Cutting insert and edge replaceable end mill

Abstract

To provide a cutting insert and an edge replaceable end mill, which enable the cutting insert to be stably supported with an insert mounting seat while improving finishing surface accuracy with a secondary cutting edge, can suppress biting caused by the intrusion of chips between the insert mounting seat and the cutting insert, and can increase holder rigidity.SOLUTION: A cutting edge 14 has a main cutting edge 17 disposed on the first side of four sides of a quadrangular surface 11, a sub-cutting edge 18 disposed on the second side, and a corner edge 19. The sub-cutting edge 18 has a curved edge portion 18a that is connected to the corner edge 19 and forms a curved shape protruding toward a front side, and a linear edge portion 18b that is connected to the curved edge portion 18a and linearly extends toward a rear side as extending toward the opposite side to the curved edge portion 18a in the left-right direction. A flank 16 has a first sub-flank 16b that is connected to the curved edge portion 18a and forms a curved surface shape protruding toward the front side; and a planar second sub-flank 16c that is connected to the linear edge portion 18b.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a cutting insert and an indexable end mill. [Background technology]

[0002] A cutting tool described in Patent Document 1 is known as a conventional indexable end mill. The cutting tool of Patent Document 1 includes a rectangular plate-shaped cutting insert and a cylindrical holder. The holder has a chip discharge groove that extends spirally around the tool central axis (rotation axis) and a plurality of insert mounting seats that are arranged in a stepped pattern along the chip discharge groove. A plurality of common cutting inserts that are identical in shape are removably attached to the plurality of insert mounting seats.

[0003] The cutting insert comprises a cutting face arranged on a rectangular surface facing the rotation direction of the end mill, a side surface facing the tip side in the tool axial direction along the tool central axis, and a clearance surface arranged across a side surface facing outward in the tool radial direction perpendicular to the tool central axis, and a cutting edge arranged on a ridge portion connecting the cutting face and the clearance surface.

[0004] The cutting edge has a main cutting edge extending in the longitudinal direction of the rectangular surface, a minor cutting edge extending in the lateral direction of the rectangular surface, a convex curved corner edge connected to the main cutting edge and the minor cutting edge, and an inner edge connected to the end of the minor cutting edge opposite to the corner edge in the lateral direction. In an indexable end mill, the main cutting edge functions as a peripheral edge, and the minor cutting edge functions as a bottom edge. The inner edge may also function as a cutting edge during ramping, for example.

[0005] In addition, the multiple insert mounting seats arranged in a stepped pattern along the chip discharge groove include a frontmost (first stage) insert mounting seat located at the most forward end in the tool axial direction, and non-frontmost insert mounting seats (second stage and subsequent stages) located rearward of the frontmost insert mounting seat in the tool axial direction.

[0006] The insert mounting seat other than the leading end has a first wall surface that contacts the seating surface facing away from the rake face of the cutting insert, a second wall surface that contacts the side surface of the cutting insert facing inward in the tool radial direction, and a third wall surface that contacts the side surface of the cutting insert facing the tip side in the tool axial direction. The first wall surface supports the cutting insert from the side opposite to the end mill rotation direction. The second wall surface supports the cutting insert from the inside in the tool radial direction. The third wall surface supports the cutting insert from the tip side in the tool axial direction.

[0007] The most advanced insert mounting seat has a first wall surface that contacts the seating surface facing away from the rake face of the cutting insert, a second wall surface that contacts the side surface of the cutting insert facing inward in the tool radial direction, and a fourth wall surface that contacts the side surface of the cutting insert facing the rear end side in the tool axial direction. The first wall surface supports the cutting insert from the side opposite to the end mill rotation direction. The second wall surface supports the cutting insert from the inside in the tool radial direction. The fourth wall surface supports the cutting insert from the rear end side in the tool axial direction.

[0008] In this way, the wall surfaces (third wall surface, fourth wall surface) that support the cutting insert from the tool axial direction are different between the insert mounting seats other than the most front end (second row and subsequent rows) and the most front end (first row) insert mounting seat. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] Patent No. 7052176 Summary of the Invention [Problem to be solved by the invention]

[0010] In this type of indexable end mill, the minor cutting edge (bottom cutting edge) of the cutting insert attached to the insert mounting seat at the very front finishes the machined surface of the workpiece. By forming this minor cutting edge into a curved shape with a large radius of curvature that is convex toward the tip in the tool axial direction, it is possible to improve the accuracy of the finished surface.

[0011] However, when the minor cutting edge is formed in a convex curved shape, the portion of the flank of the cutting insert that is connected to the minor cutting edge (the minor flank) is formed in a curved shape that is convex toward the tip side in the tool axial direction. Therefore, when the third wall surface of the insert mounting seat other than the tip end (the second stage or later) is brought into contact with the minor flank, this contact becomes a point contact or a line contact, making it difficult for the third wall surface to stably support the cutting insert.

[0012] On the other hand, the inner blade does not require strict machining accuracy compared to the minor cutting edge. Therefore, it is possible to form the part of the flank that is connected to the inner blade (the inner blade flank) flat and make the third wall surface contact the inner blade flank. In this case, the contact between the third wall surface and the inner blade flank is surface contact, making it easy to increase the contact area.

[0013] However, the inner flank is disposed radially inward of the minor flank, and accordingly, the third wall surface supporting the inner flank is disposed far away from the main cutting edge and the corner edge in the radial direction of the tool. Therefore, even if the third wall surface is brought into contact with the inner flank, it is difficult to stably support the cutting insert.

[0014] Furthermore, in the case of a configuration in which the third wall surface is in contact with the inner cutting edge flank, in order to prevent contact between the wall portion of the insert mounting seat adjacent to the outer side of the third wall surface in the tool radial direction and the secondary flank surface of the cutting insert, it is necessary to cut out the wall portion in a concave shape. Since chips are likely to enter this concave cutout (gap), the chips are likely to become caught. In addition, the concave cutout reduces the rigidity of the holder.

[0015] One of the objects of the present invention is to provide a cutting insert and an indexable end mill that can stably support the cutting insert by the insert mounting seat while improving the finishing surface accuracy by the auxiliary cutting edge, can suppress jamming due to the intrusion of chips between the insert mounting seat and the cutting insert, and can increase the holder rigidity. [Means for solving the problem]

[0016] In order to solve the above problems, the present invention provides the following means.

[0017] [First aspect of the present invention] The insert has a rake face arranged on a rectangular surface facing the insert axial direction along which the insert central axis extends, a side surface facing a front-rear direction perpendicular to the insert axial direction, and a clearance surface arranged across the side surface facing a left-right direction perpendicular to the insert axial direction and the front-rear direction, and a cutting edge arranged on a ridge portion connecting the rake face and the clearance surface, the cutting edge being a main cutting edge arranged on a first side of the four sides of the rectangular surface extending in the front-rear direction, a minor cutting edge arranged on a second side of the four sides extending in a direction intersecting with the first side, and a cutting edge arranged on the rectangular surface. a corner edge disposed at a corner portion between the first side and the second side and connected to the main cutting edge and the minor cutting edge, the minor cutting edge having a curved blade portion connected to the corner edge and forming a curved shape that convex toward the front side, and a straight blade portion connected to the curved blade portion and extending in a straight line toward the rear side as it approaches the opposite side to the curved blade portion in the left-right direction, and the flank surface has a first minor flank surface connected to the curved blade portion and forming a curved shape that convex toward the front side, and a second minor flank surface that is planar and connected to the straight blade portion.

