Cutting insert and edge replaceable end mill

Abstract

In a cutting insert and an edge replaceable end mill according to the present invention, a cutting blade (14) has: a main cutting blade (17) that is disposed on a first side of four sides of a quadrangular surface (11); a sub-cutting blade (18) that is disposed on a second side; and a corner blade (19). The sub-cutting blade (18) has a curved blade part (18a) that is connected to the corner blade (19), and forms a curved shape protruding toward a front side; and a linear blade part (18b) that is connected to the curved blade part (18a), and linearly extends toward a rear side as extending toward the side opposite to the curved blade part (18a) in the left-right direction. A flank (16) has: a first sub-flank (16b) that is connected to the curved blade part (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 blade part (18b).

Description

Cutting inserts and indexable end mills

[0001] This application claims priority to Japanese Patent Application No. 2023-169985, filed on September 29, 2023, the contents of which are incorporated herein by reference.

[0002] A known example of a conventional indexable end mill is the cutting tool described in Patent Document 1. 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 extending spirally around the tool's central axis (rotation axis) and a plurality of insert mounting seats arranged in a stepped pattern along the chip discharge groove. A plurality of common cutting inserts having the same shape are removably mounted in the plurality of insert mounting seats.

[0003] The cutting insert has a rake face arranged on a rectangular surface facing the rotation direction of the end mill, a flank face arranged across a side surface facing the tip side in the tool axial direction along the tool central axis and 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 rake face and the flank face.

[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 cutting edge connected to the end of the minor cutting edge opposite the corner edge in the lateral direction. In an indexable end mill, the main cutting edge functions as a peripheral cutting edge, and the minor cutting edge functions as a bottom cutting edge. The inner cutting 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 leading-edge (first-stage) insert mounting seat that is located at the most forward end in the tool axial direction, and other insert mounting seats (second stage and subsequent) that are located rearward of the leading-edge insert mounting seat in the tool axial direction.

[0006] The insert mounting seats other than the leading end have 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 insert mounting seat at the forefront 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 axis direction are different between the insert mounting seats other than the most front end (second stage and beyond) and the most front end (first stage) insert mounting seat.

[0009] Japanese Patent No. 7052176 (B1)

[0010] In this type of indexable end mill, the minor cutting edge (bottom cutting edge) of the cutting insert attached to the insert seat at the very front end finishes the machined surface of the workpiece. By forming this minor cutting edge into a curved shape with a large radius of curvature that 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 curve, 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 (the second or subsequent stage) 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 cutting edge does not require as strict machining precision as the minor cutting edge. Therefore, it is possible to form the part of the flank surface that connects to the inner cutting edge (the inner cutting edge flank surface) into a flat shape and make the third wall surface contact the inner cutting edge flank surface. In this case, the contact between the third wall surface and the inner cutting edge flank surface becomes a surface contact, making it easy to increase the contact area.

[0013] However, since the inner cutting edge flank is located radially inward relative to the minor flank, the third wall surface supporting the inner cutting edge flank is also located far away from the main cutting edge and the corner edge in the tool radial direction. Therefore, even if the third wall surface is brought into contact with the inner cutting edge, 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, it is necessary to form a concave cutout in the wall portion of the insert mounting seat adjacent to the third wall surface on the outer side in the tool radial direction to prevent contact between the secondary flank of the cutting insert. Since chips can easily enter this concave cutout (gap), they are likely to become trapped. Furthermore, 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 with the insert mounting seat while improving the finishing surface accuracy with 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 rigidity of the holder.

