Cutting tool for cutting arc-shaped surface in inner cavity of motorcycle engine box body

Abstract

The utility model discloses a cutting tool for cutting an arc-shaped surface in an inner cavity of a box body of a motorcycle engine. The cutting tool comprises a tool bar and a tool disc, a connecting part is arranged at one end of the cutter bar, and a mounting hole matched with the connecting part is formed in the middle of the cutter head; the connecting part of the cutter bar is arranged in the mounting hole in a sleeving manner, the end part of the cutter bar extends out of the cutter head, and the cutter head can rotate under the action of external force, is located at a locking station after rotating to a certain angle, and is located at an unlocking station after rotating reversely; the rotating direction of the cutter head rotating to the locking station is opposite to the rotating direction of the cutter head and the cutter bar, when the cutter head is located at the locking station, the mounting hole of the cutter head is in clamping fit with the middle of the connecting part of the cutter bar, the mounting hole and the tail end of the connecting part are crossed, and the tail end of the connecting part compresses and positions the cutter head; when the cutterhead is located at the unlocking station, the mounting hole of the cutterhead rotates to the initial position and corresponds to the connecting part, and the cutterhead can be pulled out of the connecting part of the guide rod under the action of external force.

Description

Technical Field

[0001] This utility model relates to the field of motorcycle engine housing processing, specifically to a cutting tool for cutting the arc-shaped surface inside the cavity of a motorcycle engine housing. Background Technology

[0002] The engine housing is a crucial component of a motorcycle engine, housing the transmission system. To achieve a compact structure, some engine housings require an arc-shaped space next to the transmission gear for gear installation. During machining, due to the complex shape of the housing, the machining area for this arc-shaped space is usually limited, often obstructed by internal protrusions. Machining can only be performed by inserting a cutting tool through an external through-hole adjacent to the arc-shaped space. If the diameter of the arc-shaped space differs significantly from the diameter of the through-hole, and is much larger than the through-hole itself, conventional cutting tools cannot achieve the desired large-diameter arc-shaped clearance surface after cutting. For example, existing eccentric back boring tools can only machine stepped holes with small differences in upper and lower diameters, and are unsuitable for holes with large differences. Parachute-type cutting tools can close before cutting, open when rotating to a certain speed, and close again after machining. However, when machining a single arc-shaped surface with a thickness greater than 10mm, these tools suffer from uneven stress and severe tool damage.

[0003] To address the aforementioned issues, the applicant intends to design a cutting tool capable of passing through a small hole to cut inside the housing and create an arc-shaped clearance space. Summary of the Invention

[0004] In view of the above-mentioned shortcomings of the existing technology, the purpose of this utility model is to provide a cutting tool for cutting the arc-shaped surface in the inner cavity of a motorcycle engine housing, and to solve the problem that the cutting tool in the existing technology cannot pass through a small-diameter through hole to perform arc-shaped cutting on the workpiece.

