A modular end mill capable of quick change of the tool head

Abstract

The application relates to the technical field of milling cutters, and discloses a modular vertical milling cutter capable of quickly replacing a cutter head, which comprises a cutter handle, a threaded hole is formed in the bottom of the cutter handle, a threaded adapter is threadedly connected in the threaded hole, an outer milling cutter is fixedly connected to the bottom of the threaded adapter, an air inlet channel is formed in the top of the cutter handle, a threaded channel is formed in the bottom of the outer milling cutter, an air cavity in communication with the threaded channel is formed in the threaded adapter, a mounting rod is slidably connected in the air cavity, an inner milling cutter is fixedly connected to the bottom of the mounting rod, a sealing box is fixedly connected to the top of the mounting rod, a sealing plate is fixedly connected to the top of the sealing box, a fixing ring is fixedly connected in the threaded channel, a return spring is fixedly connected to the bottom of the fixing ring, and the modular vertical milling cutter capable of quickly replacing the cutter head can avoid the problem that the cutter head of a traditional milling cutter is in an integral structure, so that after a groove is milled, a drill bit needs to be replaced to perform a punching work.

Description

Technical Field

[0001] This invention relates to the field of modular end mill technology, specifically a modular end mill with a quick-change cutting head. Background Technology

[0002] A milling cutter is a rotating cutting tool with one or more cutting teeth used for milling operations. With the development of society, the demand for workpieces of different models and shapes has increased, and milling cutters have also diversified into different types. Among them, end mills and face mills are the most commonly used types of milling cutters. The difference between end mills and face mills is that end mills have cutting edges distributed on both the cylindrical surface and the end face. The main cutting edge is usually designed with a helical groove to improve cutting stability, while there is generally no cutting edge in the center of the end face. Face mills, on the other hand, usually have a disc-shaped structure, with the end face as the main cutting edge, and are suitable for high-efficiency machining of large flat surfaces. End mills are also the most commonly used type of milling cutter on CNC machine tools. Common shapes include flat-bottom, ball-end, and round-nose mills.

[0003] Compared to traditional end mills, which are mostly made of solid carbide or welded structures and cannot achieve free combination of modular cutter heads and shanks, modular end mills adopt a split design, including replaceable cutter heads and shanks, which can be replaced individually and freely combined, making them relatively more convenient to use.

[0004] When milling plate-shaped workpieces, existing modular end mills often drill holes at the four corners of the workpiece. For some workpieces, a larger diameter groove is usually drilled at the four corners before drilling to ensure the workpiece meets future usage standards. This groove is mainly used for the subsequent insertion of nuts, and then drilling is performed in the groove. Although the cutting head and shank of the modular end mill can be separated, the cutting head is a single piece. This means that after milling the groove, it is often necessary to change the drill bit or move the workpiece to the next machining point before drilling can be performed, which reduces the workpiece's machining efficiency. Therefore, we propose a modular end mill with a quick-change cutting head. Summary of the Invention

[0005] The purpose of this invention is to provide a modular end mill with a quick-change cutting head, in order to solve the problems mentioned in the background art.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a modular end mill capable of quick-change cutting head, comprising a shank, a threaded hole at the bottom of the shank, a threaded connector threaded into the threaded hole, an external end mill fixedly connected to the bottom of the threaded connector, an air inlet channel at the top of the shank, a threaded channel at the bottom of the external end mill, an air chamber communicating with the threaded channel within the threaded connector, a mounting rod slidably connected within the air chamber, an internal end mill fixedly connected to the bottom of the mounting rod, a sealing box fixedly connected to the top of the mounting rod, and a sealing plate fixedly connected to the top of the sealing box;

[0007] A fixing ring is fixedly connected inside the threaded channel, and a return spring is fixedly connected to the bottom of the fixing ring. The bottom of the return spring is rotatably connected to the top of the sealing plate.

[0008] Preferably, a limiting frame is fixedly connected inside the air intake channel, an air intake pipe is fixedly connected to the limiting frame, and a fine corrugated pipe is fixedly connected to the bottom of the air intake pipe.