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

[0017] [Aspect 1 of the present invention] A cutting edge is provided which is provided on a quadrangular 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 flank surface which is provided across the side surface facing a left-right direction perpendicular to the insert axial direction and the front-rear direction, and a cutting edge which is provided on a ridge line portion where the rake face and the flank face are connected, and the cutting edge is provided on a first side of the quadrangular surface which extends in the front-rear direction, and a minor cutting edge which is provided on a second side of the four sides which extends in a direction intersecting with the first side, and and a corner edge that is arranged at a corner portion between the first side and the second side and is connected to the major cutting edge and the minor cutting edge, wherein the minor cutting edge has a curved edge portion that is connected to the corner edge and has a curved shape that is convex toward the front side, and a straight edge portion that is connected to the curved edge portion and extends in a straight line toward the rear side as it approaches the opposite side from the curved edge portion in the left-right direction, and the flank surface has a first minor flank surface that is connected to the curved edge portion and has a curved shape that is convex toward the front side, and a flat second minor flank surface that is connected to the straight edge portion.

[0018] In the cutting insert and indexable end mill of the present invention, the minor cutting edge that finishes the machining surface of the workpiece has a curved cutting edge 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 cutting edge can improve the accuracy of the finished surface. The minor cutting edge also has a straight cutting edge portion that is located on the inside of the curved cutting edge in the tool radial direction (the opposite side of the corner edge of the curved cutting edge in the left-right direction in the cutting insert). The straight cutting edge extends linearly toward the rear end side (rear side) in the tool axial direction as it moves away from the curved cutting edge in the tool radial direction (left-right direction).

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

[0020] Furthermore, unlike the configuration of the present invention in which the third wall surface contacts the inner cutting edge flank, the present invention has a configuration in which the third wall surface contacts the second minor flank (minor flank). Therefore, the third wall surface is positioned closer to the main cutting edge or corner edge in the tool radial direction. That is, the third wall surface contacts the cutting insert at a more outer position in the tool radial direction, resulting in a so-called "outer contact." Therefore, according to the present invention, the cutting insert can be stably supported by the third wall surface.

[0021] Furthermore, since the third wall surface is configured to contact the secondary relief surface, there is no need to provide a recessed notch (gap) or the like to prevent contact between the third wall surface and the secondary relief surface. As a result, chips do not get into the recessed notch or the like, and chip bite can be suppressed. Furthermore, since there is no need to provide a recessed notch or the like, the rigidity of the holder can be stably ensured.

[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 using the secondary cutting edge, and it is possible to suppress jamming due to chips entering between the insert mounting seat and the cutting insert, thereby increasing the rigidity of the holder.

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

[0024] In this case, when the cutting insert is attached to the insert mounting seat at the forefront (first stage), the entire minor cutting edge 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 (rear side in the cutting insert). In other words, the entire minor cutting edge becomes 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, thereby improving cutting efficiency and extending tool life while maintaining good surface finish accuracy.

[0026] [Aspect 3 of the present invention] The cutting insert according to aspect 1 or 2, wherein a minor cutting edge relief angle formed between an imaginary line extending along the left-right direction and the straight cutting 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 entire minor cutting edge can be stably formed into a positive dish. When the minor cutting edge relief angle is 5.0° or less, the gap between the straight cutting edge and the machined surface of the workpiece is prevented from becoming too large, and the minor cutting edge's function as a finishing edge is more stable.

[0028] [Aspect 4 of the present invention] The cutting insert according to any one of Aspects 1 to 3, wherein 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.

[0029] [Aspect 5 of the present invention] The cutting insert according to any one of Aspects 1 to 4, wherein the entire second minor flank surface 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.

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

[0031] A sixth aspect of the present invention is a cutting insert comprising: the cutting insert according to any one of the first to fifth aspects; and a columnar holder extending in a tool axis direction along a tool central axis, wherein the holder has a chip discharge groove extending spirally from a front end face of the holder facing the tool axis direction toward a rear end side thereof in a direction opposite to a rotation direction of an end mill around the tool central axis; and a plurality of insert mounting seats arranged in a stepped manner along the chip discharge groove, wherein a plurality of the cutting inserts are provided, and each of the cutting inserts is detachably mounted to a corresponding one of the insert mounting seats, and the plurality of insert mounting seats include a leading-edge insert mounting seat arranged furthest to the front end in the tool axis 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 rake face in the insert axial direction; a second wall surface that faces outward in a tool radial direction perpendicular to the tool center axis and contacts a side surface of the cutting insert that faces in the left-right direction; and a third wall surface that faces rearward in the tool axial direction and contacts a side surface of the cutting insert that faces in the front-to-rear direction, wherein the third wall surface contacts the second minor relief surface.

