Abstract: An earth-boring tool includes a body, a plurality of fixed blades, a first plurality of cutting elements secured to the plurality of fixed blades, a plurality of removable blade assemblies removably coupled to the body, and a second plurality of cutting elements secured to the plurality of removable blade assemblies, each cutting element of the second plurality of cutting elements exhibiting an aggressiveness that is less than an aggressiveness of each cutting element of the first plurality of cutting elements. A method of forming an earth-boring tool includes forming a body and a plurality of fixed blades extending from the body, securing a first plurality of cutting elements to the plurality of fixed blades, removably coupling at least one removable blade assembly to the body, and securing a second plurality of cutting elements to the at least one removable blade assembly.

Abstract: An earth-boring tool includes a body, a plurality of fixed blades, a first plurality of cutting elements secured to the plurality of fixed blades, a plurality of removable blade assemblies removably coupled to the body, and a second plurality of cutting elements secured to the plurality of removable blade assemblies, each cutting element of the second plurality of cutting elements exhibiting an aggressiveness that is less than an aggressiveness of each cutting element of the first plurality of cutting elements. A method of forming an earth-boring tool includes forming a body and a plurality of fixed blades extending from the body, securing a first plurality of cutting elements to the plurality of fixed blades, removably coupling at least one removable blade assembly to the body, and securing a second plurality of cutting elements to the at least one removable blade assembly.

Abstract: A hybrid earth-boring bit comprising a bit body having a central axis, at least one, preferably three fixed blades, depending downwardly from the bit body, each fixed blade having a leading edge, and at least one rolling cutter, preferably three rolling cutters, mounted for rotation on the bit body. A rolling cutter is located between two fixed blades.

Abstract: A hybrid earth-boring bit comprising a bit body having a central axis, at least one, preferably three fixed blades, depending downwardly from the bit body, each fixed blade having a leading edge, and at least one rolling cutter, preferably three rolling cutters, mounted for rotation on the bit body. A rolling cutter is located between two fixed blades.

Abstract: A hybrid earth-boring bit comprising a bit body having a central axis, at least one, preferably three fixed blades, depending downwardly from the bit body, each fixed blade having a leading edge, and at least one rolling cutter, preferably three rolling cutters, mounted for rotation on the bit body. A rolling cutter is located between two fixed blades.

Abstract: An earth-boring drill bit is described, the bit having a bit body having a central longitudinal axis that defines an axial center of the bit body and configured at its upper extent for connection into a drill string; at least one primary fixed blade extending downwardly from the bit body and inwardly toward, but not proximate to, the central axis of the drill bit; at least one secondary fixed blade extending radially outward from proximate the central axis of the drill bit; a plurality of fixed cutting elements secured to the primary and secondary fixed blades; at least one bit leg secured to the bit body; and a rolling cutter mounted for rotation on the bit leg; wherein the fixed cutting elements on at least one fixed blade extend from a center of the bit outward toward a gage region of the bit but do not include a gage cutting region, and wherein at least one roller-cone cutter portion extends from substantially the drill bit's gage region inwardly toward the center of the bit, an apex of the roller-cone cu

Abstract: An earth-boring drill bit is described, the bit having a bit body having a central longitudinal axis that defines an axial center of the bit body and configured at its upper extent for connection into a drill string; at least one primary fixed blade extending downwardly from the bit body and inwardly toward, but not proximate to, the central axis of the drill bit; at least one secondary fixed blade extending radially outward from proximate the central axis of the drill bit; a plurality of fixed cutting elements secured to the primary and secondary fixed blades; at least one bit leg secured to the bit body; and a rolling cutter mounted for rotation on the bit leg; wherein the fixed cutting elements on at least one fixed blade extend from a center of the bit outward toward a gage region of the bit but do not include a gage cutting region, and wherein at least one roller cone cutter portion extends from substantially the drill bit's gage region inwardly toward the center of the bit, an apex of the roller cone cu

Abstract: A method of improving the service life of a drill bit comprises creating a weldment between load bearing portions of the drill bit where the weldment has a preselected root gap greater than about 25 mils and a preselected root face greater than about 25 mils, and where the weldment has a material property greater than the materials being joined.

Abstract: A bit body is configured at its upper extent for connection into a drillstring. At least one fixed blade extends downwardly from the bit body, and has a radially outermost gage surface. A plurality of fixed cutting elements is secured to the fixed blade, preferably in a row at its rotationally leading edge. At least one bit leg is secured to the bit body and a rolling cutter is mounted for rotation on the bit leg. At least one stabilizer pad is disposed between the bit leg and the fixed blade, the stabilizer pad extending radially outward to substantially the gage surface. The radially outermost gage surface of each blade can extend axially downward parallel to the bit axis or angled (non-parallel), spirally or helically, relative to the bit axis.

Abstract: An earth boring drill bit is described, the bit having a bit body having a central longitudinal axis that defines an axial center of the bit body and configured at its upper extent for connection into a drillstring; at least one primary fixed blade extending downwardly from the bit body and inwardly toward, but not proximate to, the central axis of the drill bit; at least one secondary fixed blade extending radially outward from proximate the central axis of the drill bit; a plurality of fixed cutting elements secured to the primary and secondary fixed blades; at least one bit leg secured to the bit body; and a rolling cutter mounted for rotation on the bit leg; wherein the fixed cutting elements on at least one fixed blade extend from the center of the bit outward toward the gage of the bit but do not include a gage cutting region, and wherein at least one roller cone cutter portion extends from substantially the drill bit's gage region inwardly toward the center of the bit, the apex of the roller cone cutte

