Cutting inserts, replaceable tip rotary cutting tools

Abstract

This invention provides a cutting insert that enables highly efficient machining while ensuring the strength of the corner cutting edge and suppressing the temperature rise of the main cutting edge. [Solution] A polygonal plate-shaped cutting insert comprising a rake face, a seating face, a side surface, and a mounting hole opening in the rake face and seating face and penetrating the cutting insert in the thickness direction. A cutting edge is provided at the intersecting ridge line of the rake face and the side surface. The cutting edge includes a corner cutting edge and a main cutting edge connected to the corner cutting edge. The main cutting edge is linear in both a front view of the rake face and a front view of the side surface including the relief face of the main cutting edge. The corner cutting edge includes a first arc cutting edge connected to the main cutting edge and an outermost arc cutting edge located at the outermost part of the corner cutting edge, wherein the first arc cutting edge and the outermost arc cutting edge are arc-shaped cutting edges having different radii of curvature from each other.

Description

Technical Field

[0001] The present invention relates to a cutting insert and an indexable rotary cutting tool with replaceable cutting edges.

Background Art

[0002] Conventionally, an indexable rotary cutting tool provided with a cutting insert has been known. Patent Document 1 discloses a cutting insert capable of enhancing the rigidity of a corner edge and improving machining efficiency.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In rough machining where a high load is applied to the cutting edge, high strength is required for both the main cutting edge and the corner edge. To improve the strength of the corner edge, it is effective to increase the radius of curvature of the corner edge. However, when the radius of curvature of the corner edge is increased, the length of the main cutting edge becomes shorter. Since the temperature rise due to cutting resistance concentrates on the main cutting edge, when the main cutting edge is short, there is a problem that local temperature rise occurs and wear around the main cutting edge tends to progress.

Means for Solving the Problems

[0005] (1) According to one aspect of the present invention, a polygonal plate-shaped cutting insert comprising a rake face constituting one of a pair of polygonal faces, a seating face constituting the other of a pair of polygonal faces, a side surface connecting the rake face and the seating face, and a mounting hole opening in the rake face and the seating face and penetrating the cutting insert in the thickness direction, wherein a cutting edge portion is provided at the intersecting ridge line of the rake face and the side surface, and the cutting edge portion includes a corner blade and a main cutting blade connected to the corner blade, and the main cutting blade is A cutting insert is provided, wherein the rake face is linear in both a front view and a front view of the side surface including the relief face of the main cutting edge, and the corner cutting edge includes a first arc cutting edge connected to the main cutting edge and an outermost arc cutting edge located at the outermost periphery of the corner cutting edge, the first arc cutting edge and the outermost arc cutting edge being arc-shaped cutting edges having different radii of curvature from each other, and at least one of the first arc cutting edge and the outermost arc cutting edge includes a plurality of linear sub-cutting edges arranged in an arc shape.

[0006] In this configuration, the main cutting edges are linear when viewed from two mutually orthogonal directions, so that during cutting, the entire length of the main cutting edge in the direction in which it extends cuts into the workpiece evenly. As a result, the temperature distribution when the cutting edge heats up due to cutting resistance is distributed across the entire main cutting edge. Since localized temperature increases do not occur on the main cutting edge, rake face wear of the main cutting edge due to temperature increases can be suppressed. Furthermore, by constructing the corner blade with arc-shaped cutting edges having different radii of curvature, the outermost arc-shaped cutting edge with a large radius of curvature is placed at the outermost part of the corner blade, and the outermost arc-shaped cutting edge and the main cutting edge 21 can be connected over a short distance by a first arc-shaped cutting edge with a relatively small radius of curvature. By placing the arc-shaped cutting edge with a large radius of curvature at the outermost part, the strength of the corner blade can be improved. In addition, by shortening the connection length between the outermost arc-shaped cutting edge and the main cutting edge, a greater length of the main cutting edge can be secured. By making the main cutting edge longer, the temperature rise area can be distributed more widely, and localized temperature rises can be suppressed, thereby further reducing wear on the rake face. Thus, this configuration provides a cutting insert that enables highly efficient machining while ensuring the strength of the corner cutting edge and suppressing the temperature rise of the main cutting edge.

[0007] (2) In (1), both the first arc blade and the outermost peripheral arc blade may be configured to be composed of a plurality of linear small cutting blades arranged side by side in an arc shape. (3) In (1) or (2), when the radius of curvature Rout of the outermost peripheral arc blade is the largest among the radii of curvature of the plurality of arc-shaped cutting blades constituting the corner blade, and the total cutting edge length of the corner blade is L2 and the cutting edge length of the outermost peripheral arc blade is Lout, a configuration satisfying L2 - Lout < Lout may be adopted. (4) In any one of (1) to (3), the length of the linear small cutting blade may be configured to be 1 / 20 or more and 1 / 3 or less with respect to the total length L2 of the corner blade.

[0008] (5) In any one of (1) to (4), the corner blade may be configured to be composed of only arc-shaped cutting blades having two types of radii of curvature.

[0009] (6) In any one of (1) to (5), when the main cutting blade is a linear cutting blade, and the cutting edge length of the main cutting blade is L1 and the diameter of the inscribed circle of the rake face is D1, a configuration satisfying 0.35×D1 ≦ L1 ≦ 0.60×D1 may be adopted.

[0010] (7) In any one of (1) to (6), the seating surface and the cutting edge portion are parallel to each other in a front view of the side surface including the relief surface of the main cutting blade. The cutting edge portion includes the corner blade, the main cutting blade, a wiper blade adjacent to the opposite side of the corner blade of the main cutting blade, and an inner peripheral arc blade adjacent to the opposite side of the main cutting blade of the wiper blade. When the cutting edge length of the main cutting blade is L1 and the cutting edge length of the wiper blade is L3, a configuration satisfying 0.25 ≦ L3 / L1 ≦ 0.50 may be adopted.

