Method for machining a bore in a shaft
By first forming a coarse hole inside the shaft in the blank of the load-limiting shaft and then performing heat treatment, followed by drilling and honing, the machining problem of the shaft inner hole was solved, achieving a high-efficiency and low-cost machining effect.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- WUHAN MARINE MACHINERY PLANT
- Filing Date
- 2025-01-03
- Publication Date
- 2026-07-21
AI Technical Summary
Machining the inner hole of the load-limiting shaft is difficult, especially when the depth exceeds 120mm, the drill bit wears out severely, resulting in low machining efficiency and high cost. Conventional processes cannot meet the accuracy requirements.
The process involves first rough machining to form a coarse hole inside the shaft, then quenching and tempering, followed by a combination of drilling and honing. This process includes rough turning, drilling the coarse hole inside the shaft, quenching and tempering, finishing the outer diameter and end face, and honing in stages, which reduces the machining difficulty and improves the accuracy.
It effectively reduces the machining difficulty of the inner hole of the shaft, improves machining efficiency and accuracy, meets the drawing size requirements, and reduces the overall machining cost.
Smart Images
Figure CN119952418B_ABST
Abstract
Description
Technical Field
[0001] This disclosure belongs to the field of machining technology, and specifically relates to a method for machining the inner hole of a shaft. Background Technology
[0002] The load-limiting shaft is a crucial component in chain drive assemblies, typically made of 40CrNiMo alloy steel, which boasts a high strength rating. As a vital part of the chain drive, the load-limiting shaft requires heat treatment during use to enhance its overall mechanical properties, ensuring a hardness of HRC50 or higher. The load-limiting shaft has an internal bore to accommodate the telescopic rod; therefore, the dimensional tolerances and straightness of this bore have stringent requirements, necessitating strict control during manufacturing.
[0003] In related technologies, the manufacturing process of load-limiting shafts generally includes: first, heat treatment (i.e., tempering) is performed on the load-limiting shaft to improve its mechanical properties and overall hardness. Then, the load-limiting shaft is precision-machined, and during the precision-machined process, an alloy steel drill bit is used to drill an inner hole inside the load-limiting shaft.
[0004] However, since the mechanical properties and overall hardness of the load-limiting shaft are significantly improved after heat treatment, drilling the load-limiting shaft with alloy steel drill bits is difficult. In particular, when the drilling depth exceeds 120mm, the drill bit wears out greatly, making it difficult to continue drilling. This results in high machining difficulty and low machining efficiency for the inner hole of the shaft. Summary of the Invention
[0005] This disclosure provides a method for machining the inner hole of a shaft, which can reduce the machining difficulty of the inner hole. The technical solution is as follows:
[0006] This disclosure provides a method for machining an inner hole of a shaft. The method includes: rough machining a blank of a load-limiting shaft to create an inner coarse hole; quenching and tempering the blank of the load-limiting shaft; finishing the outer circle and end face of the blank of the load-limiting shaft; and honing the inner coarse hole to obtain the inner hole.
[0007] In another implementation of this disclosure, the rough machining of the load limiting shaft blank to create an inner coarse hole includes: rough turning the two end faces and outer circle of the load limiting shaft blank; marking the machining positioning lines for the inner hole on the rough-turned load limiting shaft blank; and drilling the inner coarse hole on the load limiting shaft blank using a drill bit according to the machining positioning lines.
[0008] In another implementation of this disclosure, the diameter of the inner coarse hole is 0.8 to 1 mm smaller than the diameter of the inner bore.
[0009] In another implementation of this disclosure, the heat treatment of the blank of the load limiting shaft includes: placing the blank of the load limiting shaft upright on a tray, such that the extension direction of the coarse hole in the shaft is vertical; placing the tray and the blank of the load limiting shaft in a heating furnace for heating, and then quenching them after heating; and placing the tray and the blank of the load limiting shaft in the heating furnace for tempering.
