Double drill bit

Abstract

A dual-drill bit system comprises a main drill bit and an auxiliary drill bit. The width of the cutting edges and the angle of the digging position can be set by adjusting the positions of the cutting edges of the main drill bit and the auxiliary drill bit. The dual-drill bit 1 of this invention includes a main drill bit 2 and an auxiliary drill bit 3. Both the main drill bit and the auxiliary drill bit are equipped with, at least at the upper and lower parts of the front ends of their bases 4 and 13, with mountain-shaped superhard drill tips 7, 9, 14, and 15 protruding along the digging direction. The top of the mountain-shaped tip of the auxiliary drill bit is located further rearward in the digging direction compared to the top of the mountain-shaped tip of the main drill bit. The top of the mountain-shaped tip of the main drill bit 2 is near the hole wall, near the pile core, or located in the center, with the hole wall direction perpendicular to the digging direction. The top of the mountain-shaped tip of the auxiliary drill bit 3 is near the hole wall, near the pile core, or located in the center, with the hole wall direction perpendicular to the digging direction.

Description

Technical Field

[0001] This invention relates to excavation tools used on the front end of casing, and particularly to a dual drill bit that integrates a main drill bit and an auxiliary drill bit. Background Technology

[0002] Currently, a common pile construction method for pouring concrete underground to form piles is the so-called full casing method. This method involves pressing a casing into the ground, using a grab bucket to excavate and remove sediment while protecting the borehole wall, and then pouring concrete into the excavated hole. In this full casing method, cutting drill bits for the inner, middle, and outer cutting edges are mounted on the front end of the casing via a drill bit holder, and the cutting drill bits are used to excavate by rotating the casing.

[0003] Here, as such a cutting drill bit, there is a digging cutting drill bit installed circumferentially along the front end of the casing pipe. The cutting drill bit includes a head with a cutting edge having an ultra-hard drill tip fixed at the front end, and legs provided with a retainer for fixing to the casing pipe (see, for example, Patent Document 1).

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2016-223196 Summary of the Invention

[0007] The problem that the invention aims to solve

[0008] However, Patent Document 1 only discloses a cutting drill bit for excavation, without disclosing that the main drill bit and the auxiliary drill bit are integrated, and that the width of the cutting edges and the angle of the digging position can be varied by adjusting the cutting edge positions of the main drill bit and the auxiliary drill bit.

[0009] The present invention was made in view of the above-mentioned problems, and its object is to provide a twin bit in which the main bit and the auxiliary bit are integrated, and the width of the cutting edges and the angle of the digging position of the two bits can be varied by adjusting the cutting edge positions of the main bit and the auxiliary bit.

[0010] Technical solutions for solving the problem

[0011] To address the aforementioned problems, one aspect of the present invention provides a dual drill bit comprising a main drill bit and an auxiliary drill bit. Both the main drill bit and the auxiliary drill bit are provided with a superhard drill tip in a mountain-shaped form protruding in the digging direction at least at the upper and lower parts of the front end of their bases. The top of the mountain-shaped form of the superhard drill tip of the auxiliary drill bit is located behind the top of the mountain-shaped form of the superhard drill tip of the main drill bit in the digging direction.

[0012] Invention Effects

[0013] According to the present invention, a dual drill bit can be provided, wherein the main drill bit and the auxiliary drill bit are integrated, and the width of the cutting edges and the angle of the digging position of the two bits can be varied by adjusting the cutting edge position of the main drill bit and the cutting edge position of the auxiliary drill bit. Attached Figure Description

[0014] Figure 1 (a) to Figure 1 (d) is a configuration diagram of the dual drill bits according to the first embodiment of the present invention.

[0015] Figure 2 (a) to Figure 2 (d) is a configuration diagram of the dual drill bits according to the second embodiment of the present invention.

[0016] Figure 3 (a) to Figure 3 (d) is a configuration diagram of the dual drill bits according to the third embodiment of the present invention.

[0017] Figure 4 (a) to Figure 4 (d) is a configuration diagram of the dual drill bits according to the fourth embodiment of the present invention.

[0018] Figure 5 (a) to Figure 5 (d) is a configuration diagram of the dual drill bits according to the fifth embodiment of the present invention.

[0019] Figure 6 (a) to Figure 6 (d) is a configuration diagram of the dual drill bits according to the sixth embodiment of the present invention.

[0020] Figure 7 (a) to Figure 7 (d) is a configuration diagram of the dual drill bits according to the seventh embodiment of the present invention.

[0021] Figure 8 (a) to Figure 8 (d) is a configuration diagram of the dual drill bits according to the eighth embodiment of the present invention.

[0022] Figure 9 (a) and Figure 9 (b) is a diagram showing the state of the double drill bit installed on the casing.

[0023] Figure 10 (a) and Figure 10 (b) is a diagram showing the state of the double drill bit installed on the casing.

[0024] Figure 11 (a) and Figure 11 (b) is a diagram showing the state of the double drill bit installed on the casing.

[0025] Figure 12 (a) and Figure 12 (b) is a diagram showing the state of the double drill bit installed on the casing.

[0026] Figure 13 (a) and Figure 13 (b) is a diagram showing the state of the double drill bit installed on the casing.

[0027] Figure 14 (a) and Figure 14 (b) is a diagram showing the state of the double drill bit installed on the casing.

[0028] Figure 15 (a) to Figure 15 (d) is a configuration diagram of an improved example of the dual drill bit according to the first embodiment of the present invention. Detailed Implementation

[0029] The embodiments of the present invention will now be described with reference to the accompanying drawings.

[0030] The dual drill bit of the present invention has the following features.

[0031] (1) A main drill bit and an auxiliary drill bit are arranged side by side in a direction perpendicular to the digging direction. The cutting edge of the auxiliary drill bit is located behind the cutting edge of the main drill bit in the digging direction, forming a so-called step structure. Therefore, the load applied to the inner plate (or outer plate) of the casing can be reduced and the digging efficiency can be improved. At the same time, the retention of excavated soil (or cuttings) generated when digging with a single cutting edge is prevented, thereby improving the digging efficiency.

[0032] (2) The base material shape of the main drill bit cutting edge can be selected from a straight shape or an inclined shape forming an angle with the base material. In addition, by adjusting the cutting edge position of the main drill bit and the cutting edge position of the auxiliary drill bit, the width of the two cutting edges and the angle of the digging position can be set. Therefore, not only can the digging position of the cutting edge be expanded, further reducing the load applied to the inner plate (or outer plate) of the casing, further reducing the retention of excavated soil (or cuttings), but also the upward flow of excavated soil (or cuttings) can be controlled.

[0033] (3) An auxiliary superhard drill tip is provided in the base material part of the cutting edge. Therefore, wear resistance can be improved. The hardness of the superhard drill tip can be freely selected according to the object being excavated.

[0034] (4) The dual drill bits in this embodiment are used for bidirectional rotation. Therefore, digging can be performed in both forward and reverse directions.

[0035] <First Implementation Method>

[0036] Figure 1 (a) to Figure 1 (d) A configuration of the dual drill bits according to the first embodiment of the present invention is shown and described. More specifically, Figure 1 (a) shows a top view of the dual drill bit. Figure 1 (b) shows a three-dimensional view of the dual drill bit. Figure 1 (c) represents the side view of the dual drill bit. Figure 1 (d) shows a front view of the dual-drill bit. In this dual-drill bit, the main drill bit is a straight outer cutting edge, and the auxiliary drill bit is a middle cutting edge attached to the inside. By using the auxiliary drill bit as the middle cutting edge, digging can be performed at the midpoint between the cutting edges of the outer and inner cutting edges, which not only improves digging efficiency but also makes it easier to remove the object being dug out. It should be noted that, in order to clearly show the structure of each part, only... Figure 1 (a) shows the hardened thickened portion.

[0037] As shown in these figures, the dual drill bit 1 is configured such that the front cutting edges of the main drill bit 2 and the auxiliary drill bit 3 form a step backward in the digging direction.

[0038] The main drill bit 2 consists of a base 4 and two legs 5 and 6 extending from the base 4. Hereinafter, the side of the base 4 will also be referred to as the front end of the dual drill bit 1, and the sides of the legs 5 and 6 will also be referred to as the casing mounting side or the rear end of the dual drill bit 1. The direction facing the front end is the digging direction, and the direction perpendicular to this digging direction is the hole wall direction or the core direction (also referred to as the thickness direction of the dual drill bit 1). The direction perpendicular to the digging direction and the hole wall direction or core direction is called the width direction of the dual drill bit 1.

[0039] In this context, "pile core direction" refers to the "pile center" in all pile engineering projects used for foundation construction, including precast piles, cast-in-situ piles, and steel pipe piles. It specifically refers to the center of the casing and excavation wings used in various pile extraction and obstacle removal projects. Conversely, "hole wall direction" refers to the outer perimeter of the pile in all pile engineering projects used for foundation construction, including precast piles, cast-in-situ piles, and steel pipe piles, as well as the outer perimeter of the casing and excavation wings used in various pile extraction and obstacle removal projects. In other words, it refers to the hole wall of an underground borehole constructed by excavating the ground or obstacles.

[0040] The base 4 has a mountain-shaped top that protrudes in the excavation direction, i.e., the front end of the dual drill bit 1. Moreover, superhard drill tips 7 and 8 are respectively provided at the front end and the two mountain-shaped parts of the base 4.

