A slant-thread drill pipe

Abstract

This utility model relates to the field of drill pipe technology, specifically a helical thread drill pipe, including a drill pipe body. One end of the drill pipe body is a male connector end, and the other end is a female connector end. The male connector end has an external thread, and the female connector end has an internal thread that mates with the external thread. The thread profiles of the external and internal threads are asymmetrical. The external thread includes a first sidewall, a bottom of the external thread, a second sidewall, and a top of the external thread connected in sequence. The angle θ between the first sidewall and the drill pipe axis is greater than the angle β between the second sidewall and the drill pipe axis. The internal thread includes a third sidewall, a bottom of the internal thread, a fourth sidewall, and a top of the internal thread connected in sequence. The angle θ between the third sidewall and the drill pipe axis is greater than the angle β between the fourth sidewall and the drill pipe axis. The male connector end has a first outer shoulder and a second outer shoulder. The inner wall of the female connector end has a first inner shoulder and a second inner shoulder. The included angles θ and β reduce the harmful radial force generated by traditional symmetrical threads under tension, ensuring connection stability.

Description

Technical Field

[0001] This utility model relates to the field of drill pipe technology, and in particular to a helical thread drill pipe. Background Technology

[0002] In drilling operations such as mineral exploration, engineering surveying, and geological exploration, drill pipes are connected by threads to form a drill string thousands of meters long, transmitting torque, delivering drilling fluid, and withstanding complex tensile, compressive, bending, and torsional loads. Traditional drill pipe joints generally use symmetrical trapezoidal threads. This design is adequate for shallow wells (within 1000 meters), but as drilling depths extend to 1000 to 1500 meters and above, its inherent structural defects become apparent. The main problems are as follows: Symmetrical trapezoidal threads have symmetrical tooth angles on both sides. When subjected to a large axial tensile force, a significant radial force is generated on the thread flank. This force causes the male connector to expand outward and the female connector to contract inward, producing a strong wedging effect. This greatly increases the contact stress on the thread engagement surface, which can lead to fracture of the threaded connection when the load is too large.

[0003] The male connector has the thinnest wall thickness at the end, and this thin wall thickness bears greater stress, making the thread at the small end of the drill pipe the most prone to breakage in the entire drill string.

[0004] Therefore, the core technical challenge faced by those skilled in the art is: how to improve the geometry of the drill pipe thread to optimize the stress distribution of the threaded connection, reduce the stress at the small end of the male connector, and thus reduce the risk of drill pipe breakage during operation. Utility Model Content

[0005] The purpose of this invention is to improve the geometry of the drill pipe thread to optimize the stress distribution of the threaded connection, reduce the stress at the small end of the male connector, and thus reduce the risk of drill pipe breakage during operation.

[0006] To achieve the above objectives, this utility model adopts the following technical solution: a helical thread drill rod, comprising a drill rod body, one end of which is a male connector end and the other end is a female connector end. The male connector end is provided with an external thread, and the female connector end is provided with an internal thread that mates with the external thread. The thread profiles of the external and internal threads are asymmetrical. The external thread includes a first sidewall, the bottom of the external thread, a second sidewall, and the top of the external thread, which are connected in sequence. The angle θ between the first sidewall and the drill pipe axis is greater than the angle β between the second sidewall and the drill pipe axis. The internal thread includes a third sidewall, the bottom of the internal thread, a fourth sidewall, and the top of the internal thread connected in sequence; the angle θ between the third sidewall and the drill pipe axis is greater than the angle β between the fourth sidewall and the drill pipe axis. The male connector end has a first outer shoulder at the end closest to the drill pipe body and a second outer shoulder at the end furthest from the drill pipe body; the female connector end has a first inner shoulder that abuts against the first outer shoulder and a second inner shoulder that abuts against the second outer shoulder; when the male connector end and the female connector end are tightened, the first outer shoulder and the first inner shoulder, as well as the second outer shoulder and the second inner shoulder, simultaneously form a metal-to-metal sealing contact.

[0007] Preferably, the angle θ between the first sidewall, the third sidewall and the drill pipe axis is 75°-85°; and the angle β between the second sidewall, the fourth sidewall and the drill pipe axis is 40°-50°.

[0008] Preferably, the bottom of the external thread of the external thread and the bottom of the internal thread of the internal thread are arc-shaped, and the height of the bottom of the external thread and the bottom of the internal thread in the direction of the drill rod axis is L5, where L5 is 4-5mm.