[0010] In another implementation of this disclosure, the honing of the inner bore of the shaft to obtain the inner bore includes: using a series of honing heads to progressively enlarge the inner bore of the shaft so that the diameter and roughness of the inner bore of the shaft meet the requirements. The series of honing heads includes multiple honing heads with different diameters, and the diameters of the multiple honing heads gradually increase.
[0011] In another implementation of this disclosure, the diameter of the plurality of honing heads is 0.5-3 mm, and the diameter of the plurality of honing heads gradually increases.
[0012] In another implementation of this disclosure, the finishing of the outer diameter and end face of the blank of the load-limiting shaft includes: placing the blank of the load-limiting shaft in a lathe, such that the center line of the coarse hole inside the shaft coincides with the rotation center of the lathe; correcting the blank of the load-limiting shaft so that the end face of the blank of the load-limiting shaft is parallel to the worktable; finishing turning one end face of the blank of the load-limiting shaft, and using the finished end face as the reference for the remaining finishing; finishing turning the outer diameter and the other end face of the blank of the load-limiting shaft so that all dimensions of the load-limiting shaft meet the drawing requirements.
[0013] In another implementation of this disclosure, before finishing the outer circle and end face of the blank of the load limiting shaft, the machining method further includes:
[0014] Ultrasonic testing is performed on the blank of the load limiting shaft to detect whether there are any defects in the blank.
[0015] In another implementation of this disclosure, the processing method further includes: deburring and cleaning the honed load-limiting shaft.
[0016] In another implementation of this disclosure, the processing method further includes: annealing the rough-machined blank of the load limiting shaft before performing heat treatment on the blank of the load limiting shaft.
[0017] The beneficial effects of the technical solutions provided in this disclosure are:
[0018] When machining the inner hole of a load-limiting shaft using the above machining method, the method first rough-machines the inner hole in the blank of the load-limiting shaft, and then performs heat treatment on the load-limiting shaft. This allows the inner hole to be machined before the heat treatment, reducing the machining difficulty of the inner hole and thus improving the overall machining efficiency of the inner hole process. Next, the blank of the load-limiting shaft is heat-treated to ensure that the structural strength of the final machined load-limiting shaft meets the usage requirements. Then, the method performs finish machining on the outer diameter and end face of the blank of the load-limiting shaft, and hones the inner hole. This finish machining ensures that the load-limiting shaft meets the dimensional requirements of the drawing, while honing allows for further machining of the inner hole, ensuring that the surface roughness and other dimensional requirements of the inner hole also meet the dimensional requirements of the drawing after honing, thus obtaining the inner hole.
[0019] In other words, the above processing method can effectively solve the processing problem of the inner hole of the load limiting shaft, and the inner hole obtained after honing can also effectively improve its processing accuracy. Attached Figure Description
[0020] To more clearly illustrate the technical solutions in the embodiments of this disclosure, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this disclosure. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0021] Figure 1 This is a schematic diagram of the load limiting shaft in related technologies;
[0022] Figure 2 This is a flowchart of a method for machining an inner hole of a shaft according to an embodiment of this disclosure;
[0023] Figure 3 This is a flowchart of another method for machining the inner hole of a shaft provided in this embodiment of the present disclosure;
[0024] Figure 4 A schematic diagram of the blank for a load-limiting shaft;
[0025] Figure 5 This is a structural schematic diagram of a blank for a load-limiting shaft with an internal coarse hole.
[0026] The symbols in the diagram represent the following meanings:
[0027] 100. Load limiting shaft;
[0028] 101. First axle segment; 102. Second axle segment; 103. Third axle segment; 104. Fourth axle segment; 105. Fifth axle segment; 106. Sixth axle segment;
[0029] 1010, Inner hole of the shaft;
[0030] 1020, Countersunk hole. Detailed Implementation
[0031] To make the objectives, technical solutions, and advantages of this disclosure clearer, the embodiments of this disclosure will be described in further detail below with reference to the accompanying drawings.
