knives

Abstract

This application provides a cutting tool, including a tool holder and a cutting head. The cutting head includes a main body and multiple cutting sections. The main body is connected to the tool holder and coaxially arranged. The multiple cutting sections are spaced apart circumferentially on the main body. Each cutting section includes a first cutting tool body, a second cutting tool body, a third cutting tool body, and a fourth cutting tool body. The first, second, third, and fourth cutting tool bodies are sequentially connected along the extension direction of the tool holder. The first cutting tool body is located at the end of the main body away from the tool holder, and the fourth cutting tool body is located at the end of the main body close to the tool holder. The first cutting tool body cuts a first chamfer at the connection between the countersunk hole portion and the bottom hole portion of a countersunk hole. The second and third cutting tool bodies cut the main body portion of the countersunk hole portion, and the fourth cutting tool body cuts a second chamfer at the opening of the countersunk hole portion. The above-described cutting tool improves the efficiency and quality of machining countersunk holes and can be used in forming tool design and machining technology.

Description

Technical Field

[0001] This application relates to the field of machining tool technology, specifically to a cutting tool. Background Technology

[0002] Currently, a complete countersunk hole includes a bottom hole, a countersunk section, a chamfer at the junction of the bottom hole and the countersunk section, and a chamfer at the opening of the countersunk section. When machining the countersunk section, the chamfer at the junction of the bottom hole and the countersunk section, and the chamfer at the opening of the countersunk section, the countersunk section is usually machined first with a countersunk cutter, and then a chamfering cutter is used to machine the chamfer at the junction of the bottom hole and the countersunk section and the chamfer at the opening of the countersunk section, respectively. However, this method involves many steps in forming a countersunk hole, resulting in low efficiency. In addition, this method often requires multiple tool changes, and each tool change introduces positioning errors, leading to poor quality countersunk holes. Utility Model Content

[0003] In view of the above, it is necessary to provide a cutting tool to improve the efficiency and quality of forming countersunk holes.

[0004] This application provides a cutting tool, including a tool holder and a cutting head. The cutting head includes a main body and multiple cutting parts. The main body is connected to the tool holder and coaxially arranged. The multiple cutting parts are spaced apart along the circumference of the main body. Each cutting part includes a first cutting tool body, a second cutting tool body, a third cutting tool body, and a fourth cutting tool body. The first cutting tool body, the second cutting tool body, the third cutting tool body, and the fourth cutting tool body are connected sequentially along the extension direction of the tool holder. The first cutting tool body is located at the end of the main body away from the tool holder, and the fourth cutting tool body is located at the end of the main body close to the tool holder. The first cutting tool body is used to cut a first chamfer at the connection between the countersunk hole portion and the bottom hole portion of a countersunk hole. The second and third cutting tool bodies are used to cut the main body portion of the countersunk hole portion, and the fourth cutting tool body is used to cut a second chamfer at the opening of the countersunk hole portion.

[0005] In some embodiments, the clearance angle of the first cutting tool body is greater than the clearance angles of the second, third, and fourth cutting tool bodies.

[0006] In some embodiments, the clearance angle of the first cutting tool body is in the range of 4 degrees to 6 degrees; and / or, the clearance angle of the second cutting tool body is in the range of 3 degrees to 5 degrees; and / or, the clearance angle of the third cutting tool body is in the range of 3 degrees to 5 degrees; and / or, the clearance angle of the fourth cutting tool body is in the range of 3 degrees to 5 degrees.

[0007] In some embodiments, the clearance angle of the first cutting tool body is 5 degrees, the clearance angle of the second cutting tool body is 4 degrees, the clearance angle of the third cutting tool body is 4 degrees, and the clearance angle of the fourth cutting tool body is 4 degrees.

