A processing method for ensuring position accuracy of a differential housing cross axle hole of a commercial vehicle

Abstract

The application discloses a kind of processing methods for ensuring the position accuracy of differential housing cross axle hole of commercial vehicle, to ensure the concentricity of the chamfering of the two ends of differential housing, self-centering three-jaw chuck is used, and the use of three-jaw chuck is broken, the micro-deformation of three-jaw chuck system is used, the two ends of differential housing are clamped at the same time by three-jaw chuck, so that the chamfering of the two ends of differential housing is processed, the end face and the outer circle positioning clamping of the past are changed, the self-centering fixture is used, the chamfering of the two ends of differential housing is centered, and the flange end face is axially positioned, so that the position accuracy of differential housing cross axle hole is ensured.The application greatly guarantees the processing quality, the yield is 100%, improves the processing speed and efficiency, and reduces the cost.Practice proves that even personnel without operating experience can operate, and the key characteristic control process becomes ordinary processing process.

Description

Technical Field

[0001] This invention relates to the field of differential housing machining technology, specifically to a machining method that ensures the positional accuracy of the cross shaft hole in a commercial vehicle differential housing. Background Technology

[0002] Currently, the market for machining differential housings ( Figure 1 and Figure 2 The cross shaft hole E (as shown) is mainly machined by positioning the outer circle of the flange end face (the large end and the small end) and the flange end face (end face), or by positioning the inner hole and the end face.

[0003] In the process of realizing this invention, the inventors discovered that: The existing two positioning and clamping methods have the following disadvantages: 1. The machining accuracy requirements for the flange outer diameter locating surface of the differential housing's cross shaft hole are extremely high (e.g., the flange outer diameter with a diameter of ¢264 on the subsequent locating surface drawing requires a tolerance zone within 0.052mm, while the machining process requires the tolerance zone to be controlled within 0.02mm in this step to ensure the positional accuracy of the cross shaft hole). This necessitates: firstly, high precision requirements for the machining equipment, and secondly, high skill levels for the operators; in the entire machining process of the differential housing, the machining of the cross shaft hole and the locating surface become the key control steps. 2. During mass production, it is impossible for every differential housing to maintain the same tolerance value on the flange outer diameter locating surface when machining the cross shaft hole (the axial center line of each differential housing after positioning and clamping is offset and does not coincide). This results in small positioning clearance, unsmooth clamping, reduced clamping efficiency, and low unit labor productivity. At the same time, because it is impossible for every flange outer diameter locating surface to maintain the same tolerance value, the position accuracy of the machined cross shaft hole does not meet the requirements, leading to product scrap, high scrap rate, and increased production costs. Summary of the Invention

[0004] To address the shortcomings of existing differential machining and positioning methods, this invention proposes a machining method that ensures the positional accuracy of the cross shaft hole in the differential housing of commercial vehicles.

[0005] Inventive concept: During the process of invention, the inventor discovered that the inner ends of both the flanged end (large end) and the flanged end (small end) of the differential housing need to be chamfered (chamfer B for the large end and chamfer A for the small end, such as...). Figure 1 and Figure 2As shown, if the differential housing is positioned and clamped by centering the two chamfers at both ends and axially positioning the flange end face, it will not be affected by the error of the flange outer circle caused by the previous process. Even personnel without operating experience can operate the machine, turning the key characteristic control process into a normal machining process. However, the current machining method for the chamfers at both ends of the differential housing is mainly completed in two steps. The first step is to clamp the large end of the differential housing on a lathe with a three-jaw chuck and machine the chamfer of the inner hole of the large end. The second step is to machine the chamfer of the inner hole of the small end on a lathe with a center rest. Because machining the chamfers at both ends of the differential housing on two sets of fixtures will result in a large coaxiality error of the chamfers at both ends of the differential housing, in order to achieve the positioning method of chamfer centering and flange end face axial positioning, two problems need to be solved: one is to solve the problem of concentricity in the machining of the chamfers at both ends of the differential housing, and the other is to solve the problem of how to center the chamfers of the inner holes at both ends of the differential housing.