[0032] Aspect 7 of the present invention is an indexable end mill according to Aspect 6, wherein the cutting edge has an inner cutting edge that is located on the second side and is arranged on the opposite side of the corner edge of the minor cutting edge in the left-right direction, the flank surface has a planar inner cutting edge flank surface that is connected to the inner cutting edge, the cutting insert has a shape that is rotationally symmetrical by 180° about 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 a tip side in the tool axis direction and contacts a side surface of the cutting insert that faces in the front-rear direction, and the fourth wall surface contacts the inner cutting edge flank surface.

[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 axis direction, this contact becomes a surface contact, making it easy to increase the contact area.

[0034] Furthermore, the inner cutting edge flank facing the rear end of the cutting insert in the tool axial direction is positioned radially closer to the main cutting edge or corner edge at the tip outer periphery used for cutting. That is, the fourth wall surface contacts the cutting insert radially outward, resulting in a so-called "outer contact." Therefore, according to the above configuration of the present invention, the cutting insert can be stably supported by the fourth wall surface.

[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 with the insert mounting seat while improving the finishing surface accuracy with 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.

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

[0037] A cutting insert 1 and an indexable end mill 10 according to one 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, for example, metal. 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 has a quadrangular plate shape, specifically a rectangular plate shape or a parallelogram plate shape, centered on the insert central axis C. Also, as shown in FIGS. 7 to 11, the indexable end mill 10 has a substantially cylindrical shape centered on the tool central axis O.

[0039] The indexable end mill 10 includes a holder 2, a cutting insert 1 that is detachably 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 that have the same shape.

[0040] [Definition of Directions] In this embodiment, an XYZ Cartesian coordinate system (three-dimensional Cartesian coordinate system) is appropriately set in each of FIGS. 1 to 4, and the 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 referred to as 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. The 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 figure, the Y-axis direction is the 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 the 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 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] The direction perpendicular to the insert central axis C is called the insert radial direction. Within the insert radial direction, the direction approaching the insert central axis C is called the insert radial inner direction, and the direction away from the insert central axis C is called the insert radial outer direction. Furthermore, 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 referred to as 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 referred to as the front end side, and the direction from the body 2b to the shank 2a is referred to as the rear end side. Note that the body 2b is the part of the holder 2 to which the cutting insert 1 is attached, and therefore may also be referred to as the cutting portion 2b.

[0046] The direction perpendicular to the tool center axis O is called the tool radial direction. Of the tool radial directions, the direction approaching the tool center axis O is called the inner tool radial direction, and the direction away from the tool center 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. Of 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 of 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, cemented carbide. As shown in Figures 1 to 4, the cutting insert 1 of this embodiment has a shape that is 180° rotationally symmetric about the insert central axis C. Furthermore, the cutting insert 1 does not have a shape that is inverted symmetric. The cutting insert 1 of this embodiment is a so-called single-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 insert axial direction, an outer peripheral surface 13 facing radially outward from the insert and extending circumferentially around the insert, a cutting edge 14, and a through hole 15.

[0050] One of the quadrangular surfaces 11 has a quadrangular shape, and in this embodiment, it has a rectangular or parallelogram shape. As shown in FIG. 2 , the longitudinal direction of the one of the quadrangular 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 quadrangular 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 quadrangular surfaces 11 may be referred to as first sides, and the short sides may be referred to as second sides. Cutting edges 14 are arranged on the four sides of the one of the quadrangular surfaces (surface) 11.

