Necking tool for small tubes

Abstract

The utility model relates to metal tubular product machining technical field, especially a kind of necking tool for small pipe material.The necking tool for small pipe material provided by the utility model includes rack, multi-petal chuck, shaft sleeve and drive assembly.The top end of the multi-petal chuck forms forming cavity, the inner diameter of the shaft sleeve gradually changes along the extension direction of the petal, when the drive assembly drives the shaft sleeve to move, the shaft sleeve forces the petal to gather, and the pipe material necking is realized by the forming cavity reducing.It avoids the radial deviation and axial slip of pipe material by the uniform extrusion of multi-petal chuck and gradually changing shaft sleeve, significantly improves the necking size accuracy and roundness;structure is simple and does not need high-cost equipment, convenient operation, adapts to small and medium batch multi-specification production, effectively improves the stability and production applicability of small pipe material necking quality.

Description

Technical Field

[0001] This utility model relates to the field of metal pipe processing technology, and in particular to a necking tool for small pipes. Background Technology

[0002] In the field of metal pipe processing, the necking process is a key step that reduces the diameter of the pipe end using external force. It is widely used in pipe connections and sealing structure manufacturing in industries such as automotive, aerospace, and hydraulics / pneumatics. The quality of pipe necking directly affects the subsequent assembly accuracy, sealing performance, and overall product reliability. Therefore, strict requirements are placed on the necking dimensional accuracy (usually requiring tolerance control within ±0.1mm) and roundness (generally requiring a roundness error of no more than 0.08mm). Currently, for the necking processing of small pipes (outer diameter 5~50mm), the industry generally uses special fixtures in conjunction with presses, spinning machines, or manual hydraulic equipment. In existing technologies, special fixtures typically employ single-end positioning or simple radial clamping structures. Specific implementation methods mainly fall into two categories: one is to apply axial pressure to the pipe end using a press-driven punch, causing plastic deformation of the pipe within a mold; the other is to use a spinning machine to drive rollers to rotate around the pipe axis, achieving necking through gradual feeding.

[0003] However, traditional clamps often employ single-sided clamping or single-point positioning, which can easily lead to eccentric displacement of the pipe during the necking process due to insufficient radial constraint. Simultaneously, the lack of a stable anti-slip structure in the axial direction causes axial slippage of the pipe under pressure. This uneven force distribution can result in excessive ellipticity and uneven wall thickness at the necking area. In actual production, the necking dimensional deviation often exceeds 0.05mm, and the roundness error generally exceeds 0.06mm, making it difficult to meet high-precision assembly requirements. Furthermore, press-driven methods suffer from large instantaneous impact forces and low force control precision, easily causing wrinkles or cracks at the pipe ends. While spinning machines can achieve progressive deformation, they are prone to excessive local plastic deformation due to uneven radial force distribution in thin-walled small pipes (wall thickness ≤1mm), and the equipment purchase and maintenance costs are high, making them unsuitable for small-batch, multi-specification production scenarios.

[0004] The aforementioned problems make it difficult for existing small pipe shrinking processes to meet the high-quality, fast-paced production demands of modern manufacturing in terms of precision control, production efficiency, and cost control. Therefore, there is an urgent need to develop a shrinking tooling equipment for small pipes that combines high precision and high efficiency. Utility Model Content

[0005] Based on this, it is necessary to address the above-mentioned shortcomings by providing a tooling for narrowing small pipes, comprising: a frame, a multi-lobed chuck fixed to the frame, a bushing sleeved on the multi-lobed chuck, and a drive assembly pulsatingly connected to the bushing sleeve. The multi-lobed chuck includes: a base fixed to the frame, and a plurality of lobes spaced apart from each other on the base. The tips of the plurality of lobes together form a forming cavity for narrowing small pipes. The bushing sleeve is hollow inside and has a first opening and a second opening at both ends. The diameter of the first opening is smaller than the diameter of the second opening. The inner diameter of the bushing gradually decreases along the direction from the second opening to the first opening. The drive assembly drives the bushing to move along the extension direction of the lobes. When narrowing small pipes, the bushing moves towards the base, forcing the plurality of lobes to converge, and the narrowing of the forming cavity forces the end diameter of the small pipe to decrease.

