Earth-boring tools may comprise rotatable cutting elements rotatably connected to protruding journals, which may be at least partially located within inner bores extending through the rotatable cutting elements. A rotationally leading end of one of the protruding journals may not extend beyond a cutting face of its associated rotatable cutting element. Alternatively, a protruding journal may comprise a chip breaker protruding from a cutting face of a rotatable cutting element. Methods of removing an earth formation may include directing cuttings forward, away from a cutting face of a rotatable cutting element when the cuttings reach an inner bore of the rotatable cutting element, and rotating the rotatable cutting element around a protruding journal at least partially located in the inner bore.

A rotary tool for milling tubing in a borehole comprises at least one cutter with a cutter body and a cutting surface on the body. Each cutter is shaped and positioned on the tool so as to reduce tensile stress in the cutter, thereby reducing risk of the cutter becoming chipped or broken in use and produces swarf of reduced rigidity, less likely to form a blockage in the borehole.

A cutting element includes a body, a non-planar cutting face formed on a first end of the body, and an edge formed around a perimeter of the cutting face. The cutting face includes a central raised portion, and the edge has an edge angle defined between the cutting face and a side surface of the body. The edge angle varies around the perimeter of the cutting face and includes an acute edge angle defined by a portion of the cutting face extending downwardly from the edge to a depth from the cutting angle. The portion of the edge defining the acute edge angle may be directly adjacent: a side surface of the cutting element; a bevel of the cutting element; or a flat region at the perimeter of the cutting element or bevel.

Earth-boring tools may comprise rotatable cutting elements rotatably connected to protruding journals, which may be at least partially located within inner bores extending through the rotatable cutting elements. A rotationally leading end of one of the protruding journals may not extend beyond a cutting face of its associated rotatable cutting element. Alternatively, a protruding journal may comprise a chip breaker protruding from a cutting face of a rotatable cutting element. Methods of removing an earth formation may include directing cuttings forward, away from a cutting face of a rotatable cutting element when the cuttings reach an inner bore of the rotatable cutting element, and rotating the rotatable cutting element around a protruding journal at least partially located in the inner bore.

An earth-boring tool having at least one cutting element with a multi-friction cutting face provides for the steering of formation cuttings as the cuttings slide across the cutting face. The multi-friction cutting element includes a diamond table bonded to a substrate of superabrasive material. The diamond table has a cutting face formed thereon with a cutting edge extending along a periphery of the cutting face. The cutting face has a first area having an average surface finish roughness less than an average surface finish roughness of a second area of the cutting face, the two areas separated by a boundary having a proximal end proximate a tool crown and a distal end remote from the tool crown.

Provided is a novel wear-resistant and collision-resistant polycrystalline diamond compact (PDC) drill bit with rostriform teeth and a plurality of blades, including an upper joint and a drill matrix. The PDC drill bit with rostriform teeth and a plurality of blades breaks rocks jointly by the primary teeth by way of penetration-splitting and the secondary teeth by way of shearing, so that the torque needed to break the rocks is greatly reduced. The design of the plurality of blades balances force distribution between rocks and blades at a shaft bottom, so that the abrasion loss of the teeth within a unit time is reduced. The present invention solves the technical problems in the prior art that cutting positions are abraded, and the teeth are fed slowly and are unreasonably distributed.

Provided is a novel wear-resistant and collision-resistant polycrystalline diamond compact (PDC) drill bit with rostriform teeth and a plurality of blades, including an upper joint and a drill matrix. The PDC drill bit with rostriform teeth and a plurality of blades breaks rocks jointly by the primary teeth by way of penetration-splitting and the secondary teeth by way of shearing, so that the torque needed to break the rocks is greatly reduced. The design of the plurality of blades balances force distribution between rocks and blades at a shaft bottom, so that the abrasion loss of the teeth within a unit time is reduced. The present invention solves the technical problems in the prior art that cutting positions are abraded, and the teeth are fed slowly and are unreasonably distributed.

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.