Method for designing structure of MJ internal thread depth detection gauge

Abstract

The application discloses a structure design method of an MJ internal thread depth detection gauge, and comprises the following steps: S1, according to the observation difficulty of the detection result of the orifice structure of the MJ internal thread, the design of the thread structure and the design of the depth size, the structure form of the depth detection gauge is selected, and then the working part structure of the depth detection gauge is designed; S2, according to the size tolerance band of the design depth size of the MJ internal thread, the working size of the working part on the depth detection gauge and the wear limit are respectively calculated and obtained; S3, according to the definition of the design depth size of the MJ internal thread, the thread front end of the depth detection gauge is designed, so that the thread front end of the depth detection gauge can contact the last tooth top profile of the MJ internal thread during detection; and S4, according to the thread tolerance band of the connecting bolt and the thread tolerance band of the MJ internal thread, the thread tolerance band of the depth detection gauge is designed, so that the thread tolerance band of the depth detection gauge does not occupy the thread tolerance band of the MJ internal thread.

Description

Technical Field

[0001] This invention relates to the field of internal thread inspection technology, and in particular, to a structural design method for an MJ internal thread depth inspection gauge. Background Technology

[0002] MJ internal threads are a type of thread with high fatigue strength and are widely used in aerospace parts. In order to meet the requirements of bolt assembly, the depth dimension of MJ internal threads is a key dimension that needs to be precisely controlled on aerospace parts. After the MJ internal threads on aerospace parts are machined, a special depth inspection gauge is usually used to check whether the depth dimension of the MJ internal threads is qualified.

[0003] Existing MJ internal thread depth measurement gauges typically use a go end thread plug gauge in conjunction with calipers to indirectly measure the depth dimension. First, the length of the go end thread plug gauge is measured and recorded with calipers. Then, the go end thread plug gauge is screwed into the MJ internal thread hole on the aerospace part. Next, the length of the exposed part of the go end thread plug gauge is measured and recorded with calipers. The two length dimensions are subtracted to obtain the depth dimension of the MJ internal thread, thereby determining whether the depth dimension of the MJ internal thread meets the design requirements. However, this method of inspection has low measurement accuracy and low accuracy of the inspection results. Moreover, the measurement process is relatively cumbersome, resulting in low inspection efficiency during the mass production and processing of aerospace parts, and it no longer meets the current inspection needs. Summary of the Invention

[0004] This invention provides a structural design method for an MJ internal thread depth detection gauge to solve the technical problems of low accuracy and low detection efficiency of existing MJ internal thread depth detection gauges.

[0005] According to one aspect of the present invention, a structural design method for an MJ internal thread depth inspection gauge is provided for inspecting whether the depth dimension of an MJ internal thread on an aerospace part is qualified. The structural design method includes the following steps: S1, selecting the structural form of the depth inspection gauge based on the inspection results of the orifice structure of the MJ internal thread, the design thread structure, and the design depth dimension, thereby designing the working part structure of the depth inspection gauge; S2, calculating the working dimension and wear limit of the working part on the depth inspection gauge based on the dimensional tolerance zone of the design depth dimension of the MJ internal thread. To ensure that the working dimension tolerance zone and wear limit tolerance zone of the working part on the depth inspection gauge are distributed within the dimensional tolerance zone of the design depth dimension of the MJ internal thread; S3, according to the definition of the design depth dimension of the MJ internal thread, design the thread tip of the depth inspection gauge to ensure that the thread tip of the depth inspection gauge can contact the last tooth crest surface of the MJ internal thread during inspection; S4, according to the thread tolerance zone of the connecting bolt and the thread tolerance zone of the MJ internal thread, design the thread tolerance zone of the depth inspection gauge to ensure that the thread tolerance zone of the depth inspection gauge does not occupy the thread tolerance zone of the MJ internal thread.

[0006] As a further improvement to the above technical solution: Step S1 specifically includes: when the difficulty of observing the inspection results of the hole structure of the MJ internal thread is small, select a single-head dual-size depth inspection gauge; when the difficulty of observing the inspection results of the hole structure of the MJ internal thread is large, select a double-head dual-size depth inspection gauge or a combined stepped depth inspection gauge; when the designed thread structure of the MJ internal thread is ≥6mm and the designed depth dimension is ≥8P, shorten the threaded part on the working part of the depth inspection gauge to make a cylindrical part, where P is the pitch of the MJ internal thread.