[0018] In the cutting insert and indexable end mill of the present invention, the auxiliary cutting edge that finishes the machining surface of the workpiece has a curved blade portion that is curved and convex toward the tip side in the tool axial direction (the front side in the cutting insert). Therefore, the curved blade portion can improve the accuracy of the finished surface. The auxiliary cutting edge also has a straight blade portion that is arranged on the inside of the curved blade portion in the tool radial direction (the opposite side to the corner blade of the curved blade portion in the left-right direction in the cutting insert). The straight blade portion extends linearly toward the rear end side (rear side) in the tool axial direction as it heads toward the opposite side to the curved blade portion in the tool radial direction (left-right direction).

[0019] The flank has a first minor flank having a convex curved shape connected to the curved cutting portion of the minor cutting edge, and a second minor flank having a flat shape connected to the straight cutting portion of the minor cutting edge. Therefore, by bringing the third wall surface of the insert mounting seat other than the forefront (second and subsequent stages) into contact with the second minor flank facing the tip side (front side) of the cutting insert in the tool axial direction, this contact becomes a surface contact, making it easy to increase the contact area.

[0020] Also, unlike the present invention, for example, in a configuration in which the third wall surface is in contact with the inner cutting edge flank, in the present invention, the third wall surface is in contact with the second minor flank (minor flank). Therefore, in the present invention, the third wall surface is disposed closer to the main cutting edge and the corner edge in the tool radial direction. In other words, the third wall surface comes into contact with the cutting insert on the outer side in the tool radial direction, which is called "outer contact." Therefore, according to the present invention, the cutting insert can be stably supported by the third wall surface.

[0021] In addition, since the third wall surface is configured to contact the secondary relief surface, there is no need to provide a concave cutout (gap) or the like to prevent contact between the third wall surface and the secondary relief surface. Therefore, chips do not get into the concave cutout, etc., and it is possible to suppress the chips from getting caught. In addition, since there is no need to provide a concave cutout, it is possible to stably ensure the rigidity of the holder.

[0022] As described above, according to the present invention, the cutting insert can be stably supported by the insert mounting seat while improving the finishing surface accuracy by the auxiliary cutting edge, jamming due to the intrusion of chips between the insert mounting seat and the cutting insert can be suppressed, and the holder rigidity can be increased.

[0023] [Aspect 2 of the present invention] 2. The cutting insert according to claim 1, wherein the curved blade portion extends rearward from a connection point between the curved blade portion and the corner blade toward a side opposite the corner blade in the left-right direction.

[0024] In this case, when the cutting insert is attached to the insert mounting seat at the very front (first stage), the minor cutting edge as a whole extends from the connection point with the corner edge toward the inside in the tool radial direction (in the cutting insert, as it moves away from the corner edge in the left-right direction) toward the rear end side in the tool axial direction (in the cutting insert, the rear side). In other words, the entire minor cutting edge is a so-called "positive dish" and is inclined with respect to an imaginary plane perpendicular to the tool center axis.

[0025] This reduces the contact area between the minor cutting edge and the workpiece surface (corresponding to the virtual plane), suppressing so-called solid contact and reducing cutting resistance. It is possible to improve cutting efficiency and extend tool life while maintaining good surface finish accuracy.

[0026] [Embodiment 3 of the present invention] The cutting insert according to aspect 1 or 2, wherein a minor cutting edge relief angle formed between a virtual straight line extending along the left-right direction and the straight edge portion when viewed from the insert axial direction is 0.2° or more and 5.0° or less.

[0027] When the minor cutting edge relief angle is 0.2° or more, the minor cutting edge as a whole can be stably formed into a positive dish. Also, when the minor cutting edge relief angle is 5.0° or less, the gap between the straight cutting edge portion and the machined surface of the workpiece is prevented from becoming too large, and the minor cutting edge functions as a finishing edge more stably.

[0028] [Embodiment 4 of the present invention] A cutting insert according to any one of aspects 1 to 3, wherein the left-right center of the second minor clearance surface is located closer to the main cutting edge in the left-right direction than the left-right center of the cutting insert.

[0029] [Embodiment 5 of the present invention] The cutting insert according to any one of aspects 1 to 4, wherein the second minor clearance surface is located entirely on the main cutting edge side in the left-right direction relative to the left-right center of the cutting insert.

[0030] In the above configuration, when the third wall surface of the insert mounting seat other than the leading edge (second and subsequent steps) is brought into contact with the second minor relief surface, the third wall surface is disposed closer to the main cutting edge and the corner edge in the tool radial direction, which allows the cutting insert to be supported more stably by the third wall surface.

[0031] [Aspect 6 of the present invention] A cutting insert according to any one of aspects 1 to 5, and a columnar holder extending in a tool axial direction along a tool central axis, the holder having a chip discharge groove that extends in a spiral shape in a direction opposite to a direction of end mill rotation around the tool central axis from a front end surface of the holder facing the tool axial direction toward a rear end side, and a plurality of insert mounting seats that are arranged in a stepped shape along the chip discharge groove, the cutting insert being provided in a plurality of cutting inserts, each of the cutting inserts being removably attached to each of the insert mounting seats, the plurality of insert mounting seats being a leading end insert mounting seat that is arranged at the front end side in the tool axial direction, an insert mounting seat other than the forefront that is arranged rearward of the forefront insert mounting seat in the tool axial direction, wherein the insert mounting seat other than the forefront has a first wall surface that faces in the end mill rotation direction and contacts a seating surface of the cutting insert that faces opposite the cutting face in the insert axial direction, a second wall surface that faces outward in a tool radial direction perpendicular to the tool central axis and contacts a side surface of the cutting insert facing in the left-right direction, and a third wall surface that faces toward the rear end side of the tool axial direction and contacts a side surface of the cutting insert facing in the front-to-rear direction, wherein the third wall surface contacts the second minor relief surface.

[0032] [Seventh aspect of the present invention] The indexable end mill of aspect 6, wherein the cutting edge has an inner blade located on the second side and arranged on the opposite side of the corner edge of the minor cutting edge in the left-right direction, the flank has a planar inner blade flank connected to the inner blade, the cutting insert has a shape that is rotationally symmetrical by 180 degrees around the insert central axis, and the insert mounting seat at the most distal end has the first wall surface, the second wall surface, and a fourth wall surface that faces toward the tip side in the tool axis direction and contacts the side surface of the cutting insert facing the front-to-rear direction, and the fourth wall surface contacts the inner blade flank.

[0033] In the above configuration, by bringing the fourth wall surface of the most advanced (first stage) insert mounting seat into contact with the inner cutting edge relief surface facing the rear end (rear side) of the cutting insert in the tool axial direction, this contact becomes a surface contact, making it easy to increase the contact area.