[0051] One of the quadrangular surfaces 11 has a rake surface 11a. That is, the cutting insert 1 is equipped with the rake surface 11a. The rake surface 11a is arranged at least on the outer periphery of the quadrangular surface 11. The rake surface 11a is arranged along the long and short sides of the quadrangular surface 11. The rake surface 11a extends along the cutting edge 14. The rake surface 11a is arranged 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 radially inward from the cutting edge 14 toward the other side (back side) in the axial direction of the insert. In other words, when the X-Y plane is used as the reference plane, the rake angle of the rake face 11a is a positive angle (regular angle).

[0053] Although not shown, the other quadrangular surface 12 has a quadrangular shape, and in this embodiment, it has a rectangular or parallelogram shape. 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 flat and perpendicular to the insert central axis C. In other words, the seating surface 12a is a flat surface extending parallel to the XY plane.

[0055] As shown in Figures 1 to 4, the outer peripheral surface 13 is annular and extends around the insert center axis C. The outer peripheral surface 13 has a pair of side surfaces (front and rear side surfaces) facing in the front-to-rear direction and a pair of side surfaces (left and right side surfaces) facing in the left-to-right direction. One end of the outer peripheral surface 13 on one side (front surface side) in the insert axial direction is connected to the outer peripheral edge of one of the quadrangular surfaces (front surface) 11. The other end of the outer peripheral surface 13 on the other side (rear surface side) in the insert axial direction is connected to the outer peripheral edge of the other quadrangular 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 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 toward the other side in the insert axial direction. This makes it easy to provide a clearance angle between the processing surface of the workpiece and the flank 16 during cutting, increasing 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 line connecting the rake face 11a and the flank 16. 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 major cutting edge 17, a minor cutting edge 18, a corner edge 19, and an inner cutting edge 20. The major cutting edge 17 is disposed on a first side (long side in this embodiment) of the four sides of one of the rectangular surfaces 11 that extends in the front-rear direction. As shown in Fig. 2, when the cutting insert 1 is viewed from the insert axial direction (Z-axis direction), the major cutting edge 17 has a substantially linear shape extending in the front-rear direction. More specifically, the major 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 moves toward 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 (a short side in this embodiment) of the four sides of one of the rectangular faces 11, the second side extending in a direction intersecting with the first side. During cutting, the minor cutting edge 18 functions as a bottom cutting edge of the indexable end mill 10.

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

[0064] 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. Also, Fig. 12 is a view of 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 cutting edge portion 18a has a curved shape that is convex toward the front side (the tip side in the tool axial direction). More specifically, the curved cutting edge 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 cutting edge 18 a as viewed from the insert axial direction is, for example, R 50 mm or more and R 200 mm or less. The curved cutting edge 18 a 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 of 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 foremost position of the curved blade portion 18a toward the left. 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 cutting edge portion 18a is linear when the cutting insert 1 is viewed from the front-rear direction (Y-axis direction). The curved cutting edge portion 18a extends toward the other side (-Z side) in the insert axial direction as it moves toward the opposite side from the corner edge 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 that is closer to the insert center in the left-right direction so as to be tangential to the curved blade portion 18a. As shown in Figures 2 and 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 from the connection point with the curved blade portion 18a that is located at the frontmost of the straight blade portions 18b.

[0070] As shown in Fig. 2, when viewed from the insert axial direction, the minor cutting edge relief angle θ formed between an imaginary straight line VL extending in the left-right direction and the straight cutting edge portion 18b may be, for example, 0.2° to 5.0°, 0.3° to 4.5°, or 0.5° to 4.0°. When the cutting insert 1 is attached to the holder 2 as shown in Fig. 12, the minor cutting edge relief 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.

