Processing method of graphite holder for polycrystalline silicon reduction furnace

Abstract

The application relates to a processing method of a graphite holder for a polycrystalline silicon reduction furnace, which changes a traditional outside clamping mode into an inner supporting clamping through three tapered fingers, the taper of the tapered fingers is equal to that of a large taper hole, therefore, each tapered finger can abut against and tightly fit the surface of the large taper hole, so that the three tapered fingers are in inner supporting clamping cooperation with the large taper hole, and because the surface of the tapered finger is provided with anti-skid lines, the friction between the tapered finger and the surface of the large taper hole is relatively large, so that the once-processed semi-finished product can be prevented from sliding off the tapered finger, thereby ensuring that the once-processed semi-finished product is stably clamped by the three tapered fingers, meanwhile, because the stepped projection is provided and the diameter of the stepped projection is smaller than that of the outer circle, the machining of the outer circle can be completed by one cutting of the machine tool cutter head, the cutter need not be connected, and the machining of the first chamfer can be completed in the outer circle machining process, and the processing method disclosed by the application can complete the processing of the graphite holder through a two-step method.

Description

Technical Field

[0001] This application relates to the field of graphite casing processing technology, and in particular to a processing method for a graphite casing for a polycrystalline silicon reduction furnace. Background Technology

[0002] In traditional polycrystalline silicon production, graphite components are used to connect the silicon core and electrodes. When electricity is applied, the surface of the silicon core heats up, generating high temperatures. Then, trichlorosilane and hydrogen undergo a vapor-phase chemical deposition reaction on the high-temperature silicon core surface, causing the silicon core diameter to continuously increase. Currently, commonly used graphite components include three-piece sets (clamp, graphite cap, and graphite base) and two-piece sets (graphite head and graphite clamp). The three-piece set is cumbersome and laborious to install and disassemble. There are gaps between the threads, and during the polycrystalline silicon deposition process, some polycrystalline silicon will be deposited in the gaps between the threads. It is difficult to separate the two by manually rotating the graphite clamp and graphite cap, which is time-consuming, labor-intensive, and inefficient. The disassembly process can easily damage the three-piece set, resulting in a low reuse rate. At the same time, the three-piece set is heavy and has high procurement costs. Therefore, the three-piece set is gradually being phased out.

[0003] Currently, widely used two-piece sets include graphite card holders (such as...) Figure 1 As shown in the figure, a graphite head (refer to Chinese Utility Model Patent Application No. 2020205354179) is provided with a conical hole at the top of the graphite holder for inserting the lower end of the graphite head, a conical hole at the bottom of the graphite holder for inserting an electrode, a silicon core hole at the top of the graphite head for inserting a silicon core, and a conical shape at the bottom of the graphite head to cooperate with the conical hole at the top of the graphite holder.

[0004] For the processing of graphite chucks required in the polycrystalline silicon production process, the current common method is to process square blanks using a "three-step method". Specifically, the first step is to clamp one end of the square blank onto a four-jaw chuck and turn the outer diameter of the other end; the second step is to clamp the turned outer diameter end onto a three-jaw chuck, continue turning the outer diameter with the cutting tool, and flatten the end face to process the first tapered hole; the third step is to change the position again, clamp the end with the first tapered hole onto a three-jaw chuck, flatten the end face, and process the second tapered hole to obtain the graphite chuck. In this process, due to the need to turn the outer diameter with the cutting tool and flatten the end face after multiple clamping, the accuracy of the outer diameter machining (coaxiality) of the graphite chuck is low, and the accuracy of the flattened end face machining (end face perpendicularity) is also low, resulting in a high scrap rate (non-conforming rate). At the same time, the above "three-step method" is cumbersome and requires multiple clamping, resulting in low processing efficiency and is time-consuming and labor-intensive. Summary of the Invention

[0005] Therefore, it is necessary to address the problems in existing technologies where the machining accuracy (coaxiality) of the graphite holder's outer diameter is low due to the need for cutting the outer diameter with a tool and performing multiple clamping operations to flatten the end face, resulting in low scrap rate (non-conforming rate). Furthermore, the complex machining process, requiring multiple clamping operations, leads to low machining efficiency and is time-consuming and labor-intensive. This application provides a machining method for a graphite holder used in a polycrystalline silicon reduction furnace. By changing the clamping method from the traditional external clamping to internal clamping using three tapered fingers, the machining method disclosed in this application can complete the machining of the graphite holder in a "two-step" process. In particular, the lathe cutter head can complete the machining of the outer diameter in a single cut, thereby solving the aforementioned problems in the prior art.

