Abstract: A vibration assembly of a drilling tool for drilling a wellbore penetrating a subterranean formation is disclosed. The downhole drilling tool includes a drill string, a bottomhole assembly and a drill bit. The vibration assembly includes a housing (334a) operatively connectable to the bottomhole assembly, expanders (122) positionable in the housing and radially extendable and retractable thereabout, and a radial vibrator (comprising mandrel (446), enlarger spring (48), cam portion (458) and vibration spring (570) operatively connectable to the expanders to vibrationally move the expanders against the wall of the wellbore whereby movement of the downhole tool is altered during drilling.

Abstract: In accordance with some embodiments, a downhole drilling tool comprises a bit body, a blade on an exterior portion of the bit body, and a gage pad on the blade. The gage pad includes a ball retainer and a ball located in the ball retainer such that an exposed portion of the ball is positioned to contact a wellbore and rotate in response to frictional engagement with the wellbore.

Abstract: The expandable tools disclosed herein may be used as an underreamer to enlarge a borehole, or may be used to stabilize a drilling system in a previously underreamed borehole or in a borehole that is being underreamed while drilling progresses. At least one moveable arm, which translates between a collapsed and expanded position in response to a differential pressure between the axial flowbore and the wellbore, includes a borehole-engaging surface with cutting elements and at least one nozzle to direct a fluid across the borehole-engaging surface. Flow directing elements on the external surface of the tool may be used to decrease the flow area in an annulus between the tool and the wellbore and directs fluid flow in the annulus toward the borehole-engaging surface.

Abstract: An apparatus and method for forming a borehole in an earthen formation includes a side cutting device comprised of a laterally extendable side cutting element that can be actuated from a retracted position to an extended position in which the side cutting element is selectively employed to create a larger borehole diameter in a down hole location than the remaining portion of the borehole that is closer to the borehole opening.

Abstract: A boring tool for digging holes having a vertical shaft of a first diameter extending from the soil surface to a suitable subsurface distance, and a void of a second diameter, larger than that of the first diameter, at the bottom, subsurface distance.

Abstract: An apparatus and method for forming a borehole in an earthen formation includes a side cutting device comprised of a laterally extendable side cutting element that can be actuated from a retracted position to an extended position in which the side cutting element is selectively employed to create a larger borehole diameter in a down hole location than the remaining portion of the borehole that is closer to the borehole opening.

Abstract: A down-the-hole assembly includes a housing having a central axis and a mechanical gear box positioned within the housing. The mechanical gear box is coupled to the housing such that rotation of the housing at a first rotational rate provides a rotary input to the mechanical gear box. A rotary cutting bit is coupled to the mechanical gear box. The mechanical gear box is configured to rotate said rotary cutting bit at a second rotational rate in response to that rotary input from the housing. The second rotational rate is greater than the first rotational rate. The mechanical gear box is also further configured to cause the rotary cutting bit to orbit about the central axis of the housing.

Abstract: An apparatus and method for forming a borehole in an earthen formation includes a side cutting device comprised of a laterally extendable side cutting element that can be actuated from a retracted position to an extended position in which the side cutting element is selectively employed to create a larger borehole diameter in a down hole location than the remaining portion of the borehole that is closer to the borehole opening.

Abstract: A collapsible cutter bit or rock head for use with an underground auger boring machine has an expanded position for cutting rock in front of an underground pipe and a collapsed position for withdrawing the rock head through the underground pipe. The auger boring machine is configured to bore a passage through a body of soil and rock and simultaneously lay the underground pipe in the passage. Forward rotation of the cutter bit causes expansion while collapse of the cutter bit may be driven by reverse rotation of the cutter bit or another mechanism.

Abstract: Downhole cutting tools comprise a mandrel, a housing, a sleeve and a cutting blade. The mandrel comprises an inner wall surface defining a bore, and an outer wall surface. The housing is secured to the outer wall surface of the mandrel and comprises an opening. The sleeve is engaged with the outer wall surface of the mandrel. The sleeve comprises a profile that is operatively associated with a profile of the cutting blade such that movement of the sleeve causes the profile of the piston to slide along the profile of the cutting blade. In so doing, the cutting blade is radially extended outward through the opening in the housing to abrade an object located outside the housing. Movement of the sleeve can be achieved by pumping fluid down a bore in the mandrel to slide the sleeve long the outer wall surface of the mandrel.