[0071] The left-right dimension (width) 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 also be referred to 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 cutting portion 18b extends linearly toward the other side (-Z side) in the insert axial direction as it moves toward the opposite side from the curved cutting portion 18a in the left-right direction. In this embodiment, the curved cutting portion 18a and the straight cutting portion 18b are arranged side by side in a straight line so as to form a single straight line when viewed from the front of the insert shown in FIG.

[0073] 1 to 4, the corner edge 19 is disposed at a corner between a first side (a long side in this embodiment) and a second side (a short side in this embodiment) of one of the rectangular surfaces 11, and is connected to the major cutting edge 17 and the minor cutting edge 18. In this embodiment, the corner edge 19 has a curved shape that is 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 has a curved shape that is 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 major cutting edge 17. One end of the corner edge 19 is connected to the front end of the major cutting edge 17 so as to be tangential to the front end of the major cutting edge 17. 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 center 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 tangential to the right end of the curved cutting edge portion 18a. The corner edge 19 extends forward from the end connected to the major cutting edge 17 and toward the center of the insert in the left-right direction (toward the insert center axis C).

[0075] As shown in Figures 1 to 4, the inner cutter 20 is located on the second side (the short side in this embodiment) of the four sides of one of the rectangular surfaces 11. The inner cutter 20 is located on the opposite side of the corner edge 19 of the minor cutting edge 18 in the left-right direction. In this embodiment, the inner cutter 20 is located adjacent to the minor cutting edge 18 on the left side of the minor cutting edge 18. The inner cutter 20 may function as a cutting edge, for example, during ramping. However, the inner cutter 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 cutting edge 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 cutting edge 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 cutting edge 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, when the cutting insert 1 is viewed from the front-rear direction, the inner cutting edge 20 has a curved shape that is concave toward the other side in the insert axial direction (-Z side).

[0078] Here, we will explain the components of the flank 16. As shown in Figures 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 cutting edge flank 16e.

[0079] The main flank 16a is disposed at an end of one side (+Z side) in the insert axial direction of the outer peripheral surface 13 of the cutting insert 1, on a side surface (right side surface) facing the insert outside 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 surface shape that is convex toward the insert outside in the left-right direction. Specifically, the shape of the main flank 16a in a cross section perpendicular to the insert central axis C is a curved shape that is convex toward the insert outside in the left-right direction.

[0080] The main flank 16a extends from the main cutting edge 17 toward the other side (-Z side) in the insert axial direction and then toward the insert center (left side) in the left-right direction, which 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 arranged on the other side of the main flank surface 16a in the insert axial direction among the side surfaces facing outward in the left-right direction of the outer peripheral surface 13 of the cutting insert 1. The supported surface 16f is flat and extends in the front-rear direction.

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

[0083] The first and second minor flanks 16b, 16c extend rearward from the minor 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 minor flanks (first and second minor flanks 16b, 16c) during cutting.

[0084] The first sub-flank 16b is connected to the curved cutting edge 18a and has a curved shape that is convex toward the front. Specifically, the cross section of the first sub-flank 16b perpendicular to the insert center axis C has a curved shape that is convex toward the front.

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

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

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

[0088] The corner flank 16d extends radially inward from the corner cutting edge 19 toward the other side (-Z side) in the insert axial direction, 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 arranged 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 flat shape. The inner cutter flank 16e is arranged 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 cutting edge flank 16e extends rearward from the inner cutting edge 20 toward the other side (-Z side) in the insert axial direction, which makes it easy to provide a clearance angle between the machining surface of the workpiece and the inner cutting edge flank 16e during cutting.