[0011] (8) In any one of (1) to (7), the radius of curvature Rout of the outermost peripheral arc blade may be configured to be an integer multiple of 1 mm.

[0012] (9) In any one of (1) to (8), when a virtual line VL perpendicular to the main cutting edge is defined from the center line of the mounting hole to the front view of the rake face of the cutting insert, and the intersection point of the virtual line VL and the main cutting edge is defined as point S, and the intersection point of the virtual line VL and the outer edge of the mounting hole is defined as point T, the shortest distance L5 between point S and point T may be greater than the distance L6 from the center line O1 to point T.

[0013] (10) In any one of (1) to (9), the corner blade may have an outer peripheral blade connected to the side opposite to the main cutting blade, the outermost circular arc blade and the outer peripheral blade are smoothly connected, the first circular arc blade and the main cutting blade are smoothly connected, and the main cutting blade and the wiper blade are connected via a convex curve blade that protrudes radially outward from the center line of the mounting hole.

[0014] (11) A rotary cutting tool with replaceable cutting edges, comprising a cutting insert as described in any one of (1) to (10), and a holder to which the cutting insert is detachably mounted and which rotates around a rotation axis, wherein the holder has an insert mounting seat that contacts the relief surface of the cutting insert with respect to the cutting edge and the seating surface. [Effects of the Invention]

[0015] According to one aspect of the present invention, a cutting insert that enables high-efficiency machining while ensuring the strength of the corner cutting edge and suppressing the temperature rise of the main cutting edge, and an indexable rotary cutting tool equipped with the cutting insert are provided. [Brief explanation of the drawing]

[0016] [Figure 1] Figure 1 is a perspective view showing a cutting insert of an embodiment. [Figure 2] Figure 2 is a plan view showing the configuration of the rake face of the cutting insert shown in Figure 1. [Figure 3A] Figure 3A is a magnified partial plan view showing the cutting insert. [Figure 3B]Figure 3B is a partial plan view showing an enlarged cutting insert. [Figure 4] Figure 4 is a side view showing the configuration of the side surface of the cutting insert. [Figure 5A] Figure 5A is a cross-sectional view of the cutting insert taken along the line Va-Va in FIG. 2. [Figure 5B] Figure 5B is a cross-sectional view of the cutting insert taken along the line Vb-Vb in FIG. 2. [Figure 6] Figure 6 is a side view of the tip-exchangeable rotary cutting tool. [Figure 7] Figure 7 is a perspective view of the tip-exchangeable rotary cutting tool. [Figure 8] Figure 8 is a perspective view showing the holder in a state where the cutting insert 1 is removed. [Figure 9] Figure 9 is a partial plan view showing a modified example of the cutting insert 1. [Figure 10A] Figure 10A is an explanatory view showing the arrangement pattern of the linear small cutting edges and the virtual arc in the first arc edge and the outermost peripheral arc edge. [Figure 10B] Figure 10B is an explanatory view showing the arrangement pattern of the linear small cutting edges and the virtual arc in the first arc edge and the outermost peripheral arc edge. [Figure 10C] Figure 10C is an explanatory view showing the arrangement pattern of the linear small cutting edges and the virtual arc in the first arc edge and the outermost peripheral arc edge.

Embodiments for Carrying Out the Invention

[0017] Hereinafter, embodiments to which the present invention is applied will be described in detail with reference to the drawings. In the drawings used in the following description, for the sake of clarity of the characteristic parts, parts that are not characteristic may be omitted for illustration convenience.

[0018] Figure 1 is a perspective view showing a cutting insert 1 of an embodiment. Figure 2 is a plan view showing the configuration of the rake face 2 of the cutting insert 1 shown in Figure 1. Figure 3A is a partial plan view of the cutting insert 1, showing an enlarged portion of Figure 2. Figure 3B is a partial plan view of the cutting insert 1, showing an enlarged portion of Figure 3A. Figure 4 is a side view showing the configuration of the side surface 10 of the cutting insert 1.

[0019] The cutting insert 1 has a polygonal plate shape (a rectangular plate shape in this embodiment) that is rotationally symmetric with respect to a center line O1 extending in the thickness direction. In this embodiment, the center line O1 is the central axis of the mounting hole 7 that penetrates the cutting insert 1 in the thickness direction. In the following explanation, the direction along the center line O1 may be simply referred to as the thickness direction. Similarly, the direction perpendicular to the center line O1 may be simply referred to as the radial direction. Likewise, the circumferential direction around the axis centered on the center line O1 may be simply referred to as the circumferential direction.

[0020] The cutting insert 1 comprises a rake face 2 that constitutes one of a pair of polygonal faces, a seating face 3 that constitutes the other of the pair of polygonal faces, a side surface 10 connecting the rake face 2 and the seating face 3, and a mounting hole 7 for attaching to a holder. As shown in Figure 2, the rake face 2 and the seating face 3 are formed in a substantially square shape. The seating face 3 is enclosed within the projection area of ​​the rake face 2 in the thickness direction. The side surface 10 has two side surfaces 10A that are connected to the long side of the rake face 2 and two side surfaces 10B that are connected to the short side of the rake face 2.

[0021] As shown in Figures 6 and 7, which will be explained later, the cutting insert 1 is detachably attached to the tip of the holder 31 by a clamping screw 38. Therefore, mounting holes 7 are formed in the rake face 2 and the seating face 3, penetrating the cutting insert 1 in the thickness direction. The clamping screw 38 is inserted through the mounting holes 7. The mounting holes 7 extend along the center line O1 of the cutting insert 1. The mounting holes 7 are tapered through holes with the center line O1 as the central axis.

[0022] The rake face 2 includes a reference surface 2a parallel to the seating surface 3. A cutting edge portion 20 is provided at the intersecting ridge line of the rake face 2 and the side surface 10. The cutting edge portion 20 includes an outer peripheral blade 25, a corner blade 24, a main cutting blade 21, a wiper blade 22, and an inner circumferential arc blade 26.