[0006] Preferably, the frame includes: a base, a plurality of support columns fixed on the base, a fixing plate fixed to the top of the plurality of support columns, the multi-lobed clamp fixed on the fixing plate, and the drive assembly fixed on the base.

[0007] Preferably, it further includes a plurality of first bolts, a plurality of first threaded holes are provided on the fixing plate, and a first through hole is provided on the base of the multi-lobed chuck, which is opposite to the plurality of first threaded holes. The plurality of first bolts pass through the first through hole and are threadedly connected to the first threaded hole, thereby fixing the multi-lobed chuck to the fixing plate.

[0008] Preferably, the system further includes several second bolts. The support column has second threaded holes on both ends. The fixing plate has a second through hole opposite to the second threaded hole. The base has a third through hole opposite to the second threaded hole. The second bolt passes through the second through hole and is threaded into the second threaded hole, thus fixing the fixing plate to the support column. The second bolt passes through the third through hole and is threaded into the second threaded hole, thus fixing the support column to the base.

[0009] Preferably, the fixing plate is provided with a guide post parallel to the extension direction of the clamping petals, the guide post is located next to the multi-petal clamp, and the bushing is provided with a first shaft extension hole that matches the guide post, and the bushing is sleeved on the guide post through the first shaft extension hole.

[0010] Preferably, the drive assembly includes: a cylinder fixed to the base, a pull rod fixed to the telescopic end of the cylinder, a plurality of second shaft extension holes matching the pull rod being provided on the fixing plate, the pull rod being fixedly connected to the bushing through the second shaft extension holes, the cylinder being connected to an external air source, and the cylinder being used to drive the pull rod to move the bushing on the multi-lobed chuck.

[0011] Preferably, the bushing, the multi-lobed chuck, and the telescopic shaft of the cylinder are arranged on the same central axis. A disc is provided on the telescopic shaft of the cylinder, and several of the pull rods are evenly spaced and fixedly connected to the disc around the central axis.

[0012] Preferably, the assembly further includes a plurality of third bolts. Each of the tie rods has a third threaded hole on both ends. The bushing has a fourth through hole opposite to the third threaded hole. The disc has a fifth through hole opposite to the third threaded hole. The plurality of third bolts pass through the fourth through hole and are threaded into the third threaded hole to fix the bushing to the tie rod. The plurality of third bolts pass through the fifth through hole and are threaded into the third threaded hole to fix the tie rod to the disc.

[0013] Preferably, the number of pull rods is 4 and the number of clamping petals is 6.

[0014] Preferably, the number of guide posts is four.

[0015] The aforementioned sizing fixture for small pipes, through the cooperation of a multi-lobed chuck and an inner diameter-gradient bushing, allows the drive assembly to move the bushing. When the bushing moves, the bushing applies a uniform radial extrusion force to several lobes, forcing them to converge synchronously. This ensures that the constraint force of the forming cavity on the pipe end is evenly distributed, avoiding radial eccentricity and axial slippage caused by traditional single-sided clamping or single-point positioning. This significantly reduces sizing dimensional deviations and roundness errors. At the same time, this structure does not rely on the instantaneous impact of a press or a high-cost spinning machine. It is stable in operation and simple in structure, making it more suitable for small and medium batch production scenarios and improving the stability and production applicability of sizing quality for small pipes. Attached Figure Description

[0016] Figure 1 This is a perspective view of a necking tool for small pipes in one embodiment of the present invention. Figure 2 This is a front view of a necking tool for small pipes in one embodiment of the present invention; Figure 3 This is a top view of a necking tool for small pipes in one embodiment of the present invention; Figure 4 This is an exploded view of a necking tool for small pipes in one embodiment of the present invention; Figure 5 This is a schematic diagram of the structure of a multi-lobed clamp for a constriction tool for small pipes in one embodiment of the present invention; Figure 6 This is a schematic diagram of the bushing structure of a necking tool for small pipes in one embodiment of the present invention. Figure 7 This is a schematic diagram of the bushing of a necking tool for small pipes from another perspective in one embodiment of the present invention. Figure 8 This is a schematic diagram of the drive assembly (cylinder) for a necking tool for small pipes in one embodiment of the present invention.