[0009] Preferably, the bottom of the fine corrugated tube is rotatably connected to the sealing plate via a mounting bearing, and the fine corrugated tube is in communication with the interior of the sealing box.

[0010] Preferably, the sealing box is slidably connected to a partition, the hole through which the sealing box communicates with the fine corrugated pipe is located on one side of the partition, and a limiting plate is fixedly connected to the side of the partition away from the hole through which the sealing box communicates with the fine corrugated pipe, the limiting plate being located at the bottom of one side of the partition.

[0011] Preferably, the limiting plate penetrates the sealing box and extends to its outside, and a plurality of limiting springs are fixedly connected between the side of the partition away from the limiting plate and the inner wall of the sealing box.

[0012] Preferably, the internal milling cutter is located inside the threaded channel, and the outer wall of the internal milling cutter and the inner wall of the threaded channel are in contact with each other and slidably connected.

[0013] Preferably, an exhaust channel communicating with the air intake channel is provided on one side of the handle, and a miniature air valve A is fixedly connected to the outside of the exhaust channel.

[0014] Preferably, an exhaust pipe is fixedly connected to the side of the handle away from the exhaust channel, and the exhaust pipe passes through the outer wall of the handle and communicates with the air inlet pipe.

[0015] Preferably, a miniature air valve B is fixedly connected to the exhaust pipe, and a counterweight is fixedly connected to the top of the miniature air valve B. The weight of the miniature air valve A is the same as the weight of the miniature air valve B with the added counterweight.

[0016] Preferably, a limiting groove is formed on the inner wall of the air cavity near the threaded channel, and the size of the limiting groove is the same as the size of the limiting plate.

[0017] Compared with the prior art, the beneficial effects of the present invention are:

[0018] This invention incorporates a retractable internal milling cutter within an external milling cutter. Air is supplied to the air chamber via an air delivery channel, and the air pressure forces the internal milling cutter out. Once the external milling cutter has milled large-diameter grooves at the four corners of the workpiece, the internal milling cutter is forced out, allowing drilling to be completed using a smaller-diameter internal milling cutter. This avoids the problem of traditional milling cutter heads being of integral construction, which often necessitates replacing the drill bit after milling grooves to perform drilling operations. This effectively improves the workpiece processing efficiency of the device.

[0019] When the internal milling cutter extends to its maximum stroke, the limiting plate aligns with the limiting groove. At this point, air is supplied to the sealed box through the air supply pipe. The air pressure pushes the partition, causing the limiting plate to engage with the limiting groove. The internal milling cutter is then limited by the interaction between the limiting groove and the limiting plate. This makes the internal milling cutter more stable during drilling, preventing the internal milling cutter from retracting into the threaded hole due to excessive pressure between the internal milling cutter and the workpiece caused by insufficient air pressure. This effectively improves the stability of the device during workpiece processing.

[0020] This invention, by setting up an exhaust channel connected to the air intake channel and an exhaust pipe connected to the air intake pipe, and cooperating with corresponding miniature air valves A and B, allows for the separate discharge of air from the air chamber and the sealed box. This enables the device to complete the sequential operation of the limiting plate and the internal milling cutter extension and retraction during the extension and retraction of the internal milling cutter, avoiding confusion in the sequence of the limiting plate's function during the extension and retraction operation, which could lead to the inability to complete the extension and retraction work properly. At the same time, since the diameter of the exhaust pipe is smaller than that of the exhaust channel, a counterweight is added to the miniature air valve B to balance the weight influence of the miniature air valves A and B on both sides of the cutter holder, making the milling cutter more stable during operation. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the overall structure of the present invention;

[0022] Figure 2 This is a schematic diagram of the tool holder structure of the present invention;

[0023] Figure 3 This is a schematic diagram of the connection structure between the external and internal milling cutters of the present invention;

[0024] Figure 4 This is a schematic diagram of the cross-sectional structure of the external milling cutter of the present invention;

[0025] Figure 5This is a schematic diagram of the internal milling cutter structure of the present invention;

[0026] Figure 6 This is a schematic diagram of the cross-sectional structure of the sealing box of the present invention;

[0027] Figure 7 For the present invention Figure 2 A magnified structural diagram of area A is shown below;

[0028] Figure 8 For the present invention Figure 2 The diagram shows the structure of area B.