[0005] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0006] A cutting tool for cutting an arc-shaped surface inside a motorcycle engine housing includes a tool shank and a cutting disc. One end of the tool shank has a connecting portion, and the cutting disc has a mounting hole in the middle that mates with the connecting portion. The connecting portion of the tool shank is fitted into the mounting hole, with its end extending out of the cutting disc. The cutting disc can rotate under external force and, after rotating to a certain angle, is in a locked position; after rotating in the opposite direction, it is in an unlocked position. The rotation direction of the cutting disc to the locked position is the same as the rotation direction of the cutting disc and the tool shank. When the cutting disc is in the locked position, the mounting hole of the cutting disc is tightly engaged with the middle of the connecting portion of the tool shank, and the mounting hole and the end of the connecting portion are intersecting, with the end of the connecting portion pressing and positioning the cutting disc. When the cutting disc is in the unlocked position, its mounting hole rotates back to its initial position, corresponding to the connecting portion, and the cutting disc can be pulled out from the connecting portion of the guide rod under external force. In this way, when machining the housing, first fix the end of the tool holder away from the connecting part on the cutting machine tool. Then fix the engine housing to be machined on the opposite side of the tool holder and adjust the position of the engine housing so that the small hole next to the part to be cut corresponds to the tool holder. Then move the engine housing or the tool holder so that the tool holder passes through the small hole and the connecting part extends out of the small hole, and is placed next to the part to be cut. After the tool holder and the engine housing to be cut are adjusted into place, the cutter head can be installed. When installing the cutter head, align the mounting hole of the cutter head with the connecting part of the tool holder and insert it into the connecting part, so that the middle part of the connecting part corresponds to the mounting hole and the end extends out of the mounting hole. Then rotate the cutter head until it can no longer rotate. The mounting hole of the cutter head is locked with the middle part of the connecting part, and the end is placed outside the mounting hole and crosses the mounting hole. The cutter head is rotated to the locking position to achieve locking. After the cutter head is locked, start the cutting machine tool. The drive shaft of the cutting machine tool drives the tool holder and the cutter head to rotate together to complete the cutting of the cutter head. After cutting, the relative position between the mounting hole and the connecting part of the cutter head changes after the cutter head is rotated in the opposite direction. The mounting hole and the connecting part align, allowing the cutter head to be removed from the tool holder under external force. The cutter head and the tool holder are detachably connected, so during assembly, only the tool holder needs to pass through the small hole, without considering the size of the cutter head. This allows the cutting tool to cut large holes after passing through the small hole. Furthermore, the locking and unlocking operations between the cutter head and the tool holder are convenient, facilitating its application in the cutting of other components. Additionally, because the cutter head and the connecting part are tightly fitted after rotation in the middle, and the end of the connecting part of the tool holder crosses the mounting hole and is tightly pressed against the end face of the cutter head, a tight fixing is formed. Simultaneously, the locking rotation direction is opposite to the rotation direction of the cutter head during cutting. During cutting, the cutting force is in the same direction as the locking direction, thus the cutter head and the tool holder become increasingly tighter during cutting, preventing them from falling off and ensuring a high safety factor in cutting.

[0007] Furthermore, the outer diameter of the connecting part is smaller than the outer diameter of the main body of the cutter bar, and it consists of a connecting section and a positioning section. The connecting section is cylindrical, and the positioning section is a double-sided flat-cut cylinder. The positioning section consists of a first positioning section and a second positioning section. The first positioning section is adjacent to the connecting section, and two slots are provided circumferentially at intervals on the first positioning section. The mounting hole consists of a circular sleeve hole and a rounded rectangular hole. Two oppositely arranged locking blocks are provided on the side of the rounded rectangular hole near the circular sleeve hole. The two locking blocks and the two straight sides of the rounded rectangular hole together form a through hole for the positioning section of the connecting part to pass through. The diameter of the circular sleeve hole is greater than or equal to the diameter of the connecting section. After the cutter disc rotates to the locking position, the first positioning section of the connecting part is locked between the two straight sides of the rounded rectangular hole, and the second positioning section of the connecting part extends out of the rounded rectangular hole, and the rounded rectangular hole and the second positioning section are intersecting. In this way, the two slots in the middle of the connecting part are spaced apart and located on both sides of the diameter line of their respective circumferences. After rotation, the slots are positioned between the two long sides of the rounded rectangular hole, that is, the distance between the two slots is equal to the distance between the two long sides of the rounded rectangular hole. The two slots are slots opened on the first positioning section, and the distance between the two slots is smaller than the distance between the two corresponding positions of the second positioning section. Therefore, after being clamped in the rounded rectangular hole at the slot, the extended second positioning section corresponds to the distance between the two slots directly opposite each other. This distance is greater than the distance between the two slots and the distance between the two long sides of the rounded rectangular hole. Therefore, the two opposite sides of the second positioning section extend beyond the long sides of the rounded rectangular hole, forming a clamping and positioning of the tool disc together with the end face of the tool holder body. The locking block is positioned at the two rounded corners of the rounded rectangular hole, forming a through hole with the two straight sides of the rounded rectangular hole. That is, the locking block and the two straight sides together form a through hole that mates with the positioning section. Since the positioning section is a double-sided flat-cut cylinder with rounded rectangular end faces, the through hole is also rounded rectangular, sharing sides with the two straight sides of the rounded rectangular hole, with the length of the straight side slightly shorter than the two straight sides of the rounded rectangular hole. Therefore, both the first and second positioning sections can pass through the through hole. After the first positioning section passes through the through hole and aligns with the rounded rectangular hole, it can be tightly engaged with the two straight sides of the rounded rectangular hole after rotating a certain angle.

