A tool and method for removing a damaged allen head screw

Abstract

The application relates to the technical field of machining and equipment maintenance, in particular to a tool and method for taking out a damaged inner hexagonal screw, wherein the tool comprises a two-point pre-punch, a three-point transition punch and a six-point forming punch arranged in a hierarchical order of punching, the two-point pre-punch is used to form two symmetrical predetermined positioning initial biting points at the inner hexagonal hole wall, the three-point transition punch is used to expand the biting area and preliminarily form a hexagonal biting surface, and the six-point forming punch is used to form a complete hexagonal biting surface and correct the biting hole wall. The hierarchical punching process disperses the traditional one-time strong impact into gradually increasing small amplitude shaping impacts, can significantly reduce the single impact load, reduces the risk of screw head cracking and thread hole deformation, and meets the maintenance requirements of precision parts.

Description

Technical Field

[0001] This application relates to the fields of machining and equipment maintenance technology, and in particular to a tool and method for removing damaged internal hexagon screws. Background Technology

[0002] Hex socket screws (also known as internal hexagonal screws) are widely used in aerospace and precision machinery fields due to their uniform force distribution and good anti-loosening performance. However, during long-term service or repeated disassembly, the walls of the hexagonal socket of the screw are prone to wear, stripping, chipping, and other failure modes, making it impossible for a standard hex wrench to engage effectively and the screw difficult to remove properly.

[0003] Currently, in maintenance scenarios involving external factories or limited equipment conditions, the following two methods are mainly used for handling: One method is the electric drill removal method, which involves drilling away the entire screw head. This method carries an extremely high operational risk, as the drill bit is prone to deflection and slippage. A slight mishap can damage the component's substrate or residual threaded holes, rendering the expensive component unusable. This method is almost unacceptable, especially for thin-walled precision components made of aerospace-grade aluminum alloys or titanium alloys.

[0004] The second method is the direct wedging method using a solid punch, which involves using a shaped punch with the same or larger dimensions as the nominal size of the hexagonal screw and wedging it into the damaged hole wall with a single powerful impact. This method has significant drawbacks: the single impact load is concentrated and enormous, which can easily cause the screw head to break instantly or cause plastic deformation of the threaded hole; at the same time, for precision aerospace components, the powerful impact can cause irreversible stress damage or vibration damage, which is completely inconsistent with the requirements of non-destructive repair; in addition, if the wear of the hexagonal screw is uneven, the solid punch is prone to slippage, resulting in a very low success rate of removal.

[0005] Therefore, it is essential to design a screw removal tool and corresponding method that combines low impact load, high adaptability, and high success rate. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this application provides a tool and method for removing damaged internal hexagon screws, thereby solving the problems of large impact load, easy damage to workpieces, and low success rate of removal caused by integrated punches in existing technologies.

[0007] This application provides a tool for removing a damaged internal hexagonal screw, comprising a two-point pre-punch, a three-point transition punch, and a six-point forming punch arranged in a punching sequence, wherein: The head end face of the two-point pre-punch head is provided with two symmetrically distributed punch-shaped protrusions, which are used to form two symmetrical pre-positioning initial bite points at the inner hexagonal hole wall. The head end face of the three-point transition punch is provided with three punch-shaped protrusions evenly distributed in the circumferential direction, which are used to expand the biting area and initially form a hexagonal biting surface. The head end face of the six-point forming punch is a regular hexagonal prism structure adapted to the inner hexagonal hole wall, used to form a complete hexagonal engagement surface and correct the engagement hole wall. The heads of the two-point pre-punch, three-point transition punch, and six-point forming punch are all provided with a reverse cone angle.

[0008] Preferably, the inverted cone angle is located on the side of each punch protrusion of the two-point pre-punch, the three-point transition punch, and the six-point forming punch, and the angle range of the inverted cone angle is 1 degree to 3 degrees.

[0009] Preferably, the midpoint of the line connecting the two symmetrical punch protrusions of the two-point pre-punch, the distribution center of the three punch protrusions of the three-point transition punch, and the center of the regular hexagonal end face of the six-point forming punch are all located on the same axis.

