MJ thread self-locking insert

Abstract

The invention discloses an MJ thread self-locking insert. The MJ thread self-locking insert comprises a bearing sleeve, a limiter and a limiting clamp spring, a main body of the bearing sleeve is a cylindrical section, and MJ threads are arranged in the cylindrical section and used for screwing in the connecting bolt; the lower end of the cylindrical section is provided with a self-locking area surrounding the cylindrical section by one circle and used for locking the connecting bolt. The limiter is used for restraining the screwing-in depth of the connecting bolt and comprises an ejection column and a limiting column; the ejection body comprises at least two ejection surfaces; in the screwing-in process of the connecting bolt, when the connecting bolt acts on the limiting column, the ejector body ejects out of at least one ejection face of the limiting clamping spring, and it means that the connecting bolt is installed in place.

Description

Technical Field

[0001] This invention relates to the field of fastener design, and in particular to an MJ threaded self-locking insert. Background Technology

[0002] With the increasingly urgent need for lightweight design in aerospace equipment, the application of composite material sandwich and honeycomb sandwich structures in aerospace equipment has been widely promoted. However, these materials are relatively soft as connecting substrates, so inserts are needed to locally reinforce the connection between composite material sandwich and honeycomb sandwich structures. The main structural forms include post-embedded inserts and pre-embedded inserts. Post-embedded inserts are installed after the honeycomb panel or composite material sandwich is manufactured, while pre-embedded inserts are embedded in advance during the manufacturing process of the honeycomb panel or composite material sandwich, and then formed and cured together.

[0003] Currently, the design of inserts with general structural forms is relatively well-developed. However, when applied to aerospace equipment, it is difficult to simultaneously meet the requirements of ease of installation, vibration environment adaptability, and mechanical environment adaptability. On the one hand, in high-intensity vibration environments, there is a risk of loosening of fasteners; on the other hand, many self-locking inserts applicable to vibration conditions neglect the load-bearing characteristics of the inserts, including tensile conditions. If improperly installed, significant stress concentration can occur in the self-locking zone, weakening the load-bearing capacity of the insert. Therefore, it is also necessary to consider load-bearing characteristics to achieve the self-locking function without reducing the load-bearing capacity of the insert.

[0004] In summary, a new type of MJ threaded insert needs to be designed to meet the requirements of aerospace equipment for ease of installation, adaptability to vibration environment, and adaptability to mechanical environment. Summary of the Invention

[0005] The technical problem solved by this invention is to overcome the shortcomings of the prior art and provide an MJ threaded self-locking insert, which is a new type of post-embedded insert that can ensure the high load-bearing capacity of the insert itself while meeting the requirements of convenient installation and strong vibration resistance.

[0006] The technical solution of this invention is: an MJ threaded self-locking insert, comprising a load-bearing sleeve, a limiter, and a limit snap ring; the limiter is installed at one end of the load-bearing sleeve, and the limit snap ring covers the limiter and is fixed to the load-bearing sleeve; characterized in that:

[0007] The load-bearing sleeve has a cylindrical section as its main body. The cylindrical section has an internal thread in the form of an MJ thread for screwing in the connecting bolt. At the lower end of the cylindrical section, there is a self-locking area that surrounds the cylindrical section for locking the connecting bolt.

[0008] The limiter, used to constrain the screwing depth of the connecting bolt, includes an ejector body and a limiting post; the ejector body includes at least two ejector surfaces; during the screwing of the connecting bolt, when the ejector body pushes out at least one ejector surface of the limiting spring by acting on the limiting post, it means that the connecting bolt is installed in place, and at this time the ejection force of the limiting spring and the decibel of the sound emitted during ejection are within a preset range.

[0009] Furthermore, the self-locking zone is machined upward at a distance L3 from the lower end face of the cylindrical section, where L3 ranges from 4mm-1p to 4mm+1p, and p is the pitch of the internal thread.

[0010] The distance L1-L4 between the lower end face of the limiting post and the upper end face of the self-locking area 13 of the bearing sleeve 1 ranges from 5mm-1p to 4mm+1p.

[0011] Furthermore, the limiting snap ring includes a snap ring connecting part and a hollow frustum body composed of a snap ring sheet and a deformation groove located on the snap ring connecting part;

[0012] The half-angle α1 of the top surface ranges from 10.5 to 11.5°;

[0013] The difference between the half-angle α3 of the outer surface angle of the retaining ring and the half-angle α2 of the inner surface angle of the retaining ring is in the range of 2°≤α3-α2≤3°.