[0008] Furthermore, the cutter head includes a cutter head body and cutter mounting portions distributed clockwise along the outer edge of the cutter head body. The cutter head body is rounded rectangular, and the cutter mounting portions are located on the two rounded corner sides of the cutter head body. A cutting tool is provided on the rotational side of each cutter mounting portion. The cutting tools are made of alloy steel, and the outer ends of all cutting tools are arc-shaped and located on the same circumference. The diameter of the circumference where the outer end of the cutting tool is located is equal to the diameter of the arc-shaped surface being cut. In this way, the cutter head body is rounded rectangular, and the cutter mounting portions are located on the two rounded corner sides, extending outward from the rounded corner sides and integrally formed with the cutter head body. This makes the width of the two straight sides of the cutter head smaller than the distance between the cutter mounting portions on the other two sides. Therefore, when picking up or rotating, it can be gripped at the two straight sides of the cutter head body, which is convenient for gripping, installation, and rotation operation. At the same time, the wide side of the cutter head has a certain amount of clearance, which can also adapt to the cutting of circular holes or arc-shaped concave surfaces in small spaces. The cutting tools are evenly distributed, with their outer ends in an arc shape and located on the same circumference, which can meet the requirements for cutting circular holes or arc surfaces.

[0009] Furthermore, four tool mounting parts are provided, distributed in pairs on the rounded corner sides of the cutter head body. The outer edges of all tool mounting parts are on the same circumference, and the center of the circumference where the outer edge of the tool mounting part is located overlaps with the center of the mounting hole. In this way, the tool mounting parts and the cutting tools fixed on them are evenly distributed, which facilitates manufacturing and cutting. The distance between the outer edge of the tool mounting part and the center of the mounting hole is equal. At the same time, the tool mounting parts are distributed circumferentially around the center of the mounting hole, so that each tool mounting part is subjected to balanced force during cutting, making it less prone to deformation and damage.

[0010] Furthermore, the thickness of the cutter head body is 14.9-15.2 mm, the thickness of the tool mounting part is 11.1-11.3 mm, and the width is 12-14 mm. This results in a relatively thick tool mounting part and cutter head body, providing high strength. Simultaneously, the width of the tool mounting part is wider than that of conventional cutter heads, resulting in higher overall strength and rigidity. This allows it to adapt to the requirements of unilateral cutting, has a long service life, and can meet the needs of long-term cutting. Attached Figure Description

[0011] Figure 1 This is a schematic diagram of the disassembled structure of the tool holder and the tool disc in the embodiment;

[0012] Figure 2 This is a schematic diagram of the assembly structure of the tool holder and the tool disc in the embodiment;

[0013] Figure 3 This is a front view of the cutter head in the embodiment;

[0014] Figure 4 This is a partial three-dimensional structural diagram of the tool holder in the embodiment;

[0015] Figure 5 for Figure 1 A schematic diagram of the cross-sectional structure of AA;

[0016] Figure 6 for Figure 3 Schematic diagram of the cross-sectional structure of BB;

[0017] Figure 7 This is a schematic diagram of the installation structure of the cutter head and the cutter bar after the cutter head is rotated and in the locked position in the embodiment. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of the embodiments of this utility model clearer, the technical solutions of the embodiments of this utility model will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this utility model. The components of the embodiments of this utility model described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of this utility model provided in the accompanying drawings is not intended to limit the scope of the claimed utility model, but merely represents selected embodiments of the utility model. All other embodiments obtained by those skilled in the art based on the embodiments of this utility model without inventive effort are within the scope of protection of this utility model.

[0019] It should be noted that similar reference numerals and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures. In the description of this utility model, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the figures, or the orientation or positional relationship commonly used when the product is in use. They are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this utility model. Furthermore, the terms "first," "second," and "third," etc., are only used to distinguish descriptions and should not be construed as indicating or implying relative importance. In addition, the terms "horizontal," "vertical," etc., do not indicate that the component is required to be absolutely horizontal or suspended, but can be slightly tilted. For example, "horizontal" simply means that its direction is more horizontal than "vertical," and does not mean that the structure must be completely horizontal, but can be slightly tilted. In the description of this utility model, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model based on the specific circumstances.