[0009] Preferably, the height of a single external thread and a single internal thread in the direction of the drill rod axis is L6, where L6 is 6mm-10mm.

[0010] Preferably, the height of a single external thread and a single internal thread in the direction of the drill pipe axis is 8.466 mm.

[0011] Preferably, the width of the top of the external thread 25 and the top of the internal thread perpendicular to the drill rod axis is L4, and L4 is 0.8mm-1.2mm.

[0012] Preferably, the width of the top of the external thread and the top of the internal thread perpendicular to the drill rod axis is 0.9 mm.

[0013] Preferably, both the male connector end and the female connector end have a taper, and the taper of the male connector end is greater than that of the female connector end.

[0014] Preferably, the male connector end taper is 1:22 and the female connector end taper is 1:23.

[0015] Preferably, the angle θ between the first sidewall, the third sidewall and the drill pipe axis is 80°; and the angle β between the second sidewall, the fourth sidewall and the drill pipe axis is 45°.

[0016] Compared with the prior art, the advantages and positive effects of this utility model are as follows: By designing the first and third sidewalls on the load-bearing side with large angles (θ=75°-85°, preferably 80°) and the second and fourth sidewalls on the non-load-bearing side with small angles (β=40°-50°, preferably 45°), the harmful radial force generated by traditional symmetrical threads under tension is greatly reduced. This design converts axial tension into positive pressure that promotes tight contact of the thread surfaces, rather than radial force that causes expansion and contraction of the male and female joints. This reduces the stress peak at the thread root, significantly improving the fatigue life and overload capacity of the joint. The wedge-tightening effect generated by the tilt angles θ and β after tightening improves the rigidity of the connection. Since the drill pipe connection needs to withstand a large weight, the contact surface formed by the tilt angles θ of the first and third sidewalls after connection tilts downwards. The greater the weight of the lower drill pipe, the tighter the connection, further improving the connection's stability. This achieves a self-tightening connection, becoming tighter with increasing tension.

[0017] The male connector's taper is designed to be slightly larger than the female connector's (e.g., male end 1:22, female end 1:23). This ensures that during connection, the engagement force between the small end of the male connector and the small end of the female connector is less than the engagement force between the large end, thus actively guiding and concentrating stress from the weakest small end to the stronger large end. This reduces the risk of the small end breaking due to excessive engagement force from the outset.

[0018] The tightly fitted asymmetrical threads themselves form a sealing barrier. The internal and external threads tighten further as they are tightened, and the interlocking force between the bevels is even stronger, preventing water leakage at the threaded connection. Even under high water pressure, water is less likely to flow into the threads, meaning the beveled threads offer better sealing. After the joint is tightened, the first outer shoulder, the first inner shoulder, the second outer shoulder, the second inner shoulder, and the outer step, together with the threaded pair, form a load-bearing structure. When the drill pipe is subjected to extreme loads, especially compression and bending loads, the first outer shoulder, the first inner shoulder, the second outer shoulder, the second inner shoulder, and the outer step can bear part of the load, providing a transmission path for force diversion. This reduces the burden on the end threads, avoids the common phenomenon of last-thread breakage, and further enhances the overall stability and overload protection capability of the entire connection structure. Attached Figure Description

[0019] Figure 1 This is a schematic cross-sectional view of an existing drill pipe; Figure 2 for Figure 1 An enlarged schematic diagram of point I in the existing drill pipe; Figure 3 This is a cross-sectional schematic diagram of the oblique thread drill rod of this utility model; Figure 4 for Figure 3 Enlarged schematic diagram of the external thread at point A; Figure 5 for Figure 3Enlarged schematic diagram of the internal thread at point B; Figure 6 This is a schematic cross-sectional view of the male connector end of the oblique thread drill rod of this utility model; Figure 7 This is a schematic cross-sectional view of the female connector end of the oblique thread drill rod of this utility model; Figure 8 A schematic diagram showing the connection of two oblique threaded drill rods of this utility model; Figure 9 for Figure 8 Enlarged view of point E in the middle; Explanation of reference numerals in the attached drawings: 10. Existing drill pipe; 101. Existing female connector; 102. Existing male connector; 103. Trapezoidal thread section; 104. Trapezoidal thread; 1. Drill pipe body; 2. Male connector end; 21. External thread; 22. First sidewall; 23. Bottom of external thread; 24. Second sidewall; 25. Top of external thread; 26. First outer shoulder; 27. Second outer shoulder; 28. Outer step; 3. Female connector end; 31. Internal thread; 32. Third sidewall; 33. Bottom of internal thread; 34. Fourth sidewall; 35. Top of internal thread; 36. First inner shoulder; 37. Second inner shoulder; 38. Inner step; 4. Drill pipe axis. Detailed Implementation

