Removable housing collar for horizontal drilling system

Abstract

A horizontal directional drilling system comprising a housing shaft (112) defining a central axis (A) and having a distal end portion with a splined opening (118), the housing shaft defining a sonde cavity. A drill bit (104) is provided, including a distal end portion with a cutting structure (124) and a proximal end section with a splined stem (130) receivable into the splined opening at the distal end portion of the housing shaft, wherein the cutting structure is configured to steer the drill bit toward a first side the central axis. A collar (140) is provided having an interior co-operatively defining a non-rotation interface with an exterior of the distal end portion of the housing shaft. The collar (140) surrounds the distal end portion of the housing shaft (112) to cover a joint between the drill bit (104) and the housing shaft (112).

Description

Attorney Docket No. 489825-0020- WOO 1REMOVABLE HOUSING COLLAR FOR HORIZONTAL DRILLING SYSTEMCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of priority to co-pending U.S. Provisional Patent Application No. 63 / 701,985, filed on October 1, 2024, the entire contents of which are incorporated by reference herein.BACKGROUND

[0002] The present invention relates to a horizontal drilling systems used to directionally drill and bore underground tunnels. Horizontal drilling systems commonly include a drill bit including a cutting portion and a housing. The drill bit of a horizontal drilling system is used to drill a bore hole along a guided path from chosen entry and exit points whereby a product (e.g., utility line) can then be pulled through.

[0003] When analyzing steering performance and productivity of a bit, the steering pad of the drill bit is a leading factor in both metrics. Increasing the steering pad height leads to a restriction of room in the bore hole for cuttings to flow past the drill bit limiting penetration rate of the bit. Thus, a need exists for having a device that enables a user to select between different drill bit options based on the desired performance as some operations benefit more from greater steering performance while other boring operations may not require maximum steering performance and instead demand a high rate of penetration to increase productivity.SUMMARY

[0004] The present disclosure provides, in one aspect, a horizontal directional drilling system comprising a housing shaft defining a central axis and having a distal end portion with a splined opening, the housing shaft defining a sonde cavity. A drill bit is provided, including a distal end portion with a cutting structure and a proximal end section with a splined stem receivable into the splined opening at the distal end portion of the housing shaft, wherein the cutting structure is configured to steer the drill bit toward a first side the central axis. A collar is provided having an interior co-operatively defining a non-rotation interface with an exterior of the distal end portion of the housing shaft. The collar surrounds the distal end portion of the housing shaft to cover a joint between the drill bit and the housing shaft.1MBF\489825\0020\41493539.vl-9 / 30 / 25Attorney Docket No. 489825-0020- WOO 1

[0005] In another aspect, the present disclosure provides a multi-piece steerable drill bit for horizontal directional drilling. A drill bit body includes a splined stem extending along a central axis and a head portion including an off-center cutting structure and a steering face having an angular offset from the central axis. A collar is configured cover the splined stem and extend to a rear end of the head portion, wherein the collar has a non-cylindrical interior. The collar and the splined stem include aligned receptacles configured to receive a connection pin to secure the collar and the drill bit body against axial separation. The non-cylindrical interior of the collar and the splined stem cooperatively define an annular space configured to receive a housing shaft.

[0006] In yet another aspect, the present disclosure provides a housing shaft of a horizontal directional drill head. The housing shaft includes a cylindrical body elongated about a central axis, and a sonde cavity formed in the cylindrical body. A distal end portion of the housing shaft is configured for attachment to a steerable drill bit. The distal end portion includes a splined opening configured to mate with a splined stem of the steerable drill bit, and the distal end portion includes a non-cylindrical exterior.

[0007] In yet another aspect, the present disclosure provides a method of reconfiguring a horizontal directional drilling system. The method includes disassembling a used drill head including: removing a connection pin, removing a drill bit from a distal end portion of a housing shaft including axially sliding a splined stem of the drill bit from a splined opening in the distal end portion of the housing shaft, and removing a collar from the distal end portion of the housing shaft including axially sliding a non-circular interior of the collar from a non-circular exterior of the distal end portion of the housing shaft. The method further includes selecting a new collar having a different maximum height than the collar, and reassembling the used drill head including: installing the new collar onto the distal end portion of the housing shaft including axially sliding a non-circular interior of the collar onto the non-circular exterior of the distal end portion of the housing shaft, installing the drill bit to the distal end portion of the housing shaft including axially sliding the splined stem of the drill bit into the splined opening in the distal end portion of the housing shaft, and installing the connection pin.2MBF\489825\0020\41493539.vl-9 / 30 / 25Attorney Docket No. 489825-0020- WOO 1BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Fig. 1 is a perspective view of a soft rock drill assembly of a horizontal directional drilling system according to the present disclosure.

[0009] Fig. 2 is an exploded view of the drill assembly of Fig. 1.

[0010] Fig. 3 is a top plan view of the drill assembly of Fig. 1.

[0011] Fig. 4 is a side elevation view of the drill assembly of Fig. 1.