[0023] The main cutting edge 21 and the wiper blade 22 are provided on the intersecting ridge line with the side surface 10B that is connected to the short side of the rake face 2. The outer peripheral blade 25 is provided on the intersecting ridge line with the side surface 10A that is connected to the long side of the rake face 2. A corner blade 24 is provided between the main cutting edge 21 and the outer peripheral blade 25. An inner circumferential arc blade 26 is provided on the wiper blade 22 on the side opposite the main cutting edge 21. The inner circumferential arc blade 26 is located at the corners of the rake face 2. That is, of the four corners of the rake face 2, the corner blades 24 are provided at two diagonally opposite corners, and the inner circumferential arc blades 26 are provided at the other two corners. In this embodiment, the cutting edge section 20 has a convex curve blade 23 that connects the main cutting edge 21 and the wiper blade 22. In a plan view of the rake face 2, the outer edge blade 25, corner blade 24, main cutting edge 21, convex curve blade 23, wiper blade 22, and inner circular arc blade 26 are arranged in this order in a clockwise direction.

[0024] In the cutting insert 1 of this embodiment, two cutting edges 20 are provided at 180° intervals in the circumferential direction around the center line O1. The two cutting edges 20 are arranged rotationally symmetrically around the center line O1.

[0025] The main cutting edge 21 is located on the short side of the rake face 2 and extends in a straight line in a plan view of the rake face 2. The main cutting edge 21 is the longest of the cutting edges that make up the cutting edge section 20. When the cutting insert 1 is attached to the holder 31 (see Figures 6 and 7), the main cutting edge 21 faces the workpiece and is positioned on the TD side in the rotational direction of the holder 31. In this embodiment, the main cutting edge 21 is straight in both a front view of the rake face 2 (Figure 2) and a front view of the side surface 10b including the relief surface of the main cutting edge 21 (Figure 4), as shown in Figures 2 and 4.

[0026] In this specification, the term "straight" for a cutting edge includes not only perfectly straight edges but also substantially straight edges within a certain margin of error. Specifically, in the case of a cutting insert with a main cutting edge 21 of approximately 3 mm in length, a gently curving arc shape with a radius of curvature exceeding 50 mm, or a curved shape that meanders with a meander width of 0.05 mm or less, is also included in the definition of "straight" in this specification.

[0027] The corner blade 24 is connected to the main cutting blade 21 and is located at the corner of the rake face 2. In the plan view shown in Figure 2, the corner blade 24 has a composite arc shape consisting of multiple arcs. On the other hand, the main cutting blade 21 extends in a straight line. Therefore, the boundary between the corner blade 24 and the main cutting blade 21 is determined by the boundary between the straight-shaped portion and the arc-shaped portion of the cutting blade portion 20.

[0028] The corner blade 24, as shown in an enlarged view in Figure 3A, includes a first arc blade 24a connected to the main cutting blade 21 and an outermost arc blade 24b located at the outermost part of the corner blade 24. The first arc blade 24a and the outermost arc blade 24b are arc-shaped cutting blades having different radii of curvature. The radius of curvature Rout of the outermost arc blade 24b is greater than the radius of curvature R1 of the first arc blade 24a.

[0029] As described above, in the cutting insert 1 of this embodiment, the main cutting edge 21 is linear in both a front view of the rake face 2 and a front view of the side surface 10B including the relief face of the main cutting edge 21, and the corner cutting edge 24 includes a first arc cutting edge 24a connected to the main cutting edge 21 and an outermost arc cutting edge 24b located at the outermost part of the corner cutting edge 24, and the first arc cutting edge 24a and the outermost arc cutting edge 24b are arc-shaped cutting edges having different radii of curvature from each other. With this configuration, the main cutting edge 21 is straight when viewed from either the front direction of the rake face 2 or the direction perpendicular to the rake face 2. As a result, during cutting, the entire length of the main cutting edge 21 in the direction in which it extends cuts into the workpiece uniformly. Consequently, the temperature distribution when the cutting edge heats up due to cutting resistance is distributed across the entire main cutting edge 21. Since no localized temperature rise occurs on the main cutting edge 21, wear on the rake face and flank face of the main cutting edge 21 due to temperature rise can be suppressed. Further, by configuring the corner edge 24 with arc-shaped cutting edges having different radii of curvature, an outermost peripheral arc edge 24b having a large radius of curvature is disposed at the outermost peripheral portion of the corner edge 24, and the outermost peripheral arc edge 24b and the main cutting edge 21 can be connected at a short distance by the first arc edge 24a having a relatively small radius of curvature. By disposing an arc-shaped cutting edge having a large radius of curvature at the outermost periphery, the strength of the corner edge 24 can be improved. Also, by shortening the connection length between the outermost peripheral arc edge 24b and the main cutting edge 21, a longer length of the main cutting edge 21 can be ensured. By making the main cutting edge 21 longer, the temperature rise region can be distributed more widely and local temperature rise can be suppressed, so that the wear of the rake face and the flank face can be further reduced. Thus, according to the present embodiment, there is provided a cutting insert 1 capable of high-efficiency machining that can suppress the temperature rise of the main cutting edge 21 while ensuring the strength of the corner edge 24.

[0030] Also in the present embodiment, as shown in FIG. 3A, the radius of curvature Rout of the outermost peripheral arc edge 24b is the largest among the radii of curvature of the plurality of arc-shaped cutting edges (the first arc edge 24a, the outermost peripheral arc edge 24b) constituting the corner edge. As shown in FIG. 3B, when the total cutting edge length of the corner edge 24 is L2 and the cutting edge length of the outermost peripheral arc edge is Lout, L2 - Lout < Lout. In the case of the present embodiment, L2 - Lout coincides with the length La of the first arc edge 24a, but when the corner edge 24 is composed of three or more arc-shaped cutting edges, L2 - Lout is the total length of the cutting edges other than the outermost peripheral arc edge 24b. That is, it is preferable that the length of the outermost peripheral arc edge 24b is larger than the total length of the other arc-shaped cutting edges constituting the corner edge 24. According to this configuration, by increasing both the radius of curvature and the length of the outermost peripheral arc edge 24b located at the outermost peripheral portion of the corner edge 24, the strength of the outermost peripheral arc edge 24b on which a load is applied during cutting can be increased. The strength of the entire corner edge 24 can be increased, and the life of the cutting insert 1 can be extended.