[0020] like Figure 1 , Figure 2 As shown, the two ends of the existing drill pipe 10 body are an existing female connector 101 and an existing male connector 102, respectively. Both the existing female connector 101 and the existing male connector 102 have trapezoidal thread portions 103. The difference is that the trapezoidal thread portion 103 of the existing female connector 101 is located on the inner wall side of the existing female connector 101; the trapezoidal thread portion 103 of the existing male connector 102 is located on the outer wall of the existing male connector 102, and the trapezoidal thread portion 103 is provided with several trapezoidal threads 104. The trapezoidal threads 104 on the existing female connector 101 and the existing male connector 102 face opposite directions so as to connect the two existing drill pipes 10 by threads. The taper of the existing female connector 101 and the existing male connector 102 is b, where b is 1:30. The existing male connector 102 has an outer diameter d1 of 68.6 mm. d1 minus the tooth height of the trapezoidal thread 104 is d2, which is 67.1 mm. The existing male connector 102 has an inner diameter d3 of 64.4 mm. The existing female connector 101 has an inner diameter d4 of 68.8 mm. d4 plus the tooth height of the trapezoidal thread 104 is d5, which is 70.1 mm. The existing female connector 101 has an outer diameter d6 of 73.3 mm. The total length of both the existing female connector 101 and the existing male connector 102 is L2, which is 45 mm. The overall length of the existing drill pipe 10 is L3, which is 1545 mm. Figure 2 for Figure 1The enlarged schematic diagram at point I shows a portion of the trapezoidal thread 103 and the trapezoidal thread 104 thereon. The trapezoidal thread 10 has rectangular teeth with a tooth width of p (3.175 mm) and a tooth spacing of q (6.35 mm). The existing female connector 101 and the existing male connector 102 have a taper of b (1:30). When both have the same taper, the thread engagement force at the small end of the existing male connector 102 can become too high, causing breakage. As drilling depths extend to 1000 to 1500 meters and above, the threaded connection at the trapezoidal thread joint is prone to breakage at greater drilling depths.

[0021] To solve the above problems, this utility model provides a helical thread drill rod, including a drill rod body 1. One end of the drill rod body 1 is a male connector end 2, and the other end is a female connector end 3. The outer wall of the male connector end 2 is provided with a first outer shoulder 26 at the end near the drill rod body 1 and a second outer shoulder 27 at the end away from the drill rod body 1. The inner wall of the female connector end 3 is provided with a first inner shoulder 36 that abuts against the first outer shoulder 26 and a second inner shoulder 37 that abuts against the second outer shoulder 27. When the male connector end 2 and the female connector end 3 are tightened, the first outer shoulder 26 and the first inner shoulder 36, as well as the second outer shoulder 27 and the second inner shoulder 37, simultaneously form a metal-to-metal sealed contact.

[0022] The male connector end 2 is provided with an external thread 21, and the female connector end 3 is provided with an internal thread 31 that mates with the external thread 21. The thread profiles of the external thread 21 and the internal thread 31 are asymmetrical. The external thread 21 includes a first sidewall 22, an external thread bottom 23, a second sidewall 24, and an external thread top 25 connected in sequence. The angle θ between the first sidewall 22 and the drill pipe axis 4 is greater than the angle β between the second sidewall 24 and the drill pipe axis 4. The internal thread 31 includes a third sidewall 32, an internal thread bottom 33, a fourth sidewall 34, and an internal thread top 35 connected in sequence. The angle θ between the third sidewall 32 and the drill pipe axis 4 is greater than the angle β between the fourth sidewall 34 and the drill pipe axis 4. The angle θ between the first sidewall 22, the third sidewall 32, and the drill pipe axis 4 is 75°-85°; the angle β between the second sidewall 24, the fourth sidewall 34, and the drill pipe axis 4 is 40°-50°. The angle θ between the first sidewall 22, the third sidewall 32 and the drill pipe axis 4 is 80°; the angle β between the second sidewall 24, the fourth sidewall 34 and the drill pipe axis 4 is 45°. The first sidewall 22 and the third sidewall 32, as bearing sides, convert the axial tensile force into a positive pressure that compresses the thread tooth surface, rather than the radial force that causes the male connector to expand and the female connector to contract, as is the case with traditional trapezoidal threads.