[0020] like Figures 1-7As shown, the cutting tool provided in this embodiment for cutting the arc-shaped surface inside the engine compartment of a motorcycle includes a tool holder 1 and a cutter head 2; one end of the tool holder 1 is provided with a connecting part 12, and the middle of the cutter head 2 is provided with a mounting hole 24 that mates with the connecting part 12; the connecting part 12 of the tool holder 1 is sleeved in the mounting hole 24, and its end extends out of the cutter head 2; the cutter head 2 can rotate under the action of external force, and after rotating to a certain angle, it is in a locked position, and after rotating in the opposite direction, it is in an unlocked position; The rotation direction of the cutter head 2 to the locking position is opposite to the rotation direction of the cutter head 2 and the tool bar 1. When the cutter head 2 is in the locking position, the mounting hole 24 of the cutter head 2 is locked in place with the middle of the connecting part 12 of the tool bar 1, and the mounting hole 24 and the end of the connecting part 12 are cross-shaped, with the end of the connecting part 12 pressing and positioning the cutter head 2. When the cutter head 2 is in the unlocking position, its mounting hole 24 rotates back to the initial position, corresponding to the connecting part 12, and the cutter head 2 can be pulled out from the connecting part 12 of the guide rod under the action of external force. In this way, when machining the housing, first fix the end of the tool bar 1 away from the connecting part 12 on the cutting machine tool, then fix the engine housing to be machined on the opposite side of the tool bar 1, and adjust the position of the engine housing so that the small hole next to the part to be cut corresponds to the tool bar 1. Then move the engine housing or the tool bar 1 so that the tool bar 1 passes through the small hole, and the connecting part 12 extends out of the small hole and is placed next to the part to be cut. After the tool holder 1 is adjusted to the position of the engine block to be cut, the cutter head 2 can be installed. When installing the cutter head 2, align the mounting hole 24 of the cutter head 2 with the connecting part 12 of the tool holder 1, and insert it into the connecting part 12, ensuring that the middle of the connecting part 12 corresponds to the mounting hole 24 and the end extends beyond the mounting hole 24. Then rotate the cutter head 2 until it can no longer rotate. At this point, the mounting hole 24 of the cutter head 2 is locked to the middle of the connecting part 12, and the end is positioned outside the mounting hole 24, forming a cross shape with it. The cutter head 2 is then rotated to the locking position, achieving locking. After the cutter head 2 is locked, start the cutting machine. The drive shaft of the cutting machine drives the tool holder 1 and the cutter head 2 to rotate together, completing the cutting of the cutter head 2. After cutting, manually rotate the cutter head 2 in the opposite direction. This changes the relative position between the mounting hole 24 and the connecting part 12, aligning the mounting hole 24 with the connecting part 12. Therefore, under external force, the cutter head 2 can be removed from the tool holder 1. The cutter head 2 and the cutter shank 1 are detachably connected, so during assembly, only the cutter shank 1 needs to pass through the small hole, without needing to consider the size of the cutter head 2. This allows the cutting tool 23 to cut the large hole after passing through the small hole. At the same time, the locking and unlocking operations between the cutter head 2 and the cutter shank 1 are relatively convenient, making it easy to promote and apply to the cutting of other components.Furthermore, since the cutter head 2 and the connecting part 12 are tightly fitted after rotation in the middle, and the end of the connecting part 12 of the tool holder 1 is cross-shaped with the mounting hole 24 and closely attached to the end face of the cutter head 2, it can form a tight and fixed clamping mechanism for the cutter head 2. At the same time, its locking rotation direction is opposite to the rotation direction of the cutter head 2 during cutting (while the direction of the cutting force is opposite to the rotation direction of the cutter head). Therefore, during the cutting process, the cutting force is in the same direction as the locking direction, so that the cutter head 2 and the tool holder 1 become tighter and tighter during cutting, and will not fall off, resulting in a high safety factor for cutting.