[0008] In some embodiments, the first cutting tool body has a first flank face, the second cutting tool body has a second flank face, the third cutting tool body has a third flank face, and the fourth cutting tool body has a fourth flank face. The first flank face, the second flank face, the third flank face, and the fourth flank face are connected in sequence. The width of at least one of the first flank face, the second flank face, the third flank face, and the fourth flank face is in the range of 0.9 mm to 1 mm.

[0009] In some embodiments, the second cutting tool body has a second cutting edge, the extension direction of which is perpendicular to the extension direction of the tool shank.

[0010] In some embodiments, the third cutting tool body has a third cutting edge, the extension direction of which is parallel to the extension direction of the tool holder.

[0011] In some embodiments, the first cutting tool body has a first cutting edge, the fourth cutting tool body has a fourth cutting edge, the angle between the extension direction of the first cutting edge and the extension direction of the tool shank is an acute angle, the angle between the extension direction of the fourth cutting edge and the extension direction of the tool shank is an acute angle, and the angle between the extension direction of the first cutting edge and the extension direction of the tool shank is less than or equal to the angle between the extension direction of the fourth cutting edge and the extension direction of the tool shank.

[0012] In some embodiments, the sum of the lengths of the third and fourth cutting tools in the extension direction of the tool holder is equal to the standard hole depth of the countersunk portion.

[0013] In some embodiments, a chip groove is formed between every two adjacent cutting sections.

[0014] The cutting tool in this embodiment of the application is provided with multiple cutting parts, and each cutting part includes a first cutting tool body, a second cutting tool body, a third cutting tool body, and a fourth cutting tool body. When the tool is used to machine a countersunk hole, the second and third cutting tool bodies cut the main body of the countersunk hole, the first cutting tool body cuts the first chamfer at the connection between the countersunk hole and the bottom hole, and the fourth cutting tool body cuts the second chamfer at the opening of the countersunk hole. Thus, the tool can machine the countersunk hole, the first chamfer at the connection between the bottom hole and the countersunk hole, and the second chamfer at the opening of the countersunk hole in one operation, reducing the number of machining steps and eliminating the need to change tools during the machining process. The surface of the machined countersunk hole is smooth and burr-free, thereby improving the efficiency and quality of machining countersunk holes. Attached Figure Description

[0015] Figure 1 This is a three-dimensional structural schematic diagram of a cutting tool provided in an embodiment of this application.

[0016] Figure 2 yes Figure 1 The diagram shows a three-dimensional structure of the cutting head of the tool.

[0017] Figure 3 yes Figure 1 The diagram shows the structure of the cutting head of the tool.

[0018] Figure 4 yes Figure 1 A cross-sectional view of the workpiece machined by the tool shown.

[0019] Key component symbols: Tool 100, Tool holder 10, Tool head 20, Main body 21, Cutting part 22, First cutting tool body 221, First cutting edge 2211, First rake face 2212, First flank face 2213, First clearance surface 2214, Second cutting tool body 222, Second cutting edge 2221, Second rake face 2222, Second flank face 2223, Second clearance surface 2224, Third cutting tool body 22 3, third cutting edge 2231, third rake face 2232, third flank face 2233, third clearance face 2234, fourth cutting tool body 224, fourth cutting edge 2241, fourth rake face 2242, fourth flank face 2243, fourth clearance face 2244, chip groove 23, workpiece 300, countersunk hole 310, bottom hole portion 3101, countersunk hole portion 3102, first chamfer 3103, second chamfer 3104. Detailed Implementation

[0020] The technical solutions of the embodiments of this application will be described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments.

[0021] 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. The terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

[0022] The following will describe some embodiments of this application in detail with reference to the accompanying drawings.

[0023] Please see Figure 1 and Figure 4 This application provides a cutting tool 100 for machining a portion of a countersunk hole 310 on a workpiece 300. The countersunk hole 310 can be of specifications such as M3, M4, M5, M6, M7, M8, etc., and this application does not specifically limit this. The countersunk hole 310 includes a bottom hole portion 3101, a countersunk hole portion 3102, a first chamfer 3103 at the connection between the bottom hole portion 3101 and the countersunk hole portion 3102, and a second chamfer 3104 at the opening of the countersunk hole portion 3102.