[0029] In the diagram: 1. Tool holder; 11. Inlet channel; 12. Threaded hole; 13. Exhaust channel; 2. External milling cutter; 21. Threaded connector; 22. Threaded channel; 23. Air chamber; 24. Limiting groove; 3. Mounting rod; 31. Internal milling cutter; 4. Sealing box; 41. Partition plate; 42. Limiting plate; 43. Limiting spring; 44. Sealing plate; 5. Fixing ring; 51. Return spring; 6. Limiting bracket; 61. Inlet pipe; 62. Fine corrugated pipe; 63. Mounting bearing; 64. Exhaust pipe; 7. Miniature air valve A; 71. Miniature air valve B; 72. Counterweight. Detailed Implementation

[0030] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0031] Please see Figure 1-8 This invention provides a technical solution: a modular end mill with quick-change cutting head, including a shank 1. The bottom of the shank 1 has a threaded hole 12, and a threaded connector 21 is threadedly connected to the threaded hole 12. An external end mill 2 is fixedly connected to the bottom of the threaded connector 21. The bottom of the external end mill 2 has a threaded channel 22. An air chamber 23 communicating with the threaded channel 22 is opened in the threaded connector 21. A mounting rod 3 is slidably connected in the air chamber 23. An internal end mill 31 is fixedly connected to the bottom of the mounting rod 3. When the internal end mill 31 is retracted into the threaded channel 22, its bottom is at the same level as the bottom of the external end mill 2 and forms a flat surface, avoiding any impact on the quality of the milling work during the milling process.

[0032] Furthermore, when using this end mill, the tool holder 1 is connected to the external drive tool holder. When selecting the external drive tool holder, a tool holder with a built-in air pump is selected to complete the air supply work. Then, the external milling cutter 2 is screwed into the threaded hole 12 at the bottom of the tool holder 1 through the threaded connector 21. Then, the workpiece is placed under the external milling cutter 2. Then, the external drive tool holder is used to drive the external milling cutter 2 to make it rotate at high speed. At this time, the workpiece can be milled by the cooperation of the external milling cutter 2 and the internal milling cutter 31.

[0033] Combined with appendix Figure 1 , Figure 3 and Figure 5 As shown, the top of the tool holder 1 has an air intake channel 11, which communicates with the air chamber 23 through a threaded hole 12. A sealing box 4 is fixedly connected to the top of the mounting rod 3, and a sealing plate 44 is fixedly connected to the top of the sealing box 4. A sealing ring is provided on the outer wall of the sealing plate 44, ensuring that it can divide the air chamber 23 into two parts. This ensures that when air is supplied to the air chamber 23 through the air intake channel 11, the air can be stored in the space of the air chamber 23 above the sealing plate 44, thereby increasing the air pressure in the space of the air chamber 23 above the sealing plate 44, thus pushing the sealing plate 44. An exhaust channel 13 communicating with the air intake channel 11 is provided on one side of the tool holder 1. A miniature air valve A7 is fixedly connected to the outside of channel 13, and a fixing ring 5 is fixedly connected to the inside of threaded channel 22. A return spring 51 is fixedly connected to the bottom of the fixing ring 5. When initially installed, the return spring 51 is in a contracted and stored state. The bottom of the return spring 51 is rotatably connected to the top of the sealing plate 44. Since the top of the return spring 51 is fixedly connected to the fixing ring 5, and the bottom of the return spring 51 is connected to the sealing plate 44 through an additional bearing, when the sealing plate 44 rotates and descends, the additional bearing ensures that the return spring 51 can be stretched by the moving sealing plate 44 without affecting the downward rotation of the sealing plate 44.

