An earth-boring tool comprises a bit body and first and second depth of cut control (DOCC) features mounted thereon. The first and second DOCC features comprise a first rubbing surface having a first surface area and a second rubbing surface having a second surface area, respectively, for contacting a subterranean formation. The second surface area is different from the first surface area such that the first and second DOCC features distribute a load attributable to applied weight on bit over the first and second rubbing surfaces at different rates. Methods of forming an earth-boring tool include selecting first and second DOCC features having different rates of engagement with the subterranean formation and mounting the first and second DOCC features on a bit body.

An insert for a drill bit includes a base portion. In addition, the insert includes a formation engaging portion extending from the base portion. The formation engaging portion has a longitudinal axis and includes a first end, a second end opposite the first end, a first lateral side extending from the first end to the second end, and a second lateral side extending from the first end to the second end, and an elongate crown extending longitudinally from the first end to the second end and laterally from the first lateral side to the second lateral side. The first lateral side comprises a first curved surface having a first radius of curvature in top view of the insert and the second lateral side includes a second curved surface having a second radius of curvature in top view of the insert. The first radius of curvature of the first curved surface is different than the second radius of curvature of the second curved surface.

An insert for a drill bit includes a base portion. In addition, the insert includes a formation engaging portion extending from the base portion. The formation engaging portion has a longitudinal axis and includes a first end, a second end opposite the first end, a first lateral side extending from the first end to the second end, and a second lateral side extending from the first end to the second end, and an elongate crown extending longitudinally from the first end to the second end and laterally from the first lateral side to the second lateral side. The first lateral side comprises a first curved surface having a first radius of curvature in top view of the insert and the second lateral side includes a second curved surface having a second radius of curvature in top view of the insert. The first radius of curvature of the first curved surface is different than the second radius of curvature of the second curved surface.

A cutting element assembly may include a support structure and a pin having a cylindrical exterior bearing surface. Retention elements may couple opposing ends of the pin to the support structure. The cutting element assembly also includes a rotatable cutting element including a table of polycrystalline hard material having an end cutting surface and a supporting substrate. The rotatable cutting element may have an interior sidewall defining a longitudinally extending through hole. The pin may be positioned within the through hole of the rotatable cutting element and may be supported on the opposing ends thereof by the support structure. Methods include drilling a subterranean formation including engaging a formation with one or more of the rotatable cutting elements.

A cutting element assembly may include a support structure and a pin having a cylindrical exterior bearing surface. Retention elements may couple opposing ends of the pin to the support structure. The cutting element assembly also includes a rotatable cutting element including a table of polycrystalline hard material having an end cutting surface and a supporting substrate. The rotatable cutting element may have an interior sidewall defining a longitudinally extending through hole. The pin may be positioned within the through hole of the rotatable cutting element and may be supported on the opposing ends thereof by the support structure. Methods include drilling a subterranean formation including engaging a formation with one or more of the rotatable cutting elements.

A cone arm assembly comprises an arm having a shaft extending therefrom in which the shaft is angularly surrounded by a shoulder surface on one end thereof. A cone has a recess formed therein which receives the shaft in a manner to permit a rotation of the cone relative to the shaft about a rotational axis. The cone has a base surface facing the shoulder surface of the arm. A first seal element is positioned within the recess and forms a first seal between the shaft of the arm and the cone. A second seal element is positioned within the recess and forms a second seal between the shaft of the arm and the cone. The second seal is positioned closer to the shoulder surface than the first seal. A third seal element forms a third seal between the base surface of the cone and the shoulder surface of the arm.

A drilling tool has: a casing pipe in a circular tubular shape; a cylindrical or annular ring bit rotatably fitted to a tip portion of the casing pipe; and a pilot bit inserted into an inner circumference of the ring bit for a striking force to be exerted to toward a tip end side, wherein the ring bit is engaged with and fitted to the casing pipe, projections are formed on an outer circumferential portion of the pilot bit, a recessed trench, and a housing trench, are formed in the inner circumferential part of the ring bit, a torque transmitting surface is formed in the projection, a torque receiving surface capable of abutting the torque transmitting surface is formed in the housing trench, striking force transmitting surfaces are formed in projections, and striking force receiving surfaces capable of abutting the striking force transmitting surfaces are formed in the ring bit.

A drilling tool has: a casing pipe in a circular tubular shape; a cylindrical or annular ring bit rotatably fitted to a tip portion of the casing pipe; and a pilot bit inserted into an inner circumference of the ring bit for a striking force to be exerted to toward a tip end side, wherein the ring bit is engaged with and fitted to the casing pipe, projections are formed on an outer circumferential portion of the pilot bit, a recessed trench, and a housing trench, are formed in the inner circumferential part of the ring bit, a torque transmitting surface is formed in the projection, a torque receiving surface capable of abutting the torque transmitting surface is formed in the housing trench, striking force transmitting surfaces are formed in projections, and striking force receiving surfaces capable of abutting the striking force transmitting surfaces are formed in the ring bit.

A method for estimating the wear of a drilling tool is disclosed. The method includes selecting a first incremental distance along a length of a formation. The method further includes determining a first characteristic of the formation along the first incremental distance. The method further includes deriving a first fractional wear factor, y.sub.1, for the drilling tool based on the first characteristic of the formation and a first operating condition of the cutting element. The method further includes calculating a first wear function, W.sub.f1, the cutting element based on the first fractional wear factor and estimating an amount of wear of the cutting element during a drilling operation based on the first wear function.

A cutting element assembly may include a support structure and a pin having a cylindrical exterior bearing surface. Retention elements may couple opposing ends of the pin to the support structure. The cutting element assembly also includes a rotatable cutting element including a table of polycrystalline hard material having an end cutting surface and a supporting substrate. The rotatable cutting element may have an interior sidewall defining a longitudinally extending through hole. The pin may be positioned within the through hole of the rotatable cutting element and may be supported on the opposing ends thereof by the support structure. Methods include drilling a subterranean formation including engaging a formation with one or more of the rotatable cutting elements.