[0007] Furthermore, in step S2, the calculation formula for the working dimension and wear limit of the working part of the single-head dual-size depth measuring gauge is: L (d) =(L max -0.05T)±0.03T, L (x) =(L min +0.05T)±0.03T, L (ds) =(L max -0.05T)-0.05T, L (xs) =(L min +0.05T) -0.05T, where L (d) L represents the larger end value of the working dimension of the working part of a single-head dual-size depth measuring gauge. max L represents the maximum limit dimension of the design depth of the MJ internal thread, T represents the design depth tolerance of the MJ internal thread, and L represents the maximum limit dimension of the design depth. (x) L represents the smaller end value of the working dimension of the working part on a single-head, dual-size depth measuring gauge.min L is the minimum limit dimension for the design depth of the MJ internal thread. (ds) For the wear limit of the large end value of the working dimension of the working part of the single-head dual-size depth measuring gauge, L (xs) The wear limit of the smaller end of the working dimension of the working part of the single-head dual-size depth measuring gauge.

[0008] Furthermore, in step S2, the calculation formula for the working dimension and wear limit of the working part of the dual-head, dual-size depth measuring gauge is: L (d) =(L max -0.05T)±0.03T, L (x) =(L min +0.05T)±0.03T, L (ds) =(L max -0.05T)±0.05T, L (xs) =(L min +0.05T)±0.05T, where, L (d) L represents the larger end value of the working dimension of the working part of the dual-head, dual-size depth measuring gauge. max L represents the maximum limit dimension of the design depth of the MJ internal thread, T represents the design depth tolerance of the MJ internal thread, and L represents the maximum limit dimension of the design depth. (x) L represents the smaller end value of the working dimension of the working part of the dual-head, dual-size depth measuring gauge. min L is the minimum limit dimension for the design depth of the MJ internal thread. (ds) For the wear limit of the large end value of the working dimension of the working part of the dual-head, dual-size depth measuring gauge, L (xs) The wear limit of the smaller end of the working dimension of the working part of the dual-head, dual-size depth measuring gauge.

[0009] Furthermore, in step S2, the calculation formulas for the working dimensions and wear limits of the working parts on the combined stepped depth measuring gauge are: A = 0.85T ± 0.03T, B = L min +0.1T, A (s) =0.85T±0.05T, where A is the step dimension of the combined stepped depth gauge, T is the design depth tolerance of the MJ internal thread, B is the distance between the measuring end face of the measuring column of the combined stepped depth gauge and the reference surface of the body, and L min A represents the minimum limit dimension for the design depth of the MJ internal thread. (s) This refers to the maximum distance symmetrically distributed at the top of the gauge post relative to the center plane of the step after wear of the combined stepped depth gauge.

[0010] Furthermore, after step S4, the following step is also included: when the design depth dimension of the MJ internal thread is ≥8P, and the structure of the depth detection gauge is a combined stepped type, a handle is set on the measuring column of the combined stepped depth detection gauge.

[0011] Furthermore, the design of the thread front end of the depth inspection gauge in step S3 specifically includes the following steps: cutting off the incomplete thread at the thread front end of the depth inspection gauge, and making the distance between the first tooth crest of the cut complete thread and the chamfered front end face P / 2, with a tolerance range of ±0.05, where P is the pitch of the MJ internal thread.

[0012] Furthermore, the design of the thread tolerance zone of the depth inspection gauge in step S4 specifically includes the following steps: simulating the assembly state of the connecting bolt, so that the major diameter, pitch diameter and minor diameter of the thread part of the depth inspection gauge occupy the lower deviation of the thread tolerance zone of the MJ internal thread, and at the same time occupy the upper deviation of the thread tolerance zone of the connecting bolt.

[0013] Furthermore, after step S4, there is also step S5, which involves selecting whether to set a chip removal groove on the threaded portion of the depth measurement gauge based on the pitch of the MJ internal thread.

[0014] Furthermore, step S5 also includes the step of: when the threaded portion of the depth measuring gauge is provided with a chip removal groove, the bottom arc radius of the chip removal groove is selected according to the pitch of the MJ internal thread and the nominal diameter of the threaded portion of the depth measuring gauge.

