Cutting inserts and cutting tools

Abstract

A cutting insert (1) has a first surface (11) that is a rotationally symmetric polygon, a second surface (12) located on the opposite side of the first surface (11), an outer peripheral surface (13) located between the first surface (11) and the second surface (12), and a central axis (CL) passing through the center of the first surface (11) and the center of the second surface (12); the first surface (11) includes a first edge (111), a first corner (112), a second corner (113), a front corner surface (114) provided along the first edge, a chip removal groove surface (115) provided along the front corner surface (114), and a retaining surface (115) provided along the front corner surface (114) and the chip removal groove surface (115). The cutting insert has a bevel surface (116); a first edge (111) including a first cutting edge (1111), a second cutting edge (1112), and a transition cutting edge (1113); a rake face (114) including a first rake face (1141) along the first cutting edge (1111), a second rake face (1142) along the second cutting edge (1112), and a third rake face (1143) along the transition cutting edge (1113); and a chip removal groove surface (115) that moves away from the second surface (12) as it moves away from the rake face (114), connecting the first rake face (1141) and the third rake face (1143) and moving away from the second rake face (1142). This cutting insert can achieve good chip removal effect and facilitates the reduction of insert size.

Description

Technical Field

[0001] This invention relates to the field of cutting tools, and particularly to a cutting insert and a cutting tool. Background Technology

[0002] Chinese invention patent application CN105478873A discloses a cutting insert with an asymmetrical cutting edge. This insert has two opposing surfaces and four circumferential side surfaces. The two opposing surfaces and the four circumferential side surfaces respectively form four cutting edges. Each cutting edge is divided into a first part, a second part, and a transition radius. The length of the first part is L1, and the length of the second part is L2, where L1 > L2, and the transition radius is not located at the midpoint of the cutting edge. This technical solution solves the problem of increasing the height of the shoulder portion that can be used for cutting with the cutting insert.

[0003] However, in this approach, to ensure the cutting performance of the insert, the insert generally has a large rake angle. It also requires a sufficiently large restraint surface for control and a rake angle surface for chip removal. The space between the rake angle surface and the restraint surface is small, resulting in limited chip removal space. Therefore, the inserts are generally large, requiring more raw materials and leading to higher costs. Furthermore, if the size of the insert is reduced by increasing the distance between the cutting edge and the restraint surface, problems such as decreased insert strength and difficulties in forming can easily occur. Summary of the Invention

[0004] One object of the present invention is to provide a cutting blade that achieves good chip removal effect and facilitates the reduction of blade size.

[0005] Another object of the present invention is to provide a cutting tool having the above-described cutting insert.

[0006] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0007] According to one aspect of the present invention, a cutting insert is provided, comprising:

[0008] The first surface is a rotationally symmetric polygon;

[0009] The second surface is located on the opposite side of the first surface;

[0010] The outer peripheral surface is located between the first surface and the second surface; and

[0011] A central axis passes through the center of the first surface and the center of the second surface;

[0012] The first surface includes:

[0013] First edge;

[0014] The first corner connects to the first edge;

[0015] The second corner connects to the first edge;

[0016] The front corner face is disposed along the first edge and moves closer to the second surface as it moves away from the first edge;

[0017] A chip removal groove surface is provided along the front corner face and moves away from the second surface as it moves away from the front corner face; and

[0018] The restraint surface is provided along the front corner surface and the chip removal groove surface, is closer to the second surface than the first edge, and is perpendicular to the central axis;

[0019] The first edge includes:

[0020] The first cutting edge extends from the first corner to the second corner, and approaches the second surface as it gets closer to the second corner;

[0021] The second cutting edge extends in a straight line from the second corner to the first corner, and approaches the second surface as it gets closer to the first corner; and

[0022] A transition blade portion connects the first blade portion and the second blade portion, and approaches the second surface as it gets closer to the first corner;

[0023] When viewed directly from the outer peripheral surface, the inclination angle of the transition cutting edge is greater than that of the second cutting edge;

[0024] The front corner surface includes:

[0025] The first front corner face is provided along the first cutting edge;

[0026] The second front corner face is provided along the second cutting edge; and

[0027] The third front corner face is provided along the transition edge portion;

[0028] The chip removal groove surface connects the first front corner surface and the third front corner surface, and is away from the second front corner surface.