Abstract: A downhole tool string component has at least one end adapted to connect to an adjacent tool sting component and a bore adapted to accommodate a flow of drilling fluid. A turbine is disposed within the bore and an actuating assembly is arranged such that a clutch may mechanically connect and disconnect with the turbine.

Abstract: In one aspect of the invention, a downhole tool string component has at least one end adapted to connect to an adjacent tool sting component and a bore adapted to accommodate a flow of drilling fluid. A turbine is disposed within the bore and an actuating assembly is arranged such that a clutch may mechanically connect and disconnect with the turbine.

Abstract: An underreamer that can be assembled easily is formed from a tubular body having a flow tube running to a distal end delivering fluid which moves an actuator against the underreamer arms which are hinged to a moveable stop block and stopped to positively seat the arm at the end of a key slot to rigidly hold the underreamer arm in full extension during operations. Once hydraulic pressure is released, a spring moves the arm down the slot to a position where the arm can be removed from the slot in the underreamer body. A lower sub assembly is affixed to the underreamer body to prevent premature back off of the lower sub. Jets are disposed on either side of the underreamer to remove cuttings from the well bore. The tool is adaptable in the field for several hole sizes by adjustment in the length of the stop block and the angle of the flat on the top side of the key.

Abstract: An apparatus and method for forming a borehole in an earthen formation includes a side cutting device comprised of a laterally extendable side cutting element that can be actuated from a retracted position to an extended position in which the side cutting element is selectively employed to create a larger borehole diameter in a down hole location than the remaining portion of the borehole that is closer to the borehole opening.

Abstract: An apparatus and method for forming a borehole in an earthen formation includes a side cutting device comprised of a cam assembly that includes at least one groove therein for selective extension and retraction of a laterally extending cutting element. Rotation of the side cutting device in a first direction causes the cutting element to be in a first retracted position so that a borehole having a first diameter can be formed. Rotation of the side cutting device in a second direction causes the cutting element to be in a second extended position. Rotation and retraction of the side cutting device when the cutting element is in the second extended position allows the side cutting device to create a larger borehole diameter in a down hole location.

Abstract: A tubular cutter is run in on slickline. It features onboard power to selectively actuate an anchor and to initiate a tubular cutting operation with a cutter that is extendable and rotatable on its axis and the axis of the tool that carries an on board power supply.

Abstract: A drilling device used for drilling into ground, rock or for reaming a predrilled hole includes several hammering bits in a circular shape and equipped with hammers, whereupon they together drill a hole which has a larger diameter. A casing tube can be pulled out of the hole/pushed into the drilled hole. A tubular, rotatable drill rod tube resides in the casing tube. The hammers are located in a circular shape and are each attached to the outer surface of the drill rod tube by joint/hinge attachments lying essentially in the drilling direction. Rotation of the drill rod tube in a first direction turns the hammers and associated bits outwardly from the drill rod tube, and rotation in another direction turns the hammers with their bits inwardly towards the drill rod tube so that they can be pulled away with the drill rod tube from inside the casing tube.

Abstract: A down-the-hole assembly includes a housing having a central axis and a mechanical gear box positioned within the housing. The mechanical gear box is coupled to the housing such that rotation of the housing at a first rotational rate provides a rotary input to the mechanical gear box. A rotary cutting bit is coupled to the mechanical gear box. The mechanical gear box is configured to rotate said rotary cutting bit at a second rotational rate in response to that rotary input from the housing. The second rotational rate is greater than the first rotational rate. The mechanical gear box is also further configured to cause the rotary cutting bit to orbit about the central axis of the housing.

Abstract: The present invention relates to downhole tools, and in particular an underreamer tool for use in a wellbore of an oil or gas well and a method of actuation. In an embodiment, the underreamer tool has body having a longitudinal axis and a fluid conduit, a tool element and an actuation device configured to urge the tool element relative to the body from a first configuration into a second configuration. In this embodiment, a portion of the tool has a curved actuation surface and the tool element is urged across the curved actuation surface the tool element is moved radially with respect to the body of the tool. Typically, the actuation device may include a piston driven by pressure of fluid circulated through the fluid flow conduit.

Abstract: A downhole tool comprises a body, radially extendable members mounted to the body and movable between retracted and extended positions, a cam member operatively associated with the extendable members and movable relative to the body to extend the extendable members, and a support member configurable to permit retraction of the extendable members from an extended position. The tool may be an under-reamer, and the extendable members may be cutting blades.