[0034] In addition, the inner cutting edge flank surface facing the rear end side of the cutting insert in the tool axial direction is arranged close to the main cutting edge and corner edge of the tip outer periphery used for cutting in the tool radial direction. In other words, the fourth wall surface comes into contact with the cutting insert on the outer side in the tool radial direction, which is called "outer contact." Therefore, according to the above-described configuration of the present invention, the cutting insert can be stably supported by the fourth wall surface. Effect of the Invention

[0035] According to the above-mentioned aspects of the present invention, a cutting insert and an indexable end mill are provided that can stably support the cutting insert by the insert mounting seat while improving the finishing surface accuracy by the auxiliary cutting edge, suppress jamming due to the intrusion of chips between the insert mounting seat and the cutting insert, and increase the holder rigidity. [Brief description of the drawings]

[0036] [Figure 1] FIG. 1 is a perspective view showing a cutting insert of the present embodiment. [Diagram 2]FIG. 2 is a plan view of the cutting insert of the present embodiment as viewed from the insert axial direction. [Diagram 3] FIG. 3 is a side view of the cutting insert of the present embodiment as viewed from the left and right direction. [Figure 4] FIG. 4 is a front view (rear view) of the cutting insert of this embodiment as viewed from the front-rear direction. [Diagram 5] FIG. 5 is a perspective view showing a part of the holder of the present embodiment. [Figure 6] FIG. 6 is a perspective view showing a part of the holder of the present embodiment. [Figure 7] FIG. 7 is a perspective view showing a part of the indexable end mill of this embodiment. [Figure 8] FIG. 8 is a perspective view showing a part of the indexable end mill of this embodiment. [Figure 9] FIG. 9 is a side view of a part of the indexable end mill of this embodiment as viewed from the tool radial direction. [Figure 10] FIG. 10 is a side view of a part of the indexable end mill of this embodiment as viewed from the tool radial direction. [Figure 11] FIG. 11 is a bottom view of the indexable end mill of this embodiment as viewed from the tip side in the tool axial direction. [Figure 12] FIG. 12 is an enlarged side view of a portion XII in FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0037] A cutting insert 1 and an indexable end mill 10 according to an embodiment of the present invention will be described with reference to the drawings. The indexable end mill 10 according to this embodiment is a milling tool (cutting tool) that performs milling (milling) on ​​a workpiece made of metal, for example. In this embodiment, the cutting insert 1 and the indexable end mill 10 may be simply referred to as tools.

[0038] 1 to 4, the cutting insert 1 is in the shape of a quadrangular plate, specifically, a rectangular plate or a parallelogram plate, centered on the insert central axis C. Also, as shown in Figs. 7 to 11, the indexable end mill 10 is in the shape of a substantial cylinder, centered on the tool central axis O.

[0039] The indexable end mill 10 includes a holder 2, a cutting insert 1 removably attached to the holder 2, and a fastening member 3 that fixes the cutting insert 1 to the holder 2. A plurality of cutting inserts 1 and a plurality of fastening members 3 are provided on the holder 2. The plurality of cutting inserts 1 are common items having the same shape.

[0040] [Direction definition] In this embodiment, an XYZ orthogonal coordinate system (three-dimensional orthogonal coordinate system) is appropriately set in each of Figs. 1 to 4, and components of the cutting insert 1 will be described.

[0041] In this embodiment, the direction in which the insert central axis C of the cutting insert 1 extends is called the insert axial direction. In each of Figs. 1 to 4, the insert axial direction corresponds to the Z-axis direction. The cutting insert 1 has a pair of rectangular surfaces 11, 12 facing the insert axial direction. Of the pair of rectangular surfaces 11, 12, one rectangular surface 11 faces one side (+Z side) in the insert axial direction, and the other rectangular surface 12 faces the other side (-Z side) in the insert axial direction. One rectangular surface 11 may be referred to as the front surface 11, and the other rectangular surface 12 may be referred to as the back surface 12. One side in the insert axial direction may be referred to as the front surface side in the insert axial direction or simply as the front surface side. The other side in the insert axial direction may be referred to as the back surface side in the insert axial direction or simply as the back surface side. The insert axial direction (Z-axis direction) may also be referred to as the thickness direction of the cutting insert 1.

[0042] In each drawing, the Y-axis direction is a front-rear direction perpendicular to the insert axis direction (Z-axis direction). In this embodiment, the -Y side of the front-rear direction (Y-axis direction) is called the front side, and the +Y side is called the rear side.

[0043] The X-axis direction is a left-right direction perpendicular to the insert axis direction (Z-axis direction) and the front-rear direction (Y-axis direction). In this embodiment, the -X side of the left-right direction (X-axis direction) is called the left side, and the +X side is called the right side. The direction approaching the insert central axis C in the left-right direction is called the insert center side or the insert inner side in the left-right direction. The direction away from the insert central axis C in the left-right direction is called the insert outer side in the left-right direction.

[0044] In addition, a direction perpendicular to the insert central axis C is called the insert radial direction. In the insert radial direction, a direction approaching the insert central axis C is called the insert radial inner direction, and a direction away from the insert central axis C is called the insert radial outer direction. Moreover, the direction going around the insert central axis C is called the insert circumferential direction.

[0045] 7 to 11, the direction in which the tool central axis O extends is called the tool axis direction. The holder 2 has a shank 2a and a body 2b arranged side by side in the tool axis direction. In the tool axis direction, the direction from the shank 2a to the body 2b is called the front end side, and the direction from the body 2b to the shank 2a is called the rear end side. The body 2b is the part of the holder 2 to which the cutting insert 1 is attached, and therefore may be referred to as the cutting portion 2b or the like.

[0046] The direction perpendicular to the tool central axis O is called the tool radial direction. Of the tool radial directions, the direction approaching the tool central axis O is called the inner tool radial direction, and the direction away from the tool central axis O is called the outer tool radial direction.

[0047] The direction rotating around the tool center axis O is called the tool circumferential direction. Among the tool circumferential directions, the direction in which the indexable end mill 10 is rotated during cutting is called the end mill rotation direction T, and the opposite rotation direction is called the opposite side to the end mill rotation direction T or the counter end mill rotation direction.

[0048] [Cutting insert] The cutting insert 1 is made of, for example, a cemented carbide alloy. As shown in Figs. 1 to 4, the cutting insert 1 of this embodiment has a shape that is rotationally symmetrical by 180° about the insert central axis C. The cutting insert 1 does not have a shape that is inverted symmetrical. The cutting insert 1 of this embodiment is a so-called one-sided type positive insert.

[0049] The cutting insert 1 has a pair of rectangular surfaces 11, 12 (front surface 11 and back surface 12) facing the axial direction of the insert, an outer peripheral surface 13 facing radially outward and extending circumferentially of the insert, a cutting edge 14, and a through hole 15.

[0050] One of the rectangular surfaces 11 has a quadrangular shape, and in this embodiment, has a rectangular shape or a parallelogram shape. As shown in FIG. 2, the longitudinal direction of the one of the rectangular surfaces 11 corresponds to the front-rear direction (Y-axis direction). The short side direction corresponds to the left-right direction (X-axis direction). The four sides arranged on the periphery of the one of the rectangular surfaces 11 include a pair of long sides extending in the front-rear direction and a pair of short sides extending in a direction intersecting the long sides. In this embodiment, the long sides of the one of the rectangular surfaces 11 may be called first sides, and the short sides may be called second sides. Cutting edges 14 are arranged on the four sides of the one of the rectangular surfaces (surface) 11.

[0051] One of the rectangular surfaces 11 has a rake surface 11a. That is, the cutting insert 1 is provided with a rake surface 11a. The rake surface 11a is disposed at least on the outer periphery of the rectangular surface 11. The rake surface 11a is disposed along the long side and the short side of the rectangular surface 11. The rake surface 11a extends along the cutting edge 14. The rake surface 11a is disposed adjacent to the cutting edge 14 on the inside in the insert radial direction. The rake surface 11a is connected to the cutting edge 14.