[0014] Furthermore, the difference between the upper end face diameter D3 of the ejector body and the nominal diameter D1 of the internal thread is D3-D1≥2p, where p is the pitch of the internal thread;

[0015] The difference between the outer diameter D5 of the upper end face of the retaining ring and the inner diameter D4 of the upper end face of the retaining ring 32, D5-D4, ranges from 0.5 to 0.7 mm.

[0016] Furthermore, the deformation groove divides the retaining spring into four equal parts, and the width of the deformation groove is S = D4 / 8, where D4 is the inner diameter of the upper end face of the retaining spring.

[0017] Furthermore, the self-locking zone adopts a three-point extrusion method to form a three-point compression deformation, thereby realizing the self-locking function; the length L2 of the self-locking zone is ≥3mm, and the chamfer R on both sides of the self-locking zone is ≥0.5mm.

[0018] Furthermore, the difference between the self-locking zone diameter D2 and the internal thread diameter D1, D2-D1, ranges from 1mm to 2mm.

[0019] Furthermore, all the top surfaces are formed by sequentially stacking frustum structures of the same shape.

[0020] Furthermore, the length L5 of the ejector body satisfies L5 = 8p, where p is the pitch of the internal thread.

[0021] Furthermore, the load-bearing sleeve 1 is made of metal, and the limiter 2 and the limit spring 3 are made of polytetrafluoroethylene.

[0022] The advantages of this invention compared to the prior art are:

[0023] (1) The present invention proposes a novel embedded MJ thread self-locking insert, which is a composite self-locking structure composed of a bearing sleeve, a limiter and a limit spring. After the connecting bolt is screwed into the bearing sleeve, the bolt can be locked by the three-point compression deformation of the self-locking area to achieve the anti-vibration function. Furthermore, the connection bolt can be judged by whether the limiter pushes out at least one of the limit spring surfaces.

[0024] (2) This invention proposes an insert installation indicator device that decouples the self-locking function from the load-bearing function. By designing the relationship between the length of the limiting post and the position of the self-locking zone of the load-bearing sleeve, the stress concentration point of the structure can be transmitted from the upper end face of the self-locking zone to the cross-section of the load-bearing sleeve where the lower end face of the limiting post is located. The device indicates the correct installation position by ejecting the limiting device, preventing the stress concentration point from deviating due to improper installation during use. This design can increase the load-bearing capacity of the insert under tension by 48%, as can be seen from the axial load comparison results in the comparative example and embodiment.

[0025] (3) This invention proposes a PTFE limiter and PTFE limiting snap ring for an MJ threaded self-locking insert, and their main dimensions and coupling relationship are described. This allows the limiter to achieve an ejection force of 30-50 N when the entire ejection surface of the limiter ejects the limiting snap ring, producing a crisp sound exceeding 60 dB. The main parameters affecting the ejection force and sound volume include: 1) the ejection surface angle, the outer angle of the snap ring, the inner angle of the snap ring, and their coupling relationship; 2) the diameter of the upper end face of the conical ejector, the outer diameter of the upper end face of the snap ring, the inner diameter of the upper end face of the snap ring, and their coupling relationship; and 3) the width of the deformation groove. The specific dimensions of this structure and its resulting effects are unprecedented before this patent was proposed, demonstrating its innovation. Attached Figure Description

[0026] Figure 1 This is an exploded view of the structure of the MJ threaded insert of the present invention;

[0027] Figure 2 This is a schematic diagram of the structural assembly of the MJ threaded insert of the present invention;

[0028] Figure 3 This is a schematic diagram of the load-bearing sleeve of the MJ threaded insert of the present invention;

[0029] Figure 4 This is a schematic cross-sectional view of the self-locking zone of the load-bearing sleeve of the MJ threaded insert of the present invention;

[0030] Figure 5This is a schematic diagram of the limiter for the MJ threaded insert of the present invention;

[0031] Figure 6 This is a schematic diagram of the limiting snap ring of the MJ threaded insert of the present invention;

[0032] Figure 7 This is a schematic diagram of the application and assembly of the MJ threaded insert of the present invention;

[0033] Figure 8 This is a comparative schematic diagram of the present invention. Detailed Implementation

[0034] To better understand the technical solution of the present invention, the specific embodiments of the present invention are described below.