[0024] Please refer to the following: Figure 1 and Figure 2 The cutting tool 100 includes a tool holder 10 and a cutting head 20. The cutting head 20 includes a main body 21 and a plurality of cutting sections 22. The main body 21 is connected to the tool holder 10 and is arranged substantially coaxially. The plurality of cutting sections 22 are spaced apart along the circumference of the main body 21. Each cutting section 22 includes a first cutting tool body 221, a second cutting tool body 222, a third cutting tool body 223, and a fourth cutting tool body 224. The first cutting tool body 221, the second cutting tool body 222, the third cutting tool body 223, and the fourth cutting tool body 224 are connected sequentially along the extension direction of the tool holder 10. The first cutting tool body 221 is located on the main body. The first cutting tool 221 is located at the end of the main body 21 away from the tool holder 10, and the fourth cutting tool 224 is located at the end of the main body 21 near the tool holder 10. The first cutting tool 221 is used to cut the first chamfer 3103 at the connection between the countersunk portion 3102 and the bottom hole portion 3101 of the countersunk hole 310. The second cutting tool 222 and the third cutting tool 223 are used to cut the main body of the countersunk portion 3102, and the fourth cutting tool 224 is used to cut the second chamfer 3104 at the opening of the countersunk portion 3102. It can be used in forming tool design and machining technology.

[0025] When the countersunk hole 310 is machined using the cutting tool 100, a drill bit (not shown) is first used to machine a bottom hole (not shown) on the workpiece 300. Then, the spindle (not shown) of the machining center (not shown) drives the cutting tool 100 to insert into the bottom hole and rotate. The second cutting tool body 222 and the third cutting tool body 223 cut and shape the main body of the countersunk hole 3102. The first cutting tool body 221 cuts and shapes the first chamfer 3103 at the connection between the countersunk hole 3102 and the bottom hole 3101. The fourth cutting tool body 224 cuts and shapes the second chamfer 3104 at the opening of the countersunk hole 3102. Thus, the cutting tool 100 can machine the countersunk hole 3102, the first chamfer 3103 at the connection between the bottom hole 3101 and the countersunk hole 3102, and the second chamfer 3104 at the opening of the countersunk hole 3102 in one operation, reducing the number of machining steps and eliminating the need to change tools during the machining process, thereby improving the efficiency and quality of the countersunk hole 310.

[0026] In some embodiments, a chip removal groove 23 is formed between every two adjacent cutting portions 22.

[0027] By setting the chip removal groove 23, the chips generated during the machining of the countersunk hole 310 by the cutting part 22 can be removed in time, reducing the chance of the tool 100 getting stuck. In addition, the chip removal groove 23 provides a large chip space, avoiding secondary scraping of the machined surface by the chips, thereby improving the surface finish and dimensional accuracy of the countersunk hole 310.

[0028] Please refer to the following: Figure 3In some embodiments, the first cutting tool body 221 has a first cutting edge 2211, and the fourth cutting tool body 224 has a fourth cutting edge 2241. The angle between the extension direction of the first cutting edge 2211 and the extension direction of the tool shank 10 is an acute angle, and the angle between the extension direction of the fourth cutting edge 2241 and the extension direction of the tool shank 10 is an acute angle. The angle between the extension direction of the first cutting edge 2211 and the extension direction of the tool shank 10 is less than or equal to the angle between the extension direction of the fourth cutting edge 2241 and the extension direction of the tool shank 10.

[0029] By setting a first cutting edge 2211, and ensuring that the angle between the extension direction of the first cutting edge 2211 and the extension direction of the tool holder 10 is acute, it is easier to machine the first chamfer 3103. By setting a fourth cutting edge 2241, and ensuring that the angle between the extension direction of the fourth cutting edge 2241 and the extension direction of the tool holder 10 is acute, it is easier to machine the second chamfer 3104. By setting the angle between the extension direction of the first cutting edge 2211 and the extension direction of the tool holder 10 to be less than or equal to the angle between the extension direction of the fourth cutting edge 2241 and the extension direction of the tool holder 10, it is beneficial to improve the sharpness of the first cutting edge 2211 and reduce the generation of burrs.

