A cutting element has a cutting face at an opposite axial end from a base, a side surface extending from the base to the cutting face, an edge formed at the intersection between the cutting face and the side surface, and an elongated protrusion formed at the cutting face and extending between opposite sides of the edge, wherein the elongated protrusion has a geometry including a border extending around a concave surface and sloped surfaces extending between the border and the edge, and wherein the concave surface has a major axis dimension measured between opposite sides of the border and a minor axis dimension measured perpendicularly to the major axis dimension and ranging from 50 percent to 99 percent of the major axis dimension.

A reamer for drill string pullback of a horizontal directional drill includes a shaft portion defining a central axis and a first end configured for attachment with a drill string of the horizontal directional drill. A plurality of vanes extend radially from an outer periphery of the shaft, each of the plurality of vanes defining an outer peripheral tooth base surface. On each of the plurality of vanes, a plurality of cutter teeth are individually and removably secured along the outer peripheral tooth base surface thereof, each one of the plurality of cutter teeth including a body and a PDC insert manufactured separately from the body and joined therewith. Each cutter tooth of the plurality is coupled to the respective one of the plurality of vanes by a removable fastener extending at least partially through the cutter tooth and at least partially through the one of the plurality of vanes.

A reamer for drill string pullback of a horizontal directional drill includes a shaft portion defining a central axis and a first end configured for attachment with a drill string of the horizontal directional drill. A plurality of vanes extend radially from an outer periphery of the shaft, each of the plurality of vanes defining an outer peripheral tooth base surface. On each of the plurality of vanes, a plurality of cutter teeth are individually and removably secured along the outer peripheral tooth base surface thereof, each one of the plurality of cutter teeth including a body and a PDC insert manufactured separately from the body and joined therewith. Each cutter tooth of the plurality is coupled to the respective one of the plurality of vanes by a removable fastener extending at least partially through the cutter tooth and at least partially through the one of the plurality of vanes.

A method for testing thermal fatigue resistance of a shear cutter includes: engaging the shear cutter with a rotating target cylinder; moving the shear cutter along the rotating target cylinder until the shear cutter is heated to a threshold temperature; cooling the shear cutter in response to heating of the shear cutter to the threshold temperature; and repeating the heating and cooling of the shear cutter.

A method for testing thermal fatigue resistance of a shear cutter includes: engaging the shear cutter with a rotating target cylinder; moving the shear cutter along the rotating target cylinder until the shear cutter is heated to a threshold temperature; cooling the shear cutter in response to heating of the shear cutter to the threshold temperature; and repeating the heating and cooling of the shear cutter.

In a drill bit insert of the present invention, an insert body of the drill bit insert includes: a rear end portion forming a columnar shape or a disk-like shape; an intermediate portion having an outer diameter smaller than that of the rear end portion; and an end portion having an outer diameter from the center line of the insert gradually decreasing toward the tip side, the hard surface layer is coated on the insert body from a surface of the end portion of the insert body to an outer periphery of the intermediate portion, and an outer diameter of the hard surface layer on the intermediate portion is equal to that of the rear end portion.

Systems and methods are disclosed for a rotating superhard cutting element. The rotating cutting element includes a substrate comprising a rotating portion and a stable portion. The stable portion has a cavity and is configured to be fixed to a blade of a drill bit. The rotating cutting element further includes a retainer that rotatably secures the rotating portion of the substrate in the cavity of the stable portion of the substrate, and a cutting layer on the rotating portion of the substrate. The cutting layer has a plurality of cutting surfaces. One of the plurality of cutting surfaces has a property different from another one of the plurality of cutting surfaces. The cutting layer is configured to rotate with respect to the stable portion of the substrate and use one of the plurality of cutting surfaces based on a characteristic of a formation to be cut.

A method of forming a cutting element comprises disposing diamond particles in a container and disposing a metal powder on a side of the diamond particles. The diamond particles and the metal powder are sintered so as to form a polycrystalline diamond material and a low-carbon steel material comprising less than 0.02 weight percent carbon and comprising an intermetallic precipitate on a side of the polycrystalline diamond material. Related cutting elements and earth-boring tools are also disclosed.

A sensor element for a cutting tool has a hard portion having a first sensing surface, first and second electrodes, and first and second sets of thermocouple wires, and an electrically insulating portion. The second electrode has a second sensing surface, The hard portion comprises hard and/or super-hard material and the first and second electrodes comprise electrically conductive hard and/or super-hard material, the hard portion isolating the first sensing surface from the second sensing surface. The second electrode is attached to or forms part of an electrically conductive region of the hard portion or a region attached thereto. Electric current flows between the first and second electrodes through external material when the sensing surfaces contact the material in response to the cutting tool engaging the material. The first and second electrodes are operable to indicate any one or more of a temperature of the first and second electrodes, and conductivity between the electrodes.

A sensor element for a cutting tool has a hard portion having a first sensing surface, first and second electrodes, and first and second sets of thermocouple wires, and an electrically insulating portion. The second electrode has a second sensing surface, The hard portion comprises hard and/or super-hard material and the first and second electrodes comprise electrically conductive hard and/or super-hard material, the hard portion isolating the first sensing surface from the second sensing surface. The second electrode is attached to or forms part of an electrically conductive region of the hard portion or a region attached thereto. Electric current flows between the first and second electrodes through external material when the sensing surfaces contact the material in response to the cutting tool engaging the material. The first and second electrodes are operable to indicate any one or more of a temperature of the first and second electrodes, and conductivity between the electrodes.