[0010] Preferably, the tail of the two-point pre-punch, the three-point transition punch, and the six-point forming punch is provided with a standard grip handle. The standard grip handle can be a standard cylindrical handle or a prismatic handle commonly found in the market. The tail end of the standard grip handle can optionally be provided with a connector for adapting to a hammering tool or a screwing tool.

[0011] Preferably, the two-point pre-punch, three-point transition punch, and six-point forming punch are all made of high-alloy tool steel, and the head of each punch is quenched, with a head hardness of HRC55-62.

[0012] This application also provides a method for removal based on the removal tool described in any of the above claims, comprising: Step S1, pre-punch positioning: Align the two-point pre-punch head with the damaged internal hexagonal hole and tap it to wedge it into the hole wall, forming two symmetrically distributed initial bite points; Step S2, Transition shaping: Replace the two-point pre-punch with a three-point transition punch, and punch it into the internal hexagonal hole along the initial bite point to form six transition bite points for fitting. Step S3, forming and embedding: Replace the six-point forming punch and wed it into the hole wall along the transition bite point to form a complete regular hexagonal engagement surface; Step S4, unscrew and remove: Use a screw-screw tool in conjunction with the punch shank to apply a reverse rotational torque to the punch, opposite to the screw tightening direction, so as to remove the screw smoothly.

[0013] Preferably, in step S2, the specific formation process of the six transition bite points includes: Align any one of the punch protrusions of the three-point transition punch with any one of the initial bite points formed after step S1, and strike the three-point transition punch to wedge it into the hole wall to form a four-point engagement. Rotate the three-point transition punch 180° around its own axis so that the punch protrusion is aligned with another initial bite point. Then, strike the three-point transition punch again to wedge it into the hole wall, forming six evenly distributed transition bite points on the hole wall of the internal hexagonal hole, and initially forming a hexagonal engagement surface.

[0014] Preferably, the total wedge depth in the pre-punching positioning, transition shaping, and forming embedding stages is not less than two-thirds of the original internal hexagonal hole depth.

[0015] Preferably, the single impact load in the pre-punching positioning, transition shaping, and forming embedding stages is less than the impact load required for a single forming of the one-piece punch.

[0016] Preferably, the screwing and unscrewing step can be connected after the pre-punching positioning, transition shaping and molding embedding stages. If the screw can be screwed out normally after the current step is completed, the subsequent operation steps can be omitted.

[0017] The beneficial effects of this application are as follows: This application discloses a tool and method for removing damaged internal hexagon screws. Through a graded punching process, the traditional single strong impact is dispersed into gradually increasing small-amplitude shaping impacts, which can significantly reduce the single impact load and reduce the risk of screw head breakage and thread hole deformation, thereby meeting the maintenance requirements of precision parts.

[0018] Furthermore, this application abandons the crude "one-time forming" mode of the integral punch and adopts a progressive biting point establishment method from two points to four points, and then from four points to six points. This allows the hole wall material to gradually flow and shape in the preset direction under multiple, low-energy impacts. Finally, a complete regular hexagonal engagement surface is formed by the six-point forming punch, ensuring that the force at each point in the circumferential direction is completely uniform during twisting. This fundamentally eliminates the slippage phenomenon caused by local stress concentration. Actual verification has shown that it can indeed improve the success rate of extraction. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the specific embodiments of this application or the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0020] Figure 1A front projection schematic diagram of each punch of a tool for removing a damaged hexagon socket screw provided in an embodiment of this application; Figure 2 This is a side view of the overall structure of one type of punch in one embodiment of this application; Figure 3 This is a schematic diagram illustrating the process of forming six bite points during the transitional biting stage in an embodiment of this application; Figure 4 A flowchart of the extraction method provided in the embodiments of this application. Detailed Implementation

[0021] The technical solutions of this application will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0022] The following is combined with Figures 1-4 This application describes a tool and method for removing a damaged hexagonal socket screw, as provided in an embodiment of the present application.

[0023] Reference Figures 1 to 3 As shown, this application provides a tool for removing damaged hexagon socket screws, which mainly includes a two-point pre-punch, a three-point transition punch, and a six-point forming punch arranged in a step-by-step manner.