[0006] Therefore, the technical solution of the present invention is a machining method for ensuring the positional accuracy of the cross shaft hole in the differential housing of commercial vehicles, characterized in that: (1) In order to ensure the concentricity of the chamfering of the inner holes at both ends of the differential housing, an existing hydraulic self-centering three-jaw chuck is used, including the chuck and three self-made jaws evenly distributed in the radial direction. The jaws slide radially on the chuck. The specific structure of the jaws is as follows: the upper inner side of the jaws extends downward into a concave structure, which is adapted to the outer contour of the large end of the differential housing. The upper inner side is provided with a clamping part for the outer circle of the large end of the differential housing, and the lower inner side of the jaws is provided with a clamping part for the outer circle of the small end of the differential housing. When the large end of the differential housing is clamped, the inner diameter of the circle formed by the lower parts of the three jaws is ¢+0.25mm of the outer diameter of the small end of the differential housing. The tolerance of the large end of the differential housing to be processed in this process is ¢±0.05mm and the tolerance of the small end is ¢±0.05mm. (2) The method for achieving concentricity of the chamfering at both ends of the differential housing using the self-centering three-jaw chuck described in (1) is as follows: ① First, insert the differential housing to be processed with the small end facing inward between the three jaws of the self-centering three-jaw chuck. Then slide the jaws to the outer periphery of the large end of the differential housing and clamp them in place. At the same time, the root of the jaws uses the rigid deformation of the jaws and chuck system to clamp the small end of the differential housing, thereby ensuring the positioning and clamping rigidity of the differential housing on the self-centering three-jaw chuck and avoiding vibration during processing. ② Use a cutting tool to machine the chamfers of the inner holes at both ends of the differential housing. The chamfering of the inner holes at both ends of the differential housing is completed in one clamping. Remove the housing and wait for the next process. (3) In order to center the chamfered inner holes at both ends of the differential housing, a special self-centering fixture is used, including a base for mounting on the turntable. The base has a T-shaped structure and a central through hole in the vertical direction. Multiple support blocks are spaced apart on the outer periphery of the base. The top surfaces of the support blocks are located on the same height plane and are used to position the large end flange face of the differential housing. The surface of the base is provided with an inwardly recessed groove. It also includes a pull rod, a positioning mandrel, a pressure block, and a positioning sleeve, among which: The pull rod passes through the positioning mandrel, with both ends extending from it. The lower end of the positioning mandrel is inserted into the central through hole of the base and slides with it, with a sliding clearance of ≤0.01mm. The upper part of the positioning mandrel is clearance-fitted with the inner hole of the differential housing. The lower end of the pull rod is the power connection end, and the upper end of the pull rod is fitted with the pressure block and tightened by a nut. The positioning sleeve is fitted onto the upper end of the positioning mandrel, and its inner hole slides with the positioning mandrel, with a sliding clearance of ≤0.01mm. The top of the positioning sleeve extends beyond the upper end face of the positioning mandrel and abuts against the bottom of the pressure block. The lower end of the positioning sleeve is an outer conical surface structure with a gradually decreasing outer diameter. The outer diameter of the end is smaller than the inner diameter of the small end of the differential housing. In use, this conical surface abuts against the chamfer of the inner hole of the small end of the differential housing. The lower part of the positioning mandrel has a slider protruding on its outer diameter. The upper part of the slider extends from top to bottom into an outer conical surface structure with a gradually increasing outer diameter. In use, the outer conical surface abuts against the chamfer of the inner hole of the large end of the differential housing. The lower part of the slider is a cylindrical structure that slides in conjunction with the groove of the base. The bottom surface of the slider and the bottom surface of the groove are evenly distributed with spring receiving cavities, and compression springs are installed in the spring receiving cavities.

[0007] (4) The method for centering the chamfers of the inner holes at both ends of the differential housing and axially positioning the flange end face using the self-centering fixture described in (3) is as follows: ① Place the differential housing processed in (2) into the self-centering fixture described in (3). At this time, the large end chamfer of the differential housing being processed contacts the outer conical surface of the slide table of the positioning mandrel. Under the reaction of the compression spring, it supports the differential housing to be processed and the positioning mandrel upward. The middle through hole of the base slides with the positioning mandrel. ② Insert the positioning sleeve. At this time, the outer conical surface of the positioning sleeve contacts the chamfer of the small end of the differential housing being machined, and the inner hole of the positioning sleeve slides with the positioning mandrel. ③ Insert the pressure block into the pull rod between the nut and the positioning sleeve through its opening slot; ④Activate the clamping button. At this time, the pull rod drives the pressure block to pull the positioning sleeve and press the differential housing being machined. Under the reaction force of the compression spring, it automatically centers and continues to move downward until the flange end face of the differential housing being machined contacts the upper plane of the support block. At this time, the differential housing being machined is in the positioning and clamping state, and the machining operation of the cross shaft hole can begin. ⑤ After completion, turn off the clamping button. Under the action of the compression spring, the differential housing will move upward along with the positioning sleeve, pressure block, and pull rod. Pull out the pressure block and remove the positioning sleeve to remove the machined differential housing for the next machining operation.