[0032] Unless otherwise defined, the technical or scientific terms used herein shall have the ordinary meaning understood by one of ordinary skill in the art to which this disclosure pertains. The terms “first,” “second,” “third,” and similar terms used in this patent application specification and claims do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Similarly, the terms “an” or “a” and similar terms do not indicate a quantity limitation, but rather indicate the presence of at least one. The terms “comprising” or “including” and similar terms mean that the elements or objects preceding “comprising” or “including” encompass the elements or objects listed following “comprising” or “including” and their equivalents, and do not exclude other elements or objects. The terms “connected” or “linked” and similar terms are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. The terms “upper,” “lower,” “left,” “right,” “top,” and “bottom,” etc., are used only to indicate relative positional relationships, and these relative positional relationships may change accordingly when the absolute position of the described objects changes.
[0033] The load-limiting shaft is a crucial component in chain drive assemblies, typically made of 40CrNiMo alloy steel, which boasts a high strength rating. As a vital part of the chain drive, the load-limiting shaft requires heat treatment during use to enhance its overall mechanical properties. Specifically, the overall hardness of the load-limiting shaft must reach HRC50 or higher.
[0034] Figure 1 This is a structural schematic diagram of a load-limiting shaft in related technologies, combined with... Figure 1 The load limiting shaft 100 has an elongated inner bore 1010. The length direction of the inner bore 1010 is the same as the length direction of the load limiting shaft 100. The inner diameter of the inner bore 1010 is 8 mm.
[0035] The inner bore 1010 of the shaft provides space for the telescopic rod to move. Part of the telescopic rod is movably located in the inner bore 101 of the shaft, and the telescopic rod can extend and retract relative to the load-limiting shaft 100.
[0036] To ensure that the telescopic rod does not deviate during telescopic movement, the dimensional tolerances and straightness of the inner hole 1010 of the shaft have high requirements and must be strictly controlled during the machining process.
[0037] In addition, the two end faces of the load limiting shaft 100 each have countersunk holes 1020. The inner diameter of the countersunk hole 1020 is 30 mm, and the depth of each countersunk hole 1020 along the length of the load limiting shaft 100 is 10 mm. The two countersunk holes 1020 are respectively connected to the two ends of the inner hole 1010 of the shaft.
[0038] The load limiting shaft 100 has external dimensions of Φ92×300mm. The load limiting shaft 100 includes a first shaft segment 101, a second shaft segment 102, a third shaft segment 103, a fourth shaft segment 104, a fifth shaft segment 105, and a sixth shaft segment 106 connected sequentially along its own length.
[0039] The length of the first shaft segment 101 is 14.5 mm, and the outer diameter of the first shaft segment 101 is 68 mm.
[0040] The length of the second shaft segment 102 is 55.5 mm, and the outer diameter of the second shaft segment 102 is 80 mm.
[0041] The length of the third shaft segment 103 is 60mm, and the outer diameter of the second shaft segment 102 is 92mm.
[0042] The length of the fourth shaft segment 104 is 100mm, and the outer diameter of the second shaft segment 102 is 87mm.
[0043] The fifth shaft segment 105 has a length of 55.5 mm, and the second shaft segment 102 has an outer diameter of 80 mm. The fifth shaft segment 105 and the second shaft segment 102 have the same structure.
[0044] The sixth shaft segment 106 has a length of 14.5 mm and an outer diameter of 68 mm. The sixth shaft segment 106 has the same structure as the first shaft segment 101.
[0045] One of the two countersunk holes 1020 is located in the first shaft section 101, and the other of the two countersunk holes 1020 is located in the sixth shaft section 106.
[0046] In related technologies, in order to ensure the machining quality of the inner hole 1010 of the shaft, the inner hole 1010 of the shaft is usually arranged to be completed in the final finishing process of the load limiting shaft.