[0035] like Figure 1 As shown, the MJ threaded self-locking insert designed in this invention includes a load-bearing sleeve 1, a limiter 2, and a limit spring 3. The load-bearing sleeve 1 is made of conventional metal material, while the limiter 2 and the limit spring 3 are made of PTFE (polytetrafluoroethylene).

[0036] like Figure 2 and Figure 3 As shown, the load-bearing sleeve 1 includes a load-bearing sleeve flange 11, a cylindrical section 12, a self-locking zone 13, and an internal thread 14. The structural features and main dimensional parameters of the load-bearing sleeve 1 are designed as follows:

[0037] Among them, the internal thread 14 is an MJ thread.

[0038] The self-locking zone 13 is formed by cutting the cylindrical section. After cutting out the circumferential surface, it is compressed inward at three evenly distributed points on the circumferential surface to form a three-point compression deformation, thereby achieving the self-locking function. The compression amount is preferably 0.3-0.5 mm, so that its shape is as follows: Figure 4 As shown.

[0039] Among them, the self-locking zone 13 is machined at a distance L3 from the lower end face of the cylindrical section 12, and the distance L3 is required to be 4±1p, where p is the pitch of the internal thread 14, and the same applies below.

[0040] The diameter of the self-locking region 13 is smaller than the diameter of the cylindrical section 12, and the difference between the diameter of the self-locking region 13 and the diameter of the internal thread 14 is D2-D1=1.5±0.5mm.

[0041] Among them, the length L2 of the preferred self-locking region 13 is ≥3mm.

[0042] Among them, the chamfer R on both sides of the self-locking area 13 is preferably ≥0.5mm.

[0043] like Figure 5As shown, the limiter 2 includes an ejector body 22 and a limiting post 23. The structural features and main dimensional parameters of the limiter 2 are designed as follows:

[0044] The ejector body 22 includes four identical ejector surfaces 21, with a half angle α1 of 11° ± 0.5° and a length L5 of the ejector body 22 satisfying L5 = 8p.

[0045] like Figure 6 As shown, the limiting snap ring 3 includes a snap ring flange 31, a snap ring plate 32, and a deformation groove 33. To ensure that the force of the limiter 2 pushing out the limiting snap ring 3 is controllable, the structural features and main dimensional parameters of the limiting snap ring 3 are designed as follows:

[0046] The deformation groove 33 divides the retaining spring 32 into four equal parts. Preferably, the width of the deformation groove is S = D4 / 8, where D4 is the inner diameter of the upper end face of the retaining spring 32.

[0047] The difference between the outer diameter D5 of the upper end face of the retaining spring 32 and the inner diameter D4 of the upper end face of the retaining spring 32 is D5-D4=0.6±0.1mm.

[0048] The difference between the half-angle α3 of the outer surface of the retaining ring 32 and the half-angle α2 of the inner surface of the retaining ring 32 is 2°≤α3-α2≤3°.

[0049] For the three components of the insert—load-bearing sleeve 1, limiter 2, and limit snap ring 3—the matching of the main dimensions between the components must meet the following design conditions:

[0050] To ensure that the axial load strength of the insert exceeds the bolt breaking force, the distance between the limiting post 23 of the limiter 2 and the upper end face of the self-locking area 13 of the bearing sleeve 1 is required to be L1-L4=5±1p.

[0051] To ensure that the ejector body 22 will not be inserted into the threaded hole of the bearing sleeve 1 during the installation of the limiter 2, and considering the influence of machining and assembly tolerances, the difference between the upper end face diameter D3 of the ejector body 22 and the nominal diameter D1 of the internal thread 14, D3-D1, is required to be ≥2p.

[0052] To ensure that there is no jamming during the process of the limiter 2 ejecting the limit circlip 3, the absolute value of the difference between the half-angle α1 of the ejection surface 21 of the limiter 2 and the half-angle α2 of the inner surface of the circlip 32 of the limiter 3, |α1-α2|, is required to be ≤0.5°.

[0053] To ensure that the limiting post 23 of the limiter 2 does not interfere with the threaded side of the bearing sleeve 1, and considering the influence of machining and assembly tolerances, the difference between the nominal diameter D1 of the internal thread 14 and the diameter D4 of the limiting post 23, D1-D4, is required to be ≥2p.

