Cutting insert and indexable insert end mill

Abstract

A cutting insert and an indexable insert end mill, in which a cutting edge (14) of the cutting insert has: a main cutting edge (17) disposed on a first side of four sides of a quadrangular surface (11); a secondary cutting edge (18) disposed on the second side; and an edge corner (19), and the auxiliary cutting edge (18) has: a curved edge section (18a) which is connected to the edge corner (19) and which has a curved shape protruding toward the front side; and a linear blade section (18b) that is connected to the curved blade section (18a) and that extends linearly toward the rear side as the curved blade section (18a) faces the side opposite to the curved blade section (18a) in the left-right direction, and the flank surface (16) has: a first auxiliary flank surface (16b) that is connected to the curved blade section (18a) and that has a curved surface shape that protrudes toward the front side, and a second auxiliary flank surface (16b) that is connected to the curved blade section (18a) and that has a curved surface shape that protrudes toward the rear side; and a planar second pair flank surface (16c) connected to the linear blade section (18b).

Description

Technical Field

[0001] This invention relates to a cutting insert and an indexable insert end mill.

[0002] This application claims priority under Japanese Patent Application No. 2023-169985, filed on September 29, 2023, the contents of which are incorporated herein by reference. Background Technology

[0003] As a conventional indexable insert end mill, a cutting tool as described in Patent Document 1 is known. The cutting tool of Patent Document 1 comprises rectangular plate-shaped cutting inserts and a cylindrical tool holder. The tool holder has: a chip removal groove extending spirally around the tool's central axis (rotation axis); and multiple insert mounts arranged in a stepped manner along the chip removal groove. Multiple cutting inserts of the same shape, forming a common component, are detachably mounted on the multiple insert mounts.

[0004] The cutting insert comprises: a rake face, which is arranged on a rectangular face facing the direction of rotation of the end mill; a flank face, which is arranged on a side facing the front end of the tool along the tool axis and on a side facing the outer side of the tool radial direction orthogonal to the tool axis; and a cutting edge, which is arranged on the ridge where the rake face and the flank face connect.

[0005] The cutting edge has: a main cutting edge extending along the long side of the rectangular face; a secondary cutting edge extending along the short side of the rectangular face; a convex curved cutting edge connecting the main and secondary cutting edges; and an inner cutting edge connecting to the end of the secondary cutting edge on the side opposite to the cutting edge in the short side direction. In indexable insert end mills, the main cutting edge functions as the outer peripheral cutting edge, and the secondary cutting edge functions as the bottom cutting edge. Furthermore, the inner cutting edge sometimes functions as a cutting edge, for example, when performing inclined milling.

[0006] Furthermore, the multiple blade mounts arranged in a stepped manner along the chip removal groove include: the foremost (first segment) blade mount, which is disposed on the foremost side in the tool axis; and the blade mounts other than the foremost (second segment and beyond), which are disposed on the rear end side in the tool axis.

[0007] The insert mount, excluding the foremost end, has: a first wall surface that contacts the seat surface of the cutting insert facing the side opposite to the rake face; a second wall surface that contacts the side of the cutting insert facing radially inward toward the tool; and a third wall surface that contacts the side of the cutting insert facing axially toward the foremost end of the tool. The first wall surface supports the cutting insert from the side opposite to the rotation direction of the end mill. The second wall surface supports the cutting insert from radially inward toward the tool. The third wall surface supports the cutting insert from axially toward the foremost end of the tool.

[0008] The foremost insert mount has: a first wall surface that contacts the seat surface of the cutting insert facing the opposite direction to the rake face; a second wall surface that contacts the side of the cutting insert facing radially inward toward the tool; and a fourth wall surface that contacts the side of the cutting insert facing axially toward the rear end of the tool. The first wall surface supports the cutting insert from the side opposite to the rotation direction of the end mill. The second wall surface supports the cutting insert from radially inward toward the tool. The fourth wall surface supports the cutting insert from axially toward the rear end of the tool.

[0009] Thus, in the insert mounting seats beyond the foremost point (after the second segment) and the insert mounting seats at the foremost point (the first segment), the wall surfaces (the third wall surface and the fourth wall surface) that support the cutting insert from the tool axis are different from each other.

[0010] Patent Document 1: Japanese Patent No. 7052176 (B1)

[0011] In this type of indexable insert end mill, the secondary cutting edge (bottom edge) of the cutting insert mounted on the foremost insert mount performs finishing on the workpiece's surface. By forming this secondary cutting edge into a curve with a large radius of curvature that bulges towards the front end of the tool axis, the accuracy of the finished surface can be improved.

[0012] However, when the secondary cutting edge is formed into a convex curve, the portion of the cutting insert's flank face that connects to the secondary cutting edge (the secondary flank face) is formed into a curved surface that bulges towards the front end of the tool axis. Therefore, if the third wall surface of the insert mount (after the second section) beyond the front end comes into contact with the secondary flank face, the contact is a point contact or a line contact, making it difficult to stably support the cutting insert through the third wall surface.