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

[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 metal such as steel. As shown in Figures 5 and 6, the holder 2 has a columnar shape extending in the tool axial direction along the tool central axis O. Specifically, the holder 2 has a substantially cylindrical shape centered on the tool central axis O. The holder 2 has a shank 2a and a body 2b arranged on the tip side of the shank 2a in the tool axial direction. The shank 2a and the body 2b are arranged 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 by the spindle of the machine tool in the end mill rotation direction T about the tool central axis O. During cutting, the shank 2a is fed in the tool radial direction by the spindle of the machine tool. As the shank 2a is rotated and fed in this manner, the cutting edges 14 of the multiple cutting inserts 1 attached to the body 2b cut into the workpiece, 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 2 c of the body 2 b facing the tool axis direction and an outer peripheral surface 2 d facing outward in the tool radial direction. The chip discharge groove 21 extends spirally from the tip surface 2 c facing the tool axis direction of the holder 2 toward the rear end in the opposite direction to the end mill rotation direction T around the tool central axis O.

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

[0098] The insert mounting seats 22 are arranged on the wall portion of the chip discharge groove 21 that faces 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 common cutting inserts 1 having the same shape are attached to the plurality of insert mounting seats 22. Each cutting insert 1 is detachably attached to each insert mounting seat 22.

[0100] The insert mounting seats 22 include a leading-edge insert mounting seat 22A that is positioned furthest forward in the tool axial direction, and other insert mounting seats 22B that are positioned rearward of the leading-edge insert mounting seat 22A in the tool axial direction. The leading-edge insert mounting seat 22A may also be referred to as the first-stage insert mounting seat 22A. The other insert mounting seats 22B may also be referred to as the second-stage or later insert mounting seats 22B.

[0101] As shown in Figure 5, the insert mounting seat 22A at the forefront (first stage) has 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 fourth wall surface 22c facing 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 facing the left-right direction of the cutting insert 1. Specifically, the second wall surface 22b contacts a supported surface 16f among the side surfaces facing the left-right direction of the outer peripheral surface 13 of the cutting insert 1. 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 to 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 toward the rear end 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 in the front-rear direction. Specifically, the third wall surface 22e contacts the second minor flank surface 16c of the side surface of the outer peripheral surface 13 of the cutting insert 1 facing in the front-rear direction. The third wall surface 22e is planar. 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 as it moves outward in the tool radial direction. In other words, the width dimension of the third wall surface 22e increases as it moves outward 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] 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 the cutting insert to the holder] When the cutting insert 1 is attached to the holder 2, the 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 the end mill rotation direction T, and the other rectangular surface 12 faces the opposite end mill rotation direction. In other words, the cutting insert 1 of this embodiment is a so-called side cutting insert. When the cutting insert 1 is attached to the insert mounting seat 22, although not particularly shown, the insert center axis C of the cutting insert 1 extends toward the rear end 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 radially outward from the outer peripheral surface 2d of the body 2b. The major 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 as it moves toward the rear end in the tool axial direction. Furthermore, the rotation trajectory of the major 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 a single 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 insert mounting seat 22A at the forefront protrudes further toward the tip side in the tool axial direction than the tip 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 insert mounting seat 22A at the forefront has a positive radial rake angle (positive angle).

[0112] [Effects of the Present Embodiment] In the cutting insert 1 and the indexable end mill 10 of the present embodiment, the minor cutting edge 18, which finishes the machined surface of a 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 precision of the finished surface. The minor cutting edge 18 also has a straight cutting edge portion 18b that is disposed on the inside of the curved cutting edge portion 18a in the tool radial direction (on the opposite side of 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 away from the curved cutting edge portion 18a in the tool radial direction (left-right direction).

[0113] The flank 16 has a first minor flank 16b having a convex curved surface shape connected to the curved cutting portion 18a of the minor cutting edge 18, and a second minor flank 16c having a flat surface shape connected to the straight cutting 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 stage or later) into contact with the second minor flank 16c facing the tip side (front 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.

[0114] Furthermore, unlike the configuration in which the third wall surface 22e contacts the inner cutting edge flank 16e in the present embodiment, the third wall surface 22e contacts the second minor flank 16c (minor flank). Therefore, in the present embodiment, the third wall surface 22e is positioned closer to the main cutting edge 17 and the corner edge 19 in the tool radial direction. That is, the third wall surface 22e contacts the cutting insert 1 at a more outer position in the tool radial direction, resulting in a so-called "outer contact." Therefore, according to the present embodiment, the cutting insert 1 can be stably supported by the third wall surface 22e.