[0031] In this embodiment, the corner cutting edge 24 consists only of a first arc cutting edge 24a and the outermost arc cutting edge 24b. That is, the corner cutting edge 24 consists only of arc-shaped cutting edges with two different radii of curvature. The shape of the corner cutting edge 24 is not overly complex, making it possible to create a cutting insert 1 that is easy to manufacture.

[0032] The radius of curvature Rout of the outermost circular arc cutting edge 24b is preferably an integer multiple of 1 mm. With this configuration, the calculation of the machining process by the outermost circular arc cutting edge 24b becomes simpler in CAM (Computer Aided Manufacturing), making it easier to set the machining conditions.

[0033] The wiper blade 22 is located on the opposite side of the main cutting blade 21 from the corner blade 24. The wiper blade 22 is a straight cutting blade that extends in a direction intersecting the main cutting blade 21. The wiper blade 22 extends at an inclination so that it approaches the center line O1 as it moves away from the main cutting blade 21, relative to the direction in which the main cutting blade 21 extends. Therefore, the boundary between the main cutting blade 21 and the wiper blade 22 has a shape that protrudes outward. In this embodiment, a convex curved blade 23 is provided between the main cutting blade 21 and the wiper blade 22. The convex curved blade 23 may be arc-shaped or may have a curved shape other than an arc.

[0034] The cutting insert 1 of this embodiment has an outer peripheral blade 25 connected to the opposite side of the main cutting edge 21 of the corner blade 24, the outermost circular arc blade 24b and the outer peripheral blade 25 are smoothly connected, the first circular arc blade 24a and the main cutting edge 21 are smoothly connected, and the main cutting edge 21 and the wiper blade 22 are connected via a convex curve blade 23 that protrudes radially outward from the center line O1 of the mounting hole 7. In this specification, "smoothly connected" means a connection configuration in which the directions of the tangentials of the two cutting edges coincide at the connection point of the two cutting edges, i.e., a tangential connection. With this configuration, multiple cutting edges are smoothly connected without any steps, resulting in good surface finish accuracy.

[0035] In this embodiment, the cutting insert 1 is a positive-type cutting insert. As shown in Figures 1 and 4, the side surface 10B connected to the cutting edge 20, that is, the relief surface of the cutting edge 20, is an inclined surface that is approximately aligned with the relief angle. The relief surface of the cutting edge 20 connects the rake face 2 and the seating surface 3.

[0036] Side surface 10B mainly constitutes the relief surface for the main cutting edge 21 and the wiper blade 22. Side surface 10B has a first side surface 11A connected to the main cutting edge 21 and a second side surface 11B connected to the wiper blade 22. The first side surface 11A and the second side surface 11B are separated to the left and right by a boundary region 11C that extends between the rake face 2 and the seating surface 3 in a side view. In this embodiment, the boundary region 11C is connected to the convex curved blade 23.

[0037] The boundary region 11C is the boundary ridge between the first side surface 11A and the second side surface 11B. In this embodiment, the boundary region 11C is formed in a convex curved shape so as to smoothly connect the first side surface 11A and the second side surface 11B. The convex curved blade 23 connected to the boundary region 11C is also convex curved. The width of the boundary region 11C in a side view widens or narrows according to the convex curved shape. The width of the convex curved blade 23 and the boundary region 11C are not particularly limited and can be adjusted as appropriate based on the machined surface condition of the workpiece.

[0038] Here, Figure 5A is a cross-sectional view of the cutting insert 1 along the Va-Va line in Figure 2. Figure 5B is a cross-sectional view of the cutting insert 1 along the Vb-Vb line in Figure 2. The Va-Va line is perpendicular to the main cutting edge 21, and the Vb-Vb line is perpendicular to the wiper blade 22. Figure 5A shows θ1, which is the relief angle of the main cutting edge 21, and Figure 5B shows θ2, which is the relief angle of the wiper blade 22. As shown in these figures, the relief angle θ2 of the wiper blade 22 is greater than the relief angle θ1 of the main cutting edge 21. In other words, the relief angle θ1 of the main cutting edge 21 and the relief angle θ2 of the wiper blade 22 satisfy the relationship θ1 < θ2.

[0039] Because the relief angle θ1 of the main cutting edge 21 and the relief angle θ2 of the wiper blade 22 are at different angles, the relief angles θ1 and θ2 can be designed individually. This allows the cutting edge strength of the main cutting edge 21 to be ensured by setting a smaller relief angle θ1 of the main cutting edge 21. In addition, by setting a larger relief angle θ2 of the wiper blade 22, wear on the second side surface 11B, which is the relief surface of the wiper blade 22, can be suppressed. Since both the cutting edge strength of the main cutting edge 21 and the wear resistance of the wiper blade 22 can be achieved, a cutting insert 1 with a long lifespan can be obtained.

[0040] As the relative magnitudes of the relief angles θ1 and θ2 are defined as described above, the boundary region 11C that demarcates the first side surface 11A and the second side surface 11B extends diagonally with respect to the center line O1 on side surface 10B, as shown in Figure 4. As a result, the width of the first side surface 11A in the direction along the short side of the rake face 2 gradually narrows from the rake face 2 toward the seating surface 3. On the other hand, the width of the second side surface 11B in the direction along the short side of the rake face 2 gradually widens from the rake face 2 toward the seating surface 3.