[0013] On the other hand, compared to the secondary cutting edge, the internal cutting edge does not require strict machining accuracy. Therefore, it is possible to consider forming the portion of the flank face that connects to the internal cutting edge (the internal cutting edge flank face) into a planar shape and making the third wall surface contact the internal cutting edge flank face. In this case, the contact between the third wall surface and the internal cutting edge flank face is a surface contact, which easily increases the contact area.

[0014] However, compared to the secondary flank face, the internal flank face is positioned inside the tool radially. Correspondingly, the third wall supporting the internal flank face is also positioned radially away from the main cutting edge and the cutting angle. Therefore, even with a structure that brings the third wall face into contact with the internal flank face, it is difficult to stably support the cutting insert.

[0015] Furthermore, in the configuration where the third wall surface contacts the inner cutting edge's flank face, to prevent the wall portion adjacent to the radially outer side of the tool in the insert holder from contacting the secondary flank face of the cutting insert, the wall portion needs to be cut into a concave shape. Since chips easily enter this concave cut (gap), chip bite is likely to occur. Also, because it is cut into a concave shape, the tool holder stiffness is reduced. Summary of the Invention

[0016] One of the objectives of this invention is to provide a cutting insert and an indexable insert end mill, wherein the cutting insert can improve the finishing surface accuracy through the secondary cutting edge, and can stably support the cutting insert through the insert mount, can suppress chip intrusion between the insert mount and the cutting insert and thus prevent biting, and can improve the rigidity of the tool holder.

[0017] To address the aforementioned issues, the present invention provides the following solutions.

[0018] [Embodiment 1 of the present invention]

[0019] A cutting insert includes: a rake face disposed on a quadrilateral surface facing the insert's axial direction, the insert's axial direction being the direction extending from the insert's central axis; a flank face disposed over a side facing a front-rear direction orthogonal to the insert's axial direction and a side facing a left-right direction orthogonal to both the insert's axial direction and the front-rear direction; and a cutting edge disposed on a ridge portion connecting the rake face and the flank face, the cutting edge having: a primary cutting edge disposed on a first side of the quadrilateral surface extending along the front-rear direction; and a secondary cutting edge disposed on a second side of the quadrilateral surface extending along a direction intersecting the first side. The quadrilateral has two sides; and a cutting edge, which is located at the corner between the first side and the second side of the quadrilateral surface and is connected to the main cutting edge and the secondary cutting edge. The secondary cutting edge has: a curved cutting edge connected to the cutting edge and convex to the front; and a straight cutting edge connected to the curved cutting edge and extending in a straight line to the rear in the left-right direction toward the side opposite to the curved cutting edge. The flank face has: a first secondary flank face connected to the curved cutting edge and convex to the front; and a planar second secondary flank face connected to the straight cutting edge.

[0020] In the cutting inserts and indexable insert end mills of the present invention, the secondary cutting edge for finishing the machined surface of the workpiece has a curved cutting edge portion that protrudes towards the front end side (front side in the cutting insert) in the tool axis. Therefore, the accuracy of the finished surface can be improved by the curved cutting edge portion. Furthermore, the secondary cutting edge has a straight cutting edge portion that is disposed inside the tool radial direction of the curved cutting edge portion (in the cutting insert, the side of the curved cutting edge portion opposite to the cutting angle in the left-right direction). The straight cutting edge portion extends in a straight line towards the rear end side (rear side) in the tool axis in the tool radial direction (left-right direction) towards the side opposite to the curved cutting edge portion.

[0021] The flank face has a convex curved first flank face that connects to the curved cutting edge of the secondary cutting edge, and a planar second flank face that connects to the straight cutting edge of the secondary cutting edge. Therefore, by making the third wall surface of the insert mounting base (after the second section) contact the second flank face of the cutting insert facing the tool axis, this contact is a surface contact, which easily increases the contact area.

[0022] Furthermore, unlike structures where the third wall surface contacts the inner cutting edge face, in this invention, the third wall surface contacts the second secondary cutting edge face (secondary cutting edge face). Therefore, in this invention, the third wall surface is positioned closer to the main cutting edge and the cutting edge angle in the tool radial direction. That is, the contact between the third wall surface and the cutting insert in the tool radial direction is further outward, becoming what is known as "outer contact".

[0023] Therefore, according to the present invention, the cutting blade can be stably supported by the third wall surface.

[0024] Furthermore, since the structure involves the third wall surface contacting the secondary flank face, there is no need to create concave slits (gap) to prevent contact between the third wall surface and the secondary flank face. Therefore, chips will not enter the concave slits, thus suppressing chip bite. Moreover, because concave slits are not required, the rigidity of the tool holder can be stably ensured.

[0025] In summary, according to the present invention, the finishing surface accuracy can be improved by the secondary cutting edge, the cutting insert can be stably supported by the insert mount, the biting caused by the intrusion of chips between the insert mount and the cutting insert can be suppressed, and the tool holder rigidity can be improved.

[0026] [Embodiment 2 of the present invention]

[0027] According to the cutting insert of method 1, the curved cutting edge extends rearward from the connection point between the curved cutting edge and the cutting angle in the left-right direction toward the side opposite to the cutting angle.