[0029] In some embodiments, the chip removal groove surface is closer to the second surface than the restraint surface.

[0030] In some embodiments, the chip removal groove surface has a first end closest to the first corner and a second end closest to the second corner, the first end being in contact with the first front corner surface and the second end being in contact with the third front corner surface; the chip removal groove surface has a concave portion closest to the second surface relative to the restraint surface, the concave portion being located between the first end and the second end.

[0031] In some embodiments, in the direction extending along the first edge, the deepest point is closer to the first corner than the junction of the first cutting edge and the transition cutting edge.

[0032] In some embodiments, when viewed from the direction of the restraint surface, the projected length of the distance from the first end to the second end along the direction of the first edge is L1, and the projected length of the distance from the first end to the most concave point along the direction of the first edge is L2, where L2 / L1 = 1 / 2 to 2 / 3.

[0033] In some embodiments, the included angle between the chip removal groove surface and the plane containing the restraint surface is α, and there is a first position and a second position closer to the most concave point from the first end to the most concave point, wherein the included angle α at the first position is smaller than the included angle α at the second position.

[0034] In some embodiments, the included angle α varies in the range of 0° < α < 40° at different positions between the first end and the second end.

[0035] In some embodiments, the front corner face further includes an extension surface connecting the first front corner face and the chip removal groove surface; in the direction toward the central axis, the extension surface moves closer to the second surface as it moves away from the first front corner face.

[0036] In some embodiments, the angle between the plane containing the extension surface and the plane containing the restraint surface is β, and the range of the angle β at different positions along the extension direction of the first edge is: 0°<β<35°.

[0037] In some embodiments, the projected length of the chip removal groove surface along the direction of extension of the first edge is 1 / 7 to 1 / 3 of the side length of the first surface.

[0038] In some embodiments, the length of the first cutting edge is greater than the length of the second cutting edge.

[0039] According to another aspect of the invention, the invention also provides a cutting tool, comprising a tool holder and a cutting insert as described above mounted on the tool holder.

[0040] As can be seen from the above technical solution, the present invention has at least the following advantages and positive effects: In the cutting insert of the present invention, each cutting edge on the first edge is inclined and extended, which can increase the extension length of the cutting edge and ensure the machining performance of the insert. The restraining surface is concave to the second surface compared to the cutting edge on the first surface, so there can be a large chip removal space between the restraining surface and the cutting edge, while ensuring that the first rake angle face has sufficient width and angle, which facilitates ensuring the cutting performance of the insert and guiding the chip removal. The chip removal groove can block the chips generated along the first rake angle face, causing the chips to curl and be discharged outward along the chip removal groove, avoiding the chips from scraping the second cutting edge on the same first edge that is not involved in cutting, thus providing good protection for the cutting edge. The chip removal groove guides the chips, making it easier for them to be discharged, saving the chip removal space of the cutting insert. While maintaining the same cutting edge shape, the overall shape of the cutting insert can be reduced, which is conducive to reducing the overall size of the cutting insert, reducing the amount of raw material used, and reducing costs. Attached Figure Description

[0041] Figure 1 This is a schematic diagram of an embodiment of the cutting tool of the present invention.

[0042] Figure 2 This is a schematic diagram from a perspective of an embodiment of the cutting blade of the present invention.

[0043] Figure 3 yes Figure 2 A schematic diagram of the cutting insert viewed from its outer peripheral surface.

[0044] Figure 4 yes Figure 3 Top view.

[0045] Figure 5 yes Figure 4 Enlarged view of a portion of point A in the middle.

[0046] Figure 6 yes Figure 5 Sectional view at point GG.

[0047] Figure 7 yes Figure 5 Cross-sectional view at HH.

[0048] Figure 8 yes Figure 5 Cross-sectional view at point JJ.