[0023] Both the male connector end 2 and the female connector end 3 have a taper, with the taper of the male connector end 2 being greater than that of the female connector end 3. Preferably, the taper c of the male connector end 2 is 1:22, and the taper of the female connector end 3 is 1:23. The bottom 23 of the external thread 21 and the bottom 33 of the internal thread 31 are arc-shaped, with a height L5 (4-5 mm) in the direction of the drill pipe axis 4 for both the external thread 21 and the internal thread 31. The height L6 (6-10 mm) of a single external thread 21 and a single internal thread 31 in the direction of the drill pipe axis 4 is also 8.466 mm. The width L4 (0.8-1.2 mm) of the top 25 of the external thread and the top 35 of the internal thread perpendicular to the drill pipe axis 4 is also present. The width of the top of the external thread 25 and the top of the internal thread 35, perpendicular to the drill rod axis 4, is 0.9 mm.

[0024] like Figure 3 , Figure 4 , Figure 5 , Figure 6 , Figure 7 In the embodiment shown, the axis of the drill pipe body 1 is the drill pipe axis 4; Figure 3 The diagram shows the drill pipe body 1 with two ends, including a male connector end 2 and a female connector end 3; the total length L3 of the drill pipe body 1 is 1545 mm, and the length of the male connector end 2 is L... 22 L 22 The length is (45-0.1) mm; the total length of the female connector end 3 is L. 32 L 32 The taper is (45+0.1)mm. The taper c of male connector end 2 is 1:22, and the taper c1 of female connector end 3 is 1:23. This setting ensures that the biting force between the small end of male connector end 2 and the small end of female connector end 3 is less than the biting force between the large end of male connector end 2 and the large end of female connector end 3, concentrating the stress towards the large end of male connector end 2 and female connector end 3, reducing the risk of breakage of the small end of male connector end 2 due to excessive biting force.

[0025] like Figure 4 As shown in the enlarged schematic diagram, the male connector end 2 has an external thread 21 on its outer wall. The external thread 21 includes a first sidewall 22, an external thread bottom 23, a second sidewall 24, and an external thread top 25. The length of the external thread bottom 23 in the direction of the drill rod axis 4 is L5, and L5 is 3.52 mm. The radial width of the external thread top 25 is L4, and L4 is 0.9 mm. The length of a single external thread 21 in the direction of the drill rod axis 4 is L6, and L6 is 8.466 mm. The angle between the first sidewall 22 and the drill rod axis 4 is θ, and θ is 80°. The angle between the second sidewall 24 and the drill rod axis 4 is β, and β is 45°. The length of the external thread bottom 23 in the direction of the drill rod axis 4 is L5, and L5 is 3.52 mm.

[0026] like Figure 5 As shown Figure 3 Enlarged schematic diagram of the internal thread at point B; the female connector end 3 includes an internal thread 31 set on the inner wall of the female connector end 3; the internal thread 31 includes a third side wall 32, an internal thread bottom 33, a fourth side wall 34 and an internal thread top 35; the radial width of the internal thread top 35 is L4, L4 is 0.9mm; the length of the internal thread bottom 33 in the direction of the drill rod axis 4 is L5, L5 is 3.52mm; the length of a single internal thread 31 in the direction of the drill rod axis 4 is L6, L6 is 8.466mm; the angle between the third side wall 32 and the drill rod axis 4 is θ, θ is 80°; the angle between the fourth side wall 34 and the drill rod axis 4 is β, β is 45°.

[0027] like Figure 6 The diagram shows a schematic of the male connector end 2. The outer wall of the male connector end 2, near the drill pipe body 1, has a first outer shoulder 26. The first outer shoulder 26 has an inclined surface that slopes from the outside inwards towards the drill pipe body 1, and the angle between this inclined surface and the horizontal plane is... , Preferably, the angle is 15°; the end face of the male connector 2 away from the drill pipe body 1 is provided with a second outer shoulder 27; the second outer shoulder 27 has an inclined surface that slopes from the outside to the inside towards the drill pipe body 1, and the angle between the inclined surface and the horizontal plane is 15°. , The preferred angle is 15°. The external thread 21 is located in the area between the first outer shoulder 26 and the outer step 28. The distance L1 between the outer step 28 and the end of the male connector 2 is 6mm, and 6mm is the clearance section of the external thread of the male connector 2. The outer diameter D1 of the male connector 2 is 68.6 + 0.02mm. The outer diameter D1 of the male connector 2 minus the tooth height of the external thread 21 is D2, which is 66.8 + 0.02mm. The inner diameter D3 of the male connector 2 is 64.3mm.