[0052] The rake face 11a extends from the cutting edge 14 toward the inside in the insert radial direction and toward the other side (back side) in the insert axial direction. In other words, when the XY plane is taken as the reference plane, the rake angle of the rake face 11a is a positive angle (normal angle).

[0053] Although not shown in particular, the other quadrangular surface 12 is quadrangular, and in this embodiment, is rectangular or parallelogrammatic. The surface area of ​​the other quadrangular surface (rear surface) 12 is smaller than the surface area of ​​the one quadrangular surface (front surface) 11.

[0054] 3 and 4, the other rectangular surface 12 has a seating surface 12a. The seating surface 12a is a plane perpendicular to the insert central axis C. That is, the seating surface 12a is a plane extending parallel to the XY plane.

[0055] As shown in Figs. 1 to 4, the outer peripheral surface 13 is annular and extends around the insert central axis C. The outer peripheral surface 13 has a pair of side surfaces (front side and rear side) facing in the front-rear direction and a pair of side surfaces (left side and right side) facing in the left-right direction. An end portion on one side (front surface side) of the outer peripheral surface 13 in the insert axial direction is connected to the outer peripheral edge of one of the rectangular surfaces (front surface) 11. An end portion on the other side (rear surface side) of the outer peripheral surface 13 in the insert axial direction is connected to the outer peripheral edge of the other rectangular surface (rear surface) 12.

[0056] The outer peripheral surface 13 has a flank 16. That is, the cutting insert 1 is equipped with the flank 16. The flank 16 is arranged across the side surface of the outer peripheral surface 13 facing the front-rear direction and the side surface facing the left-right direction. The flank 16 is arranged at least at one end of the outer peripheral surface 13 in the insert axial direction. The flank 16 is arranged along the long side and the short side of one of the rectangular surfaces 11. The flank 16 extends along the cutting edge 14. The flank 16 is arranged adjacent to the other side of the cutting edge 14 in the insert axial direction. The flank 16 is connected to the cutting edge 14.

[0057] The flank 16 extends radially inward from the cutting edge 14 to the other side in the insert axial direction. This makes it easy to provide a clearance angle between the flank 16 and the machining surface of the workpiece during cutting, and increases the degree of freedom in the mounting orientation of the cutting insert 1 to the holder 2. Specific components of the flank 16 will be described separately below.

[0058] The cutting edge 14 is disposed on a ridge portion where the rake face 11a and the flank face 16 are connected. The cutting edge 14 is disposed across the long and short sides of one of the rectangular faces 11, and in this embodiment, is substantially L-shaped.

[0059] A plurality of cutting edges 14 are provided on the cutting insert 1. In this embodiment, the cutting insert 1 is a single-sided positive insert having a shape rotationally symmetrical by 180° about the insert central axis C, and two cutting edges 14 (two sets) are provided at positions that are rotationally symmetrical by 180° with respect to each other about the insert central axis C. The two cutting edges 14 have a common configuration. One of the two cutting edges 14 will be described below.

[0060] The cutting edge 14 has a main cutting edge 17 , a minor cutting edge 18 , a corner edge 19 , and an inner edge 20 . The main cutting edge 17 is disposed on a first side (long side in this embodiment) extending in the front-rear direction among the four sides of one of the rectangular surfaces 11. As shown in Fig. 2, when the cutting insert 1 is viewed from the insert axial direction (Z-axis direction), the main cutting edge 17 has a substantially straight line extending in the front-rear direction. More specifically, the main cutting edge 17 has a convex curved shape with a large radius of curvature (large R) that bulges outward from the insert in the left-right direction.

[0061] 3, in a side view of the cutting insert 1 seen from the left-right direction (X-axis direction), the main cutting edge 17 extends linearly toward one side (+Z side) in the insert axial direction as it approaches the front side (-Y side). During cutting, the main cutting edge 17 functions as a peripheral cutting edge of the indexable end mill 10.

[0062] 1 and 2, the minor cutting edge 18 is disposed on a second side (in this embodiment, a short side) that extends in a direction intersecting with the first side of the four sides of one of the rectangular faces 11. The minor cutting edge 18 functions as a bottom cutting edge of the indexable end mill 10 during cutting.

[0063] The minor cutting edge 18 has a curved edge portion 18a connected to the corner edge 19, and a straight edge portion 18b connected to the curved edge portion 18a. The curved blade portion 18a is tangentially connected to the end portion of the corner blade 19 on the insert center side in the left-right direction. In this embodiment, "tangentially connected" means that two adjacent blades are smoothly connected to each other so that they have a common tangent at their connection portion (the ends of the blades).

[0064] Here, Fig. 12 shows a side view of the vicinity of the tool tip of an indexable end mill 10 in which a cutting insert 1 is attached to a holder 2, as viewed from the tool radial direction. Fig. 12 also shows the vicinity of a cutting edge 14 of the cutting insert 1 attached to the holder 2, as viewed from the insert axial direction.

[0065] 2 and 12, when the cutting insert 1 is viewed from the insert axial direction (Z-axis direction), the curved blade portion 18a has a curved shape that is convex toward the front side (the tip side in the tool axial direction). In detail, the curved blade portion 18a has a convex curved shape with a large radius of curvature (large R) that bulges toward the front side.

[0066] The radius of curvature of the curved blade portion 18a as viewed from the insert axial direction is, for example, R50 mm or more and R200 mm or less. The curved blade portion 18a may be formed of a single arc with a constant radius of curvature, or may be formed by combining multiple arcs with different radii of curvature.

[0067] In this embodiment, the curved blade portion 18a extends rearward from a connection point P between the curved blade portion 18a and the corner blade 19 toward the opposite side to the corner blade 19 in the left-right direction (as it moves away from the corner blade 19). Specifically, the curved blade portion 18a gradually extends rearward from the connection point P located at the frontmost side of the curved blade portion 18a toward the left side. The left-right dimension (width dimension) of the curved blade portion 18a is, for example, 0.2 mm or more and 1.5 mm or less.

[0068] 4, the curved blade portion 18a is linear when the cutting insert 1 is viewed from the front-rear direction (Y-axis direction). The curved blade portion 18a extends toward the other side (-Z side) in the insert axial direction as it moves toward the opposite side from the corner blade 19 in the left-right direction (X-axis direction).

[0069] The straight blade portion 18b is connected to the end of the curved blade portion 18a on the insert center side in the left-right direction so as to be in contact with it. As shown in Fig. 2 and Fig. 12, when the cutting insert 1 is viewed from the insert axial direction, the straight blade portion 18b extends linearly toward the rear side (the rear end side in the tool axial direction) as it moves toward the opposite side from the curved blade portion 18a in the left-right direction (as it moves away from the curved blade portion 18a). Specifically, the straight blade portion 18b gradually extends toward the rear side as it moves toward the left side from the connection point with the curved blade portion 18a located at the frontmost position among the straight blade portions 18b.

[0070] As shown in Fig. 2, the minor cutting edge clearance angle θ formed between an imaginary straight line VL extending in the left-right direction and the straight cutting edge portion 18b is, for example, 0.2° or more and 5.0° or less when viewed from the insert axial direction. When the cutting insert 1 is attached to the holder 2 as shown in Fig. 12, the minor cutting edge clearance angle θ corresponds to the angle formed between an imaginary plane VS perpendicular to the tool central axis O and the straight cutting edge portion 18b when viewed from the insert axial direction.