[0047] Because the load-limiting shaft underwent heat treatment in the previous machining process, its mechanical properties and overall hardness were significantly improved compared to before heat treatment. Subsequently, during finishing, drilling was performed on the load-limiting shaft to machine its inner bore. This was difficult to achieve with ordinary alloy steel drill bits, especially when the drilling depth exceeded 120mm, as drill bit wear became extremely high, making it difficult to continue drilling. Even with solid carbide drill bits, the feed rate had to be set very low. Furthermore, to prevent the carbide drill bit from breaking due to poor chip removal during machining, the cutting depth per feed was only 0.1–0.2mm, essentially relying on the grinding wear of the drill bit for machining. Therefore, the feed and retraction strokes during drilling were long, resulting in very little effective machining time and machining volume, leading to very low machining efficiency. Moreover, the high wear of solid carbide drill bits and the high tooling cost resulted in very high overall machining costs.
[0048] However, if the slender inner hole of the shaft is machined first, and then heat treatment is performed to improve the overall hardness of the load-limiting shaft, the heat treatment will cause the part to deform, which will affect the forming accuracy of the inner hole of the shaft.
[0049] Based on the above analysis of the machining process of the load limit shaft, it is clear that conventional single machining processes can no longer effectively meet its machining quality requirements, or the time and cost required to achieve its machining accuracy requirements would be enormous. Therefore, in order to solve the machining problem of the load limit shaft, a comprehensive analysis and a new machining process scheme are needed to effectively solve the above problems.
[0050] This disclosure provides a method for machining the inner hole of a shaft, such as... Figure 2 As shown, this machining method is used to machine an inner hole inside the aforementioned limiting load shaft. The machining method includes:
[0051] S201: Roughly machine the blank of the load limiting shaft so that the blank of the load limiting shaft has an internal coarse hole.
[0052] S202: Perform heat treatment on the blank of the load limit shaft.
[0053] S203: Finish machining of the outer circle and end face of the blank of the load limiting shaft.
[0054] S204: Honing the coarse hole inside the shaft to obtain the inner hole of the shaft.
[0055] When machining the inner hole of a load-limiting shaft using the above machining method, the method first rough-machines the inner hole in the blank of the load-limiting shaft, and then performs heat treatment on the load-limiting shaft. This allows the inner hole to be machined before the heat treatment, reducing the machining difficulty of the inner hole and thus improving the overall machining efficiency of the inner hole process. Next, the blank of the load-limiting shaft is heat-treated to ensure that the structural strength of the final machined load-limiting shaft meets the usage requirements. Then, the method performs finish machining on the outer diameter and end face of the blank of the load-limiting shaft, and hones the inner hole. This finish machining ensures that the load-limiting shaft meets the dimensional requirements of the drawing, while honing allows for further machining of the inner hole, ensuring that the surface roughness and other dimensional requirements of the inner hole also meet the dimensional requirements of the drawing after honing, thus obtaining the inner hole.
[0056] In other words, the above processing method can effectively solve the processing problem of the inner hole of the load limiting shaft, and the inner hole obtained after honing can also effectively improve its processing accuracy.
[0057] On the other hand, this disclosure also provides another method for machining the inner hole of a shaft, such as... Figure 3 As shown, the processing method includes:
[0058] S301: Provides a blank for a load-limiting shaft.
[0059] In this embodiment, by rough machining the blank of the load limiting shaft, the blank of the load limiting shaft has an internal coarse hole.
[0060] When rough machining the blank of the load limiting shaft, it is necessary not only to rough machine the outer surface and end face of the blank, but also to drill a coarse hole inside the blank.
[0061] Optionally, step S301 can be implemented in the following manner:
[0062] 3011: Blanking the load-limiting shaft blank.
[0063] 3012: Rough machining of the two end faces and outer circle of the load-limiting shaft.
[0064] During rough machining, the outer diameter of the blank of the load limit shaft can be rough machined first, so that the diameter of the blank of the load limit shaft after rough machining is reserved by about 8 to 15 mm.