Abstract: The present invention relates to a borehole drilling apparatus with in-line extending wings and driving method thereof. The drilling apparatus comprises a guide device rotating while moving upwardly and downwardly in a casing to fit into a borehole, extending wings for extending the diameter of a drilled hole, and a pilot bit installed at a lower portion of the guide device to strike the bottom of the borehole, wherein spiral projections formed at a lower surface of the guide device slidably engage with guide grooves formed at a side of the extending wings to each other, and a window is formed at a side of the pilot bit for advancing and retracting the extending wings so that they can spread and return linearly from the center of the pilot bit.

Abstract: Drilling device for drilling into ground, rock or for reaming a predrilled hole which drilling device comprises, if needed, a bit (2) which drills the central part of the hole and a hammer (1) for it, or the mentioned bit (2) is at least partly replaced with an endpiece which takes control of the predrilled hole whereupon in both cases the drilling device additionally comprises several hammering bits (4) placed in a circular shape and equipped with their own hammers (3) whereupon they together drill a hole which has a larger diameter and the drilling device comprises a casing tube (6) which can be pulled out of the hole/pushed into the hole which is created during drilling and belongs to the drilling device and also essentially in the middle of the drilling device residing tubular, rotatable drill rod tube (16).

Abstract: An expandable downhole tool comprises a tubular body, at least one moveable arm disposed within the tubular body and being radially translatable between a retracted position and a wellbore engaging position, and at least one piston operable to mechanically support the at least one moveable arm in the wellbore engaging position when an opposing force is exerted. A method of reaming a formation to form an enlarged borehole in a wellbore comprising disposing an expandable reamer in a retracted position in the wellbore, expanding at least one movable arm of the expandable reamer radially outwardly into engagement with the formation, reaming the formation with the at least one moveable arm to form the enlarged borehole; and mechanically supporting the at least one moveable arm in the radially outward direction during reaming.

Abstract: A downhole perforator assembly (10) for establishing communication between the interior of a tubular string (18) and a surrounding annulus (24) includes a downhole power unit (100) having a power unit housing (150) and a moveable shaft (130) and a downhole perforator (260) having a perforator housing (262), a mandrel (278) slidably positioned within the perforator housing (262) and a penetrator (288) radially outwardly extendable from the perforator housing (262). The power unit housing (150) is operably associated with the perforator housing (262) and the moveable shaft (130) operably associated with the mandrel (278) such that when the downhole power unit (100) is activated and the moveable shaft (130) is longitudinally shifted relative to the power unit housing (150), the mandrel (278) is longitudinally shifted relative to the perforator housing (262) and at least a portion of the penetrator (288) is extended radially outwardly from the perforator housing (262).

Abstract: An under reamer for expanding a borehole through an earthen formation is taught. The under reamer includes: a mandrel including an end for connection into a drill string and an opposite end and a housing including an inner bore, telescopically disposed over the mandrel and axially moveable relative to the mandrel but rotationally moveable with the mandrel. A plurality of under reamer arms are carried on the housing, the under reamer arms are formed as blocks including cutter-supporting portions in which poly-crystalline diamond compact cutters are mounted. The under reamer arms are moveable by driving the housing axially over the mandrel between a retracted position extending into the bore of the housing and an expanded position wherein the under reamers arms are pivoted out of the housing inner bore and supported therebehind by the mandrel such that the cutter-supporting portions are exposed for use to enlarge a borehole.

Abstract: In a fastener of a post-installation type which is embedded after a drilled hole is provided at concrete structure, a sleeve (2) and a plug (3) press-fitted to the sleeve are positioned by convexoconcave engagement between a projecting portion at an inner periphery of an expansion portion (6) and a recess groove (11) at a tip end of the plug (3) before installation, and therefore the separation therebetween is prevented. After installation, the projection portion at the inner periphery of the expansion portion (6) expanded is again engaged with the recess groove (12) of the tip end of the plug (3). By this positioning effect, the fastener performs an effect for preventing a loosening between the sleeve and the plug against the vibrations.