[0028] like Figure 7 The diagram shows the female connector end 3. The inner wall of the female connector end 3, away from the drill pipe body 1, has a first inner shoulder 36 that abuts against the first outer shoulder 26. The first inner shoulder 36 has an inclined surface that slopes from the inside out towards the drill pipe body 1, and the angle between this inclined surface and the horizontal plane is... , Preferably, the angle is 15°; the inner wall of the female connector end 3 near the drill pipe body 1 is provided with a second inner shoulder 37 that abuts against the second outer shoulder 27; the second inner shoulder 37 has an inclined surface that slopes from the inside out toward the drill pipe body 1, and the angle between the inclined surface and the horizontal plane is 15°. , The preferred angle is 15°. The internal thread 31 is located in the area between the first inner shoulder 36 and the inner step 38. The distance L1 between the inner step 38 and the end of the male connector 2 is 6mm. This 6mm distance represents the clearance section for the internal thread of the female connector 3. The inner step 38 is used to abut against the outer step 28 of the adjacent drill pipe during connection. The inner diameter D4 of the female connector 3 is 68.85-0.02mm. The inner diameter D4 plus the tooth height of the internal thread 31 equals D5, which is 70.65-0.02mm. The outer diameter D6 of the female connector 3 is 74.5mm.

[0029] like Figure 8 The diagram shows the connection of two drill pipe bodies 1. The parameters of the adjacent drill pipe bodies 1 after connection are as follows: the male connector end 2 extends into the female connector end 3 of the other drill pipe body 1; the external threads 21 and internal threads 31 of the male connector end 2 and female connector end 3 are tightened; the second outer shoulder 27 abuts against the second inner shoulder 37; the outer step 28 abuts against the inner step 38; and the first outer shoulder 26 abuts against the first inner shoulder 36, completing the connection of the adjacent drill pipe bodies 1. The tightly fitted asymmetrical threads themselves form a sealing barrier. The internal and external threads tighten further, and the interlocking force between the inclined surfaces is stronger, preventing water leakage at the threaded connection. Even under high water pressure, water is less likely to flow into the threads, meaning the inclined threads have better sealing performance. After the joints are tightened, the first outer shoulder 26 and the first inner shoulder 36, the second outer shoulder 27 and the second inner shoulder 37, and the outer step 28 and the inner step 38, together with the threaded pair, form a load-bearing structure. When the drill pipe is subjected to extreme loads, especially compressive and bending loads, the first outer shoulder 26 and the first inner shoulder 36, the second outer shoulder 27 and the second inner shoulder 37, and the outer step 28 and the inner step 38 can bear part of the load, providing a transmission path for force diversion. This reduces the burden on the end threads, avoids the common phenomenon of end-thread breakage, and further enhances the overall stability and overload protection capability of the entire connection structure.

[0030] Figure 9 for Figure 8 An enlarged schematic diagram at point E shows the fit between the external thread 21 and the internal thread 31. The top 25 of the external thread engages with the bottom 33 of the internal thread, and vice versa. After the second sidewall 24 and the fourth sidewall 34 are fitted together, the angle β between their mating surfaces and the drill rod axis 4 is 45°. After the first sidewall 22 and the third sidewall 32 are fitted together, the angle θ between their mating surfaces and the drill rod axis 4 is 80°. Because the drill rod connection needs to withstand a large amount of gravity, the inclination angle θ of the first sidewall 22 and the third sidewall 32 forms a downward-sloping contact surface after the connection. The greater the weight of the drill rod below, the tighter the connection is, further improving the connection's stability.