[0012] Fig. 5 is a front elevation view of the drill assembly of Fig. 1.

[0013] Fig. 6 is a cross-section view of the drill assembly taken alone line 6 — 6 of Fig. 4.

[0014] Fig. 7 is a perspective view of a soft rock drill assembly of a horizontal directional drilling system according to the present disclosure.

[0015] Fig. 8 is an exploded view of the drill assembly of Fig. 7.

[0016] Fig. 9 is a top plan view of the drill assembly of Fig. 7.

[0017] Fig. 10 is a side elevation view of the drill assembly of Fig. 7.

[0018] Fig. 11 is front elevation view of the drill assembly of Fig. 7.

[0019] Fig. 12 is a cross-section view of the drill assembly taken alone line 12 — 12 of Fig.10.

[0020] Fig. 13 is a perspective view of a soft rock drill assembly of a horizontal directional drilling system according to the present disclosure.

[0021] Fig. 14 is an exploded view of the drill assembly of Fig. 13.

[0022] Fig. 15 is a top plan view of the drill assembly of Fig. 13.

[0023] Fig. 16 is a side elevation view of the drill assembly of Fig. 13.3MBF\489825\0020\41493539.vl-9 / 30 / 25Attorney Docket No. 489825-0020- WOO 1

[0024] Fig. 17 is a front elevation view of the drill assembly of Fig. 13.

[0025] Fig. 18 is a cross-section view of the drill assembly taken alone line 18 — 18 of Fig.16.DETAILED DESCRIPTION

[0026] Figs. 1-6 illustrate a drill head 100 of a horizontal directional drilling system. The drill head 100 is configured for use with a horizontal directional drilling machine according to known construction or constructions later developed. Horizontal directional drilling machines can drill into the ground along a desired path by connecting drill rods sequentially to build up a drill string. The drill head 100 is elongated along a central axis A, having a leading end configured for cutting and a trailing end configured for attachment to the drill string. At the leading end, the drill head 100 includes a steerable drill bit 104 configured to cut through the ground to define a borehole. The location of the drill head 100 can be tracked electronically via a sonde 108 positioned in a sonde cavity of a drill head housing shaft 112. The sonde cavity can be closed by a cover 114 that is secured to the housing shaft 112 with one or more fasteners. The housing shaft 112 forms a base or proximal end of the drill head 100. A schematic example of horizontal directional drilling is shown in Fig. 1 of U.S. Patent No. 11,927,090 of Vermeer Manufacturing Company, the entire contents of which are incorporated by reference herein. In one example, the housing shaft 112 can be a modified version of a Vermeer Manufacturing “ULTRA X3”. As such, the housing shaft 112 defines the central axis A and has a distal end portion 116 with a splined opening 118.

[0027] The drill bit 104 includes a head portion or distal end portion 122 with a cutting structure 124 (e.g., multiple pointed teeth, which may be provided as replaceable inserts). The teeth of the cutting structure 124 may point in a plurality of different forward directions with respect to the central axis A. The cutting structure 124 provided by the pointed teeth is an off- center cutting structure that is not symmetrical about the central axis A. Rather, the pointed teeth that form the cutting structure 124 are positioned to one side of the central axis A (e.g., a “steering side S”). More particularly, the cutting structure 124 is positioned on one side of a plane P extending along the central axis A to bisect the drill head 100. Separate from the cutting structure 124, the drill bit 104 includes a steering face 126 that is angled (has an angular offset)4MBF\489825\0020\41493539.vl-9 / 30 / 25Attorney Docket No. 489825-0020- WOO 1 with respect to the axis A and the plane P (e.g., at an acute angle as shown in Fig. 4). As in the illustrated construction, the steering face 126 may be provided in multiple sections or segments, although a single continuous steering face is also contemplated. At one or more locations, the steering face 126 may be provided with protective elements or inserts such as tungsten carbide buttons, which reduce wear on a main body material of the drill bit 104. As will be understood by those of ordinary skill in the art, plunging the drill bit 104 into the ground causes the path of the drill head 100 and the connected drill string behind it to veer toward the steering side S. Controlling a rotational orientation of the drill head 100 with the horizontal directional drilling machine during plunging allows the operator to steer the drill head 100 for creating the borehole along a desired path (e.g., around subterranean obstacles). Opposite the steering side S with the cutting structure 124, the drill bit 104 includes a steering pad or “heel” 128. The heel 128 is the rearmost portion of the steering face 126. The heel 128 generally serves as the pivot point or reaction surface against which steering forces are borne as the cutting structure 124 veers to the steering side S.