[0041] More specifically, the superhard drill tip 7 includes, at the upper part of the front end of the base 4, an inclined portion 7a that rises at a predetermined angle from the first flat portion 9 of the base 4 towards the digging direction; and an inclined portion 7b that rises at a predetermined angle from the second flat portion 10 of the base 4 towards the digging direction. Since the length of the inclined portion 7a is less than the length of the inclined portion 7b, its top is positioned closer to the first flat portion 9. On the other hand, the superhard drill tip 8 includes, at the lower part of the front end of the base 4, an inclined portion 8a that rises at a predetermined angle from the first flat portion 9 of the base 4 towards the digging direction, and an inclined portion 8b that rises at a predetermined angle from the second flat portion 10 of the base 4 towards the digging direction. Since the length of the inclined portion 8a is less than the length of the inclined portion 8b, its top is positioned closer to the first flat portion 9.

[0042] like Figure 1 As shown in (c), the continuous tops of the inclined portions 7a and 7b of the superhard drill tip 7 and the continuous tops of the inclined portions 8a and 8b of the superhard drill tip 8 form digging edges at the top and bottom of the base 4, respectively. Furthermore, a recess 11 is formed at the front end of the base 4 between the superhard drill tips 7 and 8, which not only further reduces the retention of excavated soil (or cuttings) but also helps improve digging efficiency by controlling the upward flow of excavated soil (or cuttings).

[0043] Legs 5 and 6 extend parallel from the base 4 toward the rear end at predetermined intervals, forming a "コ" shape when viewed in plan. Holes 12 are provided on the legs 5 and 6 for mounting the double drill bit 1 onto the casing using bolts or the like.

[0044] On the other hand, the auxiliary drill bit 3 includes a base 13. The rear end portion of the base 13 is an inclined portion 13a that slopes backward in the digging direction, i.e., towards the rear end of the dual drill bits 1. An ultra-hard drill tip 13b is disposed on the inclined surface of the inclined portion 13a. The inclined portion 13a is provided with a hole that communicates with the hole portion 12 of the legs 5 and 6.

[0045] The base 13 has a so-called mountain-shaped shape with its top protruding in the digging direction, i.e., the front end of the dual drill bit 1, at both the upper and lower ends of the base 13. Superhard drill tips 14 and 15 are respectively provided at the front end and the upper and lower mountain-shaped portions of the base 13.

[0046] More specifically, the superhard drill tip 14 includes, at the upper part of the front end of the base 13, an inclined portion 14a that rises at a predetermined angle from the third plane portion 17 of the base 13 toward the digging direction, and an inclined portion 14b that rises at a predetermined angle from the second plane portion 10 toward the digging direction. Since the lengths of the inclined portions 14a and 14b are the same, their tops are located in the middle of the digging direction or the hole wall direction of the auxiliary drill bit 3. In other words, the top is located in the center of the thickness direction of the auxiliary drill bit 3. On the other hand, the superhard drill tip 15 includes, at the lower part of the front end of the base 13, an inclined portion 15a that rises at a predetermined angle from the third plane portion 17 of the base 13 toward the digging direction, and an inclined portion 15b that rises at a predetermined angle from the second plane portion 10 of the base 13 toward the digging direction. Since the lengths of the inclined portions 14a and 14b are the same, their tops are located in the middle of the digging direction or the hole wall direction of the auxiliary drill bit 3. In other words, the top is located at the center of the thickness direction of the auxiliary drill bit 3.

[0047] like Figure 1 As shown in (c), the continuous tops of the inclined portions 14a and 14b of the superhard drill tip 14 and the continuous tops of the inclined portions 15a and 15b of the superhard drill tip 15 form digging edges above and below the base 14, respectively. Furthermore, a recess 16 is formed at the front end of the base 13 between the superhard drill tips 14 and 15, which not only further reduces the retention of excavated soil (or cuttings) but also helps improve digging efficiency by controlling the upward flow of excavated soil (or cuttings).

[0048] Regarding the materials used for each part, the base material for the base 4 and legs 5 and 6 can be SCM440 (chrome steel), etc. Furthermore, the superhard drill tips 7, 8, 14, and 15 can use JIS classification symbols E3 (material name MG30), E4 (material name MG40), E5 (material name MG50), E6 (material name MG60), etc., and CIS standard G4 (CIS material type symbol VC-40) and G5 (CIS material type symbol VC-50), etc. However, they are not limited to the above materials. In addition, a hardened thickened part 18 is provided for the bases 4 and 13.

[0049] <Second Implementation Method>

[0050] Figure 2 (a) to Figure 2 (d) A configuration of the dual drill bits according to the second embodiment of the present invention is shown and described. More specifically, Figure 2 (a) shows a top view of the dual drill bit. Figure 2 (b) shows a three-dimensional view of the dual drill bit. Figure 2 (c) represents the side view of the dual drill bit. Figure 2(d) shows a front view of the dual-bit drill bit. In this dual-bit drill bit, the main drill bit is a straight outer cutting edge, and the auxiliary drill bit is a middle cutting edge attached to the outside. By using the auxiliary drill bit as the middle cutting edge, digging can be performed at the midpoint between the cutting edges of the outer and inner cutting edges, which not only improves digging efficiency but also makes the object being dug out more smoothly. It should be noted that, in order to clearly show the structure of each part, only... Figure 2 (a) Figure 2 (c) shows the hardened thickened portion.

[0051] As shown in these figures, the dual drill bits 21 are configured such that the front cutting edges of the main drill bit 22 and the auxiliary drill bit 23 form a step backward in the digging direction.

[0052] The main drill bit 22 consists of a base 24 and two legs 25 and 26 extending from the base 24. Hereinafter, the base 24 side will also be referred to as the front end of the dual drill bit 21, and the legs 25 and 26 side will also be referred to as the casing mounting side or the rear end of the dual drill bit 21. The direction facing the front end is the digging direction, and the direction perpendicular to this digging direction is the hole wall direction or the core direction (also referred to as the thickness direction of the dual drill bit 21). Furthermore, the direction perpendicular to the digging direction and the hole wall direction or core direction is referred to as the width direction of the dual drill bit 21. The definitions of the core direction and the hole wall direction are the same as those described in the first embodiment.

[0053] The base 24 has a so-called mountain-shaped shape, with the top of the upper and lower parts protruding towards the front end of the excavation direction, i.e., the front end of the dual drill bit 21. Superhard drill tips 27 and 28 are respectively provided at the front end and the upper and lower mountain-shaped parts of the base 24.

[0054] More specifically, the superhard drill tip 27 includes, at the upper part of the front end of the base 24, an inclined portion 27a that rises at a predetermined angle from the first flat portion 29 of the base 24 towards the digging direction, and an inclined portion 27b that rises at a predetermined angle from the second flat portion 30 of the base 24 towards the digging direction. Since the length of the inclined portion 27a is less than the length of the inclined portion 27b, its top is positioned close to the first flat portion 29. On the other hand, the superhard drill tip 28 includes, at the lower part of the front end of the base 24, an inclined portion 28a that rises at a predetermined angle from the first flat portion 29 of the base 24 towards the digging direction, and an inclined portion 28b that rises at a predetermined angle from the second flat portion 30 of the base 24 towards the digging direction. Since the length of the inclined portion 28a is less than the length of the inclined portion 28b, its top is positioned close to the first flat portion 29.

[0055] like Figure 2As shown in (c), the continuous tops of the inclined portions 27a and 27b of the superhard drill tip 27 and the continuous tops of the inclined portions 28a and 28b of the superhard drill tip 28 respectively form digging edges above and below the base 24. Furthermore, a recess 31 is formed at the front end of the base 24 between the superhard drill tips 27 and 28, which not only further reduces the retention of excavated soil (or cuttings) but also helps improve digging efficiency by controlling the upward flow of excavated soil (or cuttings).

[0056] Legs 25 and 26 extend parallel from the base 24 toward the rear end at predetermined intervals, forming a "コ" shape when viewed in plan. Holes 32 are provided on the legs 25 and 26 for mounting the double drill bit 21 to the casing using bolts or the like.

[0057] On the other hand, the auxiliary drill bit 23 includes a base 33. The rear end portion of the base 33 becomes an inclined portion 33a that slopes backward in the digging direction, i.e., towards the rear end of the dual drill bits 21. An ultra-hard drill tip 33b is disposed on the inclined surface of the inclined portion 33a. The inclined portion 33a is provided with a hole that communicates with the hole portion 32 of the legs 25 and 26.

[0058] The base 33 has a so-called mountain-shaped shape with its top protruding in the digging direction, i.e., the front end of the dual drill bits 21, at both the upper and lower positions. Superhard drill tips 34 and 35 are respectively provided at the front end and the upper and lower mountain-shaped portions of the base 33.

[0059] More specifically, the superhard drill tip 34 includes, at the upper part of the front end of the base 33, an inclined portion 34a that rises at a predetermined angle from the third plane portion 37 of the base 33 toward the digging direction, and an inclined portion 34b that rises at a predetermined angle from the first plane portion 29 toward the digging direction. Since the lengths of the inclined portions 34a and 34b are the same, their tops are located at the center of the auxiliary drill bit 23 in the digging direction or hole wall direction. In other words, the top is located at the center of the thickness direction of the auxiliary drill bit 23. On the other hand, the superhard drill tip 35 includes, at the lower part of the front end of the base 33, an inclined portion 35a that rises at a predetermined angle from the third plane portion 37 of the base 33 toward the digging direction, and an inclined portion 35b that rises at a predetermined angle from the first plane portion 29 of the base 33 in the digging direction. Since the lengths of the inclined portions 34a and 34b are the same, their tops are located at the center of the auxiliary drill bit 23 in the digging direction or hole wall direction. In other words, the top is located in the middle of the thickness direction of the auxiliary drill bit 23.