[0008] Preferably, the upper middle part of the positioning mandrel of the self-centering fixture extends downward with a structure in which the outer diameter gradually increases. An annular clearance groove is provided at the position corresponding to the cross shaft hole to be machined in the differential housing. The purpose is to increase the strength of the positioning mandrel, extend its service life, and prevent tool interference.

[0009] Preferably, the self-centering clamp has an opening groove on the pressure block that communicates with the central through hole. The width of the opening groove is greater than the diameter of the pull rod and less than the outer diameter of the nut, so that the nut does not need to be rotated when disassembling and assembling the differential housing, thus improving efficiency.

[0010] Preferably, the lower end of the positioning mandrel of the self-centering fixture is provided with a spiral oil groove to increase the lubrication of the contact surface with the middle through hole of the base, reduce the maintenance frequency and extend the service life.

[0011] Preferably, the outer circumferential surfaces of the self-centering clamp's pressure block and positioning sleeve are knurled to increase gripping friction and prevent slippage during operation.

[0012] Beneficial Effects: This invention breaks with the conventional use of three-jaw chucks, utilizing the rigid deformation of the jaws and chuck system to simultaneously clamp the outer diameters (large end M, small end N) of the differential housing at both ends, eliminating vibration during machining and thus achieving the chamfering of the inner holes at both ends of the differential housing. Furthermore, a self-centering fixture is used to clamp and position the chamfered inner holes at both ends of the differential housing, achieving centering and axial positioning of the flange end face, thereby ensuring the positional accuracy of the cross shaft hole of the differential housing. This method greatly guarantees machining quality, improves the yield rate, increases machining speed and efficiency, and reduces costs. Practice has proven that the yield rate using this method is 100%, and even workers without machine operating experience can operate the machine, transforming critical characteristic control processes into ordinary machining processes. Attached Figure Description

[0013] Figure 1 This is a perspective view of the differential housing described in this invention.

[0014] Figure 2 yes Figure 1 A sectional view.

[0015] Figure 3 This is a perspective view of the differential housing described in this invention on a three-jaw chuck.

[0016] Figure 4 yes Figure 3 The main view.

[0017] Figure 5 yes Figure 4 CC view.

[0018] Figure 6 This is a schematic diagram of the differential housing described in this invention on a self-centering fixture.

[0019] Figure 7 This is a perspective view of the positioning mandrel of the self-centering fixture of the present invention.

[0020] Figure 8 yes Figure 7 The main view.

[0021] Figure 9 yes Figure 8 A sectional view.

[0022] Figure 10 This is a cross-sectional view of the base of the self-centering clamp of the present invention.

[0023] Figure 11 This is a perspective view of the positioning block of the self-centering fixture of the present invention.

[0024] Figure 12 yes Figure 11 The main view.

[0025] Figure 13 yes Figure 11 A sectional view.

[0026] Figure 14 This is a perspective view of the pressure block of the self-centering clamp of the present invention.

[0027] Figure 15 yes Figure 14 BB view.

[0028] The figure shows: 1. Base; 2. Support block; 3. Tie rod; 4. Positioning spindle; 41. Slider; 42. Annular clearance groove; 43. Oil groove; 5. Pressure block; 51. Opening groove; 6. Positioning sleeve; 7. Nut; 8. Knurling; 9. Compression spring; 10. Spring receiving cavity; 11. Central through hole; 12. Slide groove; 21. Chuck; 22. Collar; 23. Screw; H. Differential housing; A. Chamfer; B. Chamfer; C. Sliding clearance; D. Flange end face; E. Cross shaft hole; M. Large end outer circle; N. Small end outer circle. Detailed Implementation

[0029] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings, but this embodiment should not be construed as a limitation of the present invention.