[0054] To ensure easy assembly, there needs to be a certain amount of free play between the limit circlip 3 and the limiter 2. The difference between the inner diameter D4 of the upper end face of the limit circlip 32 and the outer diameter D3 of the top end of the ejector body 22 of the limiter 2 is required to be D4-D3=0.2±0.05mm.

[0055] When assembling the insert, the limiting post 23 of the limiter 2 is placed into the hole on one side of the flange of the bearing sleeve 1. Then, the limiting snap ring 3 covers the ejector body 22 of the limiter 2, and the flange of the bearing sleeve 1 and the snap ring flange 31 are bonded together with the adhesive 4, which is epoxy resin. After curing for 8 hours, the insert assembly is completed.

[0056] Reference Figure 7 As shown, during the use of the insert, it is necessary to ensure that the axial load of the insert exceeds the tensile strength requirement of the bolt when matched with the connecting bolt 7 of the same strength grade. During the installation of the connecting bolt 7, the ejector body 22 of the limiter 2 is ejected from the retaining spring 32 by at least one ejector surface 21. The ejection force of the limiter 2 ejecting the limit retaining spring 3 is in the range of 30 to 50 N. After ejecting a complete ejector surface 21, a crisp sound of ≥60 dB is emitted, which indicates that the installation is in place.

[0057] During the screwing of the connecting bolt 7, if the screwing depth is insufficient, most of the stress will be diffused to the self-locking zone 13, which has weak load-bearing capacity. Therefore, this invention designs a limiter 2 to control the screwing depth. Only when the screwing depth reaches the point where the limit post 23 pushes out the retaining spring 3 is the installation considered complete. At this point, most of the thread stress will diffuse to the cylindrical section, and only a small portion of the stress will diffuse to the self-locking zone, thus improving the load-bearing capacity of the self-locking insert.

[0058] The following is a specific embodiment of the present invention:

[0059] The nominal diameter and pitch of the insert and connecting bolt 7 are MJ8×1, with a strength grade of 1100MPa, and they are matched with titanium alloy TC4 bolts of 1100MPa strength grade. The upper connector 5 has a composite material matrix, and the lower connector 6 has an aluminum alloy matrix.

[0060] The MJ threaded self-locking insert includes a load-bearing sleeve 1, a limiter 2, and a limit circlip 3. The load-bearing sleeve 1 is made of titanium alloy TC16, and the limiter 2 and the limit circlip 3 are made of PTFE.

[0061] The structural characteristics and main dimensional parameters of the load-bearing sleeve 1 are as follows:

[0062] The specification for the internal thread 14 is MJ8×1.

[0063] The diameter of the self-locking region 13 is smaller than the diameter of the cylindrical section 12, and the difference between the diameter of the self-locking region 13 and the diameter of the internal thread 14 is D2-D1 = 1.5mm.

[0064] Among them, the self-locking zone 13 is machined at a distance L3 from the lower end face of the cylindrical section 12, and the distance L3 = 5.

[0065] The length of the self-locking zone 13 is L2 = 5mm.

[0066] Among them, the chamfer R on both sides of the self-locking zone 13 is 0.6mm.

[0067] After the self-locking area 13 is cut and formed, it is extruded at three points evenly distributed around its circumference, with an extrusion amount of 0.45mm, to give it a shape like... Figure 4 As shown.

[0068] The structural features and main dimensional requirements of the limit switch 2 are as follows:

[0069] The ejector body 22 includes four identical ejector surfaces 21, with a half angle α1 of 11° and a length L5 of 8 for the ejector body 22.

[0070] The structural features and main dimensional requirements of the limiting snap ring 3 are as follows:

[0071] The deformation groove 33 divides the retaining spring 32 into four equal parts, and the width of the deformation groove S = 1 mm.

[0072] The difference between the outer diameter D5 of the upper end face of the retaining spring 32 and the inner diameter D4 of the upper end face of the retaining spring 32 is D5-D4=0.5mm.

[0073] The difference between the half-angle α3 of the outer surface of the retaining spring 32 and the half-angle α2 of the inner surface of the retaining spring 32 is α3-α2=2°, α2=11°.