[0030] In some embodiments, the angle between the extension direction of the first cutting edge 2211 and the extension direction of the tool holder 10 is a1, and the value of a1 is determined according to the taper angle of the screw head (not shown) inserted into the countersunk hole 310.

[0031] In some embodiments, the angle between the extension direction of the fourth cutting edge 2241 and the extension direction of the tool holder 10 is a2, where a2 is 45 degrees or 30 degrees. The fourth cutting edge 2241 adopts a standardized cutting edge length to ensure that the angle and length of the second chamfer 3104 meet the standard requirements.

[0032] In some embodiments, the second cutting tool body 222 has a second cutting edge 2221, the extension direction of which is perpendicular to the extension direction of the tool holder 10.

[0033] By setting the second cutting edge 2221, it is easier to cut the main body of the countersunk hole 3102; by setting the extension direction of the second cutting edge 2221 to be perpendicular to the extension direction of the tool holder 10, it is possible to effectively avoid the second cutting edge 2221 from over-cutting the bottom hole 3101, thereby improving the accuracy of cutting the main body of the countersunk hole 3102.

[0034] In some embodiments, the third cutting tool body 223 has a third cutting edge 2231, the extension direction of which is parallel to the extension direction of the tool holder 10.

[0035] By setting a third cutting edge 2231, and the extension direction of the third cutting edge 2231 being parallel to the extension direction of the tool holder 10, it is convenient to polish the main body of the countersunk hole 3102, thereby improving the quality of the main body of the countersunk hole 3102 formed by cutting.

[0036] In some embodiments, the sum of the lengths of the third cutting tool body 223 and the fourth cutting tool body 224 in the extending direction of the tool holder 10 is equal to the standard hole depth of the countersunk portion 3102.

[0037] Specifically, the sum of the lengths of the third cutting tool body 223 and the fourth cutting tool body 224 in the extension direction of the tool holder 10 is L1. The standard hole depth of the countersunk portion 3102 is determined according to the specific specifications of the countersunk hole 310. For example, for a countersunk hole 310 with a specification of M5, the standard hole depth of the countersunk portion 3102 is 5.5mm. By setting the sum of the lengths of the third cutting tool body 223 and the fourth cutting tool body 224 in the extension direction of the tool holder 10, L1, to be equal to the standard hole depth of the countersunk portion 3102, the probability of overcutting or undercutting the workpiece 300 can be reduced, thereby improving the accuracy of machining the countersunk portion 3102.

[0038] In some embodiments, the sum of twice the maximum width of the third cutting tool body 223 in the radial direction of the tool holder 10 and the standard bore diameter of the bottom hole portion 3101 is equal to the maximum bore diameter at the first chamfer 3103.

[0039] Specifically, the sum of twice the maximum radial width of the third cutting tool body 223 in the tool holder 10 and the standard diameter of the bottom hole 3101 is L2. The standard diameter of the bottom hole 3101 is determined according to the specific specifications of the countersunk hole 310. For example, for a countersunk hole 310 with a specification of M5, the standard diameter of the bottom hole 3101 is 5.5mm. By setting the sum of twice the maximum radial width of the third cutting tool body 223 in the tool holder 10 and the standard diameter of the bottom hole 3101 to L2 equal to the maximum diameter at the first chamfer 3103, the probability of overcutting or undercutting the workpiece 300 can be reduced, thereby improving the accuracy of machining the first chamfer 3103.