[0041] In this embodiment, it is preferable that the relief angles θ1 and θ2 satisfy 8°≦θ1≦18° and 12°≦θ2≦25°. By setting the relief angle θ1 within the above range, it is possible to suppress contact between the relief surface of the main cutting edge 21 and the workpiece surface while ensuring the cutting edge strength of the main cutting edge 21. This makes high-efficiency machining easier. A relief angle θ1 of 9° or more is more preferable. A relief angle θ1 of 15° or less is more preferable. By setting the relief angle θ2 within the above range, wear on the relief surface of the wiper blade 22 can be suppressed, and a high-quality machined surface can be obtained. Furthermore, the strength of the cutting edge and the overall strength of the cutting insert 1 can be ensured, thereby suppressing the occurrence of chipping of the cutting insert 1 and extending its lifespan. More preferably, the relief angle θ2 is 15° or more. More preferably, the relief angle θ2 is 20° or less.

[0042] In this embodiment, as shown in Figure 4, when the endpoint on the rake face 2 side of the boundary region 11C extending diagonally with respect to the center line O1 is called endpoint P, and the endpoint on the seating surface 3 side is called endpoint Q, endpoint P is located at a position further from the corner blade 24 than the center line O1 in a front view of the side surface 10B. In this embodiment, endpoint P is defined as the center point of the cutting edge length of the convex curve blade 23. Endpoint Q is defined as the center point of the ridge length of the ridge line 3a formed at the intersection of the boundary region 11C and the seating surface 3.

[0043] Because the endpoint P is located further from the corner cutting edge 24 than the center line O1 in a front view of the side surface 10B, the entire convex curved cutting edge 23, which is the intersection region of the boundary region 11C and the rake face 2, is located further from the corner cutting edge 24 than the center line O1. As a result, the linear main cutting edge 21 extends to a position further from the corner cutting edge 24 than the center line O1. The linear main cutting edge 21 has a larger cutting area into the workpiece than the arc-shaped cutting edge, and the heat generated by friction with the workpiece is distributed over a wider area in the longitudinal direction of the main cutting edge 21. Therefore, compared to the arc-shaped main cutting edge, localized temperature rises are less likely to occur, and the effect of suppressing wear of the rake face and flank face due to heat is obtained. In this embodiment, because the length of the linear main cutting edge 21 is increased by the above configuration, the temperature rise during cutting can be further suppressed, and wear of the rake face and flank face can be further reduced.

[0044] Figures 6 and 7 are perspective views showing the configuration of an interchangeable-tip rotary cutting tool 30 having multiple cutting inserts 1 and a holder 31 to which these cutting inserts 1 are detachably mounted. Figure 8 is a perspective view showing the holder 31 with the cutting inserts 1 removed.

[0045] The replaceable-tip rotary cutting tool 30 performs cutting by rotating the holder 31 in the rotational direction TD around the rotation axis J1. The replaceable-tip rotary cutting tool 30 has a holder 31 that rotates around the axis of the rotation axis J1 and three cutting inserts 1 attached to the holder 31.

[0046] As shown in Figure 8, the tip of the holder 31 is provided with three insert mounting seats 33. Each insert mounting seat 33 has a mounting seat bottom surface 34 and two mounting seat wall surfaces 35 and 36.

[0047] The mounting base surface 34 is rectangular in shape with an area approximately equal to that of the seating surface 3 of the cutting insert 1 and faces the rotational direction TD. The mounting base wall surface 35 is the surface facing the tip side in the direction of the rotation axis J1 and extends radially along the short side of the mounting base surface 34 in the direction of the holder 31. The mounting base wall surface 36 is the surface facing radially outward from the holder 31 and extends along the long side of the mounting base surface 34 in the direction of the rotation axis J1. A screw hole 37 is formed approximately in the center of the mounting base surface 34.

[0048] The mounting base bottom surface 34 contacts the seating surface 3 of the cutting insert 1 oppositely. The mounting base wall surface 35 contacts the side surface 10B of the cutting insert 1 oppositely. The mounting base wall surface 36 contacts the side surface 10A of the cutting insert 1 oppositely.

[0049] The cutting insert 1 is attached to the insert mounting seat 33 of the holder 31 using a clamping screw 38. The cutting insert 1 is attached to the holder 31 when the clamping screw 38, which is inserted into the mounting hole 7, is tightened into a screw hole 37 formed in the center of the bottom surface 34 of the mounting seat.

[0050] In this embodiment, the cutting insert 1 is fixed by having its seating surface 3 in close contact with the mounting base surface 34 of the holder 31, and its side surfaces 10A and 10B in contact with the mounting base wall surfaces 36 and 35, respectively. Furthermore, by tightening the clamp screw 38 into the screw hole 37, the seating surface 3 is pressed against the mounting base surface 34, and the side surfaces 10A and 10B are pressed against the mounting base wall surfaces 36 and 35.

[0051] In this embodiment, as shown in Figures 6 and 7, when attaching the cutting insert 1 to the holder 31, the second side surface 11B of the cutting insert 1 is pressed against the mounting seat wall surface 35 facing the tip side of the holder 31. In other words, the second side surface 11B, which is the relief surface of the wiper blade 22, becomes the restraining part.

[0052] In the cutting insert 1, as shown in Figure 4, the relief angle θ2 of the second side surface 11B is larger than the relief angle θ1 of the first side surface 11A. As a result, the width of the second side surface 11B in the direction perpendicular to the center line O1 increases as it approaches the seating surface 3. This configuration allows for a larger area of ​​the second side surface 11B compared to the case where the boundary region 11C extends parallel to the center line O1. In other words, a larger area of ​​the second side surface 11B, which is used as the restraining surface of the cutting insert 1 to the holder 31, can be secured. Since the contact area between the second side surface 11B and the mounting seat wall surface 35 can be increased, the restraining force of the cutting insert 1 to the holder 31 can be increased.

[0053] Furthermore, in this embodiment, it is preferable that the endpoint Q shown in Figure 4 is located on the side closer to the corner cutting edge 24 (right side in the figure) than the center line O1. This allows for a larger width to be secured in the direction perpendicular to the center line O1 of the second side surface 11B, thereby further increasing the restraining force of the cutting insert 1 on the holder 31.