[0049] The reference numerals in the attached diagram are explained as follows: 1. Cutting insert; 2. Tool holder; 3. Fastener;

[0050] 11. First surface; 111. First edge; 1111. First cutting edge; P. Connecting point; 1112. Second cutting edge; 1113. Transition cutting edge; 112. First corner; 1121. First corner cutting edge; 113. Second corner; 1131. Second corner cutting edge; 114. Front angle face; 1141. First front angle face; 1142. Second front angle face; 1143. Third front angle face; 1145. Extension surface; 115. Chip removal groove surface; 1151. First end; 1152. Second end; 1153. Deepest recess; 116. Restraining surface; 118. Groove;

[0051] 12. Second surface;

[0052] 13. Outer peripheral surface;

[0053] 14. Center hole; CL, center shaft. Detailed Implementation

[0054] Typical embodiments embodying the features and advantages of the present invention will be described in detail in the following description. It should be understood that the present invention can have various variations in different embodiments without departing from the scope of the present invention, and the descriptions and illustrations herein are for illustrative purposes only and not intended to limit the present invention.

[0055] See Figure 1 One embodiment of the present invention provides a cutting tool, which includes a tool holder 2 and a cutting insert 1 mounted on the tool holder 2 by a fastener 3.

[0056] In this embodiment, the tool holder 2 is a face milling cutter head structure. Multiple cutting inserts 1 are mounted along the circumference of the tool holder 2, and the workpiece is machined as the tool holder 2 rotates.

[0057] The specific structure of the tool holder 2 and the mating structure between the cutting insert 1 and the tool holder 2 can be flexibly set according to the actual situation, and there are no restrictions here.

[0058] The specific structure of the cutting insert 1 will be described in detail below with reference to the accompanying drawings.

[0059] See Figures 2 to 8 In this embodiment, the cutting blade 1 is an indexable blade. In particular, in this embodiment, the cutting blade 1 can also be used on both sides.

[0060] The cutting insert 1 has a first surface 11, a second surface 12 located on the opposite side of the first surface 11, and an outer peripheral surface 13 located between the first surface 11 and the second surface 12. The cutting insert 1 also has a central hole 14 penetrating the first surface 11 and the second surface 12, which is used for a fastener 3 to pass through, so that the cutting insert 1 can be mounted on the tool holder 2 (e.g., ...). Figure 1(As shown). The first surface 11 and the second surface 12 are both rotationally symmetric polygons, and the first surface 11 and the second surface 12 are centrally symmetric to each other. The center of the first surface 11 and the center of the second surface 12 are both located on the central axis CL of the central hole 14. The cutting insert 1 is rotationally symmetric about the central axis CL as a whole.

[0061] See Figure 2 The first surface 11 includes a first edge 111, a first corner 112 connecting one end of the first edge 111, a second corner 113 connecting the other end of the first edge 111, a front corner surface 114 provided along the first edge 111, a chip removal groove surface 115 provided along the front corner surface 114, and a restraint surface 116 provided along the front corner surface 114 and the chip removal groove surface 115.

[0062] The first edge 111, the first corner 112, and the second corner 113 are located at the outer edge of the first surface 11 and form the cutting edge of the cutting insert 1. The restraining surface 116 is used to constrain the cutting insert 1 on the tool holder 2. The restraining surface 116 is disposed around the central hole 14 and perpendicular to the central axis CL. The restraining surface 116 is closer to the second surface 12 than the first edge 111; that is, the restraining surface 116 is concave to the second surface 12 compared to the cutting edge on the first surface 11, thus allowing for a larger chip removal space between the restraining surface 116 and the cutting edge. The rake face 114 and the chip groove face 115 connect the first edge 111 and the restraining surface 116.

[0063] See Figure 4 The projection of the first surface 11 is approximately square, with rounded corners at the four corners. The side length of the square is defined as L0, which can be obtained by projection measurement. The outer edge of the first surface 11 has four first edges 111, each extending along the side length of the square. The distance between two opposite first edges 111 is the side length L0 of the first surface 11.

[0064] The first corner 112 and the second corner 113 are respectively connected between two adjacent first edges 111. The first corner 112 and the second corner 113 are actually the same structure; the distinction is made artificially in name only for ease of description. Specifically, they are... Figure 4With the view direction as a reference, for a specific first edge 111, the first corner 112 is located in the clockwise direction of the first edge 111, and the second corner 113 is located in the counterclockwise direction of the first edge 111. In this embodiment, both the first corner 112 and the second corner 113 are arc-shaped, with the two ends of the arc connecting to the two adjacent first edges 111 respectively. In other embodiments, the first corner 112 and the second corner 113 can also be straight lines, respectively inclinedly connected to the two adjacent first edges 111. In this case, the four corners of the square formed by the projection of the first surface 11 form oblique transitions.