[0006] A method for processing a graphite cassette for a polycrystalline silicon reduction furnace includes the following steps:

[0007] S10. Take a square blank and clamp the square blank onto a lathe using a four-jaw chuck. The end of the square blank that is clamped is the first end, and the end opposite to the first end is the second end. The second end of the square blank is machined with a flat end face by the lathe, and then a large tapered hole is machined to obtain a semi-finished product after one machining.

[0008] S20. The second end of the first-processed semi-finished product is clamped onto the lathe using a clamping mold. The clamping module includes a chuck body, three moving parts, and three jaws. The three moving parts are circumferentially arranged on the chuck body and can move synchronously along the radial direction of the chuck body. Each jaw includes a mounting part, a stepped protrusion, and a tapered finger. The stepped protrusion is located at the end of the mounting part, and the tapered finger is disposed on the stepped protrusion. The three jaws are disposed one-to-one with the moving parts. The tapered finger has the same taper as the large tapered hole, and the surface of the tapered finger is provided with anti-slip texture. The three tapered fingers are clamped and fitted with the inner support of the large tapered hole, and the second end of the first-processed semi-finished product is in contact with the stepped protrusion.

[0009] S30. The first end of the semi-finished product is machined with a flat end face using the lathe. The diameter of the stepped protrusion is smaller than the diameter of the outer circle. Then, the outer circle is machined from the first end toward the second end. The outer circle is machined in one cut without needing to connect the tools. Then, the first chamfer is machined, followed by the small tapered hole. Finally, the second chamfer is machined to obtain the graphite holder.

[0010] The technical solution adopted in this application can achieve the following beneficial effects:

[0011] In the processing method of a graphite chuck for a polycrystalline silicon reduction furnace disclosed in this application embodiment, the clamping method is changed from the traditional external clamping method to clamping by three conical fingers supporting the inner surface. Since the taper of the conical fingers is equal to that of the large conical hole, each conical finger can abut tightly against the surface of the large conical hole, ensuring a secure clamping fit between the three conical fingers and the inner surface of the large conical hole. Furthermore, because the surface of the conical fingers has anti-slip textures, the friction between the conical fingers and the surface of the large conical hole is relatively high, preventing the semi-finished product from slipping off the conical fingers during processing. This ensures that the semi-finished product is securely clamped by the three conical fingers supporting the inner surface. Simultaneously, due to the stepped protrusions, and the diameter of the stepped protrusions being smaller than the diameter of the outer circle, the machine tool cutter can complete the outer circle machining in one pass without needing to re-cut the tool. Since the diameter of the raised step is smaller than the diameter of the outer circle, the first chamfer can be completed in this outer circle machining process. The machining method disclosed in this application can complete the machining of the graphite chuck in a "two-step" process. In particular, the machine tool cutter can complete the machining of the outer circle in one cut, which avoids the problems of low accuracy (coaxiality) of the outer circle machining and low accuracy (perpendicularity) of the flat end face machining caused by the "three-step" method in the prior art, which requires tool changing and multiple clamping and end face machining. This reduces the scrap rate (defect rate). At the same time, the "two-step" machining process only requires one clamping change, which avoids multiple machining processes such as tool changing, thereby simplifying the process, reducing the number of clamping times, improving the machining efficiency of the graphite chuck, and avoiding time and labor costs. Attached Figure Description

[0012] Figure 1 This is a schematic diagram of the graphite card holder to be processed in this application;

[0013] Figure 2 This is a schematic diagram showing the semi-finished product obtained after step S10 of the present application.

[0014] Figure 3 This is a schematic diagram of step S20 of the present application, in which the second end of the semi-finished product is clamped by a clamping mold.

[0015] Figure 4 and Figure 5 This is a schematic diagram of the clamping module disclosed in an embodiment of this application;

[0016] Figure 6 for Figure 5 A magnified view of a portion of the image;

[0017] Figure 7 This is a schematic diagram of the chuck disclosed in an embodiment of this application;

[0018] Figures 8 to 10 This is a schematic diagram of the processing procedure in step S30 of the present application.