[0015] The present invention has the following beneficial effects: The structural design method of the MJ internal thread depth measuring gauge of the present invention firstly selects the structural form of the depth measuring gauge based on the difficulty of observing the inspection results of the orifice structure of the MJ internal thread, the design of the thread structure, and the design depth dimension, to ensure that the inspection results of the depth measuring gauge can be observed intuitively and clearly, thereby designing the working part structure of the depth measuring gauge; then, based on the dimensional tolerance zone of the design depth dimension of the MJ internal thread, the working dimension and wear limit of the working part on the depth measuring gauge are calculated to ensure that the working dimension tolerance zone and wear limit tolerance zone of the working part on the depth measuring gauge are distributed within the dimensional tolerance zone of the design depth dimension of the MJ internal thread, thereby ensuring the inspection accuracy of the depth measuring gauge; and finally, based on the definition of the design depth dimension of the MJ internal thread, the thread tip of the depth measuring gauge is designed to ensure that the thread tip of the depth measuring gauge is in good working order during inspection. This method allows contact with the last crest of the MJ internal thread, further improving inspection accuracy. Finally, based on the thread tolerance zones of the connecting bolt and the MJ internal thread, the thread tolerance zone of the depth inspection gauge is designed to ensure that it does not encroach on the MJ internal thread's tolerance zone, thus ensuring reliable inspection results. During inspection, the depth inspection gauge is screwed into the MJ internal thread to determine if its depth dimension is acceptable. This solution designs the structure of the depth inspection gauge based on the various design parameters of the MJ internal thread and the thread tolerance zone of the connecting bolt. The depth dimension of the MJ internal thread is then inspected using the depth inspection gauge. Compared to existing technologies, this method is simple, rapid, efficient, and accurate, suitable for inspecting the depth dimension of MJ internal threads on a large batch of aerospace parts. It is highly practical and suitable for widespread promotion and application.

[0016] In addition to the objectives, features, and advantages described above, the present invention has other objectives, features, and advantages. The invention will now be described in further detail with reference to the figures. Attached Figure Description

[0017] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings: Figure 1 This is a flowchart of the structural design method for the MJ internal thread depth detection gauge according to a preferred embodiment of the present invention; Figure 2 This is a schematic diagram of the structure of the single-head dual-size depth measuring gauge in the structural design method of the MJ internal thread depth measuring gauge of the preferred embodiment of the present invention; Figure 3 This is a schematic diagram of the structure of the single-head dual-size depth measuring gauge in the structural design method of the MJ internal thread depth measuring gauge of the preferred embodiment of the present invention; Figure 4This is a schematic diagram of the structure of the double-headed, double-size depth measuring gauge in the structural design method of the MJ internal thread depth measuring gauge of the preferred embodiment of the present invention; Figure 5 This is a schematic diagram of the structure of the double-headed, double-size depth measuring gauge in the structural design method of the MJ internal thread depth measuring gauge of the preferred embodiment of the present invention; Figure 6 This is a schematic diagram of the structure of the combined stepped depth detection gauge in the structural design method of the MJ internal thread depth detection gauge of the preferred embodiment of the present invention; Figure 7 This is a schematic diagram of the structure of the combined stepped depth measuring gauge in the structural design method of the MJ internal thread depth measuring gauge of the preferred embodiment of the present invention. Detailed Implementation

[0018] The embodiments of the present invention will be described in detail below with reference to the accompanying drawings. However, the present invention can be implemented in many different ways as defined and covered below.

[0019] Figure 1 This is a flowchart of the structural design method for the MJ internal thread depth detection gauge according to a preferred embodiment of the present invention; Figure 2 This is a schematic diagram of the structure of the single-head dual-size depth measuring gauge in the structural design method of the MJ internal thread depth measuring gauge of the preferred embodiment of the present invention; Figure 3 This is a schematic diagram of the structure of the single-head dual-size depth measuring gauge in the structural design method of the MJ internal thread depth measuring gauge of the preferred embodiment of the present invention; Figure 4 This is a schematic diagram of the structure of the double-headed, double-size depth measuring gauge in the structural design method of the MJ internal thread depth measuring gauge of the preferred embodiment of the present invention; Figure 5 This is a schematic diagram of the structure of the double-headed, double-size depth measuring gauge in the structural design method of the MJ internal thread depth measuring gauge of the preferred embodiment of the present invention; Figure 6 This is a schematic diagram of the structure of the combined stepped depth detection gauge in the structural design method of the MJ internal thread depth detection gauge of the preferred embodiment of the present invention; Figure 7 This is a schematic diagram of the structure of the combined stepped depth detection gauge in the structural design method of the MJ internal thread depth detection gauge of the preferred embodiment of the present invention.