[0028] Opposite the head portion 122, the drill bit 104 includes a proximal end section including a splined stem 130 (not visible in the assembled drill head 100, Figs. 1, 3, 4). The head portion 122 and the splined stem 130 can together form a drill bit body. In some constructions, the drill bit body has an integral monolithic construction. The splined stem 130 is receivable into the splined opening 118 at the distal end portion 116 of the housing shaft 1 12. As such, the drill bit 104 connects for rotation with the housing shaft 112 via the respective splines to establish a non-torqued connection (i.e., the parts are not joined by being threaded together). Although the connection between the drill bit 104 and the housing shaft 112 is not made by applying torque, it is a torque-transmitting connection by way of the mating splines. As such, when connected, the drill bit 104 rotates with the housing shaft 112. The drill bit 104 and the housing shaft 112 are secured against axial separation by at least one connection pin (e.g. roll pin 134). The connection pin extends along a connection pin axis that is perpendicular to and offset from the central axis A. As shown, two parallel roll pins 134 are used on opposite sides of the central axis A. Both roll pins 134 extend perpendicular to the central axis A. The roll pins 134 extend not only through respective retaining receptacles of the drill bit 104 and the housing shaft 112, but also through respective retaining receptacles of a generally cylindrical hollow collar 140 provided at the joint between the drill bit 104 and the housing shaft 112. An exterior of the collar5MBF\489825\0020\41493539.vl-9 / 30 / 25Attorney Docket No. 489825-0020- WOO 1140 can include one or more surfaces that extend continuously from one or more surfaces of the drill bit head portion 122. The forward end of the collar 140 includes a tapered surface 132 adjacent the heel 128. The tapered surface 132 is angled to lie along a plane defined by the steering face 126. Due to its direct proximity to the steering face 126 and shared orientation, the tapered collar surface 132 forms a continuous extension of the steering face 126.

[0029] The collar 140 can abut a shoulder surface 142 (Fig. 2) that forms a rear end of the drill bit head portion 122. Due to the collar 140 therebetween, the rear end of the drill bit head portion 122 is spaced from a maximum diameter portion 112A of the housing shaft 112. The axial length of the collar 140 can be less than the body of the drill bit 104. In some constructions, the axial length of the collar 140 is the same as or less than the axial length of the splined stem 130. Via the shared roll pins 134, the collar 140 also forms part of the joint between the drill bit 104 and the housing shaft 112. As such, the collar 140 and the drill bit 104 together can constitute a multi-piece drill bit assembly. The collar 140 has an interior 144 that is non-cylindrical and co-operatively defines a non-rotation interface with the exterior 148 of the distal end portion 116 of the housing shaft 112. A “non-rotation interface” refers to the fact that the parts fit together to prevent relative rotation therebetween when connected. In other words, they will maintain a prescribed timing or clocking about the central axis A. The drill bit 104 and the collar 140 have separate non-rotation interfaces with the housing shaft 112. Thus, although the drill bit 104 and the collar 140 do not engage each other to define a non-rotation interface (and in fact, the interior of the collar 140 remains spaced from the splined stem 130 to cooperatively define an annular space for receiving the distal end portion 116 of the housing shaft 112), they are held in prescribed timing or clocking via their respective interfaces with the inside / outside of the distal end portion 116 of the housing shaft 112. To achieve this, the splines of the splined opening 118 and the surfaces of the exterior 148 have a prescribed rotational orientation with respect to one another and the connection pin axis. As illustrated, the non- rotation interface provided by the collar interior 144 and the housing shaft exterior 148 is a hex interface. As such, each of the collar interior 144 and the housing shaft exterior 148 includes six flat sides. Other configurations for non-rotation interfaces are optional, including alternate polygonal, irregular, etc. For example, the illustrated hex interface provides exactly two possible connection orientations with the roll pins 134, one of which is the correct orientation (tapered6MBF\489825\0020\41493539.vl-9 / 30 / 25Attorney Docket No. 489825-0020- WOO 1 surface 132 opposite the steering side S) and one of which is incorrect (180-degrees offset). It is contemplated that the hex or other interface is modified

[0030] When the splined stem 130 is received in the splined opening 118 at the distal end portion 116 of the housing shaft 112, the splined stem 130 and the splined opening 118 define a common or shared axial span. This shared axial span can be referred to as the joint zone. The collar 140 surrounds the distal end portion 116 of the housing shaft 112 so as to surround or encompass the distal end portion 116 and the joint zone. The cross-section of Fig. 6 is taken through this joint zone, and more particularly, at the location of the roll pins 134. As such, the various receptacles for the roll pins 134 can be observed. These receptacles include, for each one of the roll pins 134, a first hole 156 through the collar 140, a second hole 158 through the distal end portion 116 of the housing shaft 112 and aligned with the first hole 156, and a groove 160 in the splined stem 130 aligned with the first and second holes 156, 158. Although the groove 160 is formed along the outside surface rather than a fully penetrating through hole, it is still considered a pin receptacle as the corresponding roll pin 134 extends at least partially through the splined stem 130 via the groove 160.

[0031] The outside diameter of the collar 140 is larger than the outside diameter of an adjacent portion of the housing shaft 112 that forms the forwardmost exposed portion of the housing shaft 112 when the drill head 100 is assembled with the collar 140. As measured from the central axis A opposite the steering side S to the outer profde of the collar 140, the collar 140 defines a maximum height Hl . Because the tapered surface 132 rises to the otherwise consistent cylindrical outer surface of the collar 140, the maximum height Hl can also be expressed as the radius of the outer surface of the collar 140. In some embodiments, the maximum height Hl can be relatively small (e.g., 1.875 inches) such that the drill head 100 provides performance that emphasizes a greater rate of penetration than other configurations disclosed herein. In particular, the small cross-sectional size can leave more room for cuttings to flow past the drill bit 104 and the collar 140.