[0065] Figure 4 See the structural schematic diagram of the blank for the load-limiting shaft. Figure 4The blank for the load-limiting shaft is a cylindrical structure. After rough machining, the outer diameter of the blank for the load-limiting shaft is 100mm.
[0066] By rough turning the outer diameter of the blank of the load limiting shaft, the black skin formed on the outer surface of the blank after oxidation can be removed.
[0067] Then, rough-machine the two end faces of the blank of the load-limiting shaft.
[0068] When rough machining the two end faces of the load limit shaft blank, a machining allowance of 10mm is required in the length of the load limit shaft blank after rough machining.
[0069] By leaving a 10mm allowance in length, clamping can be made easier.
[0070] In addition, during rough machining, the outer circles at both ends are chamfered with R1 fillets (R1 fillets are fillets with a radius of 1mm) to prevent cracks from forming during subsequent quenching.
[0071] 3013: Mark the machining positioning lines for the inner hole of the load-limiting shaft on the blank after rough machining.
[0072] Mark the machining positioning line 1011 for the inner hole of the load-limiting shaft on the blank.
[0073] In this embodiment, the machining positioning lines can be drawn on the two end faces of the blank of the load-limiting shaft. This facilitates the positioning of the drill bit during subsequent drilling.
[0074] After scribing, use a center punch to mark holes at the center of both end faces of the blank for the load-limiting shaft. This facilitates marking and prevents difficulty in viewing the markings due to unclear machining positioning lines.
[0075] 3014: Based on the machining positioning lines, drill a rough hole inside the shaft on the blank of the load-limiting shaft using a drill bit.
[0076] In this embodiment, drilling the inner hole of the shaft is also done in a machine tool.
[0077] First, the blank of the load limit shaft is straightened and clamped onto the machine tool.
[0078] Then, using an alloy steel drill bit, referencing the machining positioning lines marked on the end face of the load-limiting shaft blank, drill the inner hole of the load-limiting shaft.
[0079] Figure 5 This is a structural schematic diagram of a blank for a load-limiting shaft with an internal coarse hole, combined with... Figure 5 The diameter of the drilled inner bore is 0.8 to 1 mm smaller than that of the final formed inner bore.
[0080] It is important to note that the machining parameters of the drilling tool should be set according to the equipment and tool conditions. During the machining process, iron filings should be cleaned up in time to prevent poor chip removal from squeezing the drill bit and causing it to break.
[0081] In this embodiment, the inner hole can be drilled using a common alloy steel drill bit.
[0082] Since the blank of the load-limiting shaft was not heat-treated when it was first rough-machined, its hardness and strength have not been significantly improved. Therefore, the inner hole can be easily obtained by drilling directly with a drill bit.
[0083] The drilling method for the above internal holes can be referred to the method for drilling internal holes with a drill bit. It will not be described in detail here.
[0084] S302: Annealing is performed on the blank of the load-limiting shaft after rough machining.
[0085] This can eliminate residual stress from rough machining and prevent deformation during subsequent finishing processes.
[0086] During annealing, the rough-machined blank of the load-limiting shaft can be kept in a holding furnace at 200-500°C for 6-8 hours, and then cooled to room temperature.
[0087] S303: Perform heat treatment on the blank of the load limit shaft.
[0088] Tempering refers to a dual heat treatment method of quenching and high-temperature tempering to give the load-limiting shaft good overall mechanical properties.
[0089] High-temperature tempering is usually carried out between 300-650℃. The resulting microstructure is tempered sorbite, which has high strength, good plasticity and toughness.
[0090] In other words, tempering involves two steps: quenching and high-temperature tempering. Quenching involves heating the load-bearing limiting shaft to a certain temperature and then rapidly cooling it to achieve high hardness and strength. High-temperature tempering is then performed to eliminate the internal stress and brittleness generated during quenching, improving the workpiece's plasticity and toughness. Tempering can significantly improve the properties of steel, making it more reliable during use.
