A concentric alignment device is provided that elevates the working face of a drill bit off of the inner wall of a casing or tubing to prevent premature wear of the working face of the drill bit. In horizontal drilling applications, the working face of a drill bit has a tendency to contact or rest on the inner wall of a casing or tubing, which negatively affects the working face of a drill bit. In some embodiments, one or more optional inserts are provided on the shank of a drill bit or on a centralizing sub such that the inserts contact the inner wall of a casing or tubing instead of the working face of the drill bit. In other embodiments, blade packages on a drill bit or sub contact the inner wall of a casing or tubing and also pump drilling fluid in a downhole direction.

A drill bit (11) for the drilling, in particular the rotary percussive drilling, of a hole, in particular a tap hole of a melting furnace, the drill bit (11) comprising a drill head (10), which has at least one hard material insert (16), and a base body (12) for connecting the drill bit to a driving element, the hard material insert (16) being inserted into a seat, which is formed in an axial end face (13) of the drill head (10), in such a manner that at least a head cutting edge (18) of the hard material insert (16) protrudes beyond the axial end face (13), wherein the seat has a flank portion and a mating flank portion located opposite the flank portion, between which the hard material insert (16) is disposed, the flank portion, which is disposed opposite a recess formed in the hard material insert (16), being provided with a material projection (35) which is at least partially made of a welding material, is bonded to the drill head (10) via the welding material and protrudes into the recess so as to establish a form-fitting connection with the hard material insert (16).

A drill bit (11) for the drilling, in particular the rotary percussive drilling, of a hole, in particular a tap hole of a melting furnace, the drill bit (11) comprising a drill head (10), which has at least one hard material insert (16), and a base body (12) for connecting the drill bit to a driving element, the hard material insert (16) being inserted into a seat, which is formed in an axial end face (13) of the drill head (10), in such a manner that at least a head cutting edge (18) of the hard material insert (16) protrudes beyond the axial end face (13), wherein the seat has a flank portion and a mating flank portion located opposite the flank portion, between which the hard material insert (16) is disposed, the flank portion, which is disposed opposite a recess formed in the hard material insert (16), being provided with a material projection (35) which is at least partially made of a welding material, is bonded to the drill head (10) via the welding material and protrudes into the recess so as to establish a form-fitting connection with the hard material insert (16).

An earth-boring tool for removing subterranean formation material in a borehole comprises a tool body having a central axis defining an axial center thereof and a leg extending in an axial direction from the tool body. A bearing assembly is removably coupled to the leg and includes a bearing shaft and a base member. The base member encircles a portion of the bearing shaft and abuts against a surface of the leg. A roller cone is rotatably coupled to the bearing assembly and has a rotational axis about which the roller cone rotates on the bearing assembly when the roller cone removes subterranean formation material in the borehole. A method of assembling a rotatable cutting structure assembly including the bearing assembly includes coupling the bearing shaft to the leg by disposing a mechanical fastener through an aperture formed through the leg and into a cavity of the bearing shaft.

A cutting element may include a substrate, an upper surface of the substrate including a crest, the crest transitioning into a depressed region, and an ultrahard layer on the upper surface, thereby forming a non-planar interface between the ultrahard layer and the substrate. A top surface of the ultrahard layer includes a cutting crest extending along at least a portion of a diameter of the cutting element, the top surface having a portion extending laterally away from the cutting crest having a lesser height than a peak of the cutting crest.

A cutting insert for milling wellbore casing in a downhole environment includes a body having a cutting face and a chip-breaking face. The cutting face and chip-breaking face are oriented at a face angle relative to each other, the face angle being between 75 and 130. As the wellbore casing is milled, swarf is formed and work hardened. Further deformation of the swarf and movement along, or in contact with, the chip-breaking face breaks the swarf into chips that are readily flushed away or transported within the wellbore.

A cutting element comprises a supporting substrate, and a cutting table attached to an end of the supporting substrate. The cutting table comprises a first region and a second region. The first region comprising inter-bonded diamond particles and is substantially free of at least highly catalytic metallic compounds, one or more non-catalytic compounds within interstitial spaces between the inter-bonded diamond particles, and voids within interstitial spaces between the inter-bonded diamond particles. The second region comprising inter-bonded diamond particles, one or more non-catalytic compounds within interstitial spaces between the inter-bonded diamond particles, and one or more metallic phases within interstitial spaces between the inter-bonded diamond particles. The first region of the cutting table has a content of elemental metal of at least about 2.6 wt %. A method of forming a cutting element, and an earth-boring tool are also described.

A drilling tip that is attached to a distal end surface of a tool main body of a drilling tool which is rotated around an axis and in which a striking force is applied to a distal end side in a direction of the axis. The drilling tip includes a tip main body in which a base end portion having a columnar shape and a distal end portion protruding from this base end portion to the distal end side are integrally formed. The distal end portion includes a curved convex surface-shaped portion protruding to the distal end side of the tip main body, and a projection portion protruding to the distal end side from a surface of the curved convex surface-shaped portion.

A drilling tip that is attached to a distal end surface of a tool main body of a drilling tool which is rotated around an axis and in which a striking force is applied to a distal end side in a direction of the axis. The drilling tip includes a tip main body in which a base end portion having a columnar shape and a distal end portion protruding from this base end portion to the distal end side are integrally formed. The distal end portion includes a curved convex surface-shaped portion protruding to the distal end side of the tip main body, and a projection portion protruding to the distal end side from a surface of the curved convex surface-shaped portion.

A roof-bolt drill bit includes a bit body that is rotatable about a central axis, a coupling pocket defined in the bit body, and at least one cutting element mounted to the bit body. The at least one cutting element includes a cutting face, a cutting edge adjacent the cutting face, a back surface opposite the cutting face, and a side surface extending between the cutting edge and the back surface. The roof-bolt drill bit additionally includes a coupling attachment coupled to the bit body, the coupling attachment being positioned adjacent to a portion of the side surface of the cutting element that abuts a side surface of the coupling pocket.