[0032] After extended use of the drill head 100, portions of the drill bit 104 such as the cutting structure 124 may become worn and in need of replacement. It is known to refurbish and reuse such HDD drill bits one or more times before the drill bit is deemed spent and disposed of7MBF\489825\0020\41493539.vl-9 / 30 / 25Attorney Docket No. 489825-0020- WOO 1 or recycled. However, by providing the drill bit 104 to utilize the collar 140 to make the joint with the housing shaft 112, additional wear at the distal end portion 116 of the housing shaft 112 (e.g., particularly at the roll pin holes 158) is greatly reduced compared to prior solutions. As noted previously, the distal end portion 116 is covered by the collar 140 during use of the drill head 100 in the ground. The collar 140 provides a replaceable wear sleeve for the distal end 116 of the housing shaft 112. Although the collar 140 and its roll pin holes 156 are exposed and subject to wear during drilling, the collar 140 is substantially smaller (less material) and has a substantially smaller replacement cost. For example, the housing shaft 112 has a relatively large amount of machining work to produce the splined opening 118 and for accommodation of the sonde 108. If desired, the collar 140 can be manufactured from a more exotic metal or metal alloy (and / or subject to further hardening process(es)) to have a higher hardness than the housing shaft 112. Even in such constructions, the exotic material and / or hardening process can be avoided in the much larger housing shaft 112.

[0033] Figs. 7-12 illustrate a drill head 200 of a horizontal directional drilling system, similar to the drill head 100 in many respects. For example, the drill head 200 can use the same drill head housing shaft 112 including the sonde 108 for position tracking. The drill head 200 is elongated along a central axis A, having a leading end configured for cutting and a trailing end configured for attachment to the drill string. At the leading end, the drill head 200 includes a steerable drill bit 204 configured to cut through the ground to define a borehole. The drill bit 204 can be substantially similar to the drill bit 104 such that it is insertable into the splined opening 118 in the distal end portion 116 of the housing shaft 112. Like the drill bit 104 of the drill head 100, the drill bit 204 is joined to the housing shaft 112 with a collar 240. Although the collar 240 has a generally cylindrical hollow form and may have identical features such as the axial length and interior shape thereof, the collar 240 has a different construction than the collar 140 of the preceding description. As described in further detail below, a reconfigurable system with interchangeable parts is provided by the drill heads 100, 200.

[0034] The drill bit 204 includes a head portion or distal end portion 222 with a cutting structure 224 (e.g., multiple pointed teeth, which may be provided as replaceable inserts). The teeth of the cutting structure 224 may point in a plurality of different forward directions with respect to the central axis A. The cutting structure 224 provided by the pointed teeth is an off-8MBF\489825\0020\41493539.vl-9 / 30 / 25Attorney Docket No. 489825-0020- WOO 1 center cutting structure that is not symmetrical about the central axis A. Rather, the pointed teeth that form the cutting structure 224 are positioned to one side of the central axis A (e.g., a “steering side S”). More particularly, the cutting structure 224 is positioned on one side of a plane P extending along the central axis A to bisect the drill head 200. Separate from the cutting structure 224, the drill bit 204 includes a steering face 226 that is angled with respect to the axis A and the plane P (e.g., at an acute angle as shown in Fig. 10). As in the illustrated construction, the steering face 226 may be provided in multiple sections or segments, although a single continuous steering face is also contemplated. At one or more locations, the steering face 226 may be provided with protective elements or inserts such as tungsten carbide buttons, which reduce wear on a main body material of the drill bit 204. When plunged into the ground, the drill bit 204 is configured to veer toward the steering side S, as described above with respect to the drill bit 104.

[0035] Opposite the steering side S with the cutting structure 224, the drill head 200 includes a steering pad or “heel.” The heel generally serves as the pivot point or reaction surface against which steering forces are borne as the cutting structure 224 veers to the steering side S. The forward end of the collar 240 includes a tapered surface 232 that, together with the rearmost portion 228 of the steering face 226, forms the heel. The tapered surface 232 is angled to lie along a plane defined by the steering face 226. Due to its direct proximity to the steering face 226 and shared orientation, the tapered collar surface 232 forms a continuous extension of the steering face 226. The collar 240, which forms part of the heel for the drill head 200, can also be referred to as a steering shoe. As shown in the drawings, the outside of the collar 240 is not a consistent cylindrical surface beyond the tapered surface 232. Rather, the collar 240 has a noncircular exterior profile that extends further toward a second side of the central axis, opposite the steering side S. The extended portion forms a raised pad 266 that intersects with the tapered surface 232. The raised pad 266 (and also the outermost point of the tapered surface 232) defines a maximum height H2 (or “steering pad height H2” - radial measure from central axis A). The raised pad 266 is semi-cylindrical, having a radius exceeding a radius of another semi- cylindrical portion of the exterior surface of the collar 240. For example, the raised pad 266 can define a radially measured steering pad extension of 0.125 inch (2.00 inch radius at the raised pad 266 versus 1.875 inch radius on the steering side of the collar 240). The raised pad 266 extends in the direction opposite the steering side S.9MBF\489825\0020\41493539.vl-9 / 30 / 25Attorney Docket No. 489825-0020- WOO 1