[0065] A first corner blade 1121 is provided on the first corner 112, and a second corner blade 1131 is provided on the second corner 113. From the first corner 112 or the second corner 113 toward the central axis CL, a plane or curved surface in the form of a step can be connected to the restraint surface 116, and these planes or curved surfaces define the front angle of the first corner blade 1121 or the second corner blade 1131.

[0066] Combination Figure 2 and Figure 3 The first edge 111 includes a first cutting edge 1111, a second cutting edge 1112, and a transition cutting edge 1113 connecting the first cutting edge 1111 and the second cutting edge 1112.

[0067] The first cutting edge 1111 extends from the first corner 112 to the second corner 113, and approaches the second surface 12 as it approaches the second corner 113. The first cutting edge 1111 can extend as a whole in a straight line, or it can extend in multiple straight lines, or it can extend in a shape that combines straight lines and curves. The specific extension shape can be designed according to actual needs.

[0068] One end of the first cutting edge 1111 smoothly transitions to the first corner 112, and the other end smoothly transitions to the transition cutting edge 1113. The point where the first cutting edge 1111 and the transition cutting edge 1113 meet is marked as P. In this embodiment, the first cutting edge 1111 has a larger extension length, and the meeting point P is more inclined towards the second corner 113; that is, the distance between the meeting point P and the second corner 113 is less than the distance between the meeting point P and the first corner 112.

[0069] The second cutting edge 1112 extends from the second corner 113 toward the first corner 112, and approaches the second surface 12 as it gets closer to the first corner 112. The second cutting edge 1112 extends in a straight line, with its two ends smoothly transitioning to the second corner 113 and the transition cutting edge 1113, respectively. The length of the second cutting edge 1112 is less than the length of the first cutting edge 1111. Figure 3As shown, the angle between the second cutting edge 1112 and a plane S perpendicular to the central axis CL is defined as the inclination angle θ2 of the second cutting edge 1112.

[0070] The transition cutting edge 1113 extends in a straight line between the first cutting edge 1111 and the second cutting edge 1112, and approaches the second surface 12 as it approaches the first corner 112. For example... Figure 3 As shown, the angle between the transition cutting edge 1113 and a plane S perpendicular to the central axis CL is defined as the inclination angle θ3 of the transition cutting edge 1113. The inclination angle θ3 of the transition cutting edge 1113 is greater than the inclination angle θ2 of the second cutting edge 1112.

[0071] When in use, the cutting insert 1 consists of a first cutting edge 1111 on one of the first edges 111, a second cutting edge 1112 and a transition cutting edge 1113 on an adjacent first edge 111, and a first corner cutting edge 1121 or a second corner cutting edge 1131 connecting the two first edges 111 to perform right-angle surface machining on the workpiece. The first cutting edge 1111 generally serves as the main cutting edge, machining the side end face of the workpiece, while the combination of the second cutting edge 1112 and the transition cutting edge 1113 serves as the secondary cutting edge or finishing edge, machining the bottom face of the workpiece. In this embodiment, the first cutting edge 1111 has a large extension length, ensuring machining efficiency. The two-section structure formed by the combination of the second cutting edge 1112 and the transition cutting edge 1113, with different inclination angles, allows the secondary cutting edge to also have a suitable length even when the insert size is limited, ensuring machining performance.

[0072] See Figure 2 The rake face 114 extends a certain width from the first edge 111 toward the center hole 14, and moves closer to the second surface 12 as it moves away from the first edge 111. This inclined extension of the rake face 114 ensures the width and angle of the rake face 114, which helps to ensure the strength and sharpness of the cutting edge and the chip removal performance, thereby ensuring the cutting performance of the cutting insert 1.

[0073] Specifically, see Figure 4 The rake face 114 includes a first rake face 1141 along the first cutting edge 1111, a second rake face 1142 along the second cutting edge 1112, and a third rake face 1143 along the transition cutting edge 1113. The first rake face 1141 defines the rake angle of the first cutting edge 1111, the second rake face 1142 defines the rake angle of the second cutting edge 1112, and the third rake face 1143 defines the rake angle of the transition cutting edge 1113. The specific inclination angles and extension shapes of the first rake face 1141, the second rake face 1142, and the third rake face 1143 can be designed according to actual needs.