Abstract: An earth-boring drill bit is described, the bit having a bit body having a central longitudinal axis that defines an axial center of the bit body and configured at its upper extent for connection into a drill string; at least one primary fixed blade extending downwardly from the bit body and inwardly toward, but not proximate to, the central axis of the drill bit; at least one secondary fixed blade extending radially outward from proximate the central axis of the drill bit; a plurality of fixed cutting elements secured to the primary and secondary fixed blades; at least one bit leg secured to the bit body; and a rolling cutter mounted for rotation on the bit leg; wherein the fixed cutting elements on at least one fixed blade extend from the center of the bit outward toward the gage of the bit but do not include a gage cutting region, and wherein at least one roller cone cutter portion extends from substantially the drill bit's gage region inwardly toward the center of the bit, the apex of the roller cone cutt

Abstract: An earth boring drill bit is described, the bit having a bit body having a central longitudinal axis that defines an axial center of the bit body and configured at its upper extent for connection into a drillstring; at least one primary fixed blade extending downwardly from the bit body and inwardly toward, but not proximate to, the central axis of the drill bit; at least one secondary fixed blade extending radially outward from proximate the central axis of the drill bit; a plurality of fixed cutting elements secured to the primary and secondary fixed blades; at least one bit leg secured to the bit body; and a rolling cutter mounted for rotation on the bit leg; wherein the fixed cutting elements on at least one fixed blade extend from the center of the bit outward toward the gage of the bit but do not include a gage cutting region, and wherein at least one roller cone cutter portion extends from substantially the drill bit's gage region inwardly toward the center of the bit, the apex of the roller cone cutte

Abstract: A method of improving the service life of a drill bit comprises creating a weldment between load bearing portions of the drill bit where the weldment has a preselected root gap greater than about 25 mils and a preselected root face greater than about 25 mils, and where the weldment has a material property greater than the materials being joined.

Abstract: An earth boring drill bit designed for a specific performance, within a finished product tolerance, using components built to a looser manufacturing tolerance. The bit may be assembled by selecting a leg from a plurality of pre-manufactured legs; selecting a bit body from a plurality of pre-manufactured bit bodies, the bit body having a slot for receiving the leg; placing the leg within the slot; and fixing the leg within the slot within the finished product tolerance by placing one or more shims between the leg and the slot. The shims may be used to adjust an axial position, a radial position, and/or a circumferential position of the leg with respect to the slot. The leg and the bit body may be selected, or produced, to ensure the bit will not meet the specification, given the manufacturing tolerance, without the shims.

Abstract: A hybrid earth-boring bit comprising a bit body having a central axis, at least one, preferably three fixed blades, depending downwardly from the bit body, each fixed blade having a leading edge, and at least one rolling cutter, preferably three rolling cutters, mounted for rotation on the bit body. A rolling cutter is located between two fixed blades.

Abstract: A bit body is configured at its upper extent for connection into a drillstring. At least one fixed blade extends downwardly from the bit body, and has a radially outermost gage surface. A plurality of fixed cutting elements is secured to the fixed blade, preferably in a row at its rotationally leading edge. At least one bit leg is secured to the bit body and a rolling cutter is mounted for rotation on the bit leg. At least one stabilizer pad is disposed between the bit leg and the fixed blade, the stabilizer pad extending radially outward to substantially the gage surface. The radially outermost gage surface of each blade can extend axially downward parallel to the bit axis or angled (non-parallel), spirally or helically, relative to the bit axis.

Abstract: A hybrid earth-boring bit comprising a bit body having a central axis, at least one, preferably three fixed blades, depending downwardly from the bit body, each fixed blade having a leading edge, and at least one rolling cutter, preferably three rolling cutters, mounted for rotation on the bit body. A rolling cutter is located between two fixed blades.

Abstract: A bit body is configured at its upper extent for connection into a drillstring. At least one fixed blade extends downwardly from the bit body, and has a radially outermost gage surface. A plurality of fixed cutting elements is secured to the fixed blade, preferably in a row at its rotationally leading edge. At least one bit leg is secured to the bit body and a rolling cutter is mounted for rotation on the bit leg. At least one stabilizer pad is disposed between the bit leg and the fixed blade, the stabilizer pad extending radially outward to substantially the gage surface. The radially outermost gage surface of each blade can extend axially downward parallel to the bit axis or angled (non-parallel), spirally or helically, relative to the bit axis.

Abstract: An earth-boring bit comprising a bit body is configured at its upper end for connection into a drillstring. A fixed blade depends axially downwardly from the bit body. An axially extending slot is formed in the bit body adjacent the fixed blade. A bit leg is received and retained in the slot by engagement between the slot and correspondingly shaped bit leg, wherein the bit leg cannot be removed from the slot except by axial movement relative to the bit body. A rolling cutter is secured to the bit leg at its lower extent. A fastener secures the bit leg against movement relative to the bit body and extends through oblong apertures in the bit leg and into the bit body, the bit leg can be moved axially relative to the bit body to adjust the projection of the rolling cutter relative to the fixed blade.

Abstract: An earth boring drill bit designed for a specific performance, within a finished product tolerance, using components built to a looser manufacturing tolerance. The bit may be assembled by selecting a leg from a plurality of pre-manufactured legs; selecting a bit body from a plurality of pre-manufactured bit bodies, the bit body having a slot for receiving the leg; placing the leg within the slot; and fixing the leg within the slot within the finished product tolerance by placing one or more shims between the leg and the slot. The shims may be used to adjust an axial position, a radial position, and/or a circumferential position of the leg with respect to the slot. The leg and the bit body may be selected, or produced, to ensure the bit will not meet the specification, given the manufacturing tolerance, without the shims.