[0030] A machining method for ensuring the positional accuracy of the cross shaft hole in a commercial vehicle differential housing, characterized in that: (1) In order to ensure the concentricity of the chamfering of the inner holes at both ends of the differential housing, an existing hydraulic self-centering three-jaw chuck (such as...) is used. Figures 3 to 5 As shown), it includes a chuck 21 and three radially evenly distributed self-made jaws 22. The jaws are fixed to the slider by two screws 23 and slide radially on the chuck (with a certain amount of deformation when clamped). The specific structure of the jaws is as follows: the upper inner side of the jaws extends downward into a concave structure, which is adapted to the outer contour of the large end of the differential housing. The upper inner side is provided with a clamping part for the outer circle M of the large end of the differential housing. The lower inner side of the jaws is provided with a clamping part for the outer circle N of the small end of the differential housing. When the large end of the differential housing is clamped, the inner diameter of the circle formed by the lower parts of the three jaws is the outer diameter of the small end of the differential housing ¢+0.25mm. The tolerance of the large end of the differential housing to be processed in this process is ¢±0.05mm, and the tolerance of the small end is ¢±0.05mm. (2) The method for achieving concentricity of the chamfering at both ends of the differential housing using the self-centering three-jaw chuck described in (1) is as follows: ① First, insert the differential housing to be processed with the small end facing inward between the three jaws of the self-centering three-jaw chuck. Then slide the jaws to the outer periphery of the large end of the differential housing and clamp them in place. At the same time, the root of the jaws uses the rigid deformation of the jaws and chuck system to clamp the small end of the differential housing, thereby ensuring the positioning and clamping rigidity of the differential housing on the self-centering three-jaw chuck and preventing vibration during processing. ② Use a cutting tool to machine the chamfers of the inner holes at both ends of the differential housing. The chamfering of the inner holes at both ends of the differential housing is completed in one clamping. Remove the housing and wait for the next process. (3) In order to center the chamfers of the inner holes at both ends of the differential housing, a special self-centering fixture is used. Figures 6 to 15 As shown, the device includes a base 1 for mounting on a turntable. The base has a T-shaped structure and a central through hole 11 in the vertical direction. Six support blocks 2 are spaced apart on the outer periphery of the base. The top surfaces of the support blocks are located at the same height plane and are used to position the large end flange face D of the differential housing. The surface of the base has an inwardly recessed groove 12. It also includes a pull rod 3, a positioning spindle 4, a pressure block 5, and a positioning sleeve 6, wherein: The pull rod 3 passes through the positioning mandrel 4, with both ends extending from the mandrel. The lower end of the positioning mandrel is inserted into the central through hole of the base 1, slidingly engaging with the central through hole. The upper part of the positioning mandrel is in clearance fit with the inner hole of the differential housing, with a sliding clearance ≤ 0.01mm (to ensure the concentricity of the differential housing on the fixture, thereby ensuring machining accuracy and finished product qualification rate). The lower end of the pull rod 3 is the power connection end, and the upper end of the pull rod is equipped with the pressure block 5, which is pressed and limited by the nut 7; positioning sleeve The 6-sleeve is set on the upper outer side of the positioning mandrel 4 and slides with the positioning mandrel with a sliding clearance of ≦0.01mm (to ensure the concentricity of the differential housing on the fixture, thereby ensuring machining accuracy and finished product qualification rate). The top of the positioning sleeve 6 extends beyond the upper end face of the positioning