[0054] In this embodiment, as shown in Figure 4, in a front view of the side surface 10B of the cutting insert 1, it is preferable that the angle θ3 between the straight line L connecting endpoint P and endpoint Q and the seating surface 3 satisfies 45° ≤ θ3 ≤ 85°. By setting the angle θ3 to 45° or more, the length of the linear main cutting edge 21 can be sufficiently secured, allowing for a larger radial cutting depth ae and enabling high-efficiency machining. Furthermore, because the linear main cutting edge 21 is longer, the temperature rise during cutting can be suppressed, extending the life of the cutting insert 1. More preferably, the angle θ3 is 50° or more. By setting the angle θ3 to 85° or less, the area of ​​the second side surface 11B can be sufficiently large, and the area of ​​the restraint between the cutting insert 1 and the holder 31 can be increased. Since the cutting insert 1 can be firmly restrained, high-efficiency machining becomes easier. More preferably, the angle θ3 is 80° or less.

[0055] In this embodiment, the main cutting edge 21 is a straight cutting edge, and when the cutting edge length of the main cutting edge 21 is L1 and the inscribed circle diameter of the rake face 2 is D1, it is preferable that 0.35 × D1 ≤ L1 ≤ 0.60 × D1 is satisfied. By setting the cutting edge length L1 of the main cutting edge 21 to 0.35 × D1 or more, a sufficient length of the straight main cutting edge 21 can be secured, allowing for a larger radial cutting depth ae and enabling high-efficiency machining. Furthermore, because the straight main cutting edge 21 is longer, the temperature rise during cutting can be suppressed, extending the life of the cutting insert 1. More preferably, the cutting edge length L1 is 0.40 × D1 or more. By setting the cutting edge length L1 of the main cutting edge 21 to 0.60 × D or less, a sufficiently large area of ​​the second side surface 11B can be secured, and the area of ​​the restraint between the cutting insert 1 and the holder 31 can be increased. Since the cutting insert 1 can be firmly restrained, high-efficiency machining becomes easier. More preferably, the cutting edge length L1 is 0.55 × D1 or less.

[0056] In this embodiment, as shown in Figure 4, the seating surface 3 and the cutting edge portion 20 are parallel to each other in a front view of the side surface 10B, which includes the relief surface of the main cutting edge 21. Also, as shown in Figures 3A and 3B, the cutting edge portion 20 includes a corner blade 24, a main cutting edge 21, a wiper blade 22 adjacent to the main cutting edge 21 on the opposite side of the corner blade 24, and an inner circumferential arc blade 26 adjacent to the wiper blade 22 on the opposite side of the main cutting edge 21. When the cutting edge length of the main cutting edge 21 is L1 and the cutting edge length of the wiper blade 22 is L3, it is preferable that 0.25 ≤ L3 / L1 ≤ 0.50 is satisfied. By making the length L3 of the wiper blade 22 0.25 times or more the length of the main cutting blade 21, the straight wiper blade 22 also becomes longer. This allows for efficient finishing of the machined surface. Wear of the wiper blade 22 can also be suppressed. More preferably, L3 / L1 is 0.30 or more. If the wiper blade 22 is made too long, the main cutting blade 21 will become shorter, so it is preferable that the length of the wiper blade 22 be 0.50 times or less the length of the main cutting blade 21. More preferably, L3 / L1 is 0.45 or less.

[0057] In this embodiment, as shown in Figure 3A, in a front view of the rake face 2 of the cutting insert 1, a virtual line VL perpendicular to the main cutting edge 21 is defined from the center line O1 of the mounting hole 7. When the intersection of the virtual line VL and the main cutting edge 21 is defined as point S, and the intersection of the virtual line VL and the outer edge of the mounting hole 7 is defined as point T, it is preferable that the shortest distance L5 between point S and point T is greater than the distance L6 from the center line O1 to point T. With this configuration, a sufficient distance can be provided between the main cutting edge 21, which is subjected to load during cutting, and the periphery of the mounting hole 7, which is located near the fulcrum of the load, thereby suppressing cracking of the cutting insert 1.

[0058] Although embodiments of the present invention have been described above, the configurations and combinations thereof in the embodiments are merely examples, and additions, omissions, substitutions, and other modifications are possible without departing from the spirit of the present invention. Furthermore, the present invention is not limited by the embodiments.

[0059] (modified version) Figure 9 is a partial plan view showing a modified cutting insert 1. Figure 9 shows the portion of the cutting insert 1 around the corner cutting edge. The configuration of the modified cutting insert 1 is the same as the previous embodiment except for the area around the corner cutting edge.

[0060] The modified cutting insert 1 shown in Figure 9 has a corner cutting edge 124. The corner cutting edge 124 has a first arc cutting edge 124a and an outermost arc cutting edge 124b. The first arc blade 124a consists of a plurality (four in the illustration) of linear sub-cutting blades 4a arranged in an arc shape from the connection point S between the first arc blade 124a and the main cutting blade 21. In a plan view parallel to the center line O1, the connection point m between the linear sub-cutting blades 4a is a corner that protrudes outward from the corner blade 124. The outermost circular arc blade 124b consists of a plurality (six in the figure) of linear small cutting blades 4b arranged in an arc shape from the connection point U between the outermost circular arc blade 124b and the outer blade 25. In a plan view parallel to the center line O1, the connection point n between the linear small cutting blades 4b is a corner that protrudes outward from the corner blade 124. The first arc blade 124a and the outermost arc blade 124b are connected at connection point T. In a plan view parallel to the center line O1, connection point T is a corner that protrudes outward from the corner blade 124. The corner blade 124 is composed of multiple straight small cutting blades 4a and 4b arranged in an arc shape.