[0115] Furthermore, since the third wall surface 22e is configured to contact the secondary relief surface, there is no need to provide a recessed notch (gap) or the like to prevent contact between the third wall surface 22e and the secondary relief surface. Therefore, chips do not get into the recessed notch or the like, and chip bite can be suppressed. Furthermore, since there is no need to provide a recessed notch or the like, the rigidity of the holder can be stably ensured.

[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 minor cutting edge 18, and it is possible to suppress jamming due to the intrusion of chips between the insert mounting seat 22 and the cutting insert 1, thereby increasing the rigidity of the holder.

[0117] In this embodiment, the curved cutting edge portion 18a extends rearward from the connection point P between the curved cutting edge portion 18a and the corner edge 19 toward the opposite side from the corner edge 19 in the left-right direction. In this case, as shown in Fig. 12, when the cutting insert 1 is attached to the insert mounting seat 22A at the forefront (first stage), the entire minor cutting edge 18 extends toward the rear end side in the tool axial direction (rear side in the cutting insert 1) 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). 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 imaginary plane VS), suppressing so-called solid contact and minimizing cutting resistance. This improves cutting efficiency and extends tool life while maintaining good finished surface accuracy.

[0119] In this embodiment, as shown in Figure 2, the minor cutting edge relief angle θ formed between the imaginary line VL extending in the left-right direction and the straight cutting edge portion 18b is 0.2° or more and 5.0° or less when viewed from the insert axial direction. When the minor cutting edge relief angle θ is 0.2° or more, the entire minor cutting edge 18 can be stably formed into a positive dish. Furthermore, 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 is more stable.

[0120] Furthermore, 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 (the second or subsequent stage) is brought into contact with the second minor relief 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 the present embodiment, the fourth wall surface 22c of the insert mounting seat 22A at the forefront comes into contact with the inner cutting edge flank 16e of the cutting insert 1. In the above configuration, by bringing the fourth wall surface 22c of the insert mounting seat 22A at the forefront (first stage) into contact with the inner cutting edge flank 16e facing the rear end side (rear side) in the tool axial direction of the cutting insert 1, this contact becomes surface contact, making it easy to increase the contact area.

[0123] Furthermore, the inner cutting edge flank 16e facing the rear end side in the tool axial direction of the cutting insert 1 is disposed close to the main cutting edge 17 and the corner edge 19 on the outer periphery of the tip used for cutting in the tool radial direction. That is, the fourth wall surface 22c comes into contact with the cutting insert 1 at a position further outward in the tool radial direction, which is what is called "external contact." Therefore, according to the above 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 as will be described below, the configuration can be modified within the scope of the present invention.

[0125] In the above-described embodiment, the cutting insert 1 has a rectangular plate shape or a parallelogram plate shape, but is not limited thereto. The cutting insert 1 may have a square plate shape or a diamond plate shape centered on the insert central axis C.

[0126] The corner edge 19 of the cutting insert 1 may be a straight line that intersects the major cutting edge 17 and the minor cutting edge 18 (curved cutting portion 18 a) 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 this is not limiting. For example, the curved cutting edge portion 18a may extend gradually forward from the connection point P with the corner edge 19 toward the left, and after passing the apex that protrudes most forward, extend gradually backward toward the left.

[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 counterclockwise as viewed from the tip side in the tool axial direction as shown in FIG. 11 , but this is not limited thereto. The end mill rotation direction T may be clockwise 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 that have different functions from those in the above-described embodiment.

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

[0131] The cutting insert and indexable end mill of the present invention can improve the accuracy of the finished surface with the minor cutting edge, while stably supporting the cutting insert with the insert mounting seat, suppressing the intrusion of chips into the gap between the insert mounting seat and the cutting insert, and increasing the rigidity of the holder, and therefore have industrial applicability.