[0060] like Figure 2As shown in (c), the continuous tops of the inclined portions 34a and 34b of the superhard drill tip 34 and the continuous tops of the inclined portions 35a and 35b of the superhard drill tip 35 form digging edges above and below the base 33, respectively. Furthermore, a recess 36 is formed at the front end of the base 33 between the superhard drill tips 34 and 35, which not only further reduces the retention of excavated soil (or cuttings) but also helps improve digging efficiency by controlling the upward flow of excavated soil (or cuttings).

[0061] The material of each part is the same as that described in the first embodiment. A hardened thickened portion 38 is provided at the bases 24 and 33.

[0062] <Third Implementation Method>

[0063] Figure 3 (a) to Figure 3 (d) A configuration of the dual drill bits according to a third embodiment of the present invention is shown and described. More specifically, Figure 3 (a) shows a top view of the dual drill bit. Figure 3 (b) shows a three-dimensional view of the dual drill bit. Figure 3 (c) represents the side view of the dual drill bit. Figure 3 (d) shows a front view of the dual-drill bit. In this dual-drill bit, the main drill bit is a straight inner cutting edge, and the auxiliary drill bit is a center cutting edge attached to the inside. By using the auxiliary drill bit as the center cutting edge, digging can be performed at the midpoint between the outer and inner cutting edges, which not only improves digging efficiency but also makes it easier to remove the object being dug out. It should be noted that, in order to clearly show the structure of each part, only... Figure 3 (a) Figure 3 (c) shows the hardened thickened portion.

[0064] As shown in these figures, the dual drill bits 41 are configured such that the front cutting edges of the main drill bit 42 and the auxiliary drill bit 43 form a step backward in the digging direction.

[0065] The main drill bit 42 consists of a base 44 and two legs 45 and 46 extending from the base 44. Hereinafter, the base 44 side will also be referred to as the front end of the dual drill bit 41, and the legs 45 and 46 side will also be referred to as the casing mounting side or the rear end of the dual drill bit 41. The direction facing the front end is the digging direction, and the direction perpendicular to this digging direction is the hole wall direction or the core direction (also referred to as the thickness direction of the dual drill bit 41). Furthermore, the direction perpendicular to the digging direction and the hole wall direction or core direction is referred to as the width direction of the dual drill bit 41. The definitions of the core direction and the hole wall direction are the same as those described in the first embodiment.

[0066] The base 44 has a so-called mountain-shaped shape with its top protruding in the digging direction, i.e., the front end of the double drill bit 41, at both the upper and lower positions. Superhard drill tips 47 and 48 are respectively provided at the front end and the upper and lower mountain-shaped parts of the base 44.

[0067] More specifically, the superhard drill tip 47 includes, at the upper part of the front end of the base 44, an inclined portion 47a that rises at a predetermined angle from the first planar portion 49 of the base 44 toward the digging direction; and an inclined portion 47b that rises at a predetermined angle from the second planar portion 50 of the base 44 toward the digging direction. Since the length of the inclined portion 47a is longer than the length of the inclined portion 48b, its top is positioned closer to the second planar portion 50. On the other hand, the superhard drill tip 48 includes, at the lower part of the front end of the base 44, an inclined portion 48a that rises at a predetermined angle from the first planar portion 49 of the base 44 toward the digging direction, and an inclined portion 48b that rises at a predetermined angle from the second planar portion 50 of the base 44. Since the length of the inclined portion 48a is longer than the length of the inclined portion 48b, its top is positioned closer to the second planar portion 50.

[0068] like Figure 3 As shown in (c), the continuous tops of the inclined portions 47a and 47b of the superhard drill tip 47 and the continuous tops of the inclined portions 48a and 48b of the superhard drill tip 48 form digging edges above and below the base 44, respectively. Furthermore, a recess 51 is formed at the front end of the base 44 between the superhard drill tips 47 and 48, which not only further reduces the retention of excavated soil (or cuttings) but also helps improve digging efficiency by controlling the upward flow of excavated soil (or cuttings).

[0069] Legs 45 and 46 extend parallel from the base 44 toward the rear end at predetermined intervals, forming a "コ" shape when viewed in plan. Holes 52 are provided on the legs 45 and 46 for mounting the double drill bit 41 to the casing using bolts or the like.

[0070] On the other hand, the auxiliary drill bit 43 includes a base 53. The rear end portion of the base 53 becomes an inclined portion 53a that slopes backward in the digging direction, i.e., towards the rear end of the dual drill bits 41. An ultra-hard drill tip 53b is disposed on the inclined surface of the inclined portion 53a. The inclined portion 53a is provided with a hole that communicates with the hole portion 52 of the legs 45 and 46.

[0071] The base 53 has a so-called mountain-shaped shape with its top protruding in the digging direction, i.e., the front end of the dual drill bits 41, at both the upper and lower positions. Superhard drill tips 54 and 55 are respectively provided at the front end and the upper and lower mountain-shaped portions of the base 53.

[0072] More specifically, the superhard drill tip 54 includes, at the upper part of the front end of the base 53, an inclined portion 54a that rises at a predetermined angle from the third plane portion 57 of the base 53 toward the digging direction, and an inclined portion 54b that rises at a predetermined angle from the second plane portion 50 toward the digging direction. Since the lengths of the inclined portions 54a and 54b are the same, their tops are located at the center of the auxiliary drill bit 43 in the digging direction or hole wall direction. In other words, the top is located at the middle of the thickness direction of the auxiliary drill bit 431. On the other hand, the superhard drill tip 55 includes, at the lower part of the front end of the base 53, an inclined portion 55a that rises at a predetermined angle from the third plane portion 57 of the base 53 toward the digging direction, and an inclined portion 55b that rises at a predetermined angle from the second plane portion 50 of the base 53 in the digging direction. Since the lengths of the inclined portions 54a and 54b are the same, their tops are located at the center of the auxiliary drill bit 43 in the digging direction or hole wall direction. In other words, the top is located in the middle of the thickness direction of the auxiliary drill bit 43.

[0073] like Figure 3 As shown in (c), the continuous tops of the inclined portions 54a and 54b of the superhard drill tip 54 and the continuous tops of the inclined portions 55a and 55b of the superhard drill tip 55 form digging edges above and below the base 53, respectively. Furthermore, a recess 56 is formed at the front end of the base 53 between the superhard drill tips 54 and 55, which not only further reduces the retention of excavated soil (or cuttings) but also helps improve digging efficiency by controlling the upward flow of excavated soil (or cuttings).

[0074] The material of each part is the same as that described in the first embodiment. A hardened thickened portion 58 is provided at the base 44, 53.

[0075] <Fourth Implementation Method>

[0076] Figure 4 (a) to Figure 4 (d) A configuration of the dual drill bits according to the fourth embodiment of the present invention is shown and described. More specifically, Figure 4 (a) shows a top view of the dual drill bit. Figure 4 (b) shows a three-dimensional view of the dual drill bit. Figure 4 (c) represents the side view of the dual drill bit. Figure 4 (d) shows a front view of the dual drill bit. In this dual drill bit, the main drill bit is a straight inner cutting edge, and the auxiliary drill bit is a middle cutting edge attached to the outer edge. By using the auxiliary drill bit as the middle cutting edge, digging can be performed at the midpoint between the cutting edges of the outer and inner edges, which not only improves digging efficiency but also makes it easier to remove the object being dug out. It should be noted that, in order to clearly show the structure of each part, only... Figure 4 (a) shows the hardened thickened portion.

[0077] As shown in these figures, the dual drill bits 61 are configured such that the front cutting edges of the main drill bit 62 and the auxiliary drill bit 63 form a step backward in the digging direction.

[0078] The main drill bit 62 consists of a base 64 and two legs 65 and 66 extending from the base 64. Hereinafter, the base 64 side will also be referred to as the front end of the dual drill bit 61, and the legs 65 and 66 side will also be referred to as the casing mounting side or the rear end of the dual drill bit 61. The direction facing the front end is the digging direction, and the direction perpendicular to this digging direction is the hole wall direction or the core direction (also referred to as the thickness direction of the dual drill bit 61). Furthermore, the direction perpendicular to the digging direction and the hole wall direction or core direction is referred to as the width direction of the dual drill bit 61. The definitions of the core direction and the hole wall direction are the same as those described in the first embodiment.

[0079] The base 64 has a so-called mountain-shaped shape with its top protruding in the digging direction, i.e., the front end of the dual drill bits 61, at both the upper and lower positions. Superhard drill tips 67 and 68 are respectively provided at the front end and the upper and lower mountain-shaped portions of the base 64.

[0080] More specifically, the superhard drill tip 67 includes, at the upper part of the front end of the base 64, an inclined portion 67a that rises at a predetermined angle from the first planar portion 69 of the base 64 toward the digging direction; and an inclined portion 67b that rises at a predetermined angle from the second planar portion 70 of the base 64 toward the digging direction. Since the length of the inclined portion 67a is longer than the length of the inclined portion 67b, its top is positioned closer to the second planar portion 70. On the other hand, the superhard drill tip 68 includes, at the lower part of the front end of the base 64, an inclined portion 68a that rises at a predetermined angle from the first planar portion 69 of the base 64 toward the digging direction, and an inclined portion 68b that rises at a predetermined angle from the second planar portion 70 of the base 64. Since the length of the inclined portion 68a is longer than the length of the inclined portion 68b, its top is positioned closer to the second planar portion 70.