[0031] By designing the first sidewall 22 and third sidewall 32 of the load-bearing external thread 21 with large angles (θ=75°-85°, preferably 80°) and the second sidewall 24 and fourth sidewall 34 of the non-load-bearing internal thread 31 with small angles (β=40°-50°, preferably 45°), the harmful radial force generated by traditional symmetrical threads under tension is greatly reduced. This design converts axial tension into positive pressure that promotes tight contact of the thread surfaces, rather than radial force that causes expansion and contraction of the male and female joints. This reduces the stress peak at the thread root, significantly improving the fatigue life and overload capacity of the joint. The wedge-tightening effect generated by the tilt angles θ and β after tightening improves the rigidity of the connection. Since the drill pipe connection needs to withstand a large weight, the contact surface formed by the tilt angles θ of the first sidewall 22 and third sidewall 32 after connection tilts downwards. The greater the weight of the lower drill pipe, the tighter the connection, further improving the connection's stability. A self-tightening connection is achieved, tightening as it is pulled. The taper of male connector end 2 is designed to be slightly larger than that of female connector end 3 (e.g., male end 1:22, female end 1:23). This ensures that during connection, the interlocking force between the smaller end of male connector end 2 and the smaller end of female connector end 3 is less than that between the larger ends, thus actively guiding and concentrating stress from the weakest end to the stronger end. This reduces the risk of breakage at the smaller end of male connector end 2 due to excessive interlocking force from the outset.

Claims

1. A helical thread drill rod, comprising a drill rod body (1), characterized in that: One end of the drill pipe body (1) is a male connector end (2) and the other end is a female connector end (3). The male connector end (2) is provided with an external thread (21) and the female connector end (3) is provided with an internal thread (31) that matches the external thread (21). The thread profiles of the external thread (21) and the internal thread (31) are asymmetrical. The external thread (21) includes a first sidewall (22), the bottom of the external thread (23), the second sidewall (24) and the top of the external thread (25) connected in sequence. The angle θ between the first sidewall (22) and the drill rod axis (4) is greater than the angle β between the second sidewall (24) and the drill rod axis (4). The internal thread (31) includes a third sidewall (32), the bottom of the internal thread (33), the fourth sidewall (34) and the top of the internal thread (35) connected in sequence; the angle θ between the third sidewall (32) and the drill rod axis (4) is greater than the angle β between the fourth sidewall (34) and the drill rod axis (4); The male connector end (2) has a first outer shoulder (26) at the end near the drill pipe body (1) and a second outer shoulder (27) at the end away from the drill pipe body (1); the female connector end (3) has a first inner shoulder (36) that abuts against the first outer shoulder (26) and a second inner shoulder (37) that abuts against the second outer shoulder (27); when the male connector end (2) and the female connector end (3) are tightened, the first outer shoulder (26) and the first inner shoulder (36) and the second outer shoulder (27) and the second inner shoulder (37) simultaneously form a metal-to-metal sealed contact.

2. The oblique thread drill rod according to claim 1, characterized in that: The angle θ between the first sidewall (22), the third sidewall (32) and the drill pipe axis (4) is 75°-85°; the angle β between the second sidewall (24), the fourth sidewall (34) and the drill pipe axis (4) is 40°-50°.

3. A helical thread drill rod according to claim 1 or 2, characterized in that: The bottom of the external thread (23) of the external thread (21) and the bottom of the internal thread (33) of the internal thread (31) are arc-shaped. The height of the bottom of the external thread (23) and the bottom of the internal thread (33) in the direction of the drill rod axis (4) is L5, and L5 is 4-5mm.

4. A helical thread drill rod according to claim 1 or 2, characterized in that: The height of a single external thread (21) and a single internal thread (31) in the direction of the drill rod axis (4) is L6, and L6 is 6mm-10mm.

5. A helical thread drill rod according to claim 4, characterized in that: The height of a single external thread (21) and a single internal thread (31) in the direction of the drill rod axis (4) is 8.466 mm.

6. A helical thread drill rod according to claim 1 or 2, characterized in that: The width of the top of the external thread (25) and the top of the internal thread (35) perpendicular to the drill rod axis (4) is L4, and L4 is 0.8mm-1.2mm.

7. A helical thread drill rod according to claim 6, characterized in that: The width of the top of the external thread (25) and the top of the internal thread (35) perpendicular to the drill rod axis (4) is 0.9 mm.

8. A helical thread drill rod according to claim 1, characterized in that: Both the male connector end (2) and the female connector end (3) have a taper, and the taper of the male connector end (2) is greater than that of the female connector end (3).

9. A helical thread drill rod according to claim 8, characterized in that: The male connector end (2) has a taper of 1:22, and the female connector end (3) has a taper of 1:

23.

10. A helical thread drill rod according to claim 2, characterized in that: The angle θ between the first sidewall (22), the third sidewall (32) and the drill pipe axis (4) is 80°; the angle β between the second sidewall (24), the fourth sidewall (34) and the drill pipe axis (4) is 45°.

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