[0074] See Figure 2 and Figure 4 The chip removal groove surface 115 extends from the front corner face 114 toward the center hole 14 and moves away from the second surface 12 as it moves away from the front corner face 114. The chip removal groove surface 115 connects the first front corner face 1141 and the third front corner face 1143 and moves away from the second front corner face 1142. In the direction extending along the first edge 111, the chip removal groove surface 115 is in contact with a portion of the first front corner face 1141, a portion of the third front corner face 1143, but not with the second front corner face 1142.

[0075] The chip removal groove 115 is located between the first edge 111 and the restraint surface 116, which helps to ensure the angle and width of the rake face 114, thus guaranteeing the cutting performance of the cutting insert 1. Simultaneously, when chips generated by the first cutting edge 1111 are generated along the first rake face 1141 and encounter the chip removal groove 115, the inclined design of the chip removal groove 115 causes the chips to be blocked and curled, and then discharged away from the first surface 11 along the chip removal groove 115, i.e., outward from the cutting insert 1. This prevents chips from scraping against the second cutting edge 1112 on the same first edge 111 that is not involved in cutting, providing excellent protection for the cutting edge. The chip removal groove 115 guides the chips, making them easier to remove, saving chip removal space in the cutting insert 1. While maintaining the same cutting edge shape, the overall shape of the cutting insert 1 can be reduced, facilitating a reduction in the overall size of the cutting insert 1, reducing the amount of raw material used, and lowering costs.

[0076] Preferably, the chip removal groove surface 115 is closer to the second surface 12 than the restraint surface 116, thereby providing a larger chip processing space between the chip removal groove surface 115 and the first cutting edge 1111, which facilitates the curling and discharge of chips.

[0077] See Figure 5 In this embodiment, the front corner surface 114 further includes an extension surface 1145, and the chip removal groove surface 115 is connected to the extension surface 1145 to connect the first front corner surface 1141 and the third front corner surface 1143.

[0078] The extension surface 1145 extends from the first front corner face 1141 toward the central hole 14, and in the direction toward the central axis CL, the extension surface 1145 moves away from the first front corner face 1141 and closer to the second surface 12. In the direction extending along the first edge 111, the extension surface 1145 is in contact with a portion of the first front corner face 1141 and a portion of the third front corner face 1143, but not with the second front corner face 1142.

[0079] In this embodiment, the chip removal groove surface 115 has a first end 1151 closest to the first corner 112 and a second end 1152 closest to the second corner 113. The first end 1151 and the second end 1152 define the boundary of the chip removal groove surface 115 along the extension direction of the first edge 111. The first end 1151 is connected to the first front corner surface 1141 through the extension surface 1145, and the second end 1152 is connected to the third front corner surface 1143 through the extension surface 1145.

[0080] The distance between the first end 1151 and the second end 1152 is projected as L1 along the direction of extension of the first edge 111, which is also the projection length of the chip removal groove surface 115 along the direction of extension of the first edge 111.

[0081] In some preferred embodiments, L1 is 1 / 7 to 1 / 3 of the side length L0 of the first surface 11, i.e., L1 / L0 = 1 / 7 to 1 / 3. Within this design range, on the one hand, the chip removal groove surface 115 has sufficient length to achieve the expected chip breaking and chip removal effect; on the other hand, the chip removal groove surface 115 does not occupy too much area of ​​the first surface 11, so that the restraint surface 116 can have sufficient area to ensure the locking effect of the cutting insert 1 on the tool holder 2. In summary, the chip treatment effect and the restraint and locking effect can be balanced.

[0082] Combination Figures 5 to 8 The chip removal groove surface 115 and the extension surface 1145 surround each other to form a groove 118 that is concave to the second surface 12 compared to the restraint surface 116.

[0083] See Figures 6 to 8 The chip removal groove surface 115 and the extension surface 1145 smoothly transition and connect at the bottom of the groove 118. Figures 6 to 8 With the top and bottom positions in the view direction as references, when viewed from the first edge 111 toward the central axis CL, the chip removal groove surface 115 forms the rising portion of the groove 118, and the extension surface 1145 forms the downward sloping portion of the groove 118.