[0017] Explanation of reference numerals in the attached drawings: 100-Frame, 110-Base, 110a-Third through hole, 120-Support column, 120a-Second threaded hole, 130-Fixing plate, 130a-First threaded hole, 130b-Second through hole, 130c-Second shaft extension hole, 131-Guide column, 200-Multi-lobed chuck, 210-Base, 210a-First through hole, 220-Clamping lobe, 220a-Forming cavity, 300-Busset, 300a-First opening, 300b-Second opening, 300c-First shaft extension hole, 300d-Fourth through hole, 400-Drive assembly, 410-Cylinder, 411-Disc, 411a-Fifth through hole, 420-Tie rod, 420a-Third threaded hole, 510-First bolt, 520-Second bolt, 530-Third bolt. Detailed Implementation

[0018] To make the above-mentioned objects, features, and advantages of this utility model more apparent and understandable, the specific embodiments of this utility model will be described in detail below with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a full understanding of this utility model. However, this utility model can be implemented in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of this utility model. Therefore, this utility model is not limited to the specific embodiments disclosed below.

[0019] This utility model discloses a necking tool for small pipes, such as... Figures 1-8As shown, the assembly includes: a frame 100, a multi-lobed chuck 200, a bushing 300, and a drive assembly 400. The multi-lobed chuck 200 includes: a base 210 and a plurality of lobes 220. The multi-lobed chuck 200 is fixed to the frame via the base 210. The lobes 220 surround the base 210, and their top ends together form a forming cavity 220a for narrowing small tubes. The bushing 300 is hollow inside, and has a first opening 300a and a second opening 300b at both ends. The diameter of the first opening 300a is smaller than that of the second opening. The diameter of the bushing 300b is gradually reduced along the direction from the second opening 300b to the first opening 300a, that is, the bushing 300 forms a cavity that is narrow at the top and wide at the bottom. The bushing 300 is fitted onto the multi-lobed chuck 200. The drive assembly 400 is fixed on the frame 100 and is connected to the bushing 300 in a transmission manner. The drive assembly 400 drives the bushing 300 to move along the extension direction of the lobes 220 on the multi-lobed chuck 200. In one embodiment, it moves up and down, and in another embodiment, it moves back and forth, depending on the orientation of the device. When performing the necking operation on small tubes, the bushing 300 moves toward the base 210. As the inner diameter of the bushing 300 gradually decreases along the direction from the second opening 300b to the first opening 300a, the inner wall of the bushing 300 will exert radial extrusion force on the clamping petals 220. Under the action of this extrusion force, the bushing 300 forces several clamping petals 220 to gather together. The end of the small tube placed in the forming cavity 220a is squeezed by the forming cavity 220a, and its diameter is forced to shrink, thereby achieving the purpose of necking.

[0020] The process of using the shrunk pipe tooling provided by this utility model is as follows: Step S1, Preparation stage: Check whether all components of the shrunk pipe tooling are normal, ensure that the frame 100 is stable, the clamping segments 220 of the multi-segment chuck 200 are undamaged and deformed, the inner wall of the bushing 300 is smooth and free of foreign objects, and the drive assembly 400 is reliably connected. Step S2, Clamping the pipe: Place the end of the small pipe to be shrunk into the forming cavity 220a formed by the clamping segments 220 surrounding the top of the multi-segment chuck 200, ensuring that the pipe is placed stably and accurately. Step S3, Starting the equipment: Operate the drive assembly 400 to drive the bushing 300 to move along the extension direction (i.e., the up and down direction) of the clamping segments 220 on the multi-segment chuck 200 towards the base 210. Step S4, Narrowing Process: As the bushing 300 moves towards the base 210, it forces several clamping segments 220 to converge, causing the forming cavity 220a to shrink, thereby reducing the diameter of the small tube end and achieving narrowing. Step S5, Completion and Reset: Once the tube end has narrowed to the required size, the drive assembly 400 is operated to move the bushing 300 away from the base 210. The clamping segments 220 return to their original shape under their own elasticity, the forming cavity 220a expands, and the narrowed tube is removed, completing the narrowing process.