[0021] Furthermore, the outer diameter of the connecting part 12 is smaller than the outer diameter of the tool holder body 11, and it is composed of a connecting section 121 and a positioning section; the connecting section 121 is cylindrical, the positioning section is a double-sided flat-cut cylinder, and the positioning section is composed of a first positioning section 122 and a second positioning section 123. The first positioning section 122 is adjacent to the connecting section 121, and two slots 122a are circumferentially spaced on the first positioning section 122; the distance between the stepped surface where the tool holder body 11 and the connecting part 12 meet and the junction of the first positioning section and the second positioning section is equal to the depth of the mounting hole; the mounting hole 24 is composed of a circular sleeve hole 241 and a rounded rectangular hole 242. Two opposing locking blocks 243 are provided on one side of the rectangular hole 242 near the circular sleeve hole 241. The two locking blocks 243, together with the two straight sides of the rounded rectangular hole 242, form a through hole 244 for the positioning section of the connecting part 12 to pass through. The diameter of the circular sleeve hole 241 is larger than the diameter of the connecting section 121 (to facilitate the quick insertion of the tool holder). After the cutter disc 2 rotates to the locking position, the first positioning section 122 of the connecting part 12 is locked between the two straight sides of the rounded rectangular hole 242, and the second positioning section 123 of the connecting part 12 extends out of the rounded rectangular hole 242, and the rounded rectangular hole 242 and the second positioning section 123 are intersecting. In this way, the two locking grooves 122a in the middle of the connecting part 12 are arranged at intervals on both sides of the diameter line of their respective circumferences. After rotation, the locking grooves 122a are locked between the two long sides of the rounded rectangular hole 242, that is, the distance between the two locking grooves 122a is equal to the distance between the two long sides of the rounded rectangular hole 242. The two slots 122a are slots 122a opened on the first positioning section 122. The distance between the two slots 122a is less than the distance between the two corresponding positions of the second positioning section 123. Therefore, after being clamped in the rounded rectangular hole 242 at the slot 122a, the extended second positioning section 123 corresponds to the distance between the two slots 122a directly opposite each other. This distance is greater than the distance between the two slots 122a and the distance between the two long sides of the rounded rectangular hole 242. Therefore, the two opposite sides of the second positioning section 123 extend beyond the long side of the rounded rectangular hole 242 and together with the end face of the main body of the tool holder 1, form a clamping and positioning of the tool disc 2. The locking block 243 is located at the two rounded corners of the rounded rectangular hole 242, and forms a through hole 244 with the two straight sides of the rounded rectangular hole 242. That is, the locking block 243 and the two straight sides together form a through hole 244 that mates with the positioning section. Since the positioning section is a double-sided flat-cut cylinder with a rounded rectangular end face, the through hole 244 is also a rounded rectangle, and shares sides with the two straight sides of the rounded rectangular hole 242, with the length of the straight side being slightly shorter than the length of the two straight sides of the rounded rectangular hole 242. Thus, both the first positioning section 122 and the second positioning section 123 can pass through the through hole 244, and after the first positioning section 122 passes through the through hole 244 and aligns with the rounded rectangular hole 242, it can be tightly engaged with the two straight sides of the rounded rectangular hole 242 after rotating a certain angle.

[0022] Furthermore, the cutter head 2 includes a cutter head body 21 and cutter mounting portions 22 distributed clockwise along the outer edge of the cutter head body 21. The cutter head body 21 is in the shape of a rounded rectangle. The cutter mounting portions 22 are located on the two rounded corner sides of the cutter head body 21. A cutting cutter 23 is provided on the rotational orientation side of each cutter mounting portion 22. The outer ends of all cutting cutters 23 are arc-shaped and located on the same circumference. The diameter of the circumference where the outer end of the cutting cutter is located is equal to the diameter of the arc-shaped surface being cut. The cutter head body 21 is a rounded rectangle, with the tool mounting parts 22 located on the two rounded corner sides, extending outwards from the rounded corner sides and integrally formed with the cutter head body 21. This makes the width of the two straight sides of the cutter head 2 smaller than the distance between the tool mounting parts 22 on the other two sides, so that it can be gripped at the two straight sides of the cutter head body 21 when picked up or rotated, making it easy to grip, install, and rotate. At the same time, the wide side of the cutter head 2 has a certain amount of clearance, which can also adapt to the cutting of round holes or arc-shaped concave surfaces in small spaces. The cutting tools 23 are evenly distributed, with arc-shaped outer ends, and are located on the same circumference, which can meet the requirements for cutting round holes or arc surfaces.

[0023] In this embodiment, the cutting tool is made of alloy steel, with an arc-shaped outer end. The cutting tool 23 is provided with a beveled cutting edge on the opposite side of the tool mounting part. The beveled cutting edge is arranged radially along the circumference of the cutting tool.

[0024] Specifically, in this embodiment, the cutter head 2 has four tool mounting portions 22, distributed in pairs on the rounded corner sides of the cutter head body 21. The side of the cutter head closest to the rounded rectangular hole protrudes outward. The outer edges of all tool mounting portions 22 are on the same circumference, and the center of the circumference where the outer edge of the tool mounting portion 22 is located overlaps with the center of the mounting hole 24. In this way, the tool mounting portions 22 and the cutting tools 23 fixed on them are evenly distributed, which is convenient for manufacturing and cutting. The distance between the outer edge of the tool mounting portion 22 and the center of the mounting hole 24 is equal. At the same time, the tool mounting portions 22 are distributed circumferentially around the center of the mounting hole 24, so that each tool mounting portion 22 is subjected to balanced force during cutting, and is not easily deformed or damaged.