[0084] Combination Figures 6 to 8 The included angle α between the chip removal groove surface 115 and the plane containing the restraint surface 116 is not exactly the same at different locations. Figures 6 to 8 The included angles α are respectively labeled as α1, α2, and α3. In the direction from the first end 1151 to the second end 1152, the inclination angle of the chip removal groove surface 115 relative to the restraint surface 116 changes gradually. The specific curved surface shape can be flexibly designed, but generally, the closer to the first end 1151 or the second end 1152, the smaller the included angle α between the plane containing the chip removal groove surface 115 and the restraint surface 116. Figures 6 to 8 At the three cross-sections shown, the included angle α1 < included angle α2, and the included angle α3 < included angle α2.

[0085] Preferably, at different positions between the first end 1151 and the second end 1152, the included angle α varies within the range of 0° < α < 40°.

[0086] Similarly, the angle β between the extension surface 1145 and the plane containing the restraint surface 116 is not exactly the same at different locations. Figures 6 to 8 The included angles β are respectively labeled as β1, β2, and β3. Along the extension direction of the first edge 111, the inclination angle of the extension surface 1145 relative to the restraint surface 116 changes gradually. The side of the extension surface 1145 closest to the first edge 111 connects with the first front angle surface 1141 and the third front angle surface 1143. The extension surface 1145 also transitions with the first front angle surface 1141 and the third front angle surface 1143 through appropriate angles and shapes. The specific curved surface shape of the extension surface 1145 can be reasonably designed according to actual conditions.

[0087] Preferably, at different positions along the extension direction of the first edge 111 on the extension surface 1145, the included angle β varies within the range of 0° < β < 35°.

[0088] In addition, according to Figures 6 to 8 As can be seen from the cross-sections at different locations, the bottom of the groove 118 formed by the intersection of the chip removal groove surface 115 and the extension surface 1145 is a curved surface with a depth that is not entirely the same relative to the restraint surface 116. For example, Figure 5 As shown, the bottom of the groove 118 has the deepest point 1153 relative to the restraint surface 116, that is, the point closest to the second surface 12.

[0089] The most concave point 1153 is the position of the chip removal groove surface 115 closest to the second surface 12 relative to the restraint surface 116, and is located between the first end 1151 and the second end 1152. From the first end 1151 to the most concave point 1153, there is a first position and a second position closer to the most concave point 1153. The angle α between the chip removal groove surface 115 and the plane containing the restraint surface 116 at the first position is smaller than the corresponding angle α at the second position. In some embodiments, the angle α between the chip removal groove surface 115 and the plane containing the restraint surface 116 in the direction from the first end 1151 to the most concave point 1153 can be designed to gradually increase.

[0090] Preferably, in the direction extending along the first edge 111, the most concave point 1153 is closer to the first corner 112 than the junction P between the first cutting edge 1111 and the transition cutting edge 1113. Since the first cutting edge 1111 is inclined, and it is closer to the second surface 12 the closer it is to the transition cutting edge 1113, the groove 118 formed by the correspondingly provided chip removal groove surface 115 and the extension surface 1145 can increase the chip removal space of this part of the first cutting edge 1111. At the same time, since the most concave point 1153 is closer to the first corner 112 than the junction P, correspondingly, at the position of the junction P, the chip removal groove surface 115 forms an upward slope relative to the most concave point 1153, which is more conducive to chip removal. While ensuring the chip removal effect, it also reduces the area occupied by the chip removal groove surface 115 on the first surface 11, which can better ensure the area of ​​the restraint surface 116 and improve the restraint effect.

[0091] In some embodiments, the distance from the first end 1151 to the deepest part 1153 is projected as L2 in the direction of extension along the first edge 111. The projection length L2 is preferably 1 / 2 to 2 / 3 of the total projection length L1 of the chip removal groove surface 115, that is: L2 / L1 = 1 / 2 to 2 / 3.