[0020] like Figure 1As shown, the structural design method of the MJ internal thread depth inspection gauge in this embodiment is used to inspect whether the depth dimension of the MJ internal thread on aerospace parts is qualified. The structural design method includes the following steps: S1, based on the inspection results of the hole structure of the MJ internal thread, the difficulty of observation, the design of the thread structure, and the design depth dimension, the structural form of the depth inspection gauge is selected, thereby designing the working part structure of the depth inspection gauge; S2, based on the dimensional tolerance zone of the design depth dimension of the MJ internal thread, the working dimension and wear limit of the working part on the depth inspection gauge are calculated to ensure... The working dimension tolerance zone and wear limit tolerance zone of the working part on the depth inspection gauge are distributed within the dimensional tolerance zone of the design depth dimension of the MJ internal thread; S3, according to the definition of the design depth dimension of the MJ internal thread, design the thread tip of the depth inspection gauge to ensure that the thread tip of the depth inspection gauge can contact the last tooth crest surface of the MJ internal thread during inspection; S4, according to the thread tolerance zone of the connecting bolt and the thread tolerance zone of the MJ internal thread, design the thread tolerance zone of the depth inspection gauge to ensure that the thread tolerance zone of the depth inspection gauge does not occupy the thread tolerance zone of the MJ internal thread.Specifically, the structural design method of the MJ internal thread depth measuring gauge of the present invention first selects the structural form of the depth measuring gauge based on the difficulty of observing the inspection results of the orifice structure of the MJ internal thread, the design of the thread structure, and the design depth dimension, to ensure that the inspection results of the depth measuring gauge can be observed intuitively and clearly, thereby designing the working part structure of the depth measuring gauge; then, based on the dimensional tolerance zone of the design depth dimension of the MJ internal thread, the working dimension and wear limit of the working part on the depth measuring gauge are calculated to ensure that the working dimension tolerance zone and wear limit tolerance zone of the working part on the depth measuring gauge are distributed within the dimensional tolerance zone of the design depth dimension of the MJ internal thread, thereby ensuring the inspection accuracy of the depth measuring gauge; according to the definition of the design depth dimension of the MJ internal thread, the thread tip of the depth measuring gauge is designed to ensure that the thread tip of the depth measuring gauge can contact the last tooth crest surface of the MJ internal thread during inspection, and then... To further improve inspection accuracy, the thread tolerance zone of the depth inspection gauge is designed based on the thread tolerance zones of the connecting bolt and the MJ internal thread. This ensures that the thread tolerance zone of the depth inspection gauge does not encroach on the thread tolerance zone of the MJ internal thread. The thread tolerance zone of the depth inspection gauge is designed to meet the assembly requirements of the MJ internal thread hole on aerospace parts, ensuring reliable inspection results. During inspection, the depth inspection gauge is screwed into the MJ internal thread to determine whether the depth dimension of the MJ internal thread is qualified. This solution designs the structure of the depth inspection gauge based on the various design parameters of the MJ internal thread and the thread tolerance zone of the connecting bolt. The depth dimension of the MJ internal thread is then inspected using the depth inspection gauge. Compared to existing technologies, the inspection process is simple and rapid, with high efficiency and high accuracy. It is suitable for the depth dimension inspection of MJ internal threads on a large batch of aerospace parts, has strong practicality, and is suitable for widespread promotion and application. It should be understood that the connecting bolt is the bolt used to connect the MJ internal thread hole on aerospace parts.