[0081] like Figure 4 As shown in (c), the continuous tops of the inclined portions 67a and 67b of the superhard drill tip 67 and the continuous tops of the inclined portions 68a and 68b of the superhard drill tip 68 respectively form digging edges above and below the base 64. Furthermore, a recess 71 is formed at the front end of the base 64 between the superhard drill tips 67 and 68, which not only further reduces the retention of excavated soil (or cuttings) but also helps improve digging efficiency by controlling the upward flow of excavated soil (or cuttings).

[0082] Legs 65 and 66 extend parallel from the base 64 toward the rear end at predetermined intervals, forming a "コ" shape when viewed in plan. Holes 72 are provided on the legs 65 and 66 for mounting the double drill bit 61 onto the casing using bolts or the like.

[0083] On the other hand, the auxiliary drill bit 63 includes a base 73. The rear end portion of the base 73 becomes an inclined portion 73a that slopes rearward in the digging direction, i.e., towards the rear end of the dual drill bits 61. An ultra-hard drill tip 73b is disposed on the inclined surface of the inclined portion 73a. The inclined portion 73a is provided with a hole that communicates with the hole portion 72 of the legs 65 and 66.

[0084] The base 73 has a so-called mountain-shaped shape with its top protruding in the digging direction, i.e., the front end of the dual drill bits 61, at both the upper and lower positions. Superhard drill tips 74 and 75 are respectively provided at the front end and the upper and lower mountain-shaped portions of the base 73.

[0085] More specifically, the superhard drill tip 74 includes, at the upper part of the front end of the base 73, an inclined portion 74a that rises at a predetermined angle from the third plane portion 77 of the base 73 toward the digging direction, and an inclined portion 74b that rises at a predetermined angle from the first plane portion 69 toward the digging direction. Since the lengths of the inclined portions 74a and 74b are the same, their tops are located at the center of the auxiliary drill bit 63 in the digging direction or hole wall direction. In other words, the top is located at the middle of the thickness direction of the auxiliary drill bit 63. On the other hand, the superhard drill tip 75 includes, at the lower part of the front end of the base 73, an inclined portion 75a that rises at a predetermined angle from the third plane portion 77 of the base 73 toward the digging direction, and an inclined portion 75b that rises at a predetermined angle from the first plane portion 69 of the base 73 toward the digging direction. Since the lengths of the inclined portions 74a and 74b are the same, their tops are located at the center of the auxiliary drill bit 63 in the digging direction or hole wall direction. In other words, the top is located in the middle of the thickness direction of the auxiliary drill bit 63.

[0086] like Figure 4 As shown in (c), the continuous tops of the inclined portions 74a and 74b of the superhard drill tip 74 and the continuous tops of the inclined portions 75a and 75b of the superhard drill tip 75 form digging edges above and below the base 73, respectively. Furthermore, a recess 76 is formed at the front end of the base 73 between the superhard drill tips 74 and 75, which not only further reduces the retention of excavated soil (or cuttings) but also helps improve digging efficiency by controlling the upward flow of excavated soil (or cuttings).

[0087] The material of each part is the same as that described in the first embodiment. A hardened thickened portion 78 is provided at the base 64, 73.

[0088] <Fifth Implementation Method>

[0089] Figure 5 (a) to Figure 5 (d) A configuration of the dual drill bits according to the fifth embodiment of the present invention is shown and described. More specifically, Figure 5 (a) shows a top view of the dual drill bit. Figure 5(b) shows a three-dimensional view of the dual drill bit. Figure 5 (c) represents the side view of the dual drill bit. Figure 5 (d) shows a front view of the dual drill bit. In this dual drill bit, the main drill bit is a straight center cutting edge, and the auxiliary drill bit is a center cutting edge attached to the inside. By using the main and auxiliary drill bits as center cutting edges, digging can be performed at the midpoint between the outer and inner cutting edge positions, which not only improves digging efficiency but also makes the object being dug out more smoothly. It should be noted that, in order to clearly show the structure of each part, only... Figure 5 (a) Figure 5 (c) shows the hardened thickened portion.

[0090] As shown in these figures, the dual drill bits 81 are configured such that the front cutting edges of the main drill bit 82 and the auxiliary drill bit 83 form a step backward in the digging direction.

[0091] The main drill bit 82 consists of a base 84 and two legs 85 and 86 extending from the base 84. Hereinafter, the base 84 side will also be referred to as the front end of the dual drill bit 81, and the legs 85 and 86 side will also be referred to as the casing mounting side or the rear end of the dual drill bit 81. The direction facing the front end is the digging direction, and the direction perpendicular to this digging direction is the hole wall direction or the core direction (also referred to as the thickness direction of the dual drill bit 81). Furthermore, the direction perpendicular to the digging direction and the hole wall direction or core direction is referred to as the width direction of the dual drill bit 81. The definitions of the core direction and the hole wall direction are the same as those described in the first embodiment.

[0092] The base 84 has a so-called mountain-shaped shape with its top protruding in the digging direction, i.e., the front end of the dual drill bit 81, at both the top and bottom. Superhard drill tips 87 and 88 are respectively provided at the front end and the two mountain-shaped parts of the base 84.

[0093] More specifically, the superhard drill tip 87 includes, at the upper part of the front end of the base 84, an inclined portion 87a that rises at a predetermined angle from the first planar portion 89 of the base 84 toward the digging direction, and an inclined portion 87b that rises at a predetermined angle from the second planar portion 90 of the base 84 toward the digging direction. The length of the inclined portion 87a is the same as the length of the inclined portion 87b, and its top is located at the center of the first planar portion 89 and the second planar portion 90. In other words, the top is located at the middle of the thickness direction of the dual drill bit 81. On the other hand, the superhard drill tip 88 includes, at the lower part of the front end of the base 84, an inclined portion 88a that rises at a predetermined angle from the first planar portion 89 of the base 84 toward the digging direction, and an inclined portion 88b that rises at a predetermined angle from the second planar portion 90 of the base 84 toward the digging direction. The length of the inclined portion 88a is the same as the length of the inclined portion 88b, and its top is located at the center of the first planar portion 89 and the second planar portion 90. In other words, the top is located at the middle of the thickness direction of the dual drill bit 81.

[0094] like Figure 5 As shown in (c), the continuous tops of the inclined portions 87a and 87b of the superhard drill tip 87 and the continuous tops of the inclined portions 88a and 88b of the superhard drill tip 88 form digging edges above and below the base 84, respectively. Furthermore, a recess 91 is formed at the front end of the base 84 between the superhard drill tips 87 and 88, which not only further reduces the retention of excavated soil (or cuttings) but also helps improve digging efficiency by controlling the upward flow of excavated soil (or cuttings).

[0095] Legs 85 and 86 extend parallel from the base 84 toward the rear end at predetermined intervals, forming a "コ" shape when viewed in plan. Holes 92 are provided on the legs 85 and 86 for mounting the double drill bit 81 to the casing using bolts or the like.

[0096] On the other hand, the auxiliary drill bit 83 includes a base 93. The rear end portion of the base 93 becomes an inclined portion 93a that slopes backward in the digging direction, i.e., towards the rear end of the dual drill bits 81. An ultra-hard drill tip 93b is disposed on the inclined surface of the inclined portion 93a. The inclined portion 93a is provided with a hole that communicates with the hole portion 92 of the legs 85 and 86.

[0097] The base 93 has a so-called mountain-shaped shape with its top protruding in the digging direction, i.e., the front end of the dual drill bit 81, at two locations. Superhard drill tips 94 and 95 are respectively provided at the front end and the two mountain-shaped parts of the base 93.

[0098] More specifically, the superhard drill tip 94 includes, at the upper part of the front end of the base 93, an inclined portion 94a that rises at a predetermined angle from the third plane portion 97 of the base 93 toward the digging direction, and an inclined portion 94b that rises at a predetermined angle from the second plane portion 90 toward the digging direction. Since the lengths of the inclined portions 94a and 94b are the same, their tops are located at the center of the auxiliary drill bit 83 in the digging direction or hole wall direction. In other words, the top is located at the middle of the thickness direction of the dual drill bit 81. On the other hand, the superhard drill tip 95 includes, at the lower part of the front end of the base 93, an inclined portion 95a that rises at a predetermined angle from the third plane portion 97 of the base 93 toward the digging direction, and an inclined portion 95b that rises at a predetermined angle from the second plane portion 90 of the base 93 in the digging direction. Since the lengths of the inclined portions 95a and 95b are the same, their tops are located at the center of the auxiliary drill bit 83 in the digging direction or hole wall direction. In other words, the top is located in the middle of the thickness direction of the double drill bit 81.

[0099] like Figure 5As shown in (c), the continuous tops of the inclined portions 94a and 94b of the superhard drill tip 94 and the continuous tops of the inclined portions 95a and 95b of the superhard drill tip 95 form digging edges above and below the base 93, respectively. Furthermore, a recess 96 is formed at the front end of the base 93 between the superhard drill tips 94 and 95, which not only further reduces the retention of excavated soil (or cuttings) but also helps improve digging efficiency by controlling the upward flow of excavated soil (or cuttings).

[0100] The material of each part is the same as that described in the first embodiment. A hardened thickened portion 98 is provided at the base 84, 93.