[0024] Specifically, the head end face of the two-point pre-punch head is provided with two symmetrically distributed punch-shaped protrusions. Its structure is simple and the contact area is small. When used as a punching tool in the initial stage, it can wedge into the damaged internal hexagonal hole wall with a small impact force, forming two symmetrical pre-positioning initial bite points, laying the positioning foundation for subsequent processes.

[0025] More specifically, such as Figure 1 As shown in section a, the head end face of the two-point pre-punch has two symmetrically distributed first and second punch protrusions. The two punch protrusions are centrally symmetrically arranged with respect to the center of the end face, and the midpoint of the line connecting them coincides with the center of the end face. When the two-point pre-punch is struck and wedged into the damaged internal hexagonal hole wall, the two punch protrusions first contact the protruding parts of the hole wall, forming two symmetrically distributed indented bite points on the hole wall surface. These two bite points provide a precise positioning reference for the subsequent punch and also perform preliminary shaping of the damaged hole wall, causing the originally smooth hole wall area or irregular hole wall deformation area to deform into a preset shape.

[0026] The head face of the three-point transition punch has three evenly distributed circumferential protrusions. After the two-point pre-punch completes the initial positioning, the three-point transition punch can be used to expand the engagement area. More specifically, such as... Figure 1 As shown in section b, the head end face of the three-point transition punch has three circumferentially evenly distributed third, fourth, and fifth punch protrusions. These three protrusions are evenly spaced 120° apart circumferentially along the end face, with their distribution center coinciding with the center of the end face. Their regular three-point protrusion shape further expands the engagement area based on two-point pre-positioning, and through two wedging operations, constructs six evenly distributed transition engagement points, providing guidance for the final forming punch insertion.

[0027] The head end face of the six-point forming punch is a standard regular hexagonal prism structure, the dimensions of which are adapted to the specifications of the internal hexagonal hole of the screw. More specifically, such as Figure 1 As shown in section c, the head end face of the six-point forming punch is a regular hexagon with the distance between opposite sides matching the original nominal size of the inner hexagon of the screw to be removed. After wedging it into the hole wall after the first two shaping steps, a complete regular hexagonal engagement surface can be formed, so that the punch and the screw head can achieve uniform force in the whole circumference, providing a more reliable torque transmission interface for subsequent screwing and removal.

[0028] Furthermore, referring to Figure 1 As shown in section d, the two-point pre-punch, the three-point transition punch, and the six-point forming punch all have a standard grip shank 10 at their tails. This standard grip shank 10 can be a common standard cylindrical or prismatic shank. Optionally, a connector 20 for adapting to different striking or turning tools can be provided at the tail end of the standard grip shank 10 to improve the versatility of the tools.

[0029] Furthermore, to ensure the accuracy of the punching process, the midpoint of the line connecting the two symmetrical punching protrusions of the two-point pre-punch, the distribution center of the three punching protrusions of the three-point transition punch, and the center of the regular hexagonal end face of the six-point forming punch are all located on the same axis. This ensures that the three punching operations can be performed around the same reference axis, avoiding uneven stress on the hole wall or secondary damage caused by axis offset.

[0030] Preferably, the two-point pre-punch, three-point transition punch, and six-point forming punch are all made of high-alloy tool steel, such as Cr12MoV or SKD11, and the heads of each punch are quenched, with a head hardness of HRC55-62, to ensure that the punch protrusion can successfully cut into common screw materials on the market and have sufficient wear resistance and service life under repeated impact conditions.

[0031] In this embodiment, as Figure 2As shown, the heads of the three types of punches mentioned above are all provided with a reverse cone angle α. Specifically, the reverse cone angle is set on the side of each punch protrusion, presenting a shape that is wider at the front and narrower at the back. Specifically, it is a tapered structure that gradually narrows from the edge of the punch head end face towards the root, and the angle range is preferably 1 degree to 3 degrees. The design of the reverse cone angle provides a rear foot surface for each punch protrusion surface used for punching, making its punching surface sharper, so as to facilitate its wedging and forming. The rear end gradually tightens, which reduces the initial wedging resistance and ensures the final tightness of the engagement.