[0019] Among them: graphite base 100, outer circle 110, large conical hole 120, small conical hole 130, first chamfer 140, second chamfer 150, chuck body 200, moving part 300, chuck claw 400, mounting part 410, stepped protrusion 420, conical finger 430, anti-slip texture 431, clearance groove 440, and reinforcing block 450. Implementation

[0020] To facilitate understanding of this application, a more complete description will be provided below with reference to the accompanying drawings. Preferred embodiments of this application are shown in the drawings. However, this application can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of the disclosure of this application.

[0021] It should be noted that when an element is referred to as being "set on" another element, it can be directly on the other element or there may be an intervening element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or there may be an intervening element. The terms "vertical," "horizontal," "left," "right," "top," "bottom," "end," "top," and similar expressions used herein are for illustrative purposes only and do not represent the only possible implementation.

[0022] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein in the specification of this application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0023] Please refer to Figure 1 and Figure 10 This application discloses a method for processing a graphite holder for a polycrystalline silicon reduction furnace (hereinafter referred to as the processing method), which includes the following steps:

[0024] S10. Take a square blank and clamp it onto the lathe using a four-jaw chuck. The end of the square blank that is clamped is the first end, and the end opposite to the first end is the second end. The second end of the square blank is machined with a flat end face using the lathe, and then a large tapered hole 120 is machined to obtain a semi-finished product after one machining.

[0025] First, clamp one end (first end) of the square blank onto a four-jaw chuck. Then, flatten the other end (second end) and machine a large tapered hole of 120°. Finally, remove it from the four-jaw chuck to obtain a semi-finished product (e.g., ...). Figure 2This step is the first step in the two-step processing method.

[0026] S20. The second end of the semi-finished product is clamped onto the lathe using a clamping mold. The clamping module includes a chuck body 200, three moving parts 300, and three jaws 400. The three moving parts 300 are arranged circumferentially on the chuck body 200 and can move synchronously along the radial direction of the chuck body 200. The jaws 400 include a mounting part 410, a stepped protrusion 420, and a tapered finger 430. The stepped protrusion 420 is located at the end of the mounting part 410, and the tapered finger 430 is disposed on the stepped protrusion 420. The three jaws 400 are disposed one-to-one with the moving parts 300. The tapered finger 430 has the same taper as the large tapered hole 120, and the surface of the tapered finger 430 is provided with anti-slip texture 431. The three tapered fingers 430 are clamped and fitted with the large tapered hole 120, and the second end of the semi-finished product is in contact with the stepped protrusion 420.

[0027] The clamping module is installed on the headstock of the lathe and is used to clamp the semi-finished product for machining, so as to produce the graphite chuck 100 through the second step of the "two-step method". The graphite chuck 100 has an outer diameter 110, a large tapered hole 120 and a small tapered hole 130. The clamping module includes a chuck body 200, three moving parts 300 and three jaws 400, wherein:

[0028] Three moving parts 300 are circumferentially arranged on the chuck body 200 and can move synchronously along the radial direction of the chuck body 200. This is the same mechanical principle (movement principle of the chuck body 200 and the three moving parts 300) as in existing three-jaw chucks, and will not be elaborated further here for the sake of brevity. For details, please refer to [link to relevant documentation]. Figure 7 The chuck 400 includes a mounting portion 410, a stepped protrusion 420, and tapered fingers 430. The stepped protrusion 420 is located at the end of the mounting portion 410, and the tapered fingers 430 are disposed on the stepped protrusion 420. The three chucks 400 are correspondingly disposed on the moving parts 300, that is, they are connected to the moving parts 300 through the mounting portion 410. The mounting portion 410 and the moving parts 300 can be connected by countersunk bolts. After the three chucks 400 are installed on the three moving parts 300, the three tapered fingers 430 are aligned with the chuck body 200. When the moving parts 300 move radially along the chuck body 200, the chucks 400 also move synchronously. During the radial contraction movement of the moving parts 300 along the chuck body 200, the three tapered fingers 430 gradually form a frustum (a cone). Figure 4 During the radial expansion movement of the moving part 300 along the chuck body 200, the three tapered fingers 430 gradually open and engage with the inner support of the large tapered hole 120, thereby clamping the semi-finished product of the first processing onto the clamping module.