mandrel 4 and abuts against the bottom of the pressure block 5. The lower end of the positioning sleeve is an outer conical surface structure with a gradually decreasing outer diameter. The outer diameter of the end is smaller than the inner diameter of the small end of the differential housing. When in use, the conical surface abuts against the chamfer of the inner hole of the small end of the differential housing. The lower part of the positioning spindle 4 has a slider 41 protruding on the outer diameter. The upper part of the slider extends from top to bottom into an outer conical surface structure with a gradually increasing outer diameter. When in use, the outer conical surface abuts against the chamfer of the inner hole of the large end of the differential housing. The lower part of the slider is a cylindrical structure that slides with the groove of the base. The bottom surface of the slider and the bottom surface of the groove are evenly distributed with spring receiving cavities 10, and a compression spring 9 is provided in the spring receiving cavity. The upper middle part of the positioning mandrel 4 extends downward into a structure with a gradually increasing outer diameter. An annular clearance groove 42 is provided at the position corresponding to the cross shaft hole to be machined in the differential housing. The purpose is to increase the strength of the positioning mandrel and extend its service life. The annular clearance groove is provided to avoid tool interference. The pressure block 5 is provided with an opening groove 51 that communicates with the central through hole. The width of the opening groove is greater than the diameter of the pull rod and less than the outer diameter of the nut. When disassembling and assembling the differential housing, the nut does not need to be rotated, thus improving efficiency. The lower end of the positioning mandrel 4 is provided with a spiral oil groove 43, which increases the lubrication of the contact surface with the middle through hole of the base, reduces the maintenance frequency, and extends the service life. The outer circumferential surfaces of the pressure block 5 and the positioning sleeve 6 are provided with knurling 8 to increase friction and prevent slippage during operation; (4) The method for centering the chamfers of the inner holes at both ends of the differential housing and axially positioning the flange end face using the self-centering fixture described in (3) is as follows: ① Place the differential housing processed in (2) into the self-centering fixture described in (3). At this time, the large end chamfer B of the differential housing being processed contacts the outer conical surface of the slide table of the positioning spindle 4. Under the reaction of the compression spring 9, it supports the differential housing H to be processed and the positioning spindle 4 upward. The middle through hole of the base 1 slides with the positioning spindle 4. ② Insert the positioning sleeve 6. At this time, the outer conical surface of the positioning sleeve contacts the small end chamfer A of the differential housing being machined, and the inner hole of the positioning sleeve slides with the positioning mandrel. ③ Insert the pressure block 5 into the pull rod 3 between the nut 7 and the positioning sleeve 6 through its opening slot; ④Activate the clamping button. At this time, the pull rod 3 drives the pressure block 5 to pull the positioning sleeve 6 and press the differential housing being processed. Under the reaction force of the compression spring 9, it automatically centers and continues to move downward until the flange end face D of the differential housing being processed contacts the upper plane of the support block 2. At this time, the differential housing being processed is in the positioning and clamping state, and the processing operation of the cross shaft hole can begin. ⑤ After completion, close the clamping button. Under the action of the compression spring 9, the differential housing will move upward along with the positioning sleeve 6, the pressure block 5, and the pull rod 3. Pull out the pressure block 5 and remove the positioning sleeve 6 to remove the machined differential housing for the next machining operation.