[0040] Please refer to the reference again. Figure 2 In some embodiments, the first cutting tool body 221 has a first flank face 2213, the second cutting tool body 222 has a second flank face 2223, the third cutting tool body 223 has a third flank face 2233, and the fourth cutting tool body 224 has a fourth flank face 2243. The first flank face 2213, the second flank face 2223, the third flank face 2233, and the fourth flank face 2243 are connected in sequence. The width of at least one of the first flank face 2213, the second flank face 2223, the third flank face 2233, and the fourth flank face 2243 is in the range of 0.9mm-1mm.

[0041] By setting the width of the first flank face 2213 to a range of 0.9mm-1mm, the strength and anti-chipping ability of the first cutting tool body 221 can be improved, and the cutting vibration amplitude of the first cutting tool body 221 can be reduced, thereby improving the stability of the first cutting tool body 221 during cutting. Similarly, by setting the width of the second flank face 2223 to a range of 0.9mm-1mm, the strength, anti-chipping ability, and stability during cutting of the second cutting tool body 222 are improved; by setting the width of the third flank face 2233 to a range of 0.9mm-1mm, the strength, anti-chipping ability, and stability during cutting of the third cutting tool body 223 are improved; and by setting the width of the fourth flank face 2243 to a range of 0.9mm-1mm, the strength, anti-chipping ability, and stability during cutting of the fourth cutting tool body 224 are improved.

[0042] In some embodiments, the widths of the first flank face 2213, the second flank face 2223, the third flank face 2233, and the fourth flank face 2243 are all in the range of 0.9mm-1mm, thereby improving the strength, anti-chipping ability, and stability of the cutting part 22 during cutting.

[0043] In some embodiments, the first cutting tool body 221 has a first rake face 2212, which is connected to a first flank face 2213. The intersection of the first rake face 2212 and the first flank face 2213 forms a first cutting edge 2211. The second cutting tool body 222 has a second rake face 2222, which is connected to a second flank face 2223. The intersection of the second rake face 2222 and the second flank face 2223 forms a second cutting edge 2221. The third cutting tool body 223 has a third rake face 2232, which is coplanar with the second rake face 2222. The third rake face 2232 is connected to a third flank face 2233. The intersection of the third rake face 2232 and the third flank face 2233 forms a third cutting edge 2231. The fourth cutting tool body 224 has a fourth rake face 2242, which is connected to the fourth flank face 2243. The intersection of the fourth rake face 2242 and the fourth flank face 2243 forms the fourth cutting edge 2241.

[0044] In some embodiments, the clearance angle of the first cutting tool body 221 is greater than the clearance angles of the second cutting tool body 222, the third cutting tool body 223, and the fourth cutting tool body 224. Specifically, the clearance angle of the first cutting tool body 221 is the angle between the first flank face 2213 and the corresponding cutting plane (not shown); the clearance angle of the second cutting tool body 222 is the angle between the second flank face 2223 and the corresponding cutting plane; the clearance angle of the third cutting tool body 223 is the angle between the third flank face 2233 and the corresponding cutting plane; and the clearance angle of the fourth cutting tool body 224 is the angle between the fourth flank face 2243 and the corresponding cutting plane.

[0045] By setting the back angle of the first cutting tool body 221 to be greater than that of the second cutting tool body 222, the third cutting tool body 223, and the fourth cutting tool body 224, the friction of the first cutting edge 2211 during cutting is reduced, which is beneficial to improving cutting efficiency and improving the surface quality of the first chamfer 3103.

[0046] In some embodiments, the clearance angle of the first cutting tool body 221 is in the range of 4 degrees to 6 degrees; and / or, the clearance angle of the second cutting tool body 222 is in the range of 3 degrees to 5 degrees; and / or, the clearance angle of the third cutting tool body 223 is in the range of 3 degrees to 5 degrees; and / or, the clearance angle of the fourth cutting tool body 224 is in the range of 3 degrees to 5 degrees.