[0029] The taper of the frustum mentioned above is equal to the taper of the large conical hole 120, that is, the taper of the conical finger 430 is equal to the taper of the large conical hole 120, so that when the three conical fingers 430 open to internally support and clamp the graphite holder 100 ( Figure 10 The tapered finger 430 has a larger contact area with the inner surface of the large tapered hole 120, improving clamping reliability and preventing the graphite chuck 100 from detaching from the clamping module due to a smaller contact area, which would make it difficult to securely clamp the graphite chuck 100. Furthermore, to prevent the graphite chuck 100 from detaching from the clamping module, the surface of the tapered finger 430 is provided with anti-slip textures 431, which increases the friction between the tapered finger 430 and the inner surface of the large tapered hole 120, thereby further improving clamping reliability and further preventing the graphite chuck 100 from detaching from the clamping module during the clamping process. To facilitate the machining of end face chamfers (such as the first chamfer 140), the diameter of the step protrusion 420 is smaller than the diameter of the outer circle 110. This allows space to be reserved for the lathe cutter head to machine the first chamfer 140, greatly facilitating the machining of end face chamfers. This allows the machining of the outer circle and the first chamfer 140 to be completed in one operation, which helps to simplify the machining process. At the same time, this arrangement also allows a certain distance between the end face of the graphite chuck 100 near the chuck body 200 and the mounting part 410. This provides machining space for the lathe cutter head to machine the outer circle 110 in one pass, allowing the lathe cutter head to complete the machining of the outer circle 110 in one pass without the need for tool repositioning.

[0030] During the process of assembling a semi-finished product using a clamping mold, the three conical fingers 430 are first retracted so that the three conical fingers 430 are in a position as follows: Figure 4 As shown in the diagram, the worker holds the semi-finished product in one hand and aligns the machined large conical hole 120 with the three conical fingers 430. The three conical fingers 430 are then inserted into the large conical hole 120 until their end faces are in contact with the stepped protrusion 420. The three conical fingers 430 are then driven to open. Because the conical fingers 430 have the same taper as the large conical hole 120, each conical finger 430 gradually comes into contact with and presses tightly against the surface of the large conical hole 120 during the opening process, until the three conical fingers 430 are securely clamped within the large conical hole 120. At this point, because the surface of the conical fingers 430 has anti-slip textures 431, the friction between the conical fingers 430 and the surface of the large conical hole 120 is relatively high, preventing the semi-finished product from slipping off the conical fingers 430. This ensures that the semi-finished product is securely clamped within the three conical fingers 430. (Reference) Figure 3 .

[0031] S30. The first end of the semi-finished product is machined with a flat end face using a lathe. The diameter of the step protrusion 420 is smaller than the diameter of the outer circle 110. Then, the outer circle is machined from the first end toward the second end. The outer circle 110 is machined in one cut without needing to connect the tools. Then, the first chamfer 140 is machined, the small tapered hole 130 is machined, and finally the second chamfer 150 is machined to obtain the graphite holder 100.

[0032] Please refer to Figures 8 to 10 After the semi-finished product is clamped in one machining operation, the flat end face (first end) is machined, and then the outer diameter is turned. Because there is a stepped protrusion 420 and the diameter of the stepped protrusion 420 is smaller than the diameter of the outer diameter 110, the machine tool cutter head can complete the machining of the outer diameter 110 in one cut from the first end to the second end without needing to connect the cutter head. Since the diameter of the stepped protrusion 420 is smaller than the diameter of the outer diameter 110, the first chamfer 140 is then machined. The cutter head is then returned to the first end to machine the small tapered hole 130. Finally, the first chamfer 140 is machined to obtain the graphite clasp 100. The above steps S20 and S30 belong to the second step of the machining method - two-step method. The machining of the graphite clasp 100 is completed by the two-step method.