[0036] Opposite the head portion 222, the drill bit 204 includes a proximal end section including a splined stem 230 (not visible in the assembled drill head 200, Figs. 7, 9, 10). The head portion 222 and the splined stem 230 can be formed together as an integral body. The splined stem 230 is receivable into the splined opening 118 at the distal end portion 116 of the housing shaft 112. As such, the drill bit 204 connects for rotation with the housing shaft 112 via the respective splines to establish a non-torqued connection. Although the connection between the drill bit 204 and the housing shaft 112 is not made by applying torque, it is a torquetransmitting connection by way of the mating splines. As such, when connected, the drill bit 204 rotates with the housing shaft 112. The drill bit 204 and the housing shaft 112 are secured against axial separation by at least one roll pin 134. As shown, two parallel roll pins 134 are used on opposite sides of the central axis A. Both roll pins 134 extend perpendicular to the central axis A. The roll pins 134 extend not only through respective retaining receptacles of the drill bit 204 and the housing shaft 112, but also through respective retaining receptacles of the collar 240 provided at the joint between the drill bit 204 and the housing shaft 112.

[0037] The collar 240 can abut a shoulder surface 242 (Fig. 8) that forms a rear end of the drill bit head portion 222. The collar 240 can include one or more exterior surfaces that extend continuously from one or more surfaces of the drill bit 204. Via the shared roll pins 134, the collar 240 also forms part of the joint between the drill bit 204 and the housing shaft 112. As such, the collar 240 and the drill bit 204 together can constitute a multi-piece drill bit assembly. The collar 240 has an interior 244 co-operatively defining a non-rotation interface with the exterior 148 of the distal end portion 116 of the housing shaft 112. The drill bit 204 and the collar 240 have separate non-rotation interfaces with the housing shaft 112. Thus, although the drill bit 204 and the collar 240 do not engage each other to define a non-rotation interface (and in fact, the interior of the collar 240 remains spaced from the splined stem 230), they are held in prescribed timing or clocking via their respective interfaces with the inside / outside of the distal end portion 116 of the housing shaft 112. As illustrated, the non-rotation interface provided by the collar interior 244 and the housing shaft exterior 148 is a hex interface. The hex interface matches that provided between the collar interior 144 and the housing shaft exterior 148. Other configurations for non-rotation interfaces are optional, including alternate polygonal, irregular, etc.10MBF\489825\0020\41493539.vl-9 / 30 / 25Attorney Docket No. 489825-0020- WOO 1

[0038] When the splined stem 230 is received in the splined opening 118 at the distal end portion 116 of the housing shaft 112, the splined stem 230 and the splined opening 118 define a common or shared axial span. This shared axial span can be referred to as the joint zone. The collar 240 surrounds the distal end portion 116 of the housing shaft 112 to surround or encompass the distal end portion 116 and the joint zone. The cross-section of Fig. 12 is taken through this joint zone, and more particularly, at the location of the roll pins 134. As such, the various receptacles for the roll pins 134 can be observed. These receptacles include, for each one of the roll pins 134, a first hole 256 through the collar 240, a second hole 158 through the distal end portion 116 of the housing shaft 112 and aligned with the first hole 156, and a groove 260 in the splined stem 230 aligned with the first and second holes 256, 158. Although the groove 260 is formed along the outside surface rather than a fully penetrating through hole, it is still considered a pin receptacle as the corresponding roll pin 134 extends at least partially through the splined stem 230 via the groove 260.

[0039] The collar 240, both at the raised pad 266 and elsewhere, extends outside the outside diameter of an adjacent portion of the housing shaft 112 that forms the forwardmost exposed portion of the housing shaft 112 when the drill head 200 is assembled with the collar 240. The maximum height H2 (e.g., 2.0 inches) of the collar 240 can be greater than the maximum height Hl of the collar 140. Expressed differently, the collar 240 provides a radial steering pad extension (e g., 0.125 inch), while the collar 140 provides no radial steering pad extension (or steering pad extension = 0 due to the cylindrical shape having no raised pad). The increase in maximum height H2 and having the steering pad extend to the collar 240 may provide the drill head 200 with increased steerability (e.g., compared to the drill head 100). The first and second collars 140, 240 may be interchangeable with the same housing shaft 112 and the same or different drill bits. As such an operator may select the desired one of the collars 140, 240 on the basis of desired performance metrics and / or soil / rock conditions being drilled. This gives an operator greater flexibility to tune the drill head performance as compared with drill bit selection among multiple drill bits (e.g., different cutting structures).