[0071] The left-right dimension (width dimension) of the straight blade portion 18b is, for example, 1.0 mm or more and 3.0 mm or less. The left-right dimension of the straight blade portion 18b is greater than the left-right dimension of the curved blade portion 18a. In this embodiment, the left-right dimensions of the curved blade portion 18a and the straight blade portion 18b may be rephrased as blade length dimensions. In other words, the blade length dimension of the straight blade portion 18b is greater than the blade length dimension of the curved blade portion 18a.

[0072] 4, when the cutting insert 1 is viewed from the front-rear direction, the straight blade portion 18b extends linearly toward the other side (-Z side) in the insert axial direction as it approaches the opposite side to the curved blade portion 18a in the left-right direction. In this embodiment, when viewed from the front of the insert shown in FIG. 4, the curved blade portion 18a and the straight blade portion 18b are arranged in a straight line to form a single straight line.

[0073] As shown in Figs. 1 to 4, the corner edge 19 is disposed at a corner between a first side (long side in this embodiment) and a second side (short side in this embodiment) of one of the rectangular faces 11, and is connected to the major cutting edge 17 and the minor cutting edge 18. In this embodiment, the corner edge 19 is curved so as to be convex toward the outside of the insert in the left-right direction and toward the front side. As shown in Fig. 12, when the cutting insert 1 is attached to the holder 2, the corner edge 19 is curved so as to be convex toward the outside in the tool radial direction and toward the tip side in the tool axial direction.

[0074] As shown in FIG. 2, one end of the corner edge 19 is connected to the front end of the main cutting edge 17. One end of the corner edge 19 is connected to the front end of the main cutting edge 17 so as to be in contact with it. The other end of the corner edge 19 is connected to the end of the minor cutting edge 18 on the outer side of the insert in the left-right direction (opposite the insert central axis C). Specifically, the other end of the corner edge 19 is connected to the right end of the curved cutting edge portion 18a at a connection point P. The other end of the corner edge 19 is connected to the right end of the curved cutting edge portion 18a (minor cutting edge 18) so as to be in contact with it. The corner edge 19 extends from the one end connected to the major cutting edge 17 toward the front side toward the center of the insert in the left-right direction (the insert central axis C side).

[0075] As shown in Figs. 1 to 4, the inner blade 20 is located on a second side (short side in this embodiment) of the four sides of one of the rectangular surfaces 11. The inner blade 20 is disposed on the opposite side to the corner edge 19 of the minor cutting edge 18 in the left-right direction. In this embodiment, the inner blade 20 is disposed adjacent to the minor cutting edge 18 on the left side of the minor cutting edge 18. The inner blade 20 may function as a cutting edge, for example, during ramping. Note that the inner blade 20 does not have to function as a cutting edge.

[0076] As shown in Fig. 2, when the cutting insert 1 is viewed from the insert axial direction, the inner blade 20 extends rearward as it moves toward the opposite side from the minor cutting edge 18 in the left-right direction (as it moves away from the minor cutting edge 18). As shown in Fig. 12, when the cutting insert 1 is attached to the holder 2, the inner blade 20 extends toward the rear end side in the tool axial direction as it moves inward in the tool radial direction.

[0077] 2 and 12, when the cutting insert 1 is viewed from the insert axial direction, the inner blade 20 has a curved shape that is concave toward the rear side (the rear end side in the tool axial direction). Also, when the cutting insert 1 is viewed from the front-rear direction, as shown in Fig. 4, the inner blade 20 has a curved shape that is concave toward the other side (-Z side) in the insert axial direction.

[0078] Here, the components of the flank 16 will be described. As shown in FIGS. 1, 3 and 4, the flank 16 has a main flank 16a, a first minor flank 16b, a second minor flank 16c, a corner flank 16d and an inner blade flank 16e.

[0079] The main flank 16a is disposed at an end of one side (+Z side) in the insert axial direction among the side surface (right side surface) of the outer peripheral surface 13 of the cutting insert 1 facing the insert outer side in the left-right direction. The main flank 16a is connected to the main cutting edge 17. The main flank 16a extends in the front-rear direction along the main cutting edge 17. The main flank 16a has a curved shape that is convex toward the insert outer side in the left-right direction. Specifically, the main flank 16a has a cross-sectional shape perpendicular to the insert central axis C that is curved toward the insert outer side in the left-right direction.

[0080] The main flank 16a extends toward the center side (left side) of the insert in the left-right direction as it moves from the main cutting edge 17 toward the other side (-Z side) in the insert axial direction. This makes it easy to provide a clearance angle between the machining surface (side wall) of the workpiece and the main flank 16a during cutting.

[0081] A supported surface 16f is disposed on a portion of the outer peripheral surface 13 of the cutting insert 1 that faces the outside of the insert in the left-right direction and is located on the other side of the main clearance surface 16a in the insert axial direction. The supported surface 16f is planar and extends in the front-rear direction.

[0082] The first sub-flank 16b and the second sub-flank 16c constitute a flank (sub-flank) of the sub-cutting edge 18. The first sub-flank 16b and the second sub-flank 16c are disposed on a side surface (front side surface) facing the front-rear direction of the outer peripheral surface 13 of the cutting insert 1. In this embodiment, the first sub-flank 16b and the second sub-flank 16c are disposed on a side surface facing the front-rear direction of the outer peripheral surface 13 of the cutting insert 1, respectively, over the entire length in the insert axial direction.

[0083] The first sub-flank 16b and the second sub-flank 16c extend rearward from the sub-cutting edge 18 toward the other side (-Z side) in the insert axial direction. This makes it easy to provide a clearance angle between the machined surface (finished surface) of the workpiece and the sub-flanks (the first sub-flank 16b and the second sub-flank 16c) during cutting.

[0084] The first minor flank 16b is connected to the curved blade portion 18a. The first minor flank 16b has a curved shape that is convex toward the front side. Specifically, the first minor flank 16b has a cross-sectional shape perpendicular to the insert center axis C that is curved toward the front side.

[0085] The second sub-flank 16c is connected to the straight blade portion 18b. The second sub-flank 16c is planar. The center of the second sub-flank 16c in the left-right direction is located closer to the main cutting edge 17 (right side) than the center of the cutting insert 1 in the left-right direction. In this embodiment, the entire second sub-flank 16c is located closer to the main cutting edge 17 in the left-right direction than the center of the cutting insert 1 in the left-right direction. In other words, the entire sub-flanks (the first sub-flank 16b and the second sub-flank 16c) of the sub-cutting edge 18 are disposed closer to the main cutting edge 17 than the center of the insert in the left-right direction.

[0086] In this embodiment, the dimension of the second sub clearance surface 16c in the left-right direction is greater than the dimension of the first sub clearance surface 16b in the left-right direction.

[0087] The corner flank 16d is disposed at a corner portion between a side surface facing the left-right direction and a side surface facing the front-rear direction of the outer peripheral surface 13 of the cutting insert 1. The corner flank 16d is connected to the corner edge 19. The corner flank 16d is curved and convex toward the outside in the insert radial direction. Specifically, the corner flank 16d has a cross-sectional shape perpendicular to the insert central axis C that is curved and convex toward the outside in the insert radial direction.