[0033] In the processing method of a graphite chuck for a polycrystalline silicon reduction furnace disclosed in this application embodiment, the clamping method is changed from the traditional external clamping method to clamping by three conical fingers 430 supporting the inner surface. Since the taper of the conical fingers 430 is equal to that of the large conical hole 120, each conical finger 430 can abut and tightly fit against the surface of the large conical hole 120, allowing the three conical fingers 430 to clamp and cooperate with the inner surface of the large conical hole 120. Furthermore, because the surface of the conical fingers 430 is provided with anti-slip textures 431, the friction between the conical fingers 430 and the surface of the large conical hole 120 is relatively large, preventing the semi-finished product from slipping off the conical fingers 430 during processing. This ensures that the semi-finished product is securely clamped by the three conical fingers 430 supporting the inner surface. Simultaneously, due to the stepped protrusion 420, and the diameter of the stepped protrusion 420 being smaller than the diameter of the outer circle 110, the machine tool cutter can complete the outer circle 110 in one cut. The machining of the graphite clasp 100 does not require tool insertion, and since the diameter of the step protrusion 420 is smaller than the diameter of the outer circle 110, the first chamfer 140 can be completed in this outer circle 110 machining process. The machining method disclosed in this application can complete the machining of the graphite clasp 100 in a "two-step" manner. In particular, the machine tool head can complete the machining of the outer circle 110 in one cut, which avoids the problems of the existing "three-step" method, which requires tool insertion to turn the outer circle and multiple clampings to flatten the end face, resulting in lower accuracy (coaxiality) of the outer circle machining of the graphite clasp 100 and lower accuracy (end face perpendicularity) of the flat end face machining. This reduces the scrap rate (defect rate). At the same time, in the "two-step" machining process, only one clamping change is required, which avoids multiple machining operations such as tool insertion, thereby simplifying the process, reducing the number of clamping operations, and improving the machining efficiency of the graphite clasp 100, avoiding time and labor costs.

[0034] To further increase the friction between the tapered fingers 430 and the inner surface of the large tapered hole 120, thereby improving clamping reliability, optionally, in step S10, the large tapered hole 120 has machining marks left after machining, and in step S20, the machining marks cooperate with the anti-slip texture 431 for anti-slip. During the machining of the large tapered hole 120 by the machine tool head, machining marks will inevitably be left after the head is machined, that is, the large tapered hole 120 has machining marks left after the tool (head) is machined. These machining marks have no impact on the final use of the graphite chuck 100. In this application, these machining marks can cooperate with the anti-slip texture 431 for anti-slip, which can further increase the friction between the tapered fingers 430 and the inner surface of the large tapered hole 120, thereby further improving clamping reliability and further preventing the semi-finished product from slipping off the tapered fingers 430, thus ensuring that the semi-finished product is stably clamped by the three tapered fingers 430, improving the reliability of the machining process.

[0035] Furthermore, the machining groove and the anti-slip groove 431 are threads with opposite directions of rotation. With this configuration, during the machining process, the machining groove and the anti-slip groove 431 thread fit together. The more the semi-finished product rotates, the tighter the fit between the machining groove and the anti-slip groove 431 thread becomes. This further prevents the semi-finished product from slipping off the tapered fingers 430, thus ensuring that the semi-finished product is securely clamped and supported by the three tapered fingers 430, improving the reliability of the machining process.

[0036] As mentioned above, since the diameter of the step protrusion 420 is smaller than the diameter of the outer circle 110, the first chamfer 140 can be completed in the outer circle 110 machining process. Specifically, the diameter of the step protrusion 420 is at least 1 cm smaller than the diameter of the outer circle 110, leaving at least 1 cm of length space for the cutter to machine the chamfer in one cut, ensuring that the first chamfer 140 can be completed in the second outer circle 110 machining process, and avoiding production accidents such as tool collision.

[0037] In this application, the measures to ensure the end face machining accuracy are as follows: the end face machined in the first step (S10 step) needs to fit with the stepped protrusion 420 in the second step. This ensures that after the outer circle 110 is machined in the second step, the perpendicularity between the end face and the outer circle 110 is high, that is, the end face machining accuracy (end face perpendicularity) is high. In order to improve the fit between the end face machined in the first step and the stepped protrusion 420 in the second step, and thus improve the end face machining accuracy, optionally, a clearance groove 440 is provided at the root where the tapered finger 430 connects to the stepped protrusion 420. The root where the tapered finger 430 connects to the stepped protrusion 420 is prone to leaving an arc-shaped transition during the machining process. That is, it is impossible to machine a standard straight line intersection effect, but rather a straight line intersection with an arc. In this way, during the process of the end face machined in the first step fitting with the stepped protrusion 420 in the second step, The opening of the large conical hole 120 (where the large conical hole 120 intersects with the end face) is curved, making it difficult for the end face after the first step to fit with the stepped protrusion 420 in the second step. Therefore, a clearance groove 440 is provided at the root where the conical finger 430 connects with the stepped protrusion 420. The clearance groove 440 can avoid the opening of the large conical hole 120, thus preventing the opening of the large conical hole 120 from being curved. This avoids the end face after the first step from being difficult to fit with the stepped protrusion 420 in the second step, thereby improving the fit between the end face after the first step and the stepped protrusion 420 in the second step and ensuring the end face machining accuracy. At the same time, it can also prevent the opening of the large conical hole 120 from being curved, which would cause the conical finger 430 and the surface of the large conical hole 120 to not fit tightly, resulting in low friction between the two and unstable clamping.