[0040] Figs. 13-18 illustrate a drill head 300 of a horizontal directional drilling system, similar to the drill heads 100, 200 in many respects. For example, the drill head 300 can use the same drill head housing shaft 112 including the sonde 108 for position tracking. The drill head11MBF\489825\0020\41493539.vl-9 / 30 / 25Attorney Docket No. 489825-0020- WOO 1300 is elongated along a central axis A, having a leading end configured for cutting and a trailing end configured for attachment to the drill string. At the leading end, the drill head 300 includes a steerable drill bit 104 configured to cut through the ground to define a borehole. The drill bit 104 can be identical to the drill bit 104 shown in Figs. 1-6. As such, detailed description of the features of the drill bit 104 are not repeated. In other constructions, the drill head 300 can include a different drill bit (e.g., having a different cutting structure). The drill bit 104 is joined to the housing shaft 112 with a collar 340. Although the collar 340 has a generally cylindrical hollow form and may have identical features such as the axial length and interior shape thereof, the collar 340 has a different construction than the collars 140, 240 of the preceding description. As described in further detail below, a reconfigurable system with interchangeable parts is provided by the drill heads 100, 200, 300.

[0041] Opposite the steering side S, the drill head 300 includes a steering pad or “heel.” The heel generally serves as the pivot point or reaction surface against which steering forces are borne as the cutting structure 124 veers to the steering side S. The forward end of the collar 340 includes a tapered surface 332 that, together with the rearmost portion 128 of the steering face 126, forms the heel. The tapered surface 332 is angled to lie along a plane defined by the steering face 126. Due to its direct proximity to the steering face 126 and shared orientation, the tapered collar surface 332 forms a continuous extension of the steering face 126. The collar 340, which forms part of the heel for the drill head 300, can also be referred to as a steering shoe. As shown in the drawings, the outside of the collar 340 is not a consistent cylindrical surface beyond the tapered surface 332. Rather, the collar 340 has a non-circular exterior profile that extends further toward a second side of the central axis, opposite the steering side S. The extended portion forms a raised pad 366 that intersects with the tapered surface 332. The raised pad 366 (and also the outermost point of the tapered surface 332) defines a maximum height H3 (or “steering pad height H3” - radial measure from central axis A). The raised pad 366 is semi- cylindrical, having a radius exceeding a radius of another semi-cylindrical portion of the exterior surface of the collar 340. The raised pad 366 extends in the direction opposite the steering side S.

[0042] As noted in the preceding description, the drill bit 104 connects for rotation with the housing shaft 112 via the respective splines to establish a non-torqued connection, and the roll12MBF\489825\0020\41493539.vl-9 / 30 / 25Attorney Docket No. 489825-0020- WOO 1 pins 134 are inserted perpendicular to the central axis A to secure the drill bit 104 and the housing shaft 112 against axial separation. The roll pins 134 also extend through respective retaining receptacles of the collar 340 provided at the joint between the drill bit 104 and the housing shaft 112.

[0043] The collar 340 can abut a shoulder surface 142 (Fig. 14) that forms a rear end of the drill bit head portion 122. The collar 340 can include one or more exterior surfaces that extend continuously from one or more surfaces of the drill bit 104. Via the shared roll pins 134, the collar 340 also forms part of the joint between the drill bit 104 and the housing shaft 112. As such, the collar 340 and the drill bit 104 together can constitute a multi -piece drill bit assembly. The collar 340 has an interior 344 co-operatively defining a non-rotation interface with the exterior 148 of the distal end portion 116 of the housing shaft 112. The drill bit 104 and the collar 340 have separate non-rotation interfaces with the housing shaft 112. Thus, although the drill bit 104 and the collar 340 do not engage each other to define a non-rotation interface (and in fact, the interior of the collar 340 remains spaced from the splined stem 130), they are held in prescribed timing or clocking via their respective interfaces with the inside / outside of the distal end portion 116 of the housing shaft 112. As illustrated, the non-rotation interface provided by the collar interior 344 and the housing shaft exterior 148 is a hex interface. The hex interface matches that provided between the collar interiors 144, 244 and the housing shaft exterior 148. Other configurations for non-rotation interfaces are optional, including alternate polygonal, irregular, etc.

[0044] When the splined stem 130 is received in the splined opening 118 at the distal end portion 116 of the housing shaft 112, the splined stem 130 and the splined opening 118 define a common or shared axial span. This shared axial span can be referred to as the joint zone. The collar 340 surrounds the distal end portion 116 of the housing shaft 112 so as to surround or encompass the distal end portion 116 and the joint zone. The cross-section of Fig. 18 is taken through this joint zone, and more particularly, at the location of the roll pins 134. As such, the various receptacles for the roll pins 134 can be observed. These receptacles include, for each one of the roll pins 134, a first hole 356 through the collar 340, a second hole 158 through the distal end portion 116 of the housing shaft 112 and aligned with the first hole 156, and the groove 160 in the splined stem 130 aligned with the first and second holes 356, 158.13MBF\489825\0020\41493539.vl-9 / 30 / 25Attorney Docket No. 489825-0020- WOO 1