[0088] The corner flank 16d extends radially inward from the corner edge 19 toward the other side (-Z side) in the axial direction of the insert, thereby making it easy to provide a clearance angle between the machining surface of the workpiece and the corner flank 16d during cutting.

[0089] 1 and 4, the inner cutter flank 16e is disposed on a side surface of the outer peripheral surface 13 of the cutting insert 1 facing the front-rear direction. The inner cutter flank 16e is connected to the inner cutter 20. The inner cutter flank 16e has a planar shape. The inner cutter flank 16e is disposed on the side surface of the outer peripheral surface 13 of the cutting insert 1 facing the front-rear direction over the entire length in the insert axial direction.

[0090] The inner cutter flank 16e extends rearward from the inner cutter 20 toward the other side (-Z side) in the insert axial direction. This makes it easy to provide a clearance angle between the machining surface of the workpiece and the inner cutter flank 16e during cutting.

[0091] The left-right center of the inner cutter flank 16e is located on the opposite side (left side) of the main cutting edge 17 in the left-right direction from the left-right center of the cutting insert 1. In this embodiment, the entire inner cutter flank 16e is located on the opposite side of the main cutting edge 17 in the left-right direction from the left-right center of the cutting insert 1.

[0092] 1 and 2, the through hole 15 penetrates the cutting insert 1 in the insert axial direction. The through hole 15 extends in the cutting insert 1 in the insert axial direction and opens to the pair of rectangular surfaces 11, 12. The through hole 15 has a circular cross section perpendicular to the insert central axis C. The central axis of the through hole 15 is arranged coaxially with the insert central axis C.

[0093] [Holder] The holder 2 is made of a metal such as steel. As shown in Figs. 5 and 6, the holder 2 is columnar and extends in the tool axial direction along the tool central axis O. Specifically, the holder 2 is substantially cylindrical and centered on the tool central axis O. The holder 2 has a shank 2a and a body 2b disposed on the tip side of the shank 2a in the tool axial direction. The shank 2a and the body 2b are disposed adjacent to each other in the tool axial direction and connected to each other. The shank 2a and the body 2b are integrally formed from a single member.

[0094] The shank 2a is cylindrical and centered on the tool central axis O, and extends in the tool axial direction. The shank 2a is detachably attached to a spindle of a machine tool (not shown). The shank 2a is rotated in an end mill rotation direction T about the tool central axis O by the spindle of the machine tool. During cutting, the shank 2a is fed in the tool radial direction by the spindle of the machine tool. In this way, the shank 2a is rotated and fed, so that the cutting edges 14 of the multiple cutting inserts 1 attached to the body 2b cut into the workpiece, thereby performing milling.

[0095] The body 2b is generally cylindrical and centered on the tool central axis O, and extends in the tool axial direction. In this embodiment, the outer diameter of the body 2b is smaller than the outer diameter of the shank 2a. The body 2b has a chip discharge groove 21 and an insert mounting seat 22. That is, the holder 2 has the chip discharge groove 21 and the insert mounting seat 22.

[0096] The chip discharge groove 21 is a groove that opens to a tip surface 2c of the body 2b facing the tool axis direction and an outer peripheral surface 2d facing outward in the tool radial direction. The chip discharge groove 21 extends in a spiral shape around the tool center axis O in the opposite direction to the end mill rotation direction T as it moves from the tip surface 2c facing the tool axis direction of the holder 2 toward the rear end side.

[0097] A plurality of chip discharge grooves 21 are provided on the body 2b at intervals in the tool circumferential direction. In this embodiment, two chip discharge grooves 21 are provided at equal pitches in the tool circumferential direction. Note that the two (plural) chip discharge grooves 21 may be arranged at unequal pitches in the tool circumferential direction.

[0098] The insert mounting seat 22 is disposed on a wall portion of the chip discharge groove 21 facing the end mill rotation direction T. A plurality of insert mounting seats 22 are provided along the direction in which the spiral of the chip discharge groove 21 extends. The plurality of insert mounting seats 22 are arranged in a stepped manner along the chip discharge groove 21. Specifically, two or more insert mounting seats 22 are provided in one chip discharge groove 21, and three are provided in this embodiment.

[0099] 7 to 11, a plurality of cutting inserts 1, which are common items having the same shape, are attached to the plurality of insert mounting seats 22. Each cutting insert 1 is attached to each insert mounting seat 22 in a detachable manner.

[0100] The multiple insert mounting seats 22 include a frontmost insert mounting seat 22A arranged at the most forward end side in the tool axial direction, and a non-frontmost insert mounting seat 22B arranged at the rear end side of the frontmost insert mounting seat 22A in the tool axial direction. The frontmost insert mounting seat 22A may be referred to as a first-stage insert mounting seat 22A. The non-frontmost insert mounting seats 22B may be referred to as second-stage or subsequent insert mounting seats 22B.

[0101] As shown in Figure 5, the foremost (first stage) insert mounting seat 22A has a first wall surface 22a facing in the end mill rotation direction T, a second wall surface 22b facing outward in the tool radial direction, a fourth wall surface 22c facing toward the tip side in the tool axial direction, and a female screw hole 22d.

[0102] The first wall surface 22a contacts the seating surface 12a facing the opposite side to the rake face 11a in the insert axial direction of the cutting insert 1. The first wall surface 22a has a flat shape. The first wall surface 22a supports the cutting insert 1 from the opposite side to the end mill rotation direction T.

[0103] The second wall surface 22b contacts a side surface of the cutting insert 1 facing the left-right direction. Specifically, the second wall surface 22b contacts a supported surface 16f among the side surfaces of the outer peripheral surface 13 of the cutting insert 1 facing the left-right direction. The second wall surface 22b has a planar shape. The second wall surface 22b supports the cutting insert 1 from the inside in the tool radial direction.

[0104] The fourth wall surface 22c contacts a side surface of the cutting insert 1 facing the front-rear direction. Specifically, the fourth wall surface 22c contacts the inner cutting edge flank surface 16e among the side surfaces of the outer peripheral surface 13 of the cutting insert 1 facing the front-rear direction. The fourth wall surface 22c has a flat shape. The fourth wall surface 22c supports the cutting insert 1 from the rear end side in the tool axial direction.

[0105] The female screw hole 22d opens in the first wall surface 22a. The female screw hole 22d is a hole that extends in a direction substantially perpendicular to the direction in which the first wall surface 22a widens. The female screw hole 22d has a female screw portion on its inner circumferential surface.

[0106] 6, the insert mounting seats 22B other than the forefront (second and subsequent rows) have a first wall surface 22a facing the end mill rotation direction T, a second wall surface 22b facing outward in the tool radial direction, a third wall surface 22e facing the rear end side in the tool axial direction, and a female screw hole 22d. Note that the configurations of the first wall surface 22a, the second wall surface 22b, and the female screw hole 22d are the same as those described above, and therefore detailed description thereof will be omitted here.

[0107] The third wall surface 22e contacts the side surface of the cutting insert 1 facing the front-rear direction. Specifically, the third wall surface 22e contacts the second minor clearance surface 16c among the side surfaces of the outer peripheral surface 13 of the cutting insert 1 facing the front-rear direction. The third wall surface 22e is flat. In this embodiment, the third wall surface 22e extends in the tool radial direction. The dimension of the third wall surface 22e along the tool circumferential direction increases toward the outside in the tool radial direction. In other words, the width dimension of the third wall surface 22e increases toward the outside in the tool radial direction. The third wall surface 22e supports the cutting insert 1 from the tip side in the tool axial direction.