[0021] like Figures 2-7As shown, in this embodiment, step S1 specifically includes: when the difficulty of observing the test results of the hole structure of the MJ internal thread is small, a single-head dual-size depth measuring gauge is selected; when the difficulty of observing the test results of the hole structure of the MJ internal thread is large, a double-head dual-size depth measuring gauge or a combined stepped depth measuring gauge is selected; when the designed thread structure of the MJ internal thread is ≥6mm and the designed depth dimension is ≥8P, the threaded part on the working part of the depth measuring gauge is shortened to make a cylindrical part, where P is the pitch of the MJ internal thread. Specifically, single-head, dual-size depth gauges lack observation steps and have a relatively simple structure. Therefore, they are suitable for MJ internal threads where the hole structure is easy to observe, allowing for quick judgment of the test results while simplifying the gauge's structure and reducing manufacturing costs. Double-head, dual-size depth gauges or combined-step depth gauges have observation steps, allowing for quick judgment of the test structure by observing whether the steps are in contact with the surface. However, their structure is relatively complex, making them suitable for MJ internal threads where the hole structure is difficult to observe. When the designed thread structure of the MJ internal thread is ≥6mm and the designed depth dimension is ≥8P, the threaded portion of the working part of the depth gauge is shortened to a cylindrical part. This allows for quick judgment of the test results while ensuring accuracy, simplifying the gauge's structure and reducing manufacturing costs. It should be understood that when the hole structure of the MJ internal thread is a large-size chamfer or countersunk hole, the observation of the test results is difficult.

[0022] like Figure 2-3 As shown, in this embodiment, in step S2, the calculation formula for the working dimension and wear limit of the working part of the single-head dual-size depth measuring gauge is: L (d) =(L max -0.05T)±0.03T, L (x) =(L min +0.05T)±0.03T, L (ds) =(L max -0.05T)-0.05T, L (xs) =(L min +0.05T) -0.05T, where L (d) L represents the larger end value of the working dimension of the working part of a single-head dual-size depth measuring gauge. max L represents the maximum limit dimension of the design depth of the MJ internal thread, T represents the design depth tolerance of the MJ internal thread, and L represents the maximum limit dimension of the design depth. (x) L represents the smaller end value of the working dimension of the working part on a single-head, dual-size depth measuring gauge. min L is the minimum limit dimension for the design depth of the MJ internal thread. (ds) For the wear limit of the large end value of the working dimension of the working part of the single-head dual-size depth measuring gauge, L (xs)This refers to the wear limit of the small end of the working dimension of the working part on a single-headed, dual-size depth measuring gauge. Specifically, when the MJ internal thread depth measuring gauge is a single-headed, dual-size depth measuring gauge used for measuring MJ internal threads on aerospace parts, the working part of the single-headed, dual-size depth measuring gauge is screwed into the MJ internal thread hole on the aerospace part. When the depth of the MJ internal thread hole is between the small end value and the large end value of the working dimension of the working part on the single-headed, dual-size depth measuring gauge, the depth dimension of the MJ internal thread is considered qualified; otherwise, it is unqualified. The testing process is simple and quick, with high accuracy and efficiency.

[0023] like Figure 4-5 As shown, in this embodiment, in step S2, the calculation formula for the working dimension and wear limit of the working part of the dual-head dual-size depth measuring gauge is: L (d) =(L max -0.05T)±0.03T, L (x) =(L min +0.05T)±0.03T, L (ds) =(L max -0.05T)±0.05T, L (xs) =(L min +0.05T)±0.05T, where, L (d) L represents the larger end value of the working dimension of the working part of the dual-head, dual-size depth measuring gauge. max L represents the maximum limit dimension of the design depth of the MJ internal thread, T represents the design depth tolerance of the MJ internal thread, and L represents the maximum limit dimension of the design depth. (x) L represents the smaller end value of the working dimension of the working part of the dual-head, dual-size depth measuring gauge. min L is the minimum limit dimension for the design depth of the MJ internal thread. (ds) For the wear limit of the large end value of the working dimension of the working part of the dual-head, dual-size depth measuring gauge, L (xs) This refers to the wear limit of the small end of the working dimension of the working part on the double-headed, double-size depth measuring gauge. Specifically, when the MJ internal thread depth measuring gauge is a double-headed, double-size depth measuring gauge used for measuring the MJ internal threads on aerospace parts, the small end working part and the large end working part of the double-headed, double-size depth measuring gauge are screwed into the MJ internal thread hole in sequence. When the reference surface of the small end of the double-headed, double-size depth measuring gauge contacts the depth end face of the aerospace part, and there is a gap between the reference surface of the large end and the depth end face of the aerospace part, the depth dimension of the MJ internal thread is judged to be qualified. The testing process is simple and quick to operate, with high testing accuracy and high testing efficiency.