[0132] 1 Cutting insert 2 Holder 2c Tip surface 10 Indexable end mill 11 One of the rectangular surfaces (surface) 11a Rake face 12a Seating surface 14 Cutting edge 16 Flank face 16b First minor flank face 16c Second minor flank face 16e Inner cutting edge flank face 17 Main cutting edge 18 Minor cutting edge 18a Curved cutting edge portion 18b Straight cutting edge portion 19 Corner cutting edge 20 Inner cutting edge 21 Chip discharge groove 22 Insert mounting seat 22A Foremost insert mounting seat (first stage) 22B Insert mounting seat other than the foremost (second stage or later) 22a First wall surface 22b Second wall surface 22c Fourth wall surface 22e Third wall surface C Insert central axis O Tool central axis P Connection point T End mill rotation direction VL Virtual straight line θ Minor cutting edge relief angle

Claims

1. A cutting edge having a rake face arranged on a rectangular surface facing the insert axial direction along which the central axis of the insert extends; a side surface facing a front-to-rear direction perpendicular to the insert axial direction, and a flank surface arranged across a side surface facing a left-right direction perpendicular to the insert axial direction and the front-to-rear direction; and a cutting edge arranged on a ridge portion connecting the rake face and the flank surface, wherein the cutting edges include: a main cutting edge arranged on a first side of the rectangular surface extending in the front-to-rear direction; a minor cutting edge arranged on a second side of the four sides extending in a direction intersecting the first side; and a corner edge arranged at a corner portion between the first and second sides of the rectangular surface and connected to the main cutting edge and the minor cutting edge, wherein the minor cutting edge has: a curved blade portion connected to the corner edge and curved in a convex shape toward the front; and a straight blade portion connected to the curved blade portion and extending in a straight line toward the rear as it approaches the opposite side to the curved blade portion in the left-to-right direction, the flank includes a first minor flank connected to the curved blade portion and having a curved shape that is convex toward the front side, and a second minor flank connected to the straight blade portion and having a flat shape.

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 the opposite side from the corner blade in the left-right direction.

3. The cutting insert according to claim 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.

4. A cutting insert according to any one of claims 1 to 3, wherein the left-right center of the second minor escape surface is located closer to the main cutting edge in the left-right direction than the left-right center of the cutting insert.

5. A cutting insert according to any one of claims 1 to 3, wherein the entire 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.

6. A cutting insert according to any one of claims 1 to 3, comprising: a columnar holder extending in the tool axial direction along the tool central axis, wherein the holder has: a chip discharge groove extending in a spiral shape in a direction opposite to the end mill rotation direction around the tool central axis as it moves from a tip face of the holder facing the tool axial direction toward a rear end side; and a plurality of insert mounting seats arranged in a stepped manner along the chip discharge groove, wherein a plurality of cutting inserts are provided, and each of the cutting inserts is detachably attached to each of the insert mounting seats, wherein the plurality of insert mounting seats include: a frontmost insert mounting seat arranged at the frontmost side in the tool axial direction; and a non-frontmost insert mounting seat arranged at the rear end side of the frontmost insert mounting seat in the tool axial direction, wherein the non-frontmost insert mounting seat has: a first wall surface facing the end mill rotation direction and in contact with a seating surface facing the opposite side to the rake face in the insert axial direction of the cutting insert, an indexable end mill having 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 in the left-right direction; and a third wall surface facing a rear end side of the tool axial direction and in contact with a side surface of the cutting insert facing in the front-rear direction, wherein the third wall surface contacts the second minor clearance surface.

7. The indexable end mill as described in claim 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° about the insert central axis, and the most distal insert mounting seat has the first wall surface, the second wall surface, and a fourth wall surface that faces the tip side in the tool axial 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.

Images