Abstract: An apparatus for shaping boreholes used in seismic operations. A drill body is attached to a drill bit and is movable in axial and rotational directions. Selective operation of the drill body causes a moveable sleeve to operate a reaming bit to extend through a drill body port and into contact with the borehole wall. A cover seals the portion of the port not covered by the reaming bit to prevent loss of a transport fluid within the drill body and to prevent drill cuttings from entering the drill body interior. The cover can be integrated within the movable sleeve or can comprise a separate component. The force exerted by the drill body against the drill bit can be proportional to the force exerted by the reaming bit against the borehole wall. The reaming bit can be operated separately or simultaneously with operation of the drill bit, and can be retracted and reset to perform another shaping operation at a different position within the borehole.

Abstract: Disclosed are an expandable well bore reamer and method utilizing a pair of reaming blades pivotally mounted on a central support member, each blade having an inner and an outer mounting arm positioned on opposite sides of such central support member with a movable cam with cam members to push against the inner mounting arm of each blade to pivot the reaming blades outward to an open position.

Abstract: A downhole reaming tool is disclosed having radially extendible cutting blades extended by hydraulic pressure directed into the tool to force an inner tubular body having protrusions thereon with tapered sides forward against the walls of mating recesses defined in such radially extendible cutting blades to extend the blades.

Abstract: A underreamer drill bit assembly including a pilot bit and extendable underreaming arms operatively connected to the pilot bit. The underreaming arms have an extended position for underreaming, and a retracted position in which the overall diameter of the underreamer drill bit assembly is less than the inside diameter of the well casing, permitting the entire bit assembly to be withdrawn through the well casing. In another aspect of the invention, the bit assembly is operatively connected to a dual wall pipe assembly. A supply of compressed air is conducted through the annulus of the dual wall pipe assembly to a down hole pneumatic hammer. Exhaust air from the down hole hammer is directed to the bit assembly for continuous removal of drilling debris through a central evacuation tube of the dual wall pipe assembly. In another aspect of the invention, a pressurized, incompressible fluid is injected into the annulus between the well casing and the downhole pneumatic hammer.

Abstract: A underreamer drill bit assembly including a pilot bit and extendable underreaming arms operatively connected to the pilot bit. The underreaming arms have an extended position for underreaming, and a retracted position in which the overall diameter of the underreamer drill bit assembly is less than the inside diameter of the well casing, permitting the entire bit assembly to be withdrawn through the well casing. In another aspect of the invention, the bit assembly is operatively connected to a dual wall pipe assembly. A supply of compressed air is conducted through the annulus of the dual wall pipe assembly to a down hole pneumatic hammer. Exhaust air from the down hole hammer is directed to the bit assembly for continuous removal of drilling debris through a central evacuation tube of the dual wall pipe assembly. In another aspect of the invention, a pressurized, incompressible fluid is injected into the annulus between the well casing and the downhole pneumatic hammer.

Abstract: A down hole running tool 14 travels in a first direction through a drill pipe for installing bit segments 18 at the end of a drive sub 12 attached to the drill pipe. The tool 14 includes a first portion 82 and a second portion 84 which is retractably coupled to a leading end of the first portion 82. The first portion 82 includes a tubular extension 134 which receives a spigot 136 that extends from an upper end of the second portion 84. A pin 138 extends transversely through the tubular extension 134 and resides within opposing slots 140 formed in the spigot 136. There is a stepped reduction in the internal diameter at the lower end of the tubular extension 134 so as to form a cup-like structure 146. A spring 168 is disposed about the spigot 136 and has an upper end seated in the cup-like structure 146 and a lower end bearing against an upper face 170 of the second portion 84. The spring 168 is biased so as to push the first and second portions 82 and 84 apart in the longitudinal direction.

Abstract: A retraction system allows disengagement of retrieval latch dogs of a down hole running tool from a bit locking sleeve. The locking sleeve is slidably retained within a drive sub and includes a pair of slots which are engaged by the retrieval latch dogs when the tool is used to retrieve bit segments from the drive sub. The retraction system includes a sleeve which is slidably mounted on a main body of the tool and spring which is biased to push the sleeve over the retrieval latch dogs. The sleeve has a pair of diametrically opposed slots through which the retrieval latch dogs can extend for contacting the inner surface of the drive sub. The retraction system also includes a length of the inner surface of the drive sub which is made of progressively reducing diameter in the direction of retraction of the tool from the drive sub. The upper end of each slot is provided with a bevel for directing the retrieval latch dogs in the inward direction.