[0024] like Figure 6-7As shown, in this embodiment, in step S2, the calculation formulas for the working dimensions and wear limits of the working parts on the combined stepped depth measuring gauge are: A = 0.85T ± 0.03T, B = L min +0.1T, A (s) =0.85T±0.05T, where A is the step dimension of the combined stepped depth gauge, T is the design depth tolerance of the MJ internal thread, B is the distance between the measuring end face of the measuring column of the combined stepped depth gauge and the reference surface of the body, and L min A represents the minimum limit dimension for the design depth of the MJ internal thread. (s) This refers to the maximum distance symmetrically distributed at the upper end of the measuring column relative to the center plane of the step after wear of the combined stepped depth measuring gauge. Specifically, when the MJ internal thread depth measuring gauge is a combined stepped depth measuring gauge used for measuring the MJ internal threads on aerospace parts, the working part of the combined stepped measuring gauge is screwed into the MJ internal thread hole. When the observation surface of the measuring column of the combined stepped gauge is between the step surfaces of the main body, the depth dimension of the MJ internal thread is determined to be qualified. The testing process is simple and quick, with high accuracy and efficiency.

[0025] like Figure 7 As shown, in this embodiment, after step S4, the following step is also included: when the design depth dimension of the MJ internal thread is ≥8P, and the structure of the depth measuring gauge is a combined stepped type, a handle is provided on the measuring column of the combined stepped depth measuring gauge. Specifically, the handle facilitates the inspection personnel to apply force to screw the combined stepped depth measuring gauge into or out of the MJ internal thread hole during inspection, thereby improving inspection efficiency.

[0026] like Figure 2-7As shown in this embodiment, step S3, designing the thread tip of the depth measuring gauge, specifically includes the following steps: cutting off the incomplete thread at the thread tip of the depth measuring gauge, ensuring that the distance between the first crest of the cut-off complete thread and the chamfered front face is P / 2, with a tolerance range of ±0.05, where P is the pitch of the MJ internal thread. Specifically, by cutting off the incomplete thread at the thread tip of the depth measuring gauge, the working part of the depth measuring gauge will not penetrate deep into the bottom of the MJ internal thread hole, thus avoiding the need for increased tightening force and preventing excessive tightening force from affecting measurement accuracy. Furthermore, by ensuring that the distance between the first crest of the cut-off complete thread and the chamfered front face is P / 2, with a tolerance range of ±0.05, the thread tip of the depth measuring gauge can be positioned at the last crest of the MJ internal thread during testing, ensuring testing accuracy. It should be understood that the depth of the MJ internal thread is defined as the distance between the thread insertion end face and the last root of the complete thread. Optionally, the thread profile of the threaded portion on the working part of the depth gauge is type B, or when the pitch of the MJ internal thread is greater than 0.5 mm, the thread profile of the threaded portion on the working part of the depth gauge is type A or type B. It should be understood that the specific structure of type A and type B thread profiles is well known to those skilled in the art, and will not be elaborated upon here.

[0027] In this embodiment, step S4, designing the thread tolerance zone of the depth inspection gauge, specifically includes the following steps: simulating the assembly state of the connecting bolt, so that the major diameter, pitch diameter, and minor diameter of the thread portion of the depth inspection gauge occupy the lower deviation of the thread tolerance zone of the MJ internal thread, and simultaneously occupy the upper deviation of the thread tolerance zone of the connecting bolt. Specifically, the thread tolerance zone of the depth inspection gauge is designed by satisfying the assembly state of the MJ internal thread hole on the aerospace part to ensure reliable inspection results. Optionally, the formula for calculating the major diameter of the depth inspection gauge is: d g = ( d max -Z L (0, -T) Ld ),in, d g For depth measurement of the large diameter of the gauge, d max Z is the major diameter of the connecting bolt. L T is the distance between the maximum limit dimension of the major diameter of the depth gauge and the maximum value of the major diameter of the connecting bolt. Ld This refers to the major diameter tolerance of the depth gauge. Optionally, the formula for calculating the pitch diameter of the depth gauge is: d g2 = D 2min (0, -T) Ld2 ),in,d g2 The mean diameter of the depth measurement gauge. D 2min T is the minimum pitch diameter of the MJ internal thread. Ld2 This refers to the pitch diameter tolerance of the depth gauge. Optionally, the formula for calculating the wear limit of the pitch diameter of the depth gauge is: d g2s =D 2min -W L ,in, d g2s To determine the wear limit of the pitch diameter of the depth gauge, D 2min W is the minimum pitch diameter of the MJ internal thread. L The distance between the minimum limit dimension of the pitch diameter of the MJ internal thread and the wear limit of the pitch diameter of the depth gauge. Optionally, the formula for calculating the minor diameter of the depth gauge is: d g1max = D 1min ,in, d g1max For the small diameter of the depth measurement gauge, D 1min This represents the minimum minor diameter of the MJ internal thread. Optionally, the formula for calculating the maximum width of the tooth profile clearance groove of the depth gauge is: b max = P / 4, where b max This represents the maximum width of the tooth profile groove on the depth gauge. Optionally, the formula for calculating the radius of curvature of the tooth profile groove bottom on the depth gauge is: r max =0.144P, where r max The radius of curvature of the tooth groove bottom of the depth measurement gauge.