[0108] [Fastening member] 7 to 11, the fastening member 3 is, for example, a clamp screw. The fastening member 3 detachably fixes the cutting insert 1 to the insert mounting seat 22 (22A, 22B) of the holder 2. Specifically, the fastening member 3 is inserted into the through hole 15 of the cutting insert 1 and screwed into the female screw hole 22d of the insert mounting seat 22.

[0109] [Regarding the mounting orientation of cutting inserts to holders, etc.] When the cutting insert 1 is attached to the holder 2, a pair of rectangular surfaces 11, 12 (front surface 11 and back surface 12) of the cutting insert 1 face in the tool circumferential direction. Specifically, one rectangular surface 11 faces in the end mill rotation direction T, and the other rectangular surface 12 faces in the opposite end mill rotation direction. In other words, the cutting insert 1 of this embodiment is a so-called side blade type insert. When the cutting insert 1 is attached to the insert mounting seat 22, although not specifically shown, the insert center axis C of the cutting insert 1 extends toward the rear end side in the tool axial direction as it faces the end mill rotation direction T.

[0110] Furthermore, with the cutting insert 1 attached to the insert mounting seat 22, the cutting edge 14 protrudes outward in the tool radial direction beyond the outer circumferential surface 2d of the body 2b. The main cutting edge 17 of each cutting insert 1 attached to the multiple insert mounting seats 22 extends in the direction opposite to the end mill rotation direction toward the rear end side in the tool axial direction. Furthermore, the rotation trajectory of the main cutting edge 17 of each cutting insert 1 attached to the multiple insert mounting seats 22 about the tool central axis O is located on one imaginary cylindrical surface (not shown) centered on the tool central axis O.

[0111] 9 and 12, the cutting edge 14 of the cutting insert 1 attached to the front-most insert mounting seat 22A protrudes further toward the front end side in the tool axial direction than the front end surface 2c of the body 2b. Also, as shown in Fig. 11, the minor cutting edge 18 of the cutting insert 1 attached to the front-most insert mounting seat 22A has a radial rake angle (radial rake) that is a positive angle (normal angle).

[0112] [Effects of this embodiment] In the cutting insert 1 and the indexable end mill 10 of this embodiment, the auxiliary cutting edge 18, which finishes the machining surface of the workpiece, has a curved cutting edge portion 18a that is curved and convex toward the tip side in the tool axial direction (the front side in the cutting insert 1). Therefore, the curved cutting edge portion 18a can improve the accuracy of the finished surface. The auxiliary cutting edge 18 also has a straight cutting edge portion 18b that is arranged on the inside of the curved cutting edge portion 18a in the tool radial direction (the opposite side to the corner edge 19 of the curved cutting edge portion 18a in the left-right direction in the cutting insert 1). The straight cutting edge portion 18b extends linearly toward the rear end side (rear side) in the tool axial direction as it moves toward the opposite side to the curved cutting edge portion 18a in the tool radial direction (left-right direction).

[0113] The flank 16 has a first sub-flank 16b having a convex curved shape connected to the curved blade portion 18a of the minor cutting edge 18, and a second sub-flank 16c having a flat shape connected to the straight blade portion 18b of the minor cutting edge 18. Therefore, by bringing the third wall surface 22e of the insert mounting seat 22B other than the forefront (the second and subsequent stages) into contact with the second sub-flank 16c facing the tip side (front side) in the tool axial direction of the cutting insert 1, this contact becomes a surface contact, and it is easy to increase the contact area.

[0114] Also, unlike the configuration in which the third wall surface 22e is in contact with the inner cutting edge flank 16e in this embodiment, the third wall surface 22e is in contact with the second minor flank 16c (minor flank) in this embodiment. Therefore, in this embodiment, the third wall surface 22e is disposed closer to the main cutting edge 17 and the corner edge 19 in the tool radial direction. That is, the third wall surface 22e comes into contact with the cutting insert 1 on the outer side in the tool radial direction, which is called "outer contact". Therefore, according to this embodiment, the cutting insert 1 can be stably supported by the third wall surface 22e.

[0115] In addition, since the third wall surface 22e is configured to contact the secondary clearance surface, there is no need to provide a concave cutout (gap) or the like to prevent contact between the third wall surface 22e and the secondary clearance surface. Therefore, chips do not get into the concave cutout, etc., and it is possible to suppress the chips from getting caught. In addition, since there is no need to provide a concave cutout, it is possible to stably ensure the rigidity of the holder.

[0116] As described above, according to this embodiment, the cutting insert 1 can be stably supported by the insert mounting seat 22 while improving the finishing surface accuracy by the auxiliary cutting edge 18, and jamming due to the intrusion of chips between the insert mounting seat 22 and the cutting insert 1 can be suppressed, thereby increasing the holder rigidity.

[0117] In this embodiment, the curved blade portion 18a extends rearward from a connection point P between the curved blade portion 18a and the corner blade 19 toward the opposite side to the corner blade 19 in the left-right direction. 12, when the cutting insert 1 is attached to the insert mounting seat 22A at the forefront (first stage), the minor cutting edge 18 as a whole extends from the connection point P with the corner edge 19 toward the inside in the tool radial direction (in the cutting insert 1, as it moves away from the corner edge 19 in the left-right direction) toward the rear end side in the tool axial direction (rear side in the cutting insert 1). In other words, the entire minor cutting edge 18 is a so-called "positive dish" and is inclined with respect to an imaginary plane VS perpendicular to the tool center axis O.

[0118] This reduces the contact area between the minor cutting edge 18 and the workpiece surface (corresponding to the virtual plane VS), suppressing so-called solid contact and reducing cutting resistance. It is possible to improve cutting efficiency and extend tool life while maintaining good surface finish accuracy.

[0119] In this embodiment, as shown in Figure 2, when viewed from the insert axial direction, the minor cutting edge relief angle θ formed between the imaginary straight line VL extending along the left-right direction and the straight edge portion 18b is 0.2° or more and 5.0° or less. When the minor cutting edge relief angle θ is 0.2° or more, the entire minor cutting edge 18 can be stably made into a positive dish. Also, when the minor cutting edge relief angle θ is 5.0° or less, the gap between the straight cutting edge portion 18b and the machined surface of the workpiece is prevented from becoming too large, and the function of the minor cutting edge 18 as a finishing edge becomes more stable.

[0120] Further, the center of the second minor flank 16c in the left-right direction is located closer to the main cutting edge 17 in the left-right direction than the center of the cutting insert 1 in the left-right direction. In this embodiment, the entire second minor flank 16c is located closer to the main cutting edge 17 in the left-right direction than the center of the cutting insert 1 in the left-right direction.

[0121] In the above configuration, when the third wall surface 22e of the insert mounting seat 22B other than the forefront (second or subsequent stage) is brought into contact with the second minor clearance surface 16c, the third wall surface 22e is disposed closer to the main cutting edge 17 and the corner edge 19 in the tool radial direction. This allows the cutting insert 1 to be supported more stably by the third wall surface 22e.

[0122] In this embodiment, the fourth wall surface 22c of the insert mounting seat 22A at the forefront contacts the inner cutting edge flank surface 16e of the cutting insert 1. In the above configuration, by bringing the fourth wall surface 22c of the most distal (first stage) insert mounting seat 22A into contact with the inner cutting edge relief surface 16e facing the rear end (rear side) in the tool axial direction of the cutting insert 1, this contact becomes a surface contact, making it easy to increase the contact area.