[0101] <Sixth Implementation Method>

[0102] Figure 6 (a) to Figure 6 (d) A configuration of the dual drill bits according to the sixth embodiment of the present invention is shown and described. More specifically, Figure 6 (a) shows a top view of the dual drill bit. Figure 6 (b) shows a three-dimensional view of the dual drill bit. Figure 6 (c) represents the side view of the dual drill bit. Figure 6 (d) shows a front view of the dual drill bit. In this dual drill bit, the main drill bit is a straight center cutting edge, and the auxiliary drill bit is a center cutting edge attached to the outside. By using the main and auxiliary drill bits as center cutting edges, digging can be performed at the midpoint between the outer and inner cutting edge positions, which not only improves digging efficiency but also makes the object being dug out more smoothly. It should be noted that, in order to clearly show the structure of each part, only... Figure 6 (a) Figure 6 (c) shows the hardened thickened portion.

[0103] As shown in these figures, the dual drill bits 101 are configured such that the front cutting edges of the main drill bit 102 and the auxiliary drill bit 103 form a step backward in the digging direction.

[0104] The main drill bit 102 consists of a base 104 and two legs 105 and 106 extending from the base 104. Hereinafter, the base 104 side will be referred to as the front end of the dual drill bit 101, and the legs 105 and 106 side will be referred to as the casing mounting side or the rear end of the dual drill bit 101. The direction facing the front end is the digging direction, and the direction perpendicular to this digging direction is the hole wall direction or the core direction (also referred to as the thickness direction of the dual drill bit 101). Furthermore, the direction perpendicular to the digging direction and the hole wall direction or core direction is referred to as the width direction of the dual drill bit 101. The definitions of the core direction and the hole wall direction are the same as those described in the first embodiment.

[0105] The base 104 has a so-called mountain-shaped shape with its top protruding in the digging direction, i.e., the front end of the dual drill bit 101, at two locations. Superhard drill tips 107 and 108 are respectively provided at the front end and the two mountain-shaped parts of the base 104.

[0106] More specifically, the superhard drill tip 107 includes, at the upper part of the front end of the base 104, an inclined portion 107a that rises at a predetermined angle from the first planar portion 109 of the base 104 toward the digging direction; and an inclined portion 107b that rises at a predetermined angle from the second planar portion 110 of the base 102 toward the digging direction. The length of the inclined portion 107a is the same as the length of the inclined portion 107b, and its top is located at the center of the first planar portion 109 and the second planar portion 110. In other words, the top is located at the middle of the thickness direction of the main drill bit 102. On the other hand, the superhard drill tip 108 includes, at the lower part of the front end of the base 104, an inclined portion 108a that rises at a predetermined angle from the first planar portion 109 of the base 104 toward the digging direction, and an inclined portion 108b that rises at a predetermined angle from the second planar portion 110 of the base 104 toward the digging direction. The length of the inclined portion 108a is the same as the length of the inclined portion 108b, and its top is located at the center of the first flat portion 109 and the second flat portion 110. In other words, the top is located at the middle of the thickness direction of the main drill bit 102.

[0107] like Figure 6 As shown in (c), the continuous tops of the inclined portions 107a and 107b of the superhard drill tip 107 and the continuous tops of the inclined portions 108a and 108b of the superhard drill tip 108 respectively form digging edges above and below the base 104. Furthermore, a recess 111 is formed at the front end of the base 104 between the superhard drill tips 107 and 108, which not only further reduces the retention of excavated soil (or cuttings) but also helps improve digging efficiency by controlling the upward flow of excavated soil (or cuttings).

[0108] Legs 105 and 106 extend parallel from the base 104 toward the rear end at predetermined intervals, forming a "コ" shape when viewed in plan. Holes 112 are provided on the legs 105 and 106 for mounting the double drill bit 101 onto the casing using bolts or the like.

[0109] On the other hand, the auxiliary drill bit 103 includes a base 113. The rear end portion of the base 113 becomes an inclined portion 113a that slopes rearward in the digging direction, i.e., towards the rear end of the dual drill bits 101. An ultra-hard drill tip 113b is disposed on the inclined surface of the inclined portion 113a. The inclined portion 113a is provided with a hole that communicates with the hole portion 112 of the legs 105 and 106.

[0110] The base 113 has a so-called mountain-shaped shape with its top protruding in the excavation direction, i.e., the front end of the dual drill bit 101, at two locations. Superhard drill tips 114 and 115 are respectively provided at the front end and the two mountain-shaped parts of the base 113.

[0111] More specifically, the superhard drill tip 114 includes, at the upper part of the front end of the base 113, an inclined portion 114a that rises at a predetermined angle from the third plane portion 117 of the base 113 toward the digging direction, and an inclined portion 114b that rises at a predetermined angle from the first plane portion 109 toward the digging direction. Since the lengths of the inclined portions 114a and 114b are the same, their tops are located at the center of the auxiliary drill bit 103 in the digging direction or hole wall direction. In other words, the tops are located at the middle of the thickness direction of the auxiliary drill bit 103. On the other hand, the superhard drill tip 115 includes, at the lower part of the front end of the base 113, an inclined portion 115a that rises at a predetermined angle from the third plane portion 117 of the base 113 toward the digging direction, and an inclined portion 115b that rises at a predetermined angle from the first plane portion 109 of the base 113 toward the digging direction. Since the length of the inclined portion 114a is the same as the length of the inclined portion 114b, the top is located at the center of the auxiliary drill bit 103 in the digging direction or hole wall direction. In other words, the top is located at the center of the thickness direction of the auxiliary drill bit 103.

[0112] like Figure 6 As shown in (c), the continuous tops of the inclined portions 114a and 114b of the superhard drill tip 114 and the continuous tops of the inclined portions 115a and 115b of the superhard drill tip 115 respectively form digging edges above and below the base 113. Furthermore, a recess 116 is formed at the front end of the base 113 between the superhard drill tips 114 and 115, which not only further reduces the retention of excavated soil (or cuttings) but also helps improve digging efficiency by controlling the upward flow of excavated soil (or cuttings).

[0113] The material of each part is the same as that described in the first embodiment. A hardened thickened portion 118 is provided at the base 104, 113.

[0114] <Seventh Implementation Method>

[0115] Figure 7 (a) to Figure 7 (d) A configuration of the dual drill bits according to the seventh embodiment of the present invention is shown and described. More specifically, Figure 7 (a) shows a top view of the dual drill bit. Figure 7 (b) shows a three-dimensional view of the dual drill bit. Figure 7 (c) represents the side view of the dual drill bit. Figure 7(d) shows a front view of the dual-bit drill. In this dual-bit drill, the main drill bit is an angled outer cutting edge, and the auxiliary drill bit is a center cutting edge attached to the inside. By using the auxiliary drill bit as the center cutting edge, digging can be performed at the midpoint between the cutting edges of the outer and inner edges, which not only improves digging efficiency but also makes it easier to remove the object being dug out. To clearly show the structure of each part, only... Figure 7 (a) shows the hardened thickened portion.

[0116] As shown in these figures, the dual drill bits 121 are configured such that the front cutting edges of the main drill bit 122 and the auxiliary drill bit 123 form a step backward in the digging direction.

[0117] The main drill bit 122 consists of a base 124 and two legs 125 and 126 extending from the base 124. Hereinafter, the base 124 side will also be referred to as the front end of the dual drill bit 121, and the legs 125 and 126 side will also be referred to as the casing mounting side or the rear end of the dual drill bit 121. The direction facing the front end is the digging direction, and the direction perpendicular to this digging direction is the hole wall direction or the core direction (also referred to as the thickness direction of the dual drill bit 121). Furthermore, the direction perpendicular to the digging direction and the hole wall direction or core direction is referred to as the width direction of the dual drill bit 121. The definitions of the core direction and the hole wall direction are the same as those described in the first embodiment.

[0118] The base 124 has a so-called mountain-shaped shape with its top protruding in the digging direction, i.e., the front end of the dual drill bits 121, at two locations. Superhard drill tips 127 and 128 are respectively provided at the front end and the two mountain-shaped parts of the base 124.

[0119] More specifically, the superhard drill tip 127 includes, at the upper part of the front end of the base 124, an inclined portion 127a that rises at a predetermined angle from the first flat portion 129 of the base 124 towards the digging direction, and an inclined portion 127b that rises at a predetermined angle from the second flat portion 130 of the base 124 towards the digging direction. Since the length of the inclined portion 127a is less than the length of the inclined portion 127b, its top is positioned close to the first flat portion 129. On the other hand, the superhard drill tip 128 includes, at the lower part of the front end of the base 124, an inclined portion 128a that rises at a predetermined angle from the first flat portion 129 of the base 124 towards the digging direction, and an inclined portion 128b that rises at a predetermined angle from the second flat portion 130 of the base 124 towards the digging direction. Since the length of the inclined portion 128a is less than the length of the inclined portion 128b, its top is positioned close to the first flat portion 129.

[0120] like Figure 7As shown in (c), the continuous tops of the inclined portions 127a and 127b of the superhard drill tip 127 and the continuous tops of the inclined portions 128a and 128b of the superhard drill tip 128 respectively form digging edges above and below the base 124. Furthermore, a recess 131 is formed at the front end of the base 124 between the superhard drill tips 127 and 128, which not only further reduces the retention of excavated soil (or cuttings) but also helps improve digging efficiency by controlling the upward flow of excavated soil (or cuttings).

[0121] Legs 125 and 126 extend from the base 124 toward the rear end at predetermined intervals, making their inner planes parallel and their shape roughly "コ"-shaped when viewed from the plane. The difference from the first embodiment is that the outer surface of the leg 126 has a predetermined slope. Holes 132 are provided on the legs 125 and 126 for mounting the double drill bit 121 to the casing using bolts or the like.