[0031] Any aspects not described in detail in this specification are techniques well-known in the art.

[0032] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A machining method for ensuring the positional accuracy of the cross shaft hole in a commercial vehicle differential housing, characterized in that: (1) In order to ensure the concentricity of the chamfering of the inner holes at both ends of the differential housing, an existing hydraulic self-centering three-jaw chuck is used, including the chuck and three self-made jaws evenly distributed in the radial direction. The jaws slide radially on the chuck. The specific structure of the jaws is as follows: the upper inner side of the jaws extends downward into a concave structure, which is adapted to the outer contour of the large end of the differential housing. The upper inner side is provided with a clamping part for the outer circle of the large end of the differential housing, and the lower inner side of the jaws is provided with a clamping part for the outer circle of the small end of the differential housing. When the large end of the differential housing is clamped, the inner diameter of the circle formed by the lower parts of the three jaws is ¢+0.25mm of the outer diameter of the small end of the differential housing. The tolerance of the large end of the differential housing to be processed in this process is ¢±0.05mm and the tolerance of the small end is ¢±0.05mm. (2) The method for achieving concentricity of the chamfering at both ends of the differential housing using the self-centering three-jaw chuck described in (1) is as follows: ① First, insert the differential housing to be processed with the small end facing inward between the three jaws of the self-centering three-jaw chuck. Then slide the jaws to the outer periphery of the large end of the differential housing and clamp them in place. At the same time, the root of the jaws uses the rigid deformation of the jaws and chuck system to clamp the small end of the differential housing, thereby ensuring the positioning and clamping rigidity of the differential housing on the self-centering three-jaw chuck and avoiding vibration during processing. ② Use a cutting tool to machine the chamfers of the inner holes at both ends of the differential housing. The chamfering of the inner holes at both ends of the differential housing is completed in one clamping. Remove the housing and wait for the next process. (3) In order to center the chamfered inner holes at both ends of the differential housing, a special self-centering fixture is used, including a base for mounting on the turntable. The base has a T-shaped structure and a central through hole in the vertical direction. Multiple support blocks are spaced apart on the outer periphery of the base. The top surfaces of the support blocks are located on the same height plane and are used to position the large end flange face of the differential housing. The surface of the base is provided with an inwardly recessed groove. It also includes a pull rod, a positioning mandrel, a pressure block, and a positioning sleeve, among which: The pull rod passes through the positioning mandrel, with both ends extending from it. The lower end of the positioning mandrel is inserted into the central through hole of the base and slides with it, with a sliding clearance of ≤0.01mm. The upper part of the positioning mandrel is clearance-fitted with the inner hole of the differential housing. The lower end of the pull rod is the power connection end, and the upper end of the pull rod is fitted with the pressure block and tightened by a nut. The positioning sleeve is fitted onto the upper end of the positioning mandrel, and its inner hole slides with the positioning mandrel, with a sliding clearance of ≤0.01mm. The top of the positioning sleeve extends beyond the upper end face of the positioning mandrel and abuts against the bottom of the pressure block. The lower end of the positioning sleeve is an outer conical surface structure with a gradually decreasing outer diameter. The outer diameter of the end is smaller than the inner diameter of the small end of the differential housing. In use, this conical surface abuts against the chamfer of the inner hole of the small end of the differential housing. The lower part of the positioning mandrel has a slider protruding on its outer diameter. The upper part of the slider extends from top to bottom into an outer conical surface structure with a gradually increasing outer diameter. In use, the outer conical surface abuts against the chamfer of the inner hole of the large end of the differential housing. The lower part of the slider is a cylindrical structure that slides with the groove of the base. The bottom surface of the slider and the bottom surface of the groove are evenly distributed with spring receiving cavities, and compression springs are installed in the spring receiving cavities. (4) The method for centering the chamfers of the inner holes at both ends of the differential housing and axially positioning the flange end face using the self-centering fixture described in (3) is as follows: ① Place the differential housing processed in (2) into the self-centering fixture described in (3). At this time, the large end chamfer of the differential housing being processed contacts the outer conical surface of the slide table of the positioning mandrel. Under the reaction of the compression spring, it supports the differential housing to be processed and the positioning mandrel upward. The middle through hole of the base slides with the positioning mandrel. ② Insert the positioning sleeve. At this time, the outer conical surface of the positioning sleeve contacts the chamfer of the small end of the differential housing being machined, and the inner hole of the positioning sleeve slides with the positioning mandrel. ③ Insert the pressure block into the pull rod between the nut and the positioning sleeve through its opening slot; ④Activate the clamping button. At this time, the pull rod drives the pressure block to pull the positioning sleeve and press the differential housing being machined. Under the reaction force of the compression spring, it automatically centers and continues to move downward until the flange end face of the differential housing being machined contacts the upper plane of the support block. At this time, the differential housing being machined is in the positioning and clamping state, and the machining operation of the cross shaft hole can begin. ⑤ After completion, turn off the clamping button. Under the action of the compression spring, the differential housing will move upward along with the positioning sleeve, pressure block, and pull rod. Pull out the pressure block and remove the positioning sleeve to remove the machined differential housing for the next machining operation.

2. The machining method for ensuring the positional accuracy of the cross shaft hole in a commercial vehicle differential housing according to claim 1, characterized in that: The positioning mandrel of the self-centering fixture extends downward from the middle of its upper part into a structure with a gradually increasing outer diameter, and an annular clearance groove is provided at the position corresponding to the cross shaft hole to be machined in the differential housing.

3. The machining method for ensuring the positional accuracy of the cross shaft hole in a commercial vehicle differential housing according to claim 1 or 2, characterized in that: The self-centering clamp has an opening groove on its pressure block that communicates with the central through hole. The width of the opening groove is greater than the diameter of the pull rod and less than the outer diameter of the nut.

4. The machining method for ensuring the positional accuracy of the cross shaft hole in a commercial vehicle differential housing according to claim 1 or 2, characterized in that: The self-centering fixture has a spiral oil groove at the lower end of its positioning mandrel.

5. The machining method for ensuring the positional accuracy of the cross shaft hole in a commercial vehicle differential housing according to claim 3, characterized in that: The self-centering fixture has a spiral oil groove at the lower end of its positioning mandrel.

6. A machining method for ensuring the positional accuracy of the cross shaft hole in a commercial vehicle differential housing according to claim 1, 2, or 5, characterized in that: The outer circumferential surfaces of the pressure block and positioning sleeve of the self-centering fixture are knurled.

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