[0021] The multi-lobed chuck 220 of this utility model for sizing small pipes applies a uniform radial compressive force to all lobes 220 as the bushing 300 moves toward the base 210, causing the lobes 220 to converge synchronously toward the center. This uniform convergence ensures an extremely balanced distribution of compressive force on the pipe end from the forming cavity 220a, avoiding excessive or insufficient local force and fundamentally reducing radial offset and axial movement of small pipes. This significantly reduces the probability of sizing dimensional deviations, ensures good roundness of the sized pipe end, and effectively improves the accuracy and quality stability of the sizing process. Furthermore, this utility model's sizing fixture has a simple structural design and is easy to operate, requiring no complex disassembly. Simply ensure the pipe is correctly placed in the forming cavity 220a according to its size, and control the movement distance of the bushing 300 via the drive assembly 400 to achieve sizing, significantly shortening processing time, effectively improving overall production efficiency, and better adapting to the needs of mass production.

[0022] In one embodiment, such as Figures 1-4 As shown, the frame 100 includes: a base 110, a support column 120 fixed on the base 110, and a fixing plate 130 fixed to the top of the support column 120. The multi-lobed clamp 200 is fixed on the fixing plate 130, and the drive assembly 400 is fixed on the base 110. When the drive assembly 400 is working, it will generate a reaction force opposite to the direction of the driving force. After it is fixed to the base 110, the reaction force is directly borne by the rigidity of the base 110. The force generated by the clamping lobes 220 being squeezed by the bushing 300 is transmitted to the base 110 through the fixing plate 130 and the support column 120, achieving a balance on the same rigid basis. This closed-loop balance of forces can reduce additional impacts on other weak parts of the frame 100 and extend the service life of the components.

[0023] In one embodiment, such as Figures 1-5 As shown, the necking fixture also includes several first bolts 510. The fixing plate 130 has several first threaded holes 130a. The base 210 of the multi-lobed chuck 200 has first through holes 210a corresponding to the first threaded holes 130a. The first bolts 510 pass through the first through holes 210a and are threaded into the first threaded holes 130a, thus fixing the multi-lobed chuck 200 to the fixing plate 130. The preload of the first bolts 510 ensures a tight fit between the base 210 and the fixing plate 130, eliminating gaps and forming a rigid whole. Compared to non-removable fixing methods such as welding, bolted connections allow for quick disassembly and replacement of the multi-lobed chuck of corresponding specifications according to the necking requirements of different pipe materials (such as different diameters and necking shapes), significantly improving the versatility of the fixture. Simultaneously, when the lobes 220 wear, the base 210 is damaged, or cleaning and maintenance are required, disassembly and repair can be easily performed, reducing maintenance costs and downtime.

[0024] In one embodiment, such as Figures 1-4 As shown, the necking fixture also includes several second bolts 520. The support column 120 has second threaded holes 120a on both ends. The fixing plate 130 has second through holes 130b opposite to the second threaded holes 120a. The base 110 has a third through hole 110a opposite to the second threaded holes 120a. The second bolts 520 pass through the second through holes 130b and are threaded into the second threaded holes 120a, fixing the fixing plate 130 to the support column 120. The second bolts 520 also pass through the third through holes 110a and are threaded into the second threaded holes 120a, fixing the support column 120 to the base 110. The preload of the second bolts 520 ensures a tight fit between the support column 120, the fixing plate 130, and the base 110, eliminating gaps between components and forming a rigid integrated frame for the machine frame 100 (base 110, support column 120, fixing plate 130). Compared to non-removable connections such as welding, bolted connections allow for flexible adjustments based on actual needs: for example, the height of the fixing plate can be adjusted by replacing the support column 120 with one of different lengths (to accommodate pipes of different lengths or drive components with a 400-degree stroke); or a higher-strength support column 120 can be replaced according to the required necking precision; when the support column 120, fixing plate 130, or base 110 is partially damaged, it can be disassembled and replaced individually without the need for complete scrapping, significantly reducing maintenance costs and tooling adjustment cycles, and improving the adaptability of the tooling to different scenarios.