[0074] For the three components of the insert—load-bearing sleeve 1, limiter 2, and limit spring 3—the main dimensions between the components are as follows:

[0075] The distance L1-L4 = 5mm between the limiting post 23 of the limiter 2 and the upper end face of the self-locking area 13 of the bearing sleeve 1.

[0076] The absolute value of the difference between the half-angle α1 of the top surface 21 of the limiter 2 and the half-angle α2 of the inner surface of the retaining spring 3 is |α1-α2|=0°.

[0077] The difference between the upper end face diameter D3 of the ejector body 22 and the nominal diameter D1 of the internal thread 14 is D3-D1≥2p.

[0078] The difference between the nominal diameter D1 of the internal thread 14 and the diameter D4 of the limiting post 23 is D1-D4=2.

[0079] The difference between the inner diameter D4 of the upper end face of the retaining spring 32 and the outer diameter D3 of the top end of the ejector body 22 of the limiter 2 is D4-D3=0.2mm.

[0080] During the assembly of the insert, the limiting post 23 of the limiter 2 is inserted into the hole on one side of the flange of the bearing sleeve 1. Then, the limiting snap ring 3 covers the ejector body 22 of the limiter 2, and the bearing sleeve 1 flange is bonded to the snap ring flange 31 with epoxy resin adhesive 4. After curing for 8 hours, the assembly of the insert is completed.

[0081] After assembly, the force of the limiter 2 of the test insert pushing out the limit spring 3 was 42.2N. After the push-out body 22 of the limiter 2 was pushed out, there was a crisp sound, and the measured volume was 62dB.

[0082] The self-locking insert is bonded to the composite matrix using adhesive 4. During bolt tightening, the bolt contacts the limiting post 23 and continues tightening until a crisp click is heard, indicating that the first ejector surface 21 of the ejector body 22 has passed the retaining spring 32. At this point, the bolt is properly installed. Figure 7 As shown.

[0083] The fasteners were tested for vibration according to GJB715.3 test method, and no structural damage, cracks, fractures, loosening of locking elements, thread damage or loss of locking performance were observed.

[0084] An axial load test was conducted on the insert using a tensile testing machine. The breaking force was 47.8 kN, and the fracture location was at the thread of the connecting bolt. Therefore, the axial load of this insert can ensure that when matched with bolts of the same strength grade, the axial load exceeds the breaking force of the bolt.

[0085] Therefore, the insert in this embodiment can meet the vibration environment adaptability requirements of aerospace equipment and the mechanical environment adaptability requirements. Moreover, due to its embedded installation method, the installation process is relatively simple.

[0086] The technical effects of the present invention will be verified below through a comparative example:

[0087] like Figure 8 As shown, other structural forms of MJ threaded self-locking inserts are used for connection applications, without limit rings and limiters, and are pre-embedded self-locking inserts.

[0088] The nominal diameter and pitch of the inserts and connecting bolts are MJ8×1, with a strength grade of 1100MPa, and they are matched with titanium alloy TC4 bolts of 1100MPa strength grade. The upper connector 5 has a composite material matrix, and the lower connector 6 has an aluminum alloy matrix.

[0089] The insert is formed together with the upper connector 5. The connector needs to be finely structurally designed and allowances should be made for errors in the forming process.

[0090] When using the bolts, since the limit switch has requirements on the screwing depth and the structure is a blind hole, the bolt length only needs to be screwed in beyond twice the length of the self-locking zone 13.

[0091] The fasteners were tested for vibration according to GJB715.3 test method, and no structural damage, cracks, fractures, loosening of locking elements, thread damage or loss of locking performance were observed.

[0092] A tensile testing machine was used to conduct an axial load test on the insert. The breaking force was 32.2 kN, and the fracture location was the upper end face of the self-locking zone 13. The breaking force was 67.4% of that in the previous example. In this comparative example, the insert was subjected to a tensile load, and the screw-in depth of the bolt was not limited. Since both the bolt and the insert were under tension, according to the stress characteristic analysis and simulation analysis results, the main stress range of the bolt was concentrated in the thread near the tail end. Since the thread is close to the self-locking zone 13, most of the stress diffused to the self-locking zone, resulting in the stress concentration location being the upper end face of the self-locking zone 13, which led to a reduction in the axial load-bearing capacity of the insert.

[0093] Therefore, the insert in this comparative example can meet the vibration environment adaptability requirements of aerospace equipment, but cannot meet the mechanical environment adaptability requirements, and its installation convenience is insufficient.