[0092] The first surface 11 has been described in detail above. For the double-sided cutting insert 1 of this embodiment, the second surface 12 may have the same structure as the first surface 11, and the two are rotationally symmetrical, allowing them to be interchanged by flipping. The second surface 12 will not be described in detail here. When the cutting insert 1 is mounted on the tool holder 2, by adjusting the mounting method, either the first surface 11 or the second surface 12 can be selectively used for cutting.

[0093] See Figure 2 The outer peripheral surface 13 is connected between the first surface 11 and the second surface 12. The outer peripheral surface 13 is surrounded by a plurality of side surfaces parallel to the central axis CL. Depending on the extended shape of the outer edges of the first surface 11 and the second surface 12, the outer peripheral surface 13 may include a plane and an arc surface to adaptably connect with the first surface 11 and the second surface 12.

[0094] Although the invention has been described with reference to several typical embodiments, it should be understood that the terminology used is illustrative and exemplary, and not restrictive. Since the invention can be embodied in many forms without departing from the spirit or essence of the invention, it should be understood that the above embodiments are not limited to any of the foregoing details, but should be interpreted broadly within the spirit and scope defined by the appended claims. Therefore, all variations and modifications falling within the scope of the claims or their equivalents should be covered by the appended claims.

Claims

1. A cutting insert having: a first surface in a polygon of rotational symmetry; a second surface on an opposite side of the first surface; a peripheral surface between the first surface and the second surface; and a center axis passing through a center of the first surface and a center of the second surface; characterized in that: the first surface includes: a first edge; a first corner connecting the first edge; a second corner connecting the first edge; a rake surface disposed along the first edge and approaching the second surface as it recedes from the first edge; a flute surface disposed along the rake surface and receding from the second surface as it recedes from the rake surface; and a constraint surface disposed along the rake surface and the flute surface, closer to the second surface than the first edge, and perpendicular to the center axis; the first edge includes: a first land extending from the first corner to the second corner and approaching the second surface as it approaches the second corner; a second land extending linearly from the second corner to the first corner and approaching the second surface as it approaches the first corner; and a transition land connecting the first land and the second land and approaching the second surface as it approaches the first corner; an inclination angle of the transition land is greater than an inclination angle of the second land when viewed in a direction normal to the peripheral surface; the rake surface includes: a first rake surface disposed along the first land; a second rake surface disposed along the second land; and a third rake surface disposed along the transition land; the flute surface connects the first rake surface and the third rake surface and recedes from the second rake surface, the flute surface is closer to the second surface than the constraint surface, the flute surface has a first end closest to the first corner and a second end closest to the second corner, the first end meets the first rake surface, and the second end meets the third rake surface, the flute surface has a most concave portion closest to the second surface with respect to the constraint surface, the most concave portion is between the first end and the second end, and the most concave portion is closer to the first corner than a meeting point of the first land and the transition land in a direction extending along the first edge; a distance from the first end to the second end in a projection along a direction extending along the first edge is L1, a distance from the first end to the most concave portion in the projection along the direction extending along the first edge is L2, and L2 / L1 = 1 / 2 ~ 2 / 3; an angle between the flute surface and a plane in which the constraint surface lies is a, the angle a is smaller at a first position from the first end to the most concave portion than at a second position closer to the most concave portion; and the angle a varies in a range of 0° < a < 40° at different positions between the first end and the second end. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 2. The cutting insert according to claim 1, characterized in that, ​ 3. The cutting insert according to claim 1, characterized in that, ​ 4. The cutting insert according to claim 3, characterized in that, ​ 5. The cutting insert according to claim 1, wherein, The rake surface further comprises an extension surface connected between the first rake surface and the chip flute surface; the extension surface approaches the second surface with a distance from the first rake surface in a direction towards the central axis.

6. The cutting insert according to claim 5, characterized in that, An angle between the extension surface and a plane where the restraining surface is located is β, and the angle β varies in a range of 0°<β<35° at different positions of the extension surface along the extension direction of the first edge.

7. The cutting insert according to any one of claims 1-6, wherein, A projection length of the chip flute surface along the extension direction of the first edge is 1 / 7-1 / 3 of a side length of the first surface.

8. The cutting insert according to any one of claims 1-6, wherein, The length of the first blade part is greater than the length of the second blade part.

9. A cutting tool characterized by A cutting tool comprising a tool holder and a cutting insert as claimed in any one of claims 1-8 mounted on the tool holder.

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