[0025] In one embodiment, such as Figures 1-4 As shown, the fixed plate 130 is provided with a guide post 131 parallel to the extension direction of the clamping petals 220. The guide post 131 is located next to the multi-petal clamp 200. The bushing 300 has a first shaft extension hole 300c that matches the guide post 131. The bushing 300 is sleeved on the guide post 131 through the first shaft extension hole 300c. The guide post 131 is parallel to the extension direction of the clamping petals 200 and is fixed on the fixed plate 130, forming a stable linear reference. The first shaft extension hole 300c of the bushing 300 matches the size of the guide post 131. When the bushing 300 is sleeved on the guide post 131, the two form a sliding fit, forcing the movement trajectory of the bushing 300 to strictly follow the axis of the guide post 131 (i.e., the extension direction of the clamping petals 200), restricting the bushing 300 from radial offset or circumferential rotation. The guide post 131 constrains the squeezing force of the inner wall of the bushing 300 on the clamping petals 200 so that the squeezing force is evenly distributed on each clamping petal 200, avoiding uneven local force caused by the skewness of the bushing 300. The shrinkage process of the forming cavity 220a is more uniform, and ultimately the end roundness of the tube after shrinkage is higher and the diameter is more accurate.

[0026] In one embodiment, such as Figures 1-4 , Figure 8As shown, the drive assembly 400 includes: a cylinder 410 fixed on the base 110, a pull rod 420 fixed to the telescopic end of the cylinder 410, and a plurality of second shaft extension holes 130c matching the pull rod 420 on the fixing plate 130. The pull rod 420 passes through the second shaft extension holes 130c and is fixedly connected to the bushing 300. The cylinder 410 is connected to an external air source and is used to drive the pull rod 420 to move the bushing 300 on the multi-lobed chuck 200. The bushing 300, the multi-lobed chuck 200, and the telescopic shaft of the cylinder 410 are set on the same central axis. A disc 411 is provided on the telescopic shaft of the cylinder 410. The end of the telescopic shaft is fixed at the center of the lower surface of the disc 411. That is, the bushing 300, the multi-lobed chuck 200, the telescopic shaft of the cylinder 410, and the disc 411 are on the same central axis, eliminating the eccentricity caused by the axis offset and avoiding additional torque during force transmission. Several tie rods 420 are evenly spaced and fixedly connected to the disc 411 around the central axis. The driving force of the cylinder 410 is distributed to each tie rod 420 through the disc 411, and then the tie rods 420 act synchronously on the bushing 300, so that the driving force on the bushing 300 is symmetrically distributed along the central axis, forming a resultant force along the axial direction without radial off-center load. The inner wall conical surface of the bushing has a more uniform squeezing force on each lobed 220, which improves the dimensional accuracy and shape accuracy (roundness) of the constricted end of the pipe.

[0027] In one embodiment, such as Figures 1-8 As shown, the necking fixture also includes several third bolts 530. Each pull rod 420 has a third threaded hole 420a on both ends. The bushing 300 has a fourth through hole 300d opposite to the third threaded hole 420a. The disc 411 has a fifth through hole 411a opposite to the third threaded hole 420a. Several third bolts 530 pass through the fourth through hole 300d and are threaded into the third threaded hole 420a, fixing the bushing 300 to the pull rod 420. Several third bolts 530 pass through the fifth through hole 411a and are threaded into the third threaded hole 420a, fixing the pull rod 420 to the disc 411. The threaded connection, through the preload of the third bolts 430, can generate a stable axial clamping force, effectively preventing loosening between the pull rod 420 and the bushing 300, and between the pull rod 420 and the disc 411 due to long-term reciprocating motion under stress.

[0028] In one embodiment, such as Figures 1-8 As shown, there are 4 tie rods 420, 6 clamping petals 220, and 4 guide posts 131, which optimizes the balance of driving force transmission, the precision and uniformity of the necking forming, and the guiding stability of the bushing movement.

[0029] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0030] The embodiments described above are merely illustrative of several implementations of this utility model, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the utility model patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this utility model, and these all fall within the protection scope of this utility model. Therefore, the protection scope of this utility model patent should be determined by the appended claims.