[0122] On the other hand, the auxiliary drill bit 123 includes a base 133. The rear end portion of the base 133 becomes an inclined portion 133a that slopes rearward in the digging direction, i.e., towards the rear end of the dual drill bits 121. An ultra-hard drill tip 133b is disposed on the inclined surface of the inclined portion 133a. The inclined portion 133a is provided with a hole that communicates with the hole portion 132 of the legs 125 and 126.

[0123] The base 133 has a so-called mountain-shaped shape with its top protruding in the digging direction, i.e., the front end of the dual drill bits 121, at two locations. Superhard drill tips 134 and 135 are respectively provided at the front end and the two mountain-shaped parts of the base 133.

[0124] More specifically, the superhard drill tip 134 includes, at the upper part of the front end of the base 133, an inclined portion 134a that rises at a predetermined angle from the third plane portion 137 of the base 133 toward the digging direction, and an inclined portion 134b that rises at a predetermined angle from the second plane portion 130 toward the digging direction. Since the lengths of the inclined portions 134a and 134b are the same, their tops are located at the center of the auxiliary drill bit 123 in the digging direction or hole wall direction. In other words, the top is located at the middle of the thickness direction of the auxiliary drill bit 123. On the other hand, the superhard drill tip 135 includes, at the lower part of the front end of the base 133, an inclined portion 135a that rises at a predetermined angle from the third plane portion 137 of the base 133 toward the digging direction, and an inclined portion 135b that rises at a predetermined angle from the second plane portion 130 of the base 133 toward the digging direction. Since the length of the inclined portion 135a is the same as the length of the inclined portion 135b, the top is located at the center of the auxiliary drill bit 123 in the digging direction or hole wall direction. In other words, the top is located at the center of the auxiliary drill bit 123 in the thickness direction.

[0125] like Figure 7As shown in (c), the continuous tops of the inclined portions 134a and 134b of the superhard drill tip 134 and the continuous tops of the inclined portions 135a and 135b of the superhard drill tip 135 respectively form digging edges above and below the base 133. Furthermore, a recess 136 is formed at the front end of the base 133 between the superhard drill tips 134 and 135, which not only further reduces the retention of excavated soil (or cuttings) but also helps improve digging efficiency by controlling the upward flow of excavated soil (or cuttings).

[0126] The material of each part is the same as that described in the first embodiment. A hardened thickened portion 138 is provided at the bases 124 and 133.

[0127] <Eighth Implementation Method>

[0128] Figure 8 (a) to Figure 8 (d) A configuration of the dual drill bits according to the eighth embodiment of the present invention is shown and described. More specifically, Figure 8 (a) shows a top view of the dual drill bit. Figure 8 (b) shows a three-dimensional view of the dual drill bit. Figure 8 (c) represents the side view of the dual drill bit. Figure 8 (d) shows a front view of the dual drill bit. In this dual drill bit, the main drill bit is an angled inner cutting edge, and the auxiliary drill bit is a center cutting edge attached to the outer edge. By using the auxiliary drill bit as the center cutting edge, digging can be performed at the midpoint between the cutting edges of the outer and inner edges, which not only improves digging efficiency but also makes it easier to remove the object being dug out. To clearly show the structure of each part, only... Figure 8 (a) shows the hardened thickened portion.

[0129] As shown in these figures, the dual drill bit 141 is integrally formed with the front cutting edges of the main drill bit 142 and the auxiliary drill bit 143 forming a step in the digging direction.

[0130] The main drill bit 142 consists of a base 144 and two legs 145 and 146 extending from the base 144. Hereinafter, the base 144 side will also be referred to as the front end of the dual drill bit 141, and the legs 145 and 146 side will also be referred to as the casing mounting side or the rear end of the dual drill bit 141. The direction facing the front end is the digging direction, and the direction perpendicular to this digging direction is the hole wall direction or the core direction (also referred to as the thickness direction of the dual drill bit 141). Furthermore, the direction perpendicular to the digging direction and the hole wall direction or core direction is referred to as the width direction of the dual drill bit 141. The definitions of the core direction and the hole wall direction are the same as those described in the first embodiment.

[0131] The base 144 has a so-called mountain-shaped shape with its top protruding in the digging direction, i.e., the front end of the dual drill bit 141, at two locations. Superhard drill tips 147 and 148 are respectively provided at the front end and the two mountain-shaped parts of the base 144.

[0132] More specifically, the superhard drill tip 147 includes, at the upper part of the front end of the base 144, an inclined portion 147a that rises at a predetermined angle from the first flat portion 149 of the base 1442 toward the digging direction; and an inclined portion 147b that rises at a predetermined angle from the second flat portion 150 of the base 144 toward the digging direction. Since the length of the inclined portion 147a is longer than the length of the inclined portion 147b, its top is positioned closer to the second flat portion 150. On the other hand, the superhard drill tip 148 includes, at the lower part of the front end of the base 144, an inclined portion 148a that rises at a predetermined angle from the first flat portion 149 of the base 144 toward the digging direction, and an inclined portion 148b that rises at a predetermined angle from the second flat portion 150 of the base 144. Since the length of the inclined portion 148a is longer than the length of the inclined portion 148b, its top is positioned closer to the second flat portion 150.

[0133] like Figure 8 As shown in (c), the continuous tops of the inclined portions 147a and 147b of the superhard drill tip 147 and the continuous tops of the inclined portions 148a and 148b of the superhard drill tip 148 respectively form digging edges above and below the base 144. Furthermore, a recess 151 is formed at the front end of the base 144 between the superhard drill tips 147 and 148, which not only further reduces the retention of excavated soil (or cuttings) but also helps improve digging efficiency by controlling the upward flow of excavated soil (or cuttings).

[0134] Legs 145 and 146 extend from the base 64 toward the rear end at predetermined intervals, making their inner planes parallel and their shape roughly "コ"-shaped when viewed from the plane. The difference from the fourth embodiment described above is that the outer surface of the leg 145 has a predetermined slope. Holes 152 are provided on the legs 145 and 146 for mounting the double drill bit 141 to the casing using bolts or the like.

[0135] On the other hand, the auxiliary drill bit 143 includes a base 153. The rear end portion of the base 153 becomes an inclined portion 153a that slopes rearward in the digging direction, i.e., towards the rear end of the dual drill bits 141. An ultra-hard drill tip 153b is disposed on the inclined surface of the inclined portion 153a. The inclined portion 153a is provided with a hole that communicates with the hole portion 152 of the legs 145 and 146.

[0136] The base 153 has a so-called mountain-shaped shape with its top protruding in the digging direction, i.e., the front end of the dual drill bits 141, at two locations. Superhard drill tips 154 and 155 are respectively provided at the front end and the two mountain-shaped parts of the base 153.

[0137] More specifically, the superhard drill tip 154 ​​includes, at the upper part of the front end of the base 153, an inclined portion 154a that rises at a predetermined angle from the third plane portion 157 of the base 153 toward the digging direction, and an inclined portion 144b that rises at a predetermined angle from the first plane portion 149 toward the digging direction. Since the lengths of the inclined portions 154a and 154b are the same, their tops are located at the center of the auxiliary drill bit 143 in the digging direction or hole wall direction. In other words, the top is located at the middle of the thickness direction of the auxiliary drill bit 143. On the other hand, the superhard drill tip 155 includes, at the lower part of the front end of the base 153, an inclined portion 155a that rises at a predetermined angle from the third plane portion 157 of the base 153 toward the digging direction, and an inclined portion 155b that rises at a predetermined angle from the first plane portion 149 of the base 153 toward the digging direction. Since the length of the inclined portion 155a is the same as the length of the inclined portion 155b, the top is located at the center of the auxiliary drill bit 143 in the digging direction or hole wall direction. In other words, the top is located at the center of the auxiliary drill bit 143 in the thickness direction.

[0138] like Figure 8 As shown in (c), the continuous tops of the inclined portions 154a and 154b of the superhard drill tip 154 ​​and the continuous tops of the inclined portions 155a and 155b of the superhard drill tip 155 respectively form digging edges above and below the base 153. Furthermore, a recess 156 is formed at the front end of the base 153 between the superhard drill tips 154 and 155, which not only further reduces the retention of excavated soil (or cuttings) but also helps improve digging efficiency by controlling the upward flow of excavated soil (or cuttings).

[0139] The material of each part is the same as that described in the first embodiment. A hardened thickened portion 158 is provided at the bases 144 and 153.

[0140] The first to eighth embodiments described above show examples where the superhard drill tips at both the top and bottom of the auxiliary drill bit are both the middle cutting edge, but they can also be the outer cutting edge or the inner cutting edge.

[0141] Taking the first embodiment as an example, in the first embodiment, the top of the superhard drill tip 14 of the auxiliary drill bit 3 is located in the middle of the digging direction or the hole wall direction of the auxiliary drill bit 3. In other words, the top is located in the center (middle cutting edge) of the thickness direction of the double drill bit 1. Similarly, the top of the superhard drill tip 15 is located in the middle of the digging direction or the hole wall direction of the auxiliary drill bit 3. In other words, the top is located in the center (middle cutting edge) of the thickness direction of the double drill bit 1. Placing it close to either the digging direction or the hole wall direction can serve as the outer cutting edge and the inner cutting edge.

[0142] The following is combined Figure 15 (a) to Figure 15 (d) The auxiliary drill bit of the double drill bit in the first embodiment of the present invention is used as the inner cutting edge and the outer cutting edge, respectively, for example.

[0143] first, Figure 15 (a) and Figure 15 (b) shows an example configuration when the auxiliary drill bit is used as the inner cutting edge. Here, for the sake of simplicity, the same configuration as in the first embodiment is used instead of... Figure 1 (a) to Figure 1 (d) The same reference numerals are used in the accompanying drawings, and their descriptions are omitted.