Abstract: A drill bit assembly includes a driver adapted for attachment to a down hole pneumatic hammer. A pilot bit is coupled to the driver in a manner permitting rotational and axial movement between driver and pilot bit. A series of underreamer arms are disposed intermediate the driver and the pilot bit and engage a centrally disposed cam block on the pilot bit. Pivot pins of the underreamer arms are journaled in and move with the driver during partial rotation of the driver during arm deployment and retraction. Passageways in the driver and pilot bit direct compressed air to the working surface of the bit for discharging particles upwardly through channels in the bit and driver. Inclined surfaces on the underreaming arms cooperate with the lower end of a casing to contribute to are retraction prior to removal of the assembly through the casing.

Abstract: A drill bit assembly includes a driver adapted for attachment to a down hole pneumatic hammer. A pilot bit is coupled to the driver in a manner permitting rotational and axial movement between driver and pilot bit. A series of underreamer arms are disposed intermediate the driver and the pilot bit and engage a centrally disposed cam block on the pilot bit. Pivot pins of the underreamer arms are journaled in and move with the driver during partial rotation of the driver during arm deployment and retraction. Passageways in the driver and pilot bit direct compressed air to the working surface of the bit for discharging particles upwardly through channels in the bit and driver. Inclined surfaces on the underreaming arms cooperate with the lower end of a casing to contribute to arm retraction prior to removal of the assembly through the casing.

Abstract: A retractable drill bit system 10 comprises a drive sub 18 which is adapted for connection to a lower end of a drill 12, a tool 20 for installing and retracting drill bit segments 22 from the drive sub 18; and an insert 24 for selectively locking the bit segments 22 to an end of the drive sub 18 and releasing the bit segments 22.A plurality of recesses 5B are formed about an inner circumferential wall at one end of the drive sub 18 and a landing seat 32 formed about the inner wall upstream of the recesses 58. The area of the interior wall between the landing seat 32 and recesses 58 is profiled with a series of tapered and level surfaces.The tool 20 includes a slidable cradle 176 extending from one end about which the bit segments 22 are held during installation and retrieval. The bit segments 22 being held in place about the cradle by an elastic band 198.

Abstract: A retractable drill bit system (10) comprises a drive sub (18) which is adapted for connection to a lower end of a drill (12), a tool (20) for installing and retractable drill bit segments (22) from the drive sub (18); and an insert (24) for selectively locking the bit segments (22) to an end of the drive sub (18) and releasing the bit segments (22). A plurality of recesses (5B) are formed about an inner circumferential wall at one end of the drive sub (18) and a landing seat (32) formed about the inner wall upstream of the recesses (58). The area of the interior wall between the landing seat (32) and recesses (58) is profiled with a series of tapered and level surfaces. The tool (20) includes a slidable cradle (176) extending from one end about which the bit segments (22) are held during installation and retrieval. The bit segments (22) being held in place about the cradle by an elastic band (198).

Abstract: A device for augering a conical hole in a solid medium that includes a first elongated member that extends along a longitudinal axis and a cutting blade having a cutting section and a non-cutting section coupled to the first elongated member. The rod is adapted to be rotated about the longitudinal axis. A motor is coupled to the first elongated member which rotates the cutting blade about the longitudinal axis. A shroud is provided through which the first elongated member passes. The shroud attaches to a hydraulic unit. Activation of the hydraulic unit causes the first elongated member to move in a longitudinal direction, which causes the cutting blade to move in a radial direction thereby forming a conical hole in a solid medium. The device is used for forming holes used in foundations and anchors. Also disclosed is a method of operation of the device to form a conical hole in solid media.

Abstract: A retrievable drill bit and cutter or reamer assembly includes a fluid-drive motor, an eccentric cutter part and a concentric bit in assembly and insertable in and retrievable from the interior of a drill stem without removing the drillstem from a wellbore. The eccentric cutter is disposed on a shaft connected to the output shaft of the motor and journals an accentric cylindrical bearing member mounted on the shaft. In response to rotation of the shaft in one direction, the cutter part is displaced into a position to enlarge the wellbore to permit progress of the drillstem therethrough and in response to rotation in the opposite direction, the cutter centers itself to permit retrieval of the bit assembly throught the drillstem. The fluid-driven motor engages locking splines on a sub at the lower end of the drillstem and may be inserted in and retrieved from the drillstem by drilling fluid in forward and reverse circulation, respectively.