Claims

1. A necking tool for small pipes, characterized in that, include: The machine frame (100), a multi-lobed chuck (200) fixed to the machine frame (100), a bushing (300) sleeved on the multi-lobed chuck (200), and a drive assembly (400) connected to the bushing (300) for transmission. The multi-lobed chuck (200) includes: a base (210) fixed to the machine frame (100), and a plurality of lobes (220) arranged around the base (210) and spaced apart from each other. The top ends of the plurality of lobes (220) together form a forming cavity (220a) for narrowing small tubes. The bushing (300) is hollow inside and has a first opening (300a) and a second opening at both ends. The opening (300b) has a smaller diameter than the second opening (300b). The inner diameter of the bushing (300) gradually decreases along the direction from the second opening (300b) to the first opening (300a). The drive assembly (400) drives the bushing (300) to move along the extension direction of the clamping petals (200). When performing the necking operation of the small tube, the bushing (300) moves towards the base (210). The bushing (300) forces several clamping petals (220) to converge. The shrinking of the forming cavity (220a) forces the end diameter of the small tube to shrink.

2. The necking tool for small pipes according to claim 1, characterized in that, The frame (100) includes: a base (110), a plurality of support columns (120) fixed on the base (110), a fixing plate (130) fixed on the top of the plurality of support columns (120), the multi-lobed chuck (200) fixed on the fixing plate (130), and the drive assembly (400) fixed on the base (110).

3. The necking tool for small pipes according to claim 2, characterized in that, It also includes a plurality of first bolts (510), a plurality of first threaded holes (130a) are provided on the fixing plate (130), and the base (210) of the multi-lobed chuck (200) is provided with a first through hole (210a) opposite to the plurality of first threaded holes (130a). The plurality of first bolts (510) pass through the first through hole (210a) and are threaded to the first threaded hole (130a) to fix the multi-lobed chuck (200) on the fixing plate (130).

4. The necking tool for small pipes according to claim 2, characterized in that, It also includes several second bolts (520), the two ends of the support column (120) are provided with second threaded holes (120a), the fixing plate (130) is provided with a second through hole (130a) opposite to the second threaded hole (120a), the base (110) is provided with a third through hole (110a) opposite to the second threaded hole (120a), the second bolts (520) pass through the second through hole (130a) and are threaded to the second threaded hole (120a) and fix the fixing plate (130) to the support column (120), the second bolts (520) pass through the third through hole (110a) and are threaded to the second threaded hole (120a) and fix the support column (120) to the base (110).

5. The necking tool for small pipes according to claim 2, characterized in that, The fixing plate (130) is provided with a guide post (131) parallel to the extension direction of the clamping petals (220). The guide post (131) is located next to the multi-petal clamp (200). The bushing (300) is provided with a first shaft extension hole (300c) that matches the guide post (131). The bushing (300) is sleeved on the guide post (131) through the first shaft extension hole (300c).

6. The necking tool for small pipes according to claim 2, characterized in that, The drive assembly (400) includes: a cylinder (410) fixed on the base (110) and a pull rod (420) fixed to the telescopic end of the cylinder (410). The fixing plate (130) has a plurality of second shaft extension holes (130c) that match the pull rod (420). The pull rod (420) passes through the second shaft extension holes (130c) and is fixedly connected to the bushing (300). The cylinder (410) is connected to an external air source. The cylinder (410) is used to drive the pull rod (420) to move the bushing (300) on the multi-lobed chuck (200).

7. The necking tool for small pipes according to claim 6, characterized in that, The telescopic shafts of the bushing (300), the multi-lobed chuck (200), and the cylinder (410) are arranged on the same central axis. A disc (411) is provided on the telescopic shaft of the cylinder (410), and several of the pull rods (420) are evenly spaced and fixedly connected to the disc (411) around the central axis.

8. The necking tool for small pipes according to claim 7, characterized in that, It also includes several third bolts (530), each of the two ends of the pull rod (420) is provided with a third threaded hole (420a), the bushing (300) is provided with a fourth through hole (300d) opposite to the third threaded hole (420a), the disc (411) is provided with a fifth through hole (411a) opposite to the third threaded hole (420a), several of the third bolts (530) pass through the fourth through hole (300a) and are threaded to the third threaded hole (420a) and fix the bushing (300) to the pull rod (420), several of the third bolts (530) pass through the fifth through hole (411a) and are threaded to the third threaded hole (420a) and fix the pull rod (420) to the disc (411).

9. The necking tool for small pipes according to claim 7, characterized in that, The number of the pull rods (420) is 4, and the number of the clamping petals is 6.

10. The necking tool for small pipes according to claim 5, characterized in that, The number of guide posts (131) is 4.

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