[0038] As mentioned above, due to the stepped protrusion 420, and the diameter of the stepped protrusion 420 being smaller than the diameter of the outer circle 110, a certain distance is maintained between the end face of the graphite chuck 100 near the chuck body 200 and the mounting part 410. This allows for machining space to be reserved for the machine tool head to machine the outer circle 110 in one pass. Specifically, the height of the stepped protrusion 420 is greater than 1.5cm, reserving at least 1.5cm of height space for the head to machine the outer circle 110 in one pass, ensuring that the head can machine the outer circle 110 in one pass and avoiding production accidents such as tool collision.

[0039] Since this application changes the traditional external clamping method to internal clamping using three conical fingers 430, to prevent the chuck 400 from bending or even becoming unusable during internal clamping, and to improve strength, the chuck 400 may optionally include a reinforcing block 450. The reinforcing block 450 is located at the end of the mounting part 410, the stepped protrusion 420 is located at the end of the reinforcing block 450, and the diameter of the reinforcing block 450 is larger than the diameter of the outer circle 110. The reinforcing block 450 can improve bending strength, and even under large force, it can ensure that the chuck 400 does not bend, thus extending the service life of the chuck 400.

[0040] 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.

[0041] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A method for processing a graphite cassette for a polycrystalline silicon reduction furnace, characterized in that, Includes the following steps: S10. Take a square blank and clamp it onto a lathe using a four-jaw chuck. The clamped end of the square blank is the first end, and the end opposite to the first end is the second end. The second end of the square blank is machined with a flat end face by the lathe, and then a large tapered hole (120) is machined to obtain a semi-finished product after one machining. S20. The second end of the semi-finished product is clamped onto the lathe using a clamping mold. The clamping mold includes a chuck body (200), three moving parts (300), and three jaws (400). The three moving parts (300) are circumferentially arranged on the chuck body (200) and can move synchronously along the radial direction of the chuck body (200). The jaws (400) include a mounting part (410), a stepped protrusion (420), and a tapered finger (430). The stepped protrusion (420) is located on the mounting part. At the end of (410), the tapered finger (430) is disposed on the stepped protrusion (420), and the three claws (400) are disposed one-to-one on the moving part (300). The tapered finger (430) has the same taper as the large tapered hole (120), and the surface of the tapered finger (430) is provided with anti-slip texture (431). The three tapered fingers (430) are clamped and fitted with the large tapered hole (120), and the second end of the first-processed semi-finished product is in contact with the stepped protrusion (420). S30. The first end of the semi-finished product is flattened by the lathe, and then the outer circle is machined from the first end to the second end. The outer circle (110) is machined in one cut without the need for tool reconnection. Then the first chamfer (140) is machined, the small conical hole (130) is machined, and finally the second chamfer (150) is machined to obtain the graphite holder (100). The diameter of the step protrusion (420) is smaller than the diameter of the outer circle (110).

2. The processing method according to claim 1, characterized in that, In step S10, the large conical hole (120) has machining marks left after machining, and in step S20, the machining marks cooperate with the anti-slip marks (431) for anti-slip.

3. The processing method according to claim 2, characterized in that, The machining pattern and the anti-slip pattern (431) are threads with opposite directions of rotation.

4. The processing method according to claim 1, characterized in that, The diameter of the stepped protrusion (420) is at least 1 cm smaller than the diameter of the outer circle (110).

5. The processing method according to claim 1, characterized in that, A clearance groove (440) is provided at the root of the tapered finger (430) that connects to the stepped protrusion (420).

6. The processing method according to claim 1, characterized in that, The height of the step protrusion (420) is greater than 1.5cm.

7. The processing method according to claim 1, characterized in that, The claw (400) also includes a reinforcing block (450), which is disposed at the end of the mounting portion (410). The stepped protrusion (420) is located at the end of the reinforcing block (450), and the diameter of the reinforcing block (450) is larger than the diameter of the outer circle (110).

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