[0028] In this embodiment, step S4 is followed by step S5, which involves selecting whether to set a chip removal groove on the threaded portion of the depth measuring gauge based on the pitch of the MJ internal thread. Specifically, when the pitch of the MJ internal thread is greater than 1mm, a chip removal groove is set on the threaded portion of the depth measuring gauge to ensure smooth chip removal during the manufacturing process of the depth measuring gauge, thereby improving the manufacturing accuracy of the depth measuring gauge and indirectly ensuring the detection accuracy of the MJ internal thread.

[0029] In this embodiment, step S5 further includes the following step: when a chip removal groove is provided on the threaded portion of the depth measuring gauge, the bottom radius of the chip removal groove is selected according to the pitch of the MJ internal thread and the nominal diameter of the threaded portion of the depth measuring gauge. Specifically, when the nominal diameter of the depth measuring gauge is between 6-30mm, and the pitch of the MJ internal thread is 1mm, 1.25mm, 1.5mm, 1.75mm, or 2mm, the bottom radius of the chip removal groove is 0.6mm to ensure chip removal capability and thus improve the manufacturing accuracy of the depth measuring gauge; when the nominal diameter of the depth measuring gauge is between 18-30mm, and the pitch of the MJ internal thread is 2.5mm, 3mm, or 3.5mm, the bottom radius of the chip removal groove is 0.8mm to ensure chip removal capability and thus improve the manufacturing accuracy of the depth measuring gauge.

[0030] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A structural design method for an MJ internal thread depth inspection gauge, used to inspect whether the depth dimension of the MJ internal thread on aerospace parts is qualified, characterized in that, The structural design method includes the following steps: S1. Based on the inspection results of the orifice structure of the MJ internal thread, the difficulty of observation, the design of the thread structure and the design of the depth dimension, the structural form of the depth inspection gauge is selected, and the working part structure of the depth inspection gauge is designed. S2, based on the dimensional tolerance zone of the design depth dimension of the MJ internal thread, calculate the working dimension and wear limit of the working part on the depth measuring gauge to ensure that the working dimension tolerance zone and wear limit tolerance zone of the working part on the depth measuring gauge are distributed within the dimensional tolerance zone of the design depth dimension of the MJ internal thread; S3. Based on the definition of the design depth dimension of the MJ internal thread, design the thread front end of the depth inspection gauge to ensure that the thread front end of the depth inspection gauge can contact the last tooth crest surface of the MJ internal thread during inspection. S4. Based on the thread tolerance zone of the connecting bolt and the thread tolerance zone of the MJ internal thread, design the thread tolerance zone of the depth inspection gauge to ensure that the thread tolerance zone of the depth inspection gauge does not occupy the thread tolerance zone of the MJ internal thread.

2. The structural design method of the MJ internal thread depth detection gauge according to claim 1, characterized in that, Step S1 specifically includes: When the inspection results of the bore structure of the MJ internal thread are easy to observe, choose a single-head dual-size depth inspection gauge; When it is difficult to observe the inspection results of the hole structure of the MJ internal thread, choose a double-headed double-size depth gauge or a combined stepped depth gauge. When the design thread structure of the MJ internal thread is ≥6mm and the design depth dimension is ≥8P, the threaded part on the working part of the depth measuring gauge is shortened to make a cylindrical part, where P is the pitch of the MJ internal thread.