[0047] By setting the clearance angle of the first cutting tool body 221 to a range of 4-6 degrees, its thermal shock resistance is significantly improved, effectively preventing the first cutting edge 2211 from chipping and breaking. Furthermore, it allows for slight contact between the first flank face 2213 and the workpiece 300, thereby suppressing cutting vibration and improving cutting quality. Similarly, by setting the clearance angle of the second cutting tool body 222 to a range of 3-5 degrees, its thermal shock resistance is significantly improved, effectively preventing the second cutting edge 2221 from chipping and breaking. This also allows for slight contact between the second flank face 2223 and the workpiece 300, thereby suppressing cutting vibration and improving cutting quality. Likewise, by setting the clearance angle of the third cutting tool body 223 to a range of 3-5 degrees, its thermal shock resistance is significantly improved, effectively preventing the third cutting edge 2231 from chipping and breaking. This also allows for slight contact between the third flank face 2233 and the workpiece 300, thereby suppressing cutting vibration and improving cutting quality. By setting the clearance angle of the fourth cutting tool body 224 to a range of 3-5 degrees, the thermal shock resistance of the fourth cutting tool body 224 is greatly improved, effectively preventing the fourth cutting edge 2241 from chipping and breaking. It also allows the fourth clearance face 2243 to have slight contact with the workpiece 300, thereby suppressing cutting vibration and improving cutting quality.

[0048] In some embodiments, the clearance angle of the first cutting tool body 221 is 5 degrees, the clearance angle of the second cutting tool body 222 is 4 degrees, the clearance angle of the third cutting tool body 223 is 4 degrees, and the clearance angle of the fourth cutting tool body 224 is 4 degrees.

[0049] This setting ensures the structural strength and cutting quality of the first cutting edge 2211, the second cutting edge 2221, the third cutting edge 2231, and the fourth cutting edge 2241, while reducing the friction of the first cutting edge 2211 during cutting, thereby improving cutting efficiency.

[0050] In some embodiments, the first cutting tool body 221 further has a first clearance surface 2214, which is located on the side of the first flank face 2213 away from the first rake face 2212. The first clearance surface 2214 is connected to the first flank face 2213, and the included angle between the first clearance surface 2214 and the first flank face 2213 is an obtuse angle. The second cutting tool body 222 further has a second clearance surface 2224, which is located on the side of the second flank face 2223 away from the second rake face 2222. The second clearance surface 2224 is connected to the second flank face 2223, and the included angle between the second clearance surface 2224 and the second flank face 2223 is an obtuse angle. The third cutting tool body 223 also has a third clearance surface 2234, which is located on the side of the third flank face 2233 away from the third rake face 2232. The third clearance surface 2234 is connected to the third flank face 2233, and the included angle between the third clearance surface 2234 and the third flank face 2233 is an obtuse angle. The fourth cutting tool body 224 also has a fourth clearance surface 2244, which is located on the side of the fourth flank face 2243 away from the fourth rake face 2242. The fourth clearance surface 2244 is connected to the fourth flank face 2243, and the included angle between the fourth clearance surface 2244 and the fourth flank face 2243 is an obtuse angle.

[0051] By setting the first avoidance surface 2214, the second avoidance surface 2224, the third avoidance surface 2234 and the fourth avoidance surface 2244, the friction of the cutting part 22 during cutting is reduced, which helps to improve the cutting efficiency of the cutting part 22.

[0052] In summary, the cutting tool 100 of this application embodiment, by providing multiple cutting portions 22, and each cutting portion 22 including a first cutting tool body 221, a second cutting tool body 222, a third cutting tool body 223, and a fourth cutting tool body 224, when the cutting tool 100 is used to machine the countersunk hole 310, the second cutting tool body 222 and the third cutting tool body 223 cut and form the main body of the countersunk hole portion 3102, and the first cutting tool body 221 cuts and forms the first [unclear] at the connection between the countersunk hole portion 3102 and the bottom hole portion 3101. The chamfer 3103 and the second chamfer 3104 at the opening of the countersunk hole 3102 are formed by the fourth cutting tool body 224. The tool 100 can form the first chamfer 3103 at the connection between the countersunk hole 3102, the bottom hole 3101 and the countersunk hole 3102 and the second chamfer 3104 at the opening of the countersunk hole 3102 in one operation, reducing the number of processing steps and eliminating the need to change tools during processing. The surface of the countersunk hole 310 formed is smooth and burr-free, thereby improving the efficiency and quality of forming the countersunk hole 310.

