bit. A planar guide surface is provided on a conical end face of the drill bit. This guide surface is disposed radially opposite the cutting edge. The guide surface terminates at a concentric tip of the drill bit.

Abstract: Apparatus for stabiliing a rotary drill string and drill bit used to drill a borehole in a material, such as a subterranean formation, includes an imbalanced drill collar and a drill bit connected to the drill collar. The imbalanced drill collar creates a drill string imbalance force directed radially outwardly from the center of rotation of the drill collar through a predetermined area on the circumference of the drill collar and urges the predetermined area into contact with the borehole wall as the drill string rotates. The drill bit includes a drilling surface for contacting the material and drilling the borehole in the material, the drilling surface including a cutting zone for cutting the borehole in the material and the bearing zone having a low coefficient of friction relative to the cutting zone.

Abstract: A bit assembly for undercutting a blind bore extending along a bore axis between an open outer end and a closed inner end and having a substantially cylindrical wall of a predetermned diameter centered on the bore axis and extending between the ends comprises a pusher body normally seated in the closed inner end of the bore and having an outwardly turned camming surface inclined to the bore axis, and a bit having a shaft extending along a longitudinal bit axis and having an inner end, an outer end, and a pair of longitudinally extending sides terminating at the inner end. One of the sides is at least partially cylindrical and centered on the bit axis and the inner end is formed with a camming surface engageable with the camming surface of the body and inclined to the bit axis. A blade fixed permanently and stationarily on the inner end projects radially from the one side of the shaft, the other side being cut back toward the bit axis.

Abstract: The invention relates to an arrangement for drilling in soil and rock while simultaneously lining the drill hole with a lining tube. The arrangement includes an asymetric guide which is non-rotatably connected to a drill stem or like element, and an eccentric drill bit or crown which is journalled for limited rotation in the guide. The guide is arranged to lie solely against a part of one side of the inner surface of the lining tube during a drilling operation. Advantageously, the guide is supplemented with a guiding portion on the shank part of the drill bit located opposite the first guide. The drill arrangement enables wide adjustments to be made to the eccentric setting of the drill bit, and makes possible an advantageous forming of the cutting geometry of the drill bit.

Abstract: A diamond milling cutter for elongating a laterally opening window in a well casing set in a well bore extending into the earth. The mill has a revolving surface which engages a sidetracking whipstock or the edge of the casing being milled to urge the mill off dead center on the casing edge and enhance the cutting action. One or more eccentric lobes engage the whipstock and cause the mill to revolve on a gyrating or non-fixed axis and effect oscillation of the cutter center laterally of the edge, or a broadly conical nose on the cutting face of the mill provides a wedge action against the casing to laterally move the mill off center and enhance the cutting action.