A wellbore assembly includes a drill string, a drill bit, and a reamer assembly. The reamer assembly is coupled to the drill string uphole of the drill bit and includes a side cutter. The reamer assembly includes a spring that moves the side cutter from an extended position, in which the side cutter is retained by a portion of the reamer assembly against inward movement and in which the cutter defines a first drilling diameter greater than a drilling diameter of the drill bit, to a retracted position in which the portion of the reamer assembly has been broken by a shear force applied by the side cutter under a weight on bit applied against an inner component of the casing. In the retracted position, the side cutter is housed within the housing and defines a drilling diameter equal to or less than the drilling diameter of the drill bit.

A tool for building a wellbore includes a tool body with a flow passage extending axially therethrough, a piston chamber formed radially through the tool body that intersects the flow passage of the tool body, a piston disposed in the piston chamber, at least one actuation element that exerts a force between the piston and the piston chamber, and a sleeve disposed within the flow passage of the tool body that includes at least one cutout. When the sleeve is in a first position within the tool body, the cutout is axially offset from the piston, and when the sleeve is in a second position, the cutout is axially aligned with the piston.

A hybrid bit includes an earth-boring element and a percussion element. The earth-boring element and the percussion element are coaxially arranged, with the earth-boring element surrounding the percussion element. A reciprocating member of the percussion element may oscillate in a manner that enables a bottom end of the reciprocating member to repeatedly protrude from a bottom end of the earth-boring element and to be repeatedly withdrawn. A configuration of the earth-boring element may enable it to drill into and remove some materials from an earth formation, while the percussion element may enable the hybrid bit to drill into and remove difficult-to-drill materials, including abrasive materials and/or materials with high compressive forces, such as chert.

A hybrid bit includes an earth-boring element and a percussion element. The earth-boring element and the percussion element are coaxially arranged, with the earth-boring element surrounding the percussion element. A reciprocating member of the percussion element may oscillate in a manner that enables a bottom end of the reciprocating member to repeatedly protrude from a bottom end of the earth-boring element and to be repeatedly withdrawn. A configuration of the earth-boring element may enable it to drill into and remove some materials from an earth formation, while the percussion element may enable the hybrid bit to drill into and remove difficult-to-drill materials, including abrasive materials and/or materials with high compressive forces, such as chert.

An expandable tool includes a cutting block set. The cutting block set includes an upper cutting block and a lower cutting block, arranged longitudinally. The upper cutting block includes upper block splines having an upper block angle. The lower cutting block includes lower block splines having a lower block angle. The upper block angle is greater than the lower block angle, which directs the upper cutting block to extend radially further outward than the lower cutting block.

An expandable tool includes a cutting block set. The cutting block set includes an upper cutting block and a lower cutting block, arranged longitudinally. The upper cutting block includes upper block splines having an upper block angle. The lower cutting block includes lower block splines having a lower block angle. The upper block angle is greater than the lower block angle, which directs the upper cutting block to extend radially further outward than the lower cutting block.

A reamer includes a plurality of cutter pocket holders. The cutter pocket holders are separately manufactured and connected to a body of the reamer. The cutter pocket holders include a plurality of cutter pockets, into which cutting elements may be inserted. A radially rearward cutter pocket holder may include front-loading cutter pockets.

A reamer includes a plurality of cutter pocket holders. The cutter pocket holders are separately manufactured and connected to a body of the reamer. The cutter pocket holders include a plurality of cutter pockets, into which cutting elements may be inserted. A radially rearward cutter pocket holder may include front-loading cutter pockets.

A downhole drilling tool, forming part of a subterranean drilling system, may include at least one plate secured to an exterior of an elongate body. Electronics may be disposed between the plate and the body to be protected by the plate while still readily accessible. A dynamic element may be radially extendable from the plate to engage an inner wall of a borehole being drilled. If this radially-extendable element becomes worn or damaged from this engagement, the plate may be replaced. More expensive components of the drilling tool may be contained within the elongate body, rather than the plate, thus reducing replacement frequency. Additionally, plates including unique features may be employed at different times without altering the underlying elongate body.

A downhole assembly includes a bit and a cutting tool uphole of the bit. The cutting tool has one or more expandable cutter arms. The one or more expandable cutter arms include at least one stabilizer portion having a radial position that is about the same as a gauge of the bit when the one or more expandable cutter arms are in an expanded position. A spline on the cutter arms are used by a cutting tool to move the cutter arms.