[0144] like Figure 15 (a) and Figure 15 As shown in (b), the auxiliary drill bit 303 includes a base 313. The rear end portion of the base 313 becomes an inclined portion 313a that slopes backward in the digging direction, i.e., towards the rear end of the dual drill bits 301. An ultra-hard drill tip 313b is disposed on the inclined surface of the inclined portion 313a. The inclined portion 313a is provided with a hole that communicates with the hole portion 12 of the legs 5 and 6.

[0145] The base 313 has a so-called mountain-shaped shape with its top protruding in the excavation direction, i.e., the front end of the dual drill bit 301, at two locations. Superhard drill tips 314 and 315 are respectively provided at the front end and the two mountain-shaped parts of the base 313.

[0146] More specifically, the superhard drill tip 314 includes, at the upper part of the front end of the base 313, an inclined portion 314a that rises at a predetermined angle from the third plane portion 317 of the base 313 toward the digging direction, and an inclined portion 314b that rises at a predetermined angle from the second plane portion 10 toward the digging direction. Since the length of the inclined portion 314a is longer than the length of the inclined portion 314b, its top is close to the second plane portion 10 of the auxiliary drill bit 303. In other words, its top is close to the main drill bit 302 in the thickness direction of the auxiliary drill bit 303. On the other hand, the superhard drill tip 315 includes, at the lower part of the front end of the base 313, an inclined portion 315a that rises at a predetermined angle from the third plane portion 317 of the base 313 toward the digging direction, and an inclined portion 315b that rises at a predetermined angle from the second plane portion 10 of the base 313 toward the digging direction. Since the length of the inclined portion 315a is longer than the length of the inclined portion 315b, its top is close to the second plane 10 in the digging direction or hole wall direction of the auxiliary drill bit 303. In other words, its top is close to the main drill bit 302 in the thickness direction of the auxiliary drill bit 303.

[0147] The continuous tops of the inclined portions 314a and 314b of the superhard drill tip 314 and the continuous tops of the inclined portions 315a and 315b of the superhard drill tip 315 respectively form digging edges above and below the base 314. Furthermore, a recess 316 is formed at the front end of the base 313 between the superhard drill tips 314 and 315, which not only further reduces the retention of excavated soil (or cuttings) but also helps improve digging efficiency by controlling the upward flow of excavated soil (or cuttings).

[0148] then, Figure 15 (c) and Figure 15 (d) shows an example configuration when the auxiliary drill bit is used as the outer cutting edge. Here, for the sake of simplicity, the same configuration as in the first embodiment is used instead of... Figure 1 (a) to Figure 1 (d) The same reference numerals are used in the accompanying drawings, and their descriptions are omitted.

[0149] like Figure 15 (c) and Figure 15 As shown in (d), the auxiliary drill bit 403 includes a base 413. The rear end portion of the base 413 is an inclined portion 413a that slopes backward in the digging direction, i.e., towards the rear end of the dual drill bits 401. An ultra-hard drill tip 413b is disposed on the inclined surface of the inclined portion 413a. The inclined portion 413a is provided with a hole that communicates with the hole portion 12 of the legs 5 and 6.

[0150] The base 413 has a so-called mountain-shaped shape with its top protruding in the digging direction, i.e., the front end of the dual drill bit 401, at both the upper and lower positions. Superhard drill tips 414 and 415 are respectively provided at the front end and the upper and lower mountain-shaped parts of the base 413.

[0151] More specifically, the superhard drill tip 414 includes, at the upper part of the front end of the base 413, an inclined portion 414a that rises at a predetermined angle from the third plane portion 417 of the base 413 toward the digging direction, and an inclined portion 414b that rises at a predetermined angle from the second plane portion 10 toward the digging direction. Since the length of the inclined portion 414a is less than the length of the inclined portion 414b, its top is close to the third plane 417 of the auxiliary drill bit 403. In other words, the top is close to the side of the auxiliary drill bit 403 opposite to the side of the main drill bit 402 in the thickness direction. On the other hand, the superhard drill tip 415 includes, at the lower part of the front end of the base 413, an inclined portion 415a that rises at a predetermined angle from the third plane portion 417 of the base 413 toward the digging direction, and an inclined portion 415b that rises at a predetermined angle from the second plane portion 10 of the base 413 toward the digging direction. Since the length of the inclined portion 414a is less than the length of the inclined portion 414b, the top is close to the third plane 417 in the digging direction or hole wall direction of the auxiliary drill bit 403. In other words, the top is located near the auxiliary drill bit 403 on the side opposite to the main drill bit 402 in the thickness direction.

[0152] The continuous tops of the inclined portions 414a and 414b of the superhard drill tip 414 and the continuous tops of the inclined portions 415a and 415b of the superhard drill tip 415 respectively form digging edges above and below the base 414. Furthermore, a recess 416 is formed at the front end of the base 413 between the superhard drill tips 414 and 415, which not only further reduces the retention of excavated soil (or cuttings) but also helps improve digging efficiency by controlling the upward flow of excavated soil (or cuttings).

[0153] here, Figure 9 (a) Figure 9 (b) to Figure 13 (a) Figure 13 (b) An example of the installation of a dual-drill bit into the casing according to an embodiment of the present invention is shown and illustrated.

[0154] Figure 9 (a) Figure 9 (b) shows an installation example where the main drill bit is straight and angled, and the auxiliary drill bit is attached to the inside. In this figure, a double drill bit 201 with the main drill bit being the inner cutting edge and the auxiliary drill bit being the outer cutting edge, a double drill bit 202 with the main drill bit being the middle cutting edge and the auxiliary drill bit also being the middle cutting edge, a double drill bit 203 with the main drill bit being the angled outer cutting edge and the auxiliary drill bit being the inner cutting edge, and a double drill bit 204 with the main drill bit being the outer cutting edge and the auxiliary drill bit being the inner cutting edge are respectively installed on the casing 200.

[0155] Figure 10 (a) Figure 10(b) shows an installation example where the main drill bit is straight and angled, and the auxiliary drill bit is attached to the outside. In this figure, a double drill bit 205 with an angled outer cutting edge for the main drill bit and an inner cutting edge for the auxiliary drill bit, a double drill bit 206 with an outer cutting edge for the main drill bit and an inner cutting edge for the auxiliary drill bit, a double drill bit 207 with a middle cutting edge for the main drill bit and a middle cutting edge for the auxiliary drill bit, and a double drill bit 208 with an inner cutting edge for the main drill bit and an outer cutting edge for the auxiliary drill bit are respectively installed on the casing 200.

[0156] Figure 11 (a) Figure 11 (b) shows an installation example where the main drill bit is straight and the auxiliary drill bit is attached to the outside. In this figure, a double drill bit 209 with the main drill bit having an outer cutting edge and the auxiliary drill bit having an outer cutting edge, a double drill bit 210 with the main drill bit having an outer cutting edge and the auxiliary drill bit having a middle cutting edge, and a double drill bit 211 with the main drill bit having a straight inner cutting edge and the auxiliary drill bit having an inner cutting edge are respectively installed on the casing 200.

[0157] Figure 12 (a) Figure 12 (b) shows an installation example where the main drill bit is straight and the auxiliary drill bit is attached to the inside. In this figure, a double drill bit 212 with the main drill bit having an inner cutting edge and the auxiliary drill bit having an outer cutting edge, a double drill bit 213 with the main drill bit having an outer cutting edge and the auxiliary drill bit having a middle cutting edge, and a double drill bit 214 with the main drill bit having a straight outer cutting edge and the auxiliary drill bit having an inner cutting edge are respectively installed on the casing 200.

[0158] Figure 13 (a) Figure 13 (b) shows an installation example where the main drill bit is straight or angled and the auxiliary drill bit is attached to the outside. In this figure, a double drill bit 215 with the main drill bit having an inner cutting edge and the auxiliary drill bit having an outer cutting edge, a double drill bit 216 with the main drill bit having an angled middle cutting edge and the auxiliary drill bit having a middle cutting edge, and a double drill bit 217 with the main drill bit having an outer cutting edge and the auxiliary drill bit having an inner cutting edge are respectively installed on the casing 200.

[0159] Figure 14 (a) Figure 14 (b) shows an installation example where the main drill bit is straight or angled and the auxiliary drill bit is attached to the inside. In this figure, a double drill bit 218 with the main drill bit having an outer cutting edge and the auxiliary drill bit having an inner cutting edge, a double drill bit 219 with the main drill bit having an angled middle cutting edge and the auxiliary drill bit also having a middle cutting edge, and a double drill bit 220 with the main drill bit having an inner cutting edge and the auxiliary drill bit having an outer cutting edge are respectively installed on the casing 200.

[0160] Finally, the following design can be made in the dual drill bits of the first to eighth embodiments described above.

[0161] (a) Regarding the cutting edge positions of the main drill bit and the auxiliary drill bit

[0162] In all shapes, a stepped construction can be adopted, so that the cutting edge of the auxiliary drill bit is located 25mm below the cutting edge of the main drill bit. The reason for placing the cutting edge of the auxiliary drill bit 25mm below the cutting edge of the main drill bit is that the distance between the cutting edge of the main drill bit and the front end of the casing is 50mm, and the cutting edge of the auxiliary drill bit is located exactly in the middle (25mm below), thereby achieving the purpose of allowing the auxiliary drill bit to dig in areas that the main drill bit cannot dig.