[0053] Furthermore, those skilled in the art should recognize that the above embodiments are merely illustrative of this application and are not intended to limit this application. Any appropriate changes and variations made to the above embodiments within the essential spirit and scope of this application fall within the scope of this application's disclosure.

Claims

1. A cutting tool, characterized by The tool includes a tool holder and a tool head. The tool head includes a main body and multiple cutting parts. The main body is connected to the tool holder and coaxially arranged. The multiple cutting parts are spaced apart circumferentially on the main body. Each cutting part includes a first cutting tool body, a second cutting tool body, a third cutting tool body, and a fourth cutting tool body. The first cutting tool body, the second cutting tool body, the third cutting tool body, and the fourth cutting tool body are connected sequentially along the extension direction of the tool holder. The first cutting tool body is located at the end of the main body away from the tool holder, and the fourth cutting tool body is located at the end of the main body close to the tool holder. The first cutting tool body is used to cut a first chamfer at the connection between the countersunk hole and the bottom hole of a countersunk hole. The second and third cutting tool bodies are used to cut the main body of the countersunk hole. The fourth cutting tool body is used to cut a second chamfer at the opening of the countersunk hole.

2. The tool of claim 1 wherein, The clearance angle of the first cutting tool body is greater than that of the second, third, and fourth cutting tool bodies.

3. The tool of claim 2 wherein, The clearance angle of the first cutting tool body ranges from 4 degrees to 6 degrees; and / or, The clearance angle of the second cutting tool body ranges from 3 degrees to 5 degrees; and / or, The back angle of the third cutting tool body ranges from 3 degrees to 5 degrees; and / or, The back angle of the fourth cutting tool body ranges from 3 degrees to 5 degrees.

4. The tool of claim 2 wherein, The clearance angle of the first cutting tool body is 5 degrees, the clearance angle of the second cutting tool body is 4 degrees, the clearance angle of the third cutting tool body is 4 degrees, and the clearance angle of the fourth cutting tool body is 4 degrees.

5. The knife of claim 1, wherein, The first cutting tool body has a first flank face, the second cutting tool body has a second flank face, the third cutting tool body has a third flank face, and the fourth cutting tool body has a fourth flank face. The first flank face, the second flank face, the third flank face, and the fourth flank face are connected in sequence. The width of at least one of the first flank face, the second flank face, the third flank face, and the fourth flank face is in the range of 0.9 mm to 1 mm.

6. The knife of claim 1, wherein, The second cutting tool body has a second cutting edge, the extension direction of which is perpendicular to the extension direction of the tool holder.

7. The knife of claim 1, wherein, The third cutting tool body has a third cutting edge, and the extension direction of the third cutting edge is parallel to the extension direction of the tool holder.

8. The knife of claim 1, wherein, The first cutting tool body has a first cutting edge, the fourth cutting tool body has a fourth cutting edge, the angle between the extension direction of the first cutting edge and the extension direction of the tool shank is an acute angle, the angle between the extension direction of the fourth cutting edge and the extension direction of the tool shank is an acute angle, and the angle between the extension direction of the first cutting edge and the extension direction of the tool shank is less than or equal to the angle between the extension direction of the fourth cutting edge and the extension direction of the tool shank.

9. The knife of claim 1, wherein, The sum of the lengths of the third and fourth cutting tools in the extension direction of the tool holder is equal to the standard hole depth of the countersunk portion.

10. A tool as claimed in any one of claims 1 to 9, characterised in that, A chip groove is formed between every two adjacent cutting sections.

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