[0091] In this embodiment, the conditioning process can be implemented according to the following steps:
[0092] First, place the blank of the load-limiting shaft upright in the tray, with the length of the blank vertical. The extension direction of the inner bore of the shaft is also vertical. The inner bore of the shaft is vertical.
[0093] Next, the blanks of the tray and the load limiting shaft are placed in a heating furnace for heating and then quenched.
[0094] When heating the blank of the load-limiting shaft, the blank is placed in a pit furnace for heating, which can reduce heat treatment deformation. The heating temperature of the furnace is 300-650°C.
[0095] Then, the blanks of the tray and the load-limiting shaft are placed in a heating furnace for tempering.
[0096] During tempering, the heating temperature of the furnace is 300-650°.
[0097] After heat treatment, the mechanical properties of the blank of the load limit shaft meet the following requirements: σb≥1350MPa, σa≥1250MPa, δ5≥9% (longitudinal), ψ≥45% (longitudinal), Aku2≥27J (longitudinal, room temperature), and hardness HRC50.
[0098] S304: Perform ultrasonic testing on the blank of the load-limiting shaft.
[0099] Because the blank of the load-limiting shaft may contain internal defects after heat treatment, ultrasonic testing is necessary to inspect the blank of the load-limiting shaft to avoid these defects.
[0100] Ultrasonic testing shall be conducted in accordance with GB / T6402-2008, Level 3 acceptance. If the blank of the load-limiting shaft is found to be non-compliant with acceptance requirements after ultrasonic testing, the aforementioned steps S301-S303 shall be repeated until the blank of the load-limiting shaft meets the GB / T6402-2008, Level 3 acceptance standard.
[0101] S305: Finish machining of the outer circle and end face of the blank of the load limiting shaft.
[0102] When finishing the blank of the load limiting shaft, the blank can be placed in a lathe, and the center line of the coarse hole inside the blank can be aligned with the rotation center of the lathe.
[0103] Next, the blank of the load limit shaft is corrected so that the end face of the blank of the load limit shaft is parallel to the worktable.
[0104] Then, one end face of the blank of the load limiting shaft is precision machined, and the precision machined end face is used as the reference for the remaining finishing.
[0105] Next, the outer circle and another end face of the blank of the load limiting shaft are precision machined so that the length and outer diameter of each shaft segment in the blank of the load limiting shaft meet the requirements of the drawing.
[0106] In summary, when finishing the blank of the load-limiting shaft, the outer circle, end faces and countersunk holes of the blank are precision machined according to the drawing requirements of the load-limiting shaft, and each dimension is controlled to meet the requirements.
[0107] It should be noted that during the finishing process, the dimensional tolerances, surface roughness, and geometric tolerances of the load-bearing limit shaft should also meet the requirements.
[0108] S306: Honing the inner hole of the shaft.
[0109] Honing, also known as boring, is a finishing process performed on a surface to be finished using an oilstone (also known as a honing bar) embedded in a honing head.
[0110] During honing, the blank of the load-limiting shaft is mounted on the honing machine's worktable or in a fixture. A honing head with several honing stones is inserted into the shaft's inner bore, which was machined during roughing. The honing head is driven to rotate by the machine tool spindle and performs axial reciprocating motion. The honing stones contact the bore wall with a certain pressure, removing a very thin layer of metal, thus allowing for further grinding of the shaft's inner bore.
[0111] In this embodiment, a hard honing head is used to hone the inner hole of the shaft.
[0112] The inner hole of the shaft is honed using honing heads of various diameters. By gradually expanding the hole, the diameter of the inner hole of the load-limiting shaft is gradually increased to the required Φ8 (0 to +0.1) mm, while ensuring that the form and position tolerances and the surface roughness of the hole meet the requirements.
[0113] The above series of honing heads includes multiple honing heads with different diameters, the diameters of which gradually increase, and the diameters of the multiple honing heads are between 0.5-3mm.