Abstract: A device, for cutting an undercut in a borehole at a location spaced from the surface of a material into which the borehole is formed, includes a housing (1) with a bore therethrough and a guide sleeve (2) rotatably supported in the housing bore and having an eccentric bore therein. A bushing (3) with an eccentric bore is rotatably supported in the guide sleeve bore. A drive shaft (7) is rotatably supported in and extends through the eccentric bore of the housing and has a cutter head (9) at one end. The drive shaft (7) can be shifted from a centered position within the housing bore into an eccentric position by rotation of the bushing (3) relative to the guide sleeve (2). In the eccentric position, the cutter head (9) can penetrate into and form an undercut in the surface of the borehole. A displacable snap-in element (16) in the housing (1) prevents rotation of the guide sleeve (2).

Abstract: A device for drilling an undercut (1b) in a borehole (1a) in a target material 1, includes an axially extending guide sleeve (13) containing an axially extending eccentric bore, an eccentric bushing (14) is supported rotatably in the guide sleeve and a drive shaft (15) is supported rotatably in the eccentric bushing. A housing (10, 12) laterally encloses the guide sleeve and bears against the surface of the target material. A blocking member (25) is positioned between the housing (10, 12) and the guide sleeve (13) for permitting rotation of the guide sleeve in only one rotational direction relative to the housing (10, 12). Due to the blocking member (25) entrainment of the guide sleeve (13) is prevented when the eccentric bushing is rotated in the direction opposite to the one rotational direction.

Abstract: A sub-surface borehole underreamer is disclosed having freely rotatable precessing diamond cutters attached to extendable arms connected to the body of the underreamer. The diamond cutting face is skewed to a degree that tangential contact of the peripheral edge of the diamond cutter causes the rotating cutter to precess as the underreamer body is rotated by a drill string.

Abstract: An apparatus for creating annular cavities in the bottom of drilled holes in any medium having a body, an axle within the body at one end and rotated by a conventional drill, a reamer secured to the axle at its other end, an inner part enveloping the axle and an outer part enveloping the inner part, both parts being eccentric and rotatable with respect to each other. Their respective eccentricities are such that when opposing each other in opposite directions, the axle is parallel to the outer part. Joint rotation of the parts causes the reamer to move in a planetary manner. The outer part may be held stationary or dragged along by the inner part for joint rotation. Channels are provided within the parts to the reamer to supply cooling water to the reamer and to remove waste material generated by the reamer.

Abstract: A three roller centralizer is expandable from a position with the rollers retracted to a position with the rollers extended to a larger diameter for remaining concentric in a hole being underreamed. A diagonal camming surface is fixed on the body above each such roller. An axially shiftable diagonal camming surface is mounted on a piston below each such roller. Application of hydraulic pressure on the piston squeezes the rollers outwardly toward their extended position. After the rollers are fully extended, the lower camming surface can travel further so that axially extending surfaces above and below each roller prevent collapse of the rollers toward the retracted position. Links pivotably interconnect the carrier for such a roller and the body and lower camming surface respectively for retaining the rollers. Such a link has an elongated opening so that the carrier can move along the diagonal and axially extending surfaces instead of being limited to a circular path.

Abstract: A tool for boring cavity holes in concrete walls and the like comprises a cutting blade pivotally mounted about a transverse pin at the end of an elongate body and having a camming profiled portion. A ball is placed at the bottom of the hole which has first been bored with a conventional drill and the tool cutting blade is brought into contact with the ball while causing rapid rotation of the tool body and exerting an axial pressure. The ball cooperates with the blade camming profiled portion so as progressively to orient the blade in a transverse direction.

Abstract: An underreamer is disclosed having longitudinally telescoping upper and lower portions connectable respectively to an upper drill string and a lower drill string. A splined connection is provided between the telescoping portions having first and second engaged positions. Both of the engaged positions transmit torque between the telescoping portions. The splined connection provides a different angular and a different longitudinal position for the telescoping portions in each such position. Means is provided for pivotally mounting a cutter arm on one of the telescoping portions. Means is provided on the other telescoping portion for urging the at least one cutter arm relatively outward from the telescoping portions to an extended underreaming position when the splined connection is in its first position. The cutter arm is positioned inwardly to a retracted clearance position when the splined connection is in its second position.