[0045] The collar 340, both at the raised pad 366 and elsewhere, extends outside the outside diameter of an adjacent portion of the housing shaft 112 that forms the forwardmost exposed portion of the housing shaft 112 when the drill head 300 is assembled with the collar 340. The maximum height H3 (e.g., 2.125 inches) of the collar 340 can be greater than the maximum heights Hl, H2 of the collars 140, 240. Expressed differently, the collar 340 provides a further increased radial steering pad extension (e.g., 0.250 inch). The increase in maximum height H3 may provide the drill head 300 with increased steerability (e.g., compared to the drill head 200). The third collar 340 may be interchangeable with the first and second collars 140, 240 with the same housing shaft 112 and the same or different drill bits. As such an operator may select the desired one of the collars 140, 240, 340 on the basis of desired performance metrics and / or soil / rock conditions being drilled. This gives an operator greater flexibility to tune the drill head performance as compared with drill bit selection among multiple drill bits (e.g., different cutting structures).

[0046] A method of reconfiguring a horizontal directional drilling system can include disassembling a used drill head 100, 200, 300, selecting a new collar 140, 240, 340 having a different maximum height than the used collar 140, 240, 340, and reassembling the used drill head. Disassembling the used drill head can include removing a connection pin 134, removing the drill bit 104, 204 from the distal end portion 116 of the housing shaft 112 including axially sliding the splined stem 130, 230 from the splined opening 1 18, and removing the used collar from the distal end portion 116 including axially sliding the non-circular interior 144, 244, 344 from the non-circular exterior 148 of the distal end portion 116 of the housing shaft 112. The new collar 140, 240, 340 can be selected based on desired steerability and / or cutting rate. The reassembling of the used drill head can include installing the new collar 140, 240, 340 onto the distal end portion 116 including axially sliding the non-circular interior 144, 244, 344 of the collar 140, 240, 340 onto the non-circular exterior 148 of the distal end portion 116, installing the drill bit 104, 204 to the distal end portion 116 including axially sliding the splined stem 130, 230 of the drill bit 104, 204 into the splined opening 118 in the distal end portion 116, and installing the connection pin 134. During reassembling the used drill head, a rotational orientation of the collar 140, 240, 340 and a rotational orientation of the drill bit 104, 204 is set such that a tapered surface 32, 232, 332 on the exterior of the collar 140, 240 , 340 is in alignment with a steering face 126, 226 of the drill bit 104, 204.14MBF\489825\0020\41493539.vl-9 / 30 / 25Attorney Docket No. 489825-0020- WOO 1

[0047] The drill heads 100, 200, 300 provide three constructions of soft rock drill assemblies that, among other variations thereof, can constitute a reconfigurable or modular horizontal directional drilling system. In the drilling system, a single housing can be reconfigured and / or rebuilt in a plurality of different configurations, including not only different drill bits, but different collars with the same or different drill bits. As noted above, the different collars 140, 240, 340 provide different performance for the drilling operation, all other things being equal. The use of any of the collars 140, 240, 340 as a replaceable wear sleeve for the distal end 116 of the housing shaft 112 provides for a greatly increased usable life of the housing shaft 112, which may continue use through one or more rebuilds / replacements of drill bits and one or more replacements of the collar(s) due to wear.

[0048] Changes may be made in the above methods and systems without departing from the scope hereof. Also, aspects of various embodiments may be combined unless expressly prohibited. It should thus be noted that the matter contained in the above description or shown in the accompanying drawings should be interpreted as illustrative and not in a limiting sense. The following claims are intended to cover all generic and specific features described herein, as well as all statements of the scope of the present method and system, which, as a matter of language, might be said to fall therebetween.15MBF\489825\0020\41493539.vl-9 / 30 / 25

Claims

Attorney Docket No. 489825-0020- WOO 1CLAIMSWhat is claimed is:

1. A horizontal directional drilling system comprising: a housing shaft defining a central axis and having a distal end portion with a splined opening, the housing shaft defining a sonde cavity; a drill bit having a distal end portion with a cutting structure and a proximal end section with a splined stem receivable into the splined opening at the distal end portion of the housing shaft, wherein the cutting structure is configured to steer the drill bit toward a first side the central axis; and a collar having an interior co-operatively defining a non-rotation interface with an exterior of the distal end portion of the housing shaft, wherein the collar surrounds the distal end portion of the housing shaft to cover a joint between the drill bit and the housing shaft.

2. The horizontal directional drilling system of claim 1, further comprising a connection pin configured to extend, perpendicular to the central axis, through the collar, through the distal end portion of the housing shaft, and at least partially through the splined stem of the drill bit.

3. The horizontal directional drilling system of claim 2, wherein the connection pin is a first connection pin, and further comprising a second connection pin configured to extend, perpendicular to the central axis and parallel to the first connection pin, through the collar, through the distal end portion of the housing shaft, and at least partially through the splined stem of the drill bit.