[0032] In some specific embodiments, such as Figure 4 As shown, based on the above tools, this embodiment provides a specific removal method, which is particularly suitable for disassembling screws in high-hardness, high-precision aerospace equipment. The following describes the method in conjunction with... Figure 3 The schematic diagram shown illustrates in detail the method for removing a damaged hexagonal socket screw provided in this application embodiment. The specific operation steps are as follows: Step S1: Pre-charge positioning like Figure 3 As shown in section e, the operator first selects a suitable two-point pre-punch head according to the nominal size of the screw to be removed. The head of the two-point pre-punch head is aligned with the damaged hexagonal hole, ensuring the line connecting the first and second punch protrusions roughly follows the diagonal of the hexagonal hole. Then, the tail of the two-point pre-punch head is gently tapped with a tapping tool, causing its head to wedge into the hole wall. During this process, the two symmetrically distributed punch protrusions form two symmetrical initial bite points at corresponding positions on the hole wall, completing the initial positioning and hole wall shaping. To ensure the reliability of subsequent operations, the wedging depth in step S1 should be no less than two-thirds of the original hexagonal hole depth to ensure the initial bite points have sufficient depth and strength.

[0033] Step S2: Transitional Shaping Replace the two-point pre-punch with a three-point transition punch; firstly, as... Figure 3 As shown in section f, any one of the punch protrusions of the three-point transition punch is aligned with any one of the initial bite points formed after step S1, and then the three-point transition punch is struck to wedge into the hole wall. At this time, the punch protrusion is wedged into the corresponding initial bite point, while the other two punch protrusions form two new bite points at other positions on the hole wall, which together with the previously misaligned initial bite point form a four-point engagement state.

[0034] Subsequently, as Figure 3As shown in section g, the three-point transition punch is rotated 180° around its own axis so that the punch protrusion used for positioning is aligned with another initial bite point. Then, the three-point transition punch is struck again to wedge into the hole wall. At this time, the three rotated punch protrusions are wedged into different hole wall positions than when they were first wedged in. Together with the four bite points already formed, six evenly distributed transition bite points are formed at the hole wall, and a hexagonal engagement surface is initially formed.

[0035] It is worth noting that, since the three punch protrusions of the three-point transition punch are evenly distributed at 120° intervals along the circumference, when the punch is rotated 180°, the three punch protrusions are exactly aligned with the positions of the three punch protrusions during the first wedge insertion. Finally, the six biting points are evenly distributed at the six corners of the inner hexagonal hole, laying the foundation for the construction of the regular hexagon.

[0036] Step S3: Molding and embedding Replace the six-point forming punch with a wedge inserted into the hole wall along the transition bite point formed in step S2. Since the hole wall has been sufficiently pre-shaped in the previous two steps, the hexagonal prism structure of the six-point forming punch can wedge in smoothly, forming a complete hexagonal engagement surface within the hole wall. At this point, uniform force is applied circumferentially between the punch and the screw head, creating conditions for unscrewing and removal.

[0037] The wedging depth in this step should also be no less than two-thirds of the original internal hexagonal hole depth to ensure that the engagement surface has sufficient axial length to transmit torque.

[0038] Step S4: Twist and remove By using a screwdriver with the standard handle 10 of the punch, a reverse rotational torque is applied to the punch in the opposite direction to the screw tightening. Since a complete hexagonal engagement surface has been formed between the punch and the screw head at this time, the torque can be evenly transmitted to the circumference of the screw head, thereby achieving smooth removal of the screw.

[0039] In practice, if the screw can be unscrewed normally after step S1, the subsequent steps can be omitted and the screw can be unscrewed directly. Similarly, if the screw can be unscrewed normally after step S2, step S3 can be omitted and the screw can be unscrewed directly, instead of having to complete all three steps before unscrewing.

[0040] Furthermore, in this embodiment, preferably, the single impact load in each stage of pre-punching positioning, transition shaping, and forming embedding is less than the impact load required for a single forming of an integrated punch. Actual tests have verified that when the graded punching method of the present invention is adopted, the single impact load of each step is about 1 / 3 to 1 / 4 of the single impact load of an integrated punch, which can effectively wedge into the forming and effectively reduce the impact of instantaneous impact on the screw head and surrounding parts.