[0061] The first arc blade 124a functions as an arc-shaped cutting blade having substantially the same radius of curvature as the first arc blade 24a of the previous embodiment, as four straight small cutting edges 4a are arranged in an arc shape. Similarly, the outermost arc blade 124b functions as an arc-shaped cutting blade having substantially the same radius of curvature as the outermost arc blade 24b of the previous embodiment, as it consists of six straight small cutting edges 4b arranged in an arc shape. Therefore, the first arc cutting edge 124a and the outermost arc cutting edge 124b are substantially arc-shaped cutting edges having different radii of curvature from each other.

[0062] The number of linear small cutting blades 4a constituting the first arc blade 124a and linear small cutting blades 4b constituting the outermost arc blade 124b is not particularly limited, as long as there are two or more of each. Since manufacturing becomes difficult if there are too many linear small cutting blades 4a and 4b, it is preferable that the number of linear small cutting blades 4a and 4b be in the range of two to ten. The number of linear small cutting blades 4a and 4b may be three or more, or four or more.

[0063] The lengths of the linear small cutting edges 4a and 4b are preferably 1 / 20 to 1 / 3 of the total length L2 of the corner cutting edge. The length of the linear small cutting edge 4a is preferably 1 / 20 to 1 / 6 of the total length L2 of the corner cutting edge. By setting the lengths of the linear small cutting edges 4a and 4b within the above range, the formation accuracy of the corner cutting edge 124 can be ensured. In addition, the roughness of the machined surface can be suppressed. Furthermore, θ4 is preferably 30° and θ5 is preferably 60°.

[0064] Since the linear small cutting edges 4a and 4b are arranged in an arc shape, a common virtual arc can be defined for multiple linear small cutting edges 4a and a common virtual arc for multiple linear small cutting edges 4b. The radii of curvature of these virtual arcs can be considered as the radii of curvature of the first arc cutting edge 124a and the radii of curvature of the outermost arc cutting edge 124b.

[0065] In the case of the first arc blade 124a, the common virtual arc to which multiple linear small cutting edges 4a touch or intersect is defined as the connection point S between the first arc blade 124a and the main cutting edge 21, and the virtual arc that touches or intersects the two linear small cutting edges 4a1 and 4a2 that extend from the connection point S. In the case of the outermost circular arc blade 124b, the common virtual arc through which multiple linear small cutting edges 4b touch or intersect is defined as the connection point U between the outermost circular arc blade 124b and the outermost blade 25, and the virtual arc that touches or intersects the two linear small cutting edges 4b1 and 4b2 extending from the connection point U.

[0066] Further details will be explained below with reference to Figures 10A to 10C. Figures 10A to 10C are explanatory diagrams showing the arrangement of linear cutting edges and virtual arcs in the first arc blade 124a and the outermost arc blade 124b. In Figures 10A to 10C, the case where the number of linear cutting edges 4a and 4b is small is shown as an example to make the positional relationship between the linear cutting edges 4a and 4b and the virtual arc easier to see.

[0067] Figure 10A shows a case where the endpoints of multiple linear cutting edges 4a and multiple linear cutting edges 4b define the respective virtual arcs. The first arc blade 124a consists of two linear cutting edges 4a1 and 4a2. The outermost arc blade 124b consists of two linear cutting edges 4b1 and 4b2.

[0068] In the first arc blade 124a, the arc passing through the connection point S between the first arc blade 124a and the main cutting edge 21, the connection point m between the two linear small cutting edges 4a, and the connection point T between the first arc blade 124a and the outermost arc blade 124b is defined as the virtual arc VCa. If there are three or more linear small cutting edges 4a, the virtual arc VCa is the arc passing through the connection point S and the two connection points m from the side of connection point S.

[0069] In the outermost circular arc blade 124b, the arc passing through the connection point U between the outermost circular arc blade 124b and the outermost blade 25, the connection point n between the two linear small cutting blades 4b, and the connection point T between the outermost circular arc blade 124b and the first circular arc blade 124a is defined as the virtual arc VCb. If there are three or more linear small cutting blades 4b, the virtual arc VCb is the arc passing through the connection point U and the two connection points n from the side of connection point U.

[0070] Figure 10B shows a case where each virtual arc is defined by an arc tangent to multiple linear small cutting edges 4a from the inside, and an arc tangent to multiple linear small cutting edges 4b from the inside. The first arc blade 124a consists of three linear small cutting edges 4a1 to 4a3. The outermost arc blade 124b consists of three linear small cutting edges 4b1 to 4b3.

[0071] In the first arc blade 124a, a common arc that tangent to the three linear cutting edges 4a from the inside is defined as a virtual arc VCa. The virtual arc VCa tangent to the linear cutting edge 4a1 passing through connection point S at connection point S. The virtual arc VCa tangent to the central linear cutting edge 4a2 at the point of contact a on the linear cutting edge 4a2. The virtual arc VCa tangent to the linear cutting edge 4a3 passing through connection point T at connection point T.

[0072] In the outermost circular arc blade 124b, a common arc that tangent to the three linear cutting edges 4b from the inside is defined as a virtual arc VCb. The virtual arc VCb tangent to the linear cutting edge 4b1 passing through connection point U at connection point U. The virtual arc VCb tangent to the central linear cutting edge 4b2 at the point of contact b on the linear cutting edge 4b2. The virtual arc VCb tangent to the linear cutting edge 4b3 passing through connection point T at connection point T.

[0073] Figure 10C shows a case where each virtual arc is defined by arcs intersecting multiple linear cutting edges 4a and multiple linear cutting edges 4b. The first arc blade 124a consists of two linear cutting edges 4a1 and 4a2. The outermost arc blade 124b consists of two linear cutting edges 4b1 and 4b2.

[0074] In the first arc blade 124a, the arc passing through the connection point S between the first arc blade 124a and the main cutting edge 21, intersecting with the linear small cutting edge 4a1 at intersection c1, and intersecting with the linear small cutting edge 4a2 at intersection c2 is defined as the virtual arc VCa. In the outermost circular arc blade 124b, the arc passing through the connection point U between the outermost circular arc blade 124b and the outermost blade 25, intersecting with the linear small cutting edge 4b1 at intersection point d1, and intersecting with the linear small cutting edge 4b2 at intersection point d2 is defined as the virtual circular arc VCb. In the example shown in Figure 10C, since the linear cutting blade 4a2 and the linear cutting blade 4b2 are connected at connection point T, both virtual arcs VCa and VCb pass through connection point T.