[0034] Furthermore, after the basic shape of the workpiece is milled, the outer milling cutter 2 and the inner milling cutter 31 work together to mill grooves at the four corners of the plate-shaped workpiece. Then, the outer milling cutter 2 is raised to separate it from the workpiece. Air is then supplied to the air chamber 23 through the air inlet channel 11 and the threaded hole 12. The air pressure in the air chamber 23 pushes the inner milling cutter 31 to rotate and extend along the threaded channel 22, causing the inner milling cutter 31 to extend beyond the outer milling cutter 2. The rotating and downward-moving sealing plate 44 stretches the return spring 51. When the inner milling cutter 31… After the maximum stroke is extended, the internal milling cutter 31 is used to drill a hole in the groove. After the drilling is completed, the micro air valve A7 is opened, so that the air chamber 23 is connected to the outside through the exhaust channel 13. At this time, the air chamber 23 is unsealed. Using the rebound characteristic of the return spring 51 and its rotating connection with the sealing plate 44, the internal milling cutter 31 is retracted back into the threaded channel 22 of the external milling cutter 2, and the internal milling cutter 31 and the external milling cutter 2 form an integral structure. Then the micro air valve A7 is closed, so that the air chamber 23 is resealed.

[0035] Combined with appendix Figure 2 , Figure 3 , Figure 4 , Figure 6 , Figure 7 and Figure 8As shown, a limiting frame 6 is fixedly connected inside the air intake channel 11. An air intake pipe 61 is fixedly connected to the limiting frame 6. A fine corrugated pipe 62 is fixedly connected to the bottom of the air intake pipe 61. The bottom of the fine corrugated pipe 62 is rotatably connected to the sealing plate 44 via a mounting bearing 63. The fine corrugated pipe 62 has good ductility, and its length can change synchronously with the position of the mounting rod 3 without affecting the air delivery of the air intake channel 11. At the same time, the mounting bearing 63 is set at the connection between the bottom of the fine corrugated pipe 62 and the sealing plate 44, which can reduce the friction between the fine corrugated pipe 62 and the sealing plate 44. Since the mounting rod 3 moves and rotates during the movement, the mounting bearing 63 can ensure that the fine corrugated pipe 62 is not affected by the rotation of the mounting rod 3. Following the position of the mounting rod 3, the bearing 63 moves to complete the length adaptation. Both the inner and outer walls of the bearing 63 are equipped with sealing rings. These sealing rings improve the airtightness between the fine corrugated tube 62 and the interior of the sealing box 4, preventing air from escaping into the air chamber 23 due to poor sealing. This would result in insufficient air pressure inside the sealing box 4 to move the partition 41. The fine corrugated tube 62 and the interior of the sealing box 4 are interconnected. The sealing box 4 is slidably connected to the partition 41, and the outer wall of the partition 41 is equipped with a sealing ring. Because the partition 41 is slidably installed against the inner wall of the sealing box 4 in the lateral direction, and a sealing ring is provided at the sliding connection between the partition 41 and the inner wall of the sealing box 4, the sealing rings improve the airtightness between the fine corrugated tube 62 and the interior of the sealing box 4. The high partition 41 ensures a tight seal when separating the internal space of the sealed box 4. This allows air to accumulate and increase within the sealed box 4 on the side of the partition 41, thus increasing the air pressure only on that side. This ensures the partition 41 can be pushed. The hole connecting the sealed box 4 and the fine corrugated pipe 62 is located on one side of the partition 41. A limiting plate 42 is fixedly connected to the side of the partition 41 away from the hole connecting the sealed box 4 and the fine corrugated pipe 62. The limiting plate 42 is located at the bottom of one side of the partition 41, penetrating the sealed box 4 and extending to its exterior. The limiting plate 42 and the sealed box 4 are slidably connected. In the initial state (when the internal milling cutter 31 is retracted into the threaded channel 22 within the external milling cutter 2), the limiting plate 42... 2. The device retracts inside the sealed box 4. Several limiting springs 43 are fixedly connected between the side of the partition 41 away from the limiting plate 42 and the inner wall of the sealed box 4. The limiting springs 43 are in a retracted and charged state during initial installation. The internal milling cutter 31 is located inside the threaded channel 22. The outer wall of the internal milling cutter 31 is in contact with and slidably connected to the inner wall of the threaded channel 22. An exhaust pipe 64 is fixedly connected to the side of the tool holder 1 away from the exhaust channel 13. The exhaust pipe 64 passes through the outer wall of the tool holder 1 and communicates with the air inlet pipe 61. A miniature air valve B71 is fixedly connected to the exhaust pipe 64. A counterweight 72 is fixedly connected to the top of the miniature air valve B71. The weight of the miniature air valve B71 is the same as the weight of the miniature air valve B71 with the added counterweight 72.A limiting groove 24 is formed on the inner wall of the air chamber 23 near the threaded channel 22. The size of the limiting groove 24 is the same as the size of the limiting plate 42. Since the partition plate 41 is slidably connected to the inner wall of the sealing box 4, it can be ensured that when air enters the sealing box 4, the air pressure can be used to push the partition plate 41, thereby allowing the limiting plate 42 to smoothly engage in the limiting groove 24.