[0123] Also, the inner cutting edge flank surface 16e facing the rear end side of the cutting insert 1 in the tool axial direction is disposed close to the main cutting edge 17 and the corner edge 19 on the tip outer periphery used for cutting in the tool radial direction. That is, the fourth wall surface 22c comes into contact with the cutting insert 1 on the outer side in the tool radial direction, and is referred to as "outer contact." Therefore, according to the above-described configuration of this embodiment, the cutting insert 1 can be stably supported by the fourth wall surface 22c.

[0124] [Other configurations included in the present invention] The present invention is not limited to the above-described embodiment, and the configuration may be modified within the scope of the present invention, for example as described below.

[0125] In the above embodiment, the cutting insert 1 is shaped like a rectangular plate or a parallelogram plate, but is not limited thereto. The cutting insert 1 may be shaped like a square plate or a rhombic plate centered on the insert central axis C.

[0126] The corner edge 19 of the cutting insert 1 may be a straight line that intersects with the major cutting edge 17 and the minor cutting edge 18 (curved edge portion 18a) at an obtuse angle. That is, the corner edge 19 is not limited to the round corner shape described in the above embodiment, and may be a chamfered corner shape.

[0127] In the above embodiment, the entire minor cutting edge 18 is a positive dish, but the present invention is not limited to this. For example, the curved cutting edge 18a may extend gradually forward from the connection point P with the corner edge 19 toward the left side, and after passing the apex protruding most forward, may extend gradually backward toward the left side.

[0128] Although not specifically shown, the holder 2 may have a coolant hole that extends inside the holder 2 and opens toward the vicinity of the cutting edge 14 of each cutting insert 1 arranged in the multiple insert mounting seats 22.

[0129] In the above-described embodiment, the end mill rotation direction T in which the tool is rotated is a counterclockwise direction as viewed from the tip side in the tool axial direction as shown in Fig. 11, but is not limited thereto. The end mill rotation direction T may be a clockwise direction as viewed from the tip side in the tool axial direction. In other words, the present invention is also applicable to cutting inserts and indexable end mills having different configurations from those in the above-described embodiment.

[0130] The present invention may be combined with the various configurations described in the above-mentioned embodiments and modifications, and may include additions, omissions, substitutions, and other modifications, without departing from the spirit of the present invention. The present invention is not limited to the above-mentioned embodiments, but is limited only by the claims. [Industrial Applicability]

[0131] According to the cutting insert and the indexable end mill of the present invention, the cutting insert can be stably supported by the insert mounting seat while improving the finishing surface accuracy by the secondary cutting edge, and the intrusion of chips into the space between the insert mounting seat and the cutting insert can be suppressed, and the rigidity of the holder can be increased. Therefore, the present invention has industrial applicability. [Explanation of symbols]

[0132] 1...Cutting insert 2...Holder 2c…Tip surface 10...Replaceable end mill 11...One of the rectangular faces (front surface) 11a…Scooping surface 12a…Seating surface 14…Cutting edge 16…flank 16b…First minor relief face 16c…Second minor relief face 16e…Inner cutting edge flank 17…Main cutting edge 18…Sub-cutting edge 18a…Curved blade part 18b…Straight blade part 19…Corner blade 20…Inner blade 21...Chip discharge groove 22…Insert mounting seat 22A...The most advanced (first stage) insert mounting seat 22B…Insert mounting seat other than the most front end (second row and onward) 22a…First wall 22b…Second wall surface 22c…4th wall 22e…Third wall C…Insert center axis O…Tool center axis P…Connection point T…End mill rotation direction VL: Virtual line θ…minor cutting edge relief angle

Claims

1. a rake face disposed on a square surface facing an axial direction of the insert along which a central axis of the insert extends; a flank disposed across a side surface facing a front-rear direction perpendicular to the insert axial direction and a side surface facing a left-right direction perpendicular to the insert axial direction and the front-rear direction; A cutting edge is disposed on a ridge line portion where the rake face and the flank face are connected, The cutting blade is A main cutting edge is disposed on a first side of the rectangular surface extending in the front-rear direction; A minor cutting edge is disposed on a second side of the four sides that extends in a direction intersecting with the first side; a corner edge that is disposed at a corner portion between the first side and the second side of the quadrangular surface and is connected to the main cutting edge and the minor cutting edge, The minor cutting edge is A curved blade portion connected to the corner blade and having a curved shape that is convex toward the front side; a straight blade portion that is connected to the curved blade portion and extends linearly toward the rear side as it moves toward the opposite side to the curved blade portion in the left-right direction, The flank surface is a first sub-flank surface connected to the curved blade portion and having a curved shape that is convex toward the front side; A planar second sub-flank surface connected to the straight blade portion, Cutting insert.

2. The curved blade portion extends rearward from a connection point between the curved blade portion and the corner blade toward a side opposite to the corner blade in the left-right direction. The cutting insert according to claim 1 .

3. When viewed from the insert axial direction, a minor cutting edge relief angle formed between a virtual straight line extending along the left-right direction and the straight edge portion is 0.2° or more and 5.0° or less. The cutting insert according to claim 2 .

4. The center of the second minor flank in the left-right direction is located closer to the main cutting edge in the left-right direction than the center of the cutting insert in the left-right direction. The cutting insert according to any one of claims 1 to 3.

5. The second sub-flank surface is entirely located on the main cutting edge side in the left-right direction relative to the center of the cutting insert in the left-right direction. The cutting insert according to any one of claims 1 to 3.

6. The cutting insert according to any one of claims 1 to 3, A columnar holder extending in a tool axial direction along a tool central axis, The holder includes: A chip discharge groove extending in a spiral shape in a direction opposite to a rotation direction of the end mill around the tool central axis from a tip surface of the holder facing the tool axis direction toward a rear end side; a plurality of insert mounting seats arranged in a stepped manner along the chip discharge groove; The cutting insert is provided in plurality, Each of the cutting inserts is removably attached to each of the insert mounting seats, The plurality of insert mounting seats include a leading-edge insert mounting seat disposed at the leading end side in the tool axial direction; an insert mounting seat other than the forefront that is arranged rearward of the forefront insert mounting seat in the tool axial direction, The insert mounting seat other than the tip end is A first wall surface facing the end mill rotation direction and contacting a seating surface facing the opposite side to the rake face in the insert axial direction of the cutting insert; A second wall surface facing outward in a tool radial direction perpendicular to the tool center axis and in contact with a side surface of the cutting insert facing the left-right direction; a third wall surface facing a rear end side in the tool axial direction and in contact with a side surface of the cutting insert facing the front-rear direction, The third wall surface contacts the second minor relief surface. Replaceable blade end mill.

7. The cutting edge is located on the second side and has an inner edge disposed on the opposite side to the corner edge of the minor cutting edge in the left-right direction, The flank has a flat inner blade flank connected to the inner blade, The cutting insert has a shape rotationally symmetrical by 180° about the insert central axis, The cutting-edge insert mounting seat is The first wall surface; The second wall surface; a fourth wall surface facing a tip side in the tool axial direction and in contact with a side surface of the cutting insert facing the front-rear direction, The fourth wall surface contacts the inner blade flank surface. The indexable end mill according to claim 6.

Images