[0075] When virtual arcs VCa are defined in the manner shown in Figures 10A to 10C for a first arc blade 124a of the same shape, the virtual arc VCa defined in the manner shown in Figure 10A is located on the outermost circumference relative to the corner blade 124, the virtual arc VCa defined in the manner shown in Figure 10B is located on the innermost circumference, and the virtual arc VCa defined in the manner shown in Figure 10C is located in between them. As long as the virtual arc VCa in the first arc blade 124a and the virtual arc VCb in the outermost arc blade 124b are defined in the same manner, the virtual arcs VCa and VCb may be defined in any of the manners shown in Figures 10A to 10C.

[0076] In this modified example, both the first arc blade 124a and the outermost arc blade 124b are configured to consist of multiple linear small cutting edges 4a and 4b, but the invention is not limited to this configuration. That is, either the first arc blade 124a or the outermost arc blade 124b may be configured to consist of multiple linear small cutting edges. Alternatively, only a portion of the first arc blade 124a may consist of multiple linear small cutting edges 4a, with the remaining portion being an arc-shaped small cutting edge. Similarly, only a portion of the outermost arc blade 124b may consist of multiple linear small cutting edges 4b, with the remaining portion being an arc-shaped small cutting edge. [Explanation of Symbols]

[0077] 1…Cutting insert, 2…Rake face, 3…Seat surface, 7…Mounting hole, 10, 10A, 10B…Side, 11A…First side, 11B…Second side, 11C…Boundary region, 20…Cutting edge, 20L…Lowest point of tool, 21…Main cutting edge, 22…Wiper blade, 24…Corner blade, 30…Interchangeable tip rotary cutting tool, 31…Holder, 33…Insert mounting seat, J1…Rotation axis, L1…Cutting edge length, O1…Centerline, P, Q…Endpoints, θ1, θ2…Relief angle, θ3…Angle of line L

Claims

1. A polygonal plate-shaped cutting insert, It comprises a rake face constituting one of a pair of polygonal faces, a seating face constituting the other of the pair of polygonal faces, a side surface connecting the rake face and the seating face, and a mounting hole opening in the rake face and the seating face and penetrating the cutting insert in the thickness direction, A cutting edge is provided at the intersecting ridge between the scooping surface and the side surface. The cutting edge portion includes a corner blade and a main cutting blade connected to the corner blade. The main cutting edge is straight in both a front view of the rake face and a front view of the side including the relief face of the main cutting edge. The corner blade includes a first arc blade connected to the main cutting blade and an outermost arc blade located at the outermost part of the corner blade, The first arc blade and the outermost arc blade are arc-shaped cutting edges having different radii of curvature from each other. At least one of the first arc blade and the outermost arc blade includes a plurality of linear small cutting edges arranged in an arc shape, Cutting insert.

2. Both the first arc blade and the outermost arc blade consist of a plurality of linear small cutting edges arranged in an arc shape. The cutting insert according to claim 1.

3. The radius of curvature of the outermost circular arc blade, Route, is the largest among the multiple circular arc cutting edges that constitute the corner blade. When the total cutting edge length of the corner blade is L2 and the cutting edge length of the outermost circular arc blade is Lout, L2-Lout<Lout Satisfying A cutting insert according to claim 1 or 2.

4. The length of the aforementioned straight small cutting edge is between 1 / 20 and 1 / 3 of the total length L2 of the corner cutting edge. A cutting insert according to claim 1 or 2.

5. The aforementioned corner blade consists only of arc-shaped cutting edges with two different radii of curvature. A cutting insert according to claim 1 or 2.

6. The aforementioned main cutting edge is a straight cutting edge, When the cutting edge length of the main cutting edge is L1 and the inscribed circle diameter of the rake face is D1, 0.35 × D1 ≤ L1 ≤ 0.60 × D1 Satisfying A cutting insert according to claim 1 or 2.

7. The seating surface and the cutting edge portion are parallel to each other in a front view of the side surface including the relief surface of the main cutting edge. The cutting edge portion includes the corner blade, the main cutting blade, a wiper blade adjacent to the main cutting blade on the opposite side of the corner blade, and an inner circumferential arc blade adjacent to the wiper blade on the opposite side of the main cutting blade. When the cutting edge length of the main cutting blade is L1 and the cutting edge length of the wiper blade is L3, 0.25 ≤ L3 / L1 ≤ 0.50 Satisfying A cutting insert according to claim 1 or 2.

8. The radius of curvature of the outermost circular arc blade, Route, is an integer multiple of 1 mm. A cutting insert according to claim 1 or 2.

9. In a front view of the rake face of the cutting insert, a virtual line VL perpendicular to the main cutting edge is defined from the center line of the mounting hole, The intersection of the virtual line VL and the main cutting edge is point S. When the intersection of the imaginary line VL and the outer edge of the mounting hole is denoted as point T, The shortest distance L5 between point S and point T is greater than the distance L6 from the center line O1 to point T. A cutting insert according to claim 1 or 2.

10. The corner blade has an outer peripheral blade connected to the side opposite to the main cutting edge, The outermost circular arc blade and the outermost blade are smoothly connected, The first arc blade and the main cutting blade are smoothly connected, The main cutting blade and the wiper blade are connected via a convex curved blade that protrudes radially outward from the center line of the mounting hole. The cutting insert according to claim 7.

11. A cutting insert according to claim 1 or 2, The cutting insert is detachably mounted to a holder that rotates around a rotation axis, Equipped with, The holder has an insert mounting seat that contacts the relief surface of the cutting insert with respect to the cutting edge and the seating surface. A rotary cutting tool with replaceable cutting edges.

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