[0114] By gradually increasing the diameter of the honing head, the honing head can be made to fit against the inner wall of the coarse hole in the shaft in real time, so as to continuously grind the coarse hole in the shaft. After grinding, the coarse hole in the shaft can meet the size requirements of the inner hole in the shaft, and finally complete the machining of the inner hole in the load-limiting shaft.
[0115] S307: Deburring and cleaning the blank of the honed load-limiting shaft.
[0116] To make the surface of the load limit shaft smoother and cleaner, the blank of the honed load limit shaft is deburred and cleaned.
[0117] Then, after cleaning, the load limit shaft is air-dried and then stored with an oil seal.
[0118] In this embodiment of the disclosure, when machining the inner hole of the shaft, the machining process of the load-limiting shaft is changed, and the combination of "drilling + honing" is used to machine the inner hole of the shaft. This effectively solves the problem of machining the inner hole of the high-strength load-limiting shaft. Moreover, it can also improve the overall machining efficiency of the load-limiting shaft and reduce the process cost while ensuring the machining quality of the load-limiting shaft.
[0119] The above description is merely an optional embodiment of this disclosure and is not intended to limit this disclosure. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this disclosure should be included within the protection scope of this disclosure.
Claims
1. A method for machining the inner hole of a shaft, characterized in that, The load-limiting shaft is a 40CrNiMo alloy steel structural component, and the machining method includes: The blank of the load limiting shaft is rough machined so that the interior of the blank of the load limiting shaft has a coarse hole, the diameter of which is 0.8~1mm smaller than the diameter of the inner hole. The blank of the load limiting shaft is subjected to heat treatment, and the blank of the load limiting shaft is placed upright on a tray so that the extension direction of the coarse hole in the shaft is vertical. The blanks of the tray and the load limiting shaft are placed in a heating furnace for heating at a temperature of 300-650°C, and then quenched after heating. The blanks of the tray and the load limiting shaft are placed in the heating furnace for tempering. During tempering, the heating temperature of the heating furnace is 300-650℃. After the tempering treatment, the hardness of the blank of the load limiting shaft meets the hardness HRC50 acceptance. Ultrasonic testing is performed on the blank of the load limiting shaft to detect whether there are any defects in the blank of the load limiting shaft. The outer circle and end face of the blank of the load limiting shaft are precision machined; The shaft inner hole is gradually enlarged using a series of honing heads to achieve the required diameter and surface roughness, thus obtaining the shaft inner hole. The series of honing heads includes multiple honing heads with different diameters, each ranging from 0.5 to 3 mm, and the diameters of the multiple honing heads gradually increase. After honing, the load limiting shaft is deburred and cleaned. After cleaning, the load limiting shaft is air-dried and then stored with an oil seal.
2. The processing method according to claim 1, characterized in that, The rough machining of the load-limiting shaft blank, resulting in an internal coarse hole, includes: Roughly machine the two end faces and outer circle of the blank of the load limiting shaft; Mark the machining positioning lines of the inner hole of the load-limiting shaft on the blank after rough turning; According to the machining positioning line, a coarse hole is drilled in the blank of the load limiting shaft using a drill bit.
3. The processing method according to claim 1, characterized in that, The finishing of the outer circle and end face of the blank of the load limiting shaft includes: The blank of the load limiting shaft is placed in a lathe, and the center line of the coarse hole inside the shaft is aligned with the rotation center of the lathe. The blank of the load limiting shaft is corrected so that the end face of the blank of the load limiting shaft is parallel to the worktable. One end face of the blank of the load limiting shaft is precision machined, and the precision machined end face is used as the reference for the remaining precision machining. The outer circle and another end face of the blank of the load limiting shaft are precision machined so that all dimensions of the load limiting shaft meet the drawing requirements.
4. The processing method according to claim 1, characterized in that, The processing method further includes: annealing the rough-machined blank of the load limiting shaft before performing heat treatment on the blank of the load limiting shaft.