[0094] It is understood that this invention has been described through embodiments, and those skilled in the art will recognize that various changes or equivalent substitutions can be made to these features and embodiments without departing from the spirit and scope of this invention. Furthermore, under the teachings of this invention, these features and embodiments can be modified to adapt to specific circumstances without departing from the spirit and scope of this invention. Therefore, this invention is not limited to the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of this application are protected by this invention.

[0095] The contents not described in detail in this specification are common knowledge to those skilled in the art.

Claims

1. A MJ thread self-locking insert, comprising a force bearing sleeve (1), a position limiter (2) and a position limiting spring (3); the position limiter (2) is installed at one end of the force bearing sleeve (1), and the position limiting spring (3) covers the position limiter (2) and is fixed with the force bearing sleeve (1); characterized in that: the force bearing sleeve (1) is a cylindrical segment (12), the cylindrical segment (12) has an internal thread (14) in the form of MJ thread inside, for screwing in a connecting bolt (7); the cylindrical segment (12) has a self-locking area (13) around the cylindrical segment at the lower end, for locking the connecting bolt (7); the position limiter (2) is used for limiting the screwing depth of the connecting bolt (7), and comprises an ejection body (22) and a position limiting column (23); the ejection body (22) comprises at least two ejection surfaces (21); during the screwing in of the connecting bolt (7), the ejection body (22) is caused to eject at least one ejection surface (21) of the position limiting spring (3) by acting on the position limiting column (23), representing that the connecting bolt (7) is installed in place.

2. The MJ thread self-locking insert according to claim 1, characterized in that: the self-locking area (13) is cut and processed at a distance L3 upwards from the lower end face of the cylindrical segment (12), and the value range of L3 is 4mm-1p~4mm+1p, p being the pitch of the internal thread (14); the distance L1-L4 between the lower end face of the position limiting column (23) and the upper end face of the self-locking area (13) of the force bearing sleeve (1) has a value range of 5mm-1p~4mm+1p.

3. The MJ thread self-locking insert according to claim 1, characterized in that: the position limiting spring (3) comprises a spring connecting part and a hollow circular truncated cone body composed of a spring sheet (32) and a deformation groove (33) on the spring connecting part; the value range of the half angle a1 of the ejection surface (21) is 10.5~11.5°; the difference value of the half angle a3 of the outer face angle of the spring sheet (32) and the half angle a2 of the inner face angle of the spring sheet (32) has a value range of 2°≤a3-a2≤3°.

4. The MJ thread self-locking insert according to claim 3, characterized in that: the difference value D3-D1 of the upper end face diameter D3 of the ejection body (22) and the nominal diameter D1 of the internal thread (14) is D3-D1≥2p, p being the pitch of the internal thread (14); the difference value D5-D4 of the outer diameter D5 of the upper end face of the spring sheet (32) and the inner diameter D4 of the upper end face of the spring sheet (32) has a value range of 0.5~0.7mm; 5. The MJ thread self-locking insert according to claim 4, characterized in that: the deformation groove (33) equally divides the spring sheet (32) into four pieces, and the width S of the deformation groove (33) is S=D4 / 8, D4 being the inner diameter of the upper end face of the spring sheet (32); 6. The MJ Threaded Self-Locking Insert of claim 1, wherein: the self-locking area (13) forms three-point compression deformation amount in a three-point extrusion mode, to realize the self-locking function; the length L2 of the self-locking area (13) is L2≥3mm, and the chamfer R on both sides of the self-locking area (13) is R≥0.5mm; 7. The MJ Threaded Self-Locking Insert of claim 1, wherein: the difference value D2-D1 of the diameter D2 of the self-locking area (13) and the diameter D1 of the internal thread (14) has a value range of 1mm~2mm.

8. The MJ Threaded Self-Locking Insert of claim 1, wherein: All the ejection surfaces (21) are sequentially stacked in the shape of the same circular truncated cone structure.

9. The MJ Threaded Self-Locking Insert of claim 1, wherein: The length L5 of the ejector body (22) satisfies L5=8p, p being the pitch of the internal thread (14).

10. The MJ Threaded Self-Locking Insert of claim 1, wherein: The force bearing sleeve (1) is made of metal, and the limiting device (2) and the limiting clamp spring (3) are made of polytetrafluoroethylene.

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