[0163] (b) Width settings for the main drill bit and auxiliary drill bit

[0164] The main drill bit has a cutting edge width of 80mm, allowing the jaws of the cutting edge to engage with the retainer by 10mm at both ends. The auxiliary drill bit, with a total width of 60mm, fits perfectly within the retainer's internal dimensions. Since the main drill bit absorbs the primary impact during excavation, it is assumed that the auxiliary drill bit will experience approximately 30% less impact. Therefore, the width ratio of the main drill bit to the auxiliary drill bit can be set to 4:3. However, this width ratio can be adjusted depending on the object being excavated.

[0165] (c) Thickness settings for the main drill bit and auxiliary drill bit

[0166] Since a thickness of 40mm is the most common thickness for the main drill bit (straight section), it is set to 40mm for versatility. The thickness of the auxiliary drill bit, at 30mm, can be set to a 4:3 ratio for the same reasons as the width setting. However, this thickness ratio can be changed depending on the object being excavated.

[0167] To enable digging with the cutter head positioned 10mm further out or inward than a straight cutter head, the ratio of the thickness of the angled main drill bit (50mm) to the thickness of the auxiliary drill bit is 5:3. Combining this angled shape with a straight cut maximizes its effectiveness, preventing a simple 25% increase in impact during digging. The thickness of the angled main drill bit can be adjusted depending on the object being excavated.

[0168] (d) Regarding the tapered portion of the auxiliary drill bit

[0169] Since the auxiliary drill bit is mounted inside or outside the main drill bit, it will come into direct contact with the object being excavated. Therefore, an ultra-hard drill tip for impact and wear resistance is installed in the tapered portion of the auxiliary drill bit. It should be noted that the angle of the tapered portion can, of course, vary depending on the thickness of the auxiliary drill bit.

[0170] (e) Regarding the hardness of superhard drill tips

[0171] Of course, the hardness of the superhard drill tips of the main drill bit and auxiliary drill bit can vary depending on the object being excavated. As mentioned above, the hardness of the superhard drill tips can be set to the ordinary E type (JIS standard, coarse grain) E7~E2 and G type (JIS standard, medium grain) G5~G2, and the hardness of the superhard drill tips of the main drill bit and auxiliary drill bit can also be different.

[0172] For example: Excavation target - ultra-hard rock, main drill bit E2 + auxiliary drill bit E3

[0173] For example: Clearing obstacles – reinforced concrete beams, columns, floor slabs, etc., using a main drill bit E6 + an auxiliary drill bit E5.

[0174] As described above, the following effects can be achieved according to the embodiments of the present invention.

[0175] That is, according to an embodiment of the present invention, a dual drill bit can be provided, including a main drill bit and an auxiliary drill bit. Both the main drill bit and the auxiliary drill bit are provided with a superhard drill tip in a mountain-shaped form protruding in the digging direction at least at their upper and lower portions at the front end of their bases. The top of the mountain-shaped form of the superhard drill tip of the auxiliary drill bit is located rearward in the digging direction compared to the top of the mountain-shaped form of the superhard drill tip of the main drill bit. The top of the mountain-shaped form of the main drill bit can be near a direction perpendicular to the digging direction (i.e., the hole wall direction), near the pile core direction, or located in the center. The top of the mountain-shaped form of the auxiliary drill bit can also be near a direction perpendicular to the digging direction (i.e., the hole wall direction), near the pile core direction, or located in the center. The main drill bit also includes two legs continuous with the base, and the outer surface of the leg on the side where the auxiliary drill bit is not arranged side-by-side can have a predetermined slope.

[0176] Therefore, firstly, by arranging the main drill bit and the auxiliary drill bit side by side in a direction perpendicular to the digging direction, and forming a so-called step structure in which the cutting edge of the auxiliary drill bit is located behind the cutting edge of the main drill bit in the digging direction, the load applied to the inner plate (or outer plate) of the casing can be reduced, and the retention of excavated soil (or cuttings) generated when digging through a single cutting edge can be prevented, thereby improving digging efficiency.

[0177] Secondly, the base material shape of the main drill bit's cutting edge can be selected from a straight shape or an inclined shape at an angle to the base material, and the cutting edge position of the main drill bit and the cutting edge position of the auxiliary drill bit can be adjusted, thereby setting the width of the two cutting edges and the angle of the digging position. Therefore, it not only expands the digging position of the cutting edge, further reduces the load applied to the inner plate (or outer plate) of the casing, and further reduces the retention of excavated soil (or cuttings), but also controls the upward flow of excavated soil (or cuttings).

[0178] Third, wear resistance can be improved by equipping the base of the blade (the substrate part) with an ultra-hard drill tip.

[0179] Fourth, since the dual drill bits are used for bidirectional rotation, bidirectional excavation, including forward and reverse excavation, is possible.

[0180] The embodiments of the present invention have been described above, but the present invention is not limited thereto. Various improvements and modifications can be made without departing from its spirit.

[0181] Symbol Explanation

[0182] 1…Double drill bit; 2…Main drill bit; 3…Auxiliary drill bit; 4…Base; 5, 6…Legs; 7, 8…Superhard drill bit; 9…First flat part; 10…Second flat part; 11…Recess; 12…Hole; 13…Base; 14, 15…Superhard drill bit; 16…Recess; 17, 18…Hardened thickened part.

Claims

1. A dual-bit drill bit, comprising a main drill bit and an auxiliary drill bit, The main drill bit is provided with a first superhard drill tip in a mountain shape protruding in the digging direction at the upper part of the front end of the first base, and a second superhard drill tip in a mountain shape protruding in the digging direction at the lower part of the front end of the first base. The auxiliary drill bit is provided with a third superhard drill tip in a mountain-shaped form, protruding in the digging direction, at the upper part of the front end of the second base, and a fourth superhard drill tip in a mountain-shaped form, protruding in the digging direction, at the lower part of the front end of the second base. A first recess is formed between the first superhard drill tip and the second superhard drill tip of the main drill bit. A second recess is formed between the third and fourth superhard drill tips of the auxiliary drill bit. The top of the mountain-shaped top of the third superhard drill tip of the auxiliary drill bit is located behind the top of the mountain-shaped top of the first superhard drill tip of the main drill bit in the digging direction. The top of the mountain-shaped top of the fourth superhard drill tip of the auxiliary drill bit is located behind the top of the mountain-shaped top of the second superhard drill tip of the main drill bit in the digging direction. The second recess is located behind the first recess in the digging direction.

2. The dual drill bit according to claim 1, wherein, The main drill bit also has a first planar portion and a second planar portion located on the opposite side of the first planar portion in a direction perpendicular to the digging direction. In the vertical direction, the distance between the top of the mountain-shaped portion of the first superhard drill tip and the second superhard drill tip and the first flat portion is shorter than the distance between the top of the mountain-shaped portion of the first superhard drill tip and the second superhard drill tip and the second flat portion, or In the vertical direction, the distance between the top of the mountain-shaped portion of the first superhard drill tip and the second superhard drill tip and the first flat portion is longer than the distance between the top of the mountain-shaped portion of the first superhard drill tip and the second superhard drill tip and the second flat portion, or In the vertical direction, the distance between the top of the mountain-shaped portion of the first superhard drill tip and the second superhard drill tip and the first flat portion is equal to the distance between the top of the mountain-shaped portion of the first superhard drill tip and the second superhard drill tip and the second flat portion.

3. The dual drill bit according to claim 2, wherein, The auxiliary drill bit also has a third planar portion in the vertical direction. In the vertical direction, the third planar portion, the second planar portion, and the first planar portion are arranged in this order. In the vertical direction, the interval between the top of the mountain-shaped portion of the third and fourth superhard drill bits and the second planar portion is shorter than the interval between the top of the mountain-shaped portion of the third and fourth superhard drill bits and the third planar portion, or In the vertical direction, the interval between the top of the mountain-shaped portion of the third and fourth superhard drill bits and the second planar portion is longer than the interval between the top of the mountain-shaped portion of the third and fourth superhard drill bits and the third planar portion, or In the vertical direction, the interval between the top of the mountain-shaped portion of the third and fourth superhard drill bits and the second planar portion is equal to the interval between the top of the mountain-shaped portion of the third and fourth superhard drill bits and the third planar portion.

4. The dual drill bit according to claim 1, wherein, The main drill bit also has a first planar portion and a second planar portion located on the opposite side of the first planar portion in a direction perpendicular to the digging direction. The auxiliary drill bit also has a third planar portion in the vertical direction. In the vertical direction, the third planar portion, the second planar portion, and the first planar portion are arranged in this order. In the vertical direction, the interval between the top of the mountain-shaped portion of the third and fourth superhard drill bits and the second planar portion is shorter than the interval between the top of the mountain-shaped portion of the third and fourth superhard drill bits and the third planar portion, or In the vertical direction, the interval between the top of the mountain-shaped portion of the third and fourth superhard drill bits and the second planar portion is longer than the interval between the top of the mountain-shaped portion of the third and fourth superhard drill bits and the third planar portion, or In the vertical direction, the interval between the top of the mountain-shaped portion of the third and fourth superhard drill bits and the second planar portion is equal to the interval between the top of the mountain-shaped portion of the third and fourth superhard drill bits and the third planar portion.

5. The dual drill bit according to claim 3 or 4, wherein, The main drill bit also includes two legs that are continuous with the first base. The outer surface of the leg on the side where the auxiliary drill bit is not arranged in parallel has a specified slope.

6. The dual drill bit according to claim 1, wherein, The auxiliary drill bit has an inclined section formed by tilting the rear end portion toward the rear in the digging direction and a fifth superhard drill tip disposed on the inclined surface of the inclined section.

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