[0036] Furthermore, when the internal milling cutter 31 extends to its maximum extent, air is supplied through the air inlet pipe 61. The air is then transported into the sealed box 4 via the air inlet pipe 61 and the fine corrugated pipe 62. At this time, the air is stored between the side of the partition 41 away from the limiting plate 42 and the inner wall of the sealed box 4. As air is continuously injected, the air pressure in this space increases. This air pressure pushes the partition 41 to move, causing the limiting plate 42 to engage with the limiting groove 24, thereby fixing the mounting rod 3 and the internal milling cutter 31, making the internal milling cutter 31 more stable during drilling. Simultaneously, when the partition 41 moves due to air pressure, it stretches the limiting spring 43. After the internal milling cutter 31 is used, the micro air valve B71 is opened first, allowing air to flow into the sealed box 4. The space inside the sealed box 4 is connected to the outside through the fine corrugated pipe 62, the air inlet pipe 61 and the exhaust pipe 64. At this time, the air inside the sealed box 4 is discharged, causing the internal air pressure to decrease. At this time, the rebound and contraction characteristics of the limit spring 43 drive the partition 41 to move back to its original position and move the limit plate 42 out of the limit groove 24. At this time, the limiting effect of the mounting rod 3 and the internal milling cutter 31 can be released. Then, the micro air valve A7 is opened to retract the internal milling cutter 31. Since the diameter of the exhaust pipe 64 is smaller than that of the exhaust channel 13, a counterweight 72 is added to the micro air valve B71 to balance the weight of the micro air valve B71 and the micro air valve A7, so that the weight on both sides of the tool holder 1 is balanced, and the stability of the tool holder 1 during rotation is improved.

[0037] Working principle: First, connect the tool holder 1 to the external drive tool holder. Then, screw the external milling cutter 2 into the threaded hole 12 at the bottom of the tool holder 1 through the threaded connector 21. Then, place the workpiece under the external milling cutter 2. Then, use the external drive tool holder to drive the external milling cutter 2 to rotate at high speed. At this time, the workpiece can be milled by the cooperation of the external milling cutter 2 and the internal milling cutter 31.

[0038] After the basic shape of the workpiece is milled, the outer milling cutter 2 and the inner milling cutter 31 are used to mill grooves at the four corners of the plate-shaped workpiece. Then, the outer milling cutter 2 is raised to separate it from the workpiece. Then, air is supplied to the air chamber 23 through the air inlet channel 11 and the threaded hole 12. At this time, the air pressure in the air chamber 23 is used to push the inner milling cutter 31 to rotate and extend along the threaded channel 22, so that the inner milling cutter 31 extends out of the outer milling cutter 2 and stretches the return spring 51.

[0039] When the internal milling cutter 31 extends to its maximum stroke, air is supplied through the air inlet pipe 61. The air is then delivered into the sealed box 4 through the air inlet pipe 61 and the fine corrugated pipe 62. At this time, the air is stored between the side of the partition 41 away from the limiting plate 42 and the inner wall of the sealed box 4. As air is continuously injected, the air pressure in this space increases. This air pressure can push the partition 41 to move and cause the limiting plate 42 to be locked into the limiting groove 24, thereby fixing the mounting rod 3 and the internal milling cutter 31.