4. The horizontal directional drilling system of claim 1, wherein the non-rotation interface defined by the collar interior and the distal end portion exterior is rotationally oriented in relation to the splined opening and the splined stem to set a prescribed rotational alignment between the drill bit and the collar.16MBF\489825\0020\41493539.vl-9 / 30 / 25Attorney Docket No. 489825-0020- WOO 15. The horizontal directional drilling system of claim 4, wherein the prescribed rotational alignment between the drill bit and the collar sets a surface of the collar along an angle defined by a steering face of the drill bit.

6. The horizontal directional drilling system of claim 1, wherein the collar has a noncircular exterior profile that extends further toward a second side of the central axis, opposite the first side.

7. The horizontal directional drilling system of claim 1, wherein the drill bit has a steering face extending from the cutting structure at an angle with respect to the central axis, and wherein the collar has a tapered surface that forms an extension of the steering face of the drill bit.

8. The horizontal directional drilling system of claim 1, wherein the collar is a first collar defining a first maximum height measured from and perpendicular to the central axis, the horizontal directional drilling system further comprising a second collar interchangeable with the first collar and defining a second maximum height, greater than the first maximum height, measured from and perpendicular to the central axis.

9. The horizontal directional drilling system of claim 8, further comprising a third collar interchangeable with the first and second collars and defining a third maximum height, greater than the second maximum height, measured from and perpendicular to the central axis.

10. The horizontal directional drilling system of claim 8, wherein the second collar has a generally cylindrical exterior including a raised pad that intersects with a tapered collar surface that forms a continuous extension of a steering face of the drill bit.17MBF\489825\0020\41493539.vl-9 / 30 / 25Attorney Docket No. 489825-0020- WOO 111. A multi-piece steerable drill bit for horizontal directional drilling, the multi-piece steerable drill bit comprising: a drill bit body including a splined stem extending along a central axis and a head portion including an off-center cutting structure and a steering face having an angular offset from the central axis; and a collar configured cover the splined stem and extend to a rear end of the head portion, wherein the collar has a non-cylindrical interior, wherein the collar and the splined stem include aligned receptacles configured to receive a connection pin to secure the collar and the drill bit body against axial separation, and wherein the non-cylindrical interior of the collar and the splined stem cooperatively define an annular space configured to receive a housing shaft.

12. The multi-piece steerable drill bit of claim 11, wherein the head portion and the splined stem have an integral monolithic construction.

13. The multi-piece steerable drill bit of claim 11, wherein the collar has an exterior including at least one surface that extends continuously from one or more surfaces of the drill bit head portion.

14. The multi-piece steerable drill bit of claim 13, wherein the at least one surface of the collar exterior that extends continuously from one or more surfaces of the drill bit head portion includes a tapered surface that forms a continuous extension of the steering face.

15. The multi-piece steerable drill bit of claim 11, wherein the non-cylindrical interior of the collar defines a hex profile.18MBF\489825\0020\41493539.vl-9 / 30 / 25Attorney Docket No. 489825-0020- WOO 116. The multi-piece steerable drill bit of claim 1 1 , wherein the collar has an axial length less than the drill bit body.

17. A housing shaft of a horizontal directional drill head, the housing shaft comprising: a cylindrical body elongated about a central axis; a sonde cavity formed in the cylindrical body; and a distal end portion configured for attachment to a steerable drill bit, wherein the distal end portion includes a splined opening configured to mate with a splined stem of the steerable drill bit, and wherein the distal end portion includes a non-cylindrical exterior.

18. The housing shaft of claim 17, further comprising a pin receptacle extending along a connection pin axis perpendicular to and offset from the central axis, wherein the splines in the splined opening and the non-cylindrical exterior of the distal end portion have a prescribed rotational orientation in relation to the connection pin axis.

19. A method of reconfiguring a horizontal directional drilling system, the method comprising: disassembling a used drill head including: removing a connection pin, removing a drill bit from a distal end portion of a housing shaft including axially sliding a splined stem of the drill bit from a splined opening in the distal end portion of the housing shaft, and19MBF\489825\0020\41493539.vl-9 / 30 / 25Attorney Docket No. 489825-0020- WOO 1 removing a collar from the distal end portion of the housing shaft including axially sliding a non-circular interior of the collar from a non-circular exterior of the distal end portion of the housing shaft; selecting a new collar having a different maximum height than the collar; and reassembling the used drill head including: installing the new collar onto the distal end portion of the housing shaft including axially sliding a non-circular interior of the collar onto the non-circular exterior of the distal end portion of the housing shaft, installing the drill bit to the distal end portion of the housing shaft including axially sliding the splined stem of the drill bit into the splined opening in the distal end portion of the housing shaft, and installing the connection pin.

20. The method of claim 19, further comprising, during reassembling the used drill head, setting a rotational orientation of the collar and a rotational orientation of the drill bit such that a tapered surface on the exterior of the collar is in alignment with a steering face of the drill bit.20MBF\489825\0020\41493539.vl-9 / 30 / 25

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