3. The structural design method of the MJ internal thread depth detection gauge according to claim 2, characterized in that, In step S2, the calculation formulas for the working dimensions and wear limits of the working parts on the single-head dual-size depth measuring gauge are as follows: L (d) =(L max -0.05T)±0.03T, L (x) =(L min +0.05T)±0.03T, L (ds) =(L max -0.05T)-0.05T, L (xs) =(L min +0.05T) -0.05T, where L (d) L represents the larger end value of the working dimension of the working part of a single-head dual-size depth measuring gauge. max L represents the maximum limit dimension of the design depth of the MJ internal thread, T represents the design depth tolerance of the MJ internal thread, and L represents the maximum limit dimension of the design depth. (x) L represents the smaller end value of the working dimension of the working part on a single-head, dual-size depth measuring gauge. min L is the minimum limit dimension for the design depth of the MJ internal thread. (ds) For the wear limit of the large end value of the working dimension of the working part of the single-head dual-size depth measuring gauge, L (xs) The wear limit of the smaller end of the working dimension of the working part of the single-head dual-size depth measuring gauge.

4. The structural design method of the MJ internal thread depth detection gauge according to claim 2, characterized in that, In step S2, the calculation formulas for the working dimensions and wear limits of the working parts on the dual-head, dual-size depth measuring gauge are as follows: L (d) =(L max -0.05T)±0.03T, L (x) =(L min +0.05T)±0.03T, L (ds) =(L max -0.05T)±0.05T, L (xs) =(L min +0.05T)±0.05T, where, L (d) L represents the larger end value of the working dimension of the working part of the dual-head, dual-size depth measuring gauge. max L represents the maximum limit dimension of the design depth of the MJ internal thread, T represents the design depth tolerance of the MJ internal thread, and L represents the maximum limit dimension of the design depth. (x) L represents the smaller end value of the working dimension of the working part of the dual-head, dual-size depth measuring gauge. min L is the minimum limit dimension for the design depth of the MJ internal thread. (ds) For the wear limit of the large end value of the working dimension of the working part of the dual-head, dual-size depth measuring gauge, L (xs) The wear limit of the smaller end of the working dimension of the working part of the dual-head, dual-size depth measuring gauge.

5. The structural design method of the MJ internal thread depth detection gauge according to claim 2, characterized in that, In step S2, the calculation formulas for the working dimensions and wear limits of the working parts on the combined stepped depth measuring gauge are as follows: A = 0.85T ± 0.03T, B = L min +0.1T, A (s) =0.85T±0.05T, where A is the step dimension of the combined stepped depth gauge, T is the design depth tolerance of the MJ internal thread, B is the distance between the measuring end face of the measuring column of the combined stepped depth gauge and the reference surface of the body, and L min A represents the minimum limit dimension for the design depth of the MJ internal thread. (s) This refers to the maximum distance symmetrically distributed at the top of the gauge post relative to the center plane of the step after wear of the combined stepped depth gauge.

6. The structural design method of the MJ internal thread depth detection gauge according to claim 2, characterized in that, Step S4 is followed by the following steps: When the design depth dimension of the MJ internal thread is ≥8P, and the structure of the depth measuring gauge is a combined stepped type, a handle is set on the measuring column of the combined stepped type depth measuring gauge.

7. The structural design method for the MJ internal thread depth detection gauge according to any one of claims 1-6, characterized in that, Step S3, designing the thread tip of the depth inspection gauge, specifically includes the following steps: The incomplete thread at the front end of the depth gauge is removed, and the distance between the first crest of the complete thread after removal and the front end face of the chamfer is P / 2, with a tolerance range of ±0.05, where P is the pitch of the MJ internal thread.

8. The structural design method for the MJ internal thread depth detection gauge according to any one of claims 1-6, characterized in that, Step S4, designing the thread tolerance zone for the depth inspection gauge, specifically includes the following steps: The assembly state of the connecting bolts is simulated so that the major diameter, pitch diameter, and minor diameter of the thread portion of the depth measuring gauge occupy the lower deviation of the thread tolerance zone of the MJ internal thread, and at the same time occupy the upper deviation of the thread tolerance zone of the connecting bolt.

9. The structural design method for the MJ internal thread depth detection gauge according to any one of claims 1-6, characterized in that, Step S4 is followed by the following steps: S5, depending on the pitch of the MJ internal thread, select whether to set a chip removal groove on the threaded portion of the depth measurement gauge.

10. The structural design method of the MJ internal thread depth detection gauge according to claim 9, characterized in that, Step S5 also includes the following steps: When the threaded portion of the depth measuring gauge is equipped with a chip removal groove, the bottom radius of the chip removal groove is selected based on the pitch of the MJ internal thread and the nominal diameter of the threaded portion of the depth measuring gauge.

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