[0041] In the description of this application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc., indicating the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application.

[0042] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0043] In this application, unless otherwise expressly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection, an electrical connection, or a connection that allows communication between components; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise expressly limited. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0044] In this application, the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0045] Although embodiments of this application have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting this application. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of this application.

Claims

1. A tool for extracting a damaged Allen head screw, characterized by, This includes two-point pre-punch, three-point transition punch, and six-point forming punch, arranged in stages according to the punching sequence, wherein: The head end face of the two-point pre-punch head is provided with two symmetrically distributed punch protrusions, which are used to form two symmetrical pre-positioning initial bite points at the inner hexagonal hole wall. The head end face of the three-point transition punch is provided with three punch-shaped protrusions evenly distributed in the circumferential direction, which are used to expand the biting area and initially form a hexagonal biting surface. The head end face of the six-point forming punch is a regular hexagonal prism structure adapted to the inner hexagonal hole wall, used to form a complete hexagonal engagement surface and correct the engagement hole wall. The heads of the two-point pre-punch, three-point transition punch, and six-point forming punch are all provided with a reverse cone angle.

2. The tool for removing a damaged Allen screw according to claim 1, wherein The inverted cone angle is set on the side of each punch protrusion of the two-point pre-punch, the three-point transition punch and the six-point forming punch, and the angle range of the inverted cone angle is 1 degree to 3 degrees.

3. The tool for removing a damaged Allen screw according to claim 1, wherein The midpoint of the line connecting the two symmetrical punch protrusions of the two-point pre-punch, the distribution center of the three punch protrusions of the three-point transition punch, and the center of the regular hexagonal end face of the six-point forming punch are all located on the same axis.

4. The tool for removing a damaged Allen screw according to claim 1, wherein The two-point pre-punch, three-point transition punch, and six-point forming punch are all equipped with a standard grip handle at their tails. The tail end of the standard grip handle may optionally be equipped with a connector for adapting to a hammering tool or a screwing tool.

5. The tool for removing a damaged hexagon socket screw according to claim 1, characterized in that, The two-point pre-punch, three-point transition punch, and six-point forming punch are all made of high-alloy tool steel, and the heads of each punch are quenched, with a head hardness of HRC55-62.

6. A method for removing a damaged hexagonal socket screw based on the tool for removing a damaged hexagonal socket screw according to any one of claims 1-5, characterized in that, include: Step S1, pre-punch positioning: Align the two-point pre-punch head with the damaged internal hexagonal hole and tap it to wedge it into the hole wall, forming two symmetrically distributed initial bite points; Step S2, Transition shaping: Replace the two-point pre-punch with a three-point transition punch, and punch it into the internal hexagonal hole along the initial bite point to form six transition bite points for fitting. Step S3, forming and embedding: Replace the six-point forming punch and wed it into the hole wall along the transition bite point to form a complete regular hexagonal engagement surface; Step S4, unscrew and remove: Use a screw-screw tool in conjunction with the punch shank to apply a reverse rotational torque to the punch, opposite to the screw tightening direction, so as to remove the screw smoothly.

7. The extraction method according to claim 6, characterized in that, In step S2, the specific formation process of the six transition bite points includes: Align any one of the punch protrusions of the three-point transition punch with any one of the initial bite points formed after step S1, and strike the three-point transition punch to wedge it into the hole wall to form a four-point engagement. Rotate the three-point transition punch 180° around its own axis so that the punch protrusion is aligned with another initial bite point. Then, strike the three-point transition punch again to wedge it into the hole wall, forming six evenly distributed transition bite points on the hole wall of the internal hexagonal hole, and initially forming a hexagonal engagement surface.

8. The extraction method according to claim 6, characterized in that, The total wedge depth in the pre-punching positioning, transition shaping, and forming embedding stages is not less than two-thirds of the original internal hexagonal hole depth.

9. The extraction method according to claim 8, characterized in that, The single impact loads during the pre-punching positioning, transition shaping, and forming embedding stages are all less than the impact load required for a single forming of an integrated punch.

10. The extraction method according to claim 6, characterized in that, The pre-punching positioning, transition shaping, and molding embedding stages can all be followed by the screwing and removing step.

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