[0025] Furthermore, the thickness of the cutter head body 21 is 15mm, and the thickness of the tool mounting part 22 is 11mm, with a width of 13mm. Thus, the thickness of both the tool mounting part 22 and the cutter head body 21 is relatively large, providing high strength. Simultaneously, the width of the tool mounting part 22 is wider than that of a conventional cutter head 2, resulting in higher overall strength and rigidity. This allows it to adapt to the requirements of unilateral cutting, has a long service life, and can meet the needs of long-term cutting.

[0026] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this utility model and not to limit the technical solutions. Those skilled in the art should understand that any modifications or equivalent substitutions to the technical solutions of this utility model that do not depart from the spirit and scope of this technical solution should be covered within the scope of the claims of this utility model.

Claims

1. A cutting tool for cutting an arc surface in an inner cavity of a motorcycle engine case, characterized by, The device includes a cutter bar and a cutter head. One end of the cutter bar has a connecting portion, and the cutter head has a mounting hole in the middle that mates with the connecting portion. The connecting portion of the cutter bar is fitted into the mounting hole, with its end extending out of the cutter head. The cutter head can rotate under external force and, after rotating to a certain angle, is in a locked position; after rotating in the opposite direction, it is in an unlocked position. The rotation direction of the cutter head to the locked position is opposite to the rotation direction of the cutter head and the cutter bar. When the cutter head is in the locked position, the mounting hole of the cutter head is tightly engaged with the middle of the connecting portion of the cutter bar, and the mounting hole and the end of the connecting portion are intersecting, with the end of the connecting portion pressing and positioning the cutter head. When the cutter head is in the unlocked position, its mounting hole rotates back to its initial position, corresponding to the connecting portion, and the cutter head can be pulled out from the connecting portion of the guide rod under external force.

2. The cutting tool for cutting an arc surface in an inner cavity of a motorcycle engine case according to Claim 1, characterized by, The outer diameter of the connecting part is smaller than the outer diameter of the main body of the cutter bar, and it consists of a connecting section and a positioning section. The connecting section is cylindrical, and the positioning section is a double-sided flat-cut cylinder. The positioning section consists of a first positioning section and a second positioning section. The first positioning section is adjacent to the connecting section, and two slots are provided circumferentially at intervals on the first positioning section. The mounting hole consists of a circular sleeve hole and a rounded rectangular hole. Two oppositely arranged locking blocks are provided on the side of the rounded rectangular hole near the circular sleeve hole. The two locking blocks and the two straight sides of the rounded rectangular hole together form a through hole for the positioning section of the connecting part to pass through. The diameter of the circular sleeve hole is greater than or equal to the diameter of the connecting section. After the cutter disc rotates to the locking position, the first positioning section of the connecting part is locked between the two straight sides of the rounded rectangular hole, and the second positioning section of the connecting part extends out of the rounded rectangular hole, and the rounded rectangular hole and the second positioning section are intersecting.

3. A cutting tool for cutting an arcuate surface in an internal cavity of a motorcycle engine case according to claim 1 or 2, characterized in that, The cutter head includes a cutter head body and cutter mounting parts distributed clockwise along the outer edge of the cutter head body. The cutter head body is rounded rectangular, and the cutter mounting parts are located on the two rounded corner sides of the cutter head body. A cutting tool is provided on the rotational side of each cutter mounting part. The cutting tools are made of alloy steel, and the outer ends of all cutting tools are arc-shaped and located on the same circumference. The diameter of the circumference where the outer end of the cutting tool is located is equal to the diameter of the arc-shaped surface being cut.

4. The cutting tool for cutting an arc surface in an inner cavity of a motorcycle engine case according to claim 3, characterized in that, The tool mounting parts are provided in four pairs, distributed on the rounded corner sides of the tool disc body. The outer edges of all tool mounting parts are on the same circumference, and the center of the circumference where the outer edge of the tool mounting part is located overlaps with the center of the mounting hole.

5. A cutting tool for cutting an arcuate surface in the interior cavity of a motorcycle engine case according to claim 4, characterized in that, The thickness of the cutter head body is 14.9-15.2mm, the thickness of the cutter mounting part is 11.1-11.3mm, and the width is 12-14mm.

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