[0040] Then, the internal milling cutter 31 is used to drill holes in the groove. After the drilling is completed, the micro air valve B71 is opened to allow the space inside the sealing box 4 to be connected to the outside through the fine corrugated pipe 62, the air inlet pipe 61 and the exhaust pipe 64. At this time, the air inside the sealing box 4 is discharged, causing the internal air pressure to decrease. At this time, the rebound and contraction characteristics of the limit spring 43 drive the partition plate 41 to move back to its original position and cause the limit plate 42 to move out of the limit groove 24. At this time, the limiting effect of the mounting rod 3 and the internal milling cutter 31 can be released.

[0041] Finally, open the micro air valve A7 to connect the air chamber 23 to the outside through the exhaust channel 13. At this time, the air chamber 23 is unsealed. Utilizing the rebound characteristic of the return spring 51 and its rotating connection with the sealing plate 44, the inner milling cutter 31 retracts back into the threaded channel 22 of the outer milling cutter 2, and the inner milling cutter 31 and the outer milling cutter 2 form an integral structure. Then, close the micro air valve A7 to reseal the air chamber 23.

[0042] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0043] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A modular end mill capable of quick-change cutting head, comprising a shank (1), wherein a threaded hole (12) is provided at the bottom of the shank (1), a threaded connector (21) is internally threaded into the threaded hole (12), and an external end mill (2) is fixedly connected to the bottom of the threaded connector (21), characterized in that: The top of the tool holder (1) is provided with an air inlet channel (11), the bottom of the external milling cutter (2) is provided with a threaded channel (22), the threaded connector (21) is provided with an air chamber (23) communicating with the threaded channel (22), the air chamber (23) is slidably connected with an installation rod (3), the bottom of the installation rod (3) is fixedly connected with an internal milling cutter (31), the top of the installation rod (3) is fixedly connected with a sealing box (4), and the top of the sealing box (4) is fixedly connected with a sealing plate (44). A fixing ring (5) is fixedly connected inside the threaded channel (22), and a return spring (51) is fixedly connected to the bottom of the fixing ring (5). The bottom of the return spring (51) is rotatably connected to the top of the sealing plate (44). The intake channel (11) is fixedly connected to a limiting frame (6), and an intake pipe (61) is fixedly connected to the limiting frame (6). A fine corrugated pipe (62) is fixedly connected to the bottom of the intake pipe (61). The bottom of the fine corrugated pipe (62) is rotatably connected to the sealing plate (44) by a mounting bearing (63), and the fine corrugated pipe (62) is in communication with the interior of the sealing box (4); The sealing box (4) is slidably connected to a partition (41). The hole connecting the sealing box (4) and the fine corrugated pipe (62) is located on one side of the partition (41). A limiting plate (42) is fixedly connected to the side of the partition (41) away from the hole connecting the sealing box (4) and the fine corrugated pipe (62). The limiting plate (42) is located at the bottom of one side of the partition (41). The internal milling cutter (31) is located inside the threaded channel (22), and the outer wall of the internal milling cutter (31) and the inner wall of the threaded channel (22) are in contact with each other and are slidably connected.

2. The modular end mill according to claim 1, characterized in that: The limiting plate (42) penetrates the sealing box (4) and extends to its outside. The side of the partition (41) away from the limiting plate (42) is fixedly connected to the inner wall of the sealing box (4) by a number of limiting springs (43).

3. The modular end mill according to claim 2, characterized in that: The handle (1) has an exhaust channel (13) connected to the air intake channel (11) on one side, and a miniature air valve A (7) is fixedly connected to the outside of the exhaust channel (13).

4. The modular end mill according to claim 3, characterized in that: An exhaust pipe (64) is fixedly connected to the side of the handle (1) away from the exhaust channel (13). The exhaust pipe (64) passes through the outer wall of the handle (1) and is connected to the air inlet pipe (61).

5. The modular end mill according to claim 4, characterized in that: A miniature air valve B (71) is fixedly connected to the exhaust pipe (64), and a counterweight (72) is fixedly connected to the top of the miniature air valve B (71). The weight of the miniature air valve A (7) is the same as the weight of the miniature air valve B (71) with the added counterweight (72).

6. The modular end mill according to claim 5, characterized in that: A limiting groove (24) is provided on the inner wall of the air cavity (23) near the threaded channel (22), and the size of the limiting groove (24) is the same as the size of the limiting plate (42).

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