[0028] In this case, when the cutting insert is mounted on the foremost (first) insert mount, the secondary cutting edge extends from the point of connection with the cutting edge angle towards the rear end of the tool axis (or rear end in the cutting insert) as it moves radially inward (or, in the cutting insert, away from the cutting edge angle in the left-right direction). That is, the secondary cutting edge is designed in a so-called "positive disc shape" and thus tilted relative to an imaginary plane perpendicular to the tool's central axis.

[0029] This reduces the contact area between the secondary cutting edge and the workpiece's machined surface (equivalent to the imaginary plane), suppressing so-called seamless contact and thus minimizing cutting resistance. It effectively maintains the precision of the finished surface and improves cutting efficiency or extends tool life.

[0030] [Embodiment 3 of the present invention]

[0031] According to the cutting insert of method 1 or 2, when viewed from the axial direction of the insert, the clearance angle of the secondary cutting edge formed between the imaginary straight line extending along the left-right direction and the straight cutting edge is 0.2° or more and 5.0° or less.

[0032] If the clearance angle of the secondary cutting edge is 0.2° or greater, the entire secondary cutting edge can be stably designed into a positive disc shape. Furthermore, if the clearance angle of the secondary cutting edge is 5.0° or less, the gap between the straight cutting edge and the machined surface of the workpiece can be prevented from becoming too large, and the function of the secondary cutting edge as a finishing edge is more stable.

[0033] [Method 4 of the present invention]

[0034] According to any one of the methods 1 to 3, the center of the second secondary flank face in the left-right direction is located on the side closer to the main cutting edge in the left-right direction compared to the center of the cutting insert in the left-right direction.

[0035] [Embodiment 5 of the present invention]

[0036] According to any one of methods 1 to 4, the cutting insert, wherein the entire second flank face is located on the side of the main cutting edge in the left-right direction, compared to the center of the cutting insert in the left-right direction.

[0037] In the above structure, when the third wall surface of the insert mounting base (after the second section) is brought into contact with the second flank face, this third wall surface is positioned closer to the main cutting edge and the cutting edge angle in the tool radial direction. Therefore, the cutting insert can be supported more stably by the third wall surface.

[0038] [Solution 6 of the present invention]

[0039] An indexable insert end mill includes: a cutting insert according to any one of embodiments 1 to 5; and a cylindrical tool holder extending axially along a tool center axis, the tool holder having: a chip removal groove extending helically from a front end face of the tool holder toward a rear end face toward a side opposite to the rotation direction of the end mill in the direction surrounding the tool center axis; and a plurality of insert mounts arranged in a stepped manner along the chip removal groove, the cutting insert being provided with a plurality of inserts, each cutting insert being detachably mounted in a respective insert mount, the plurality of insert mounts including: a foremost insert mount disposed axially along the foremost side; The insert mounting base other than the foremost tip is disposed in the tool axis at a position further back than the foremost tip insert mounting base. The insert mounting base other than the foremost tip insert mounting base has: a first wall surface facing the rotation direction of the end mill and contacting the seat surface of the cutting insert, the seat surface facing the side opposite to the rake face in the insert axis; a second wall surface facing the outer side of the tool radial direction orthogonal to the tool central axis and contacting the side of the cutting insert facing the left-right direction; and a third wall surface facing the rear end side in the tool axis and contacting the side of the cutting insert facing the front-back direction, the third wall surface contacting the second flank face.

[0040] [Solution 7 of the present invention]

[0041] According to the indexable insert end mill of method 6, the cutting edge has an inner cutting edge located on the second side and disposed in the left-right direction on the side of the secondary cutting edge opposite to the cutting angle. The flank face has a planar inner cutting edge flank face connected to the inner cutting edge. The cutting insert has a shape that is 180° rotationally symmetrical about the insert's central axis. The foremost insert mounting base has: the first wall surface; the second wall surface; and the fourth wall surface, which faces the front end side of the tool axis and contacts the side of the cutting insert facing the front-rear direction. The fourth wall surface contacts the inner cutting edge flank face.

[0042] In the above structure, by making the fourth wall surface of the foremost (first segment) blade mount contact the inner cutting face of the cutting blade facing the rear end (rear side) of the tool axis, the contact is a surface contact, which easily increases the contact area.

[0043] Furthermore, the inner cutting edge face of the cutting insert facing the rear end of the tool axis is positioned radially close to the main cutting edge and cutting edge angle of the outer periphery of the front end used for cutting. That is, the fourth wall surface contacts the cutting insert further outward in the radial direction of the tool, becoming what is known as "outer contact".

[0044] Therefore, according to the above-described structure of the present invention, the cutting blade can be stably supported by the fourth wall surface.

[0045] According to the present invention, a cutting insert and an indexable insert end mill can be provided. The cutting insert can improve the finishing surface accuracy through the secondary cutting edge, and can stably support the cutting insert through the insert mount. It can suppress the biting caused by chips intruding between the insert mount and the cutting insert, and can improve the rigidity of the tool holder. Attached Figure Description

[0046] Figure 1 This is a perspective view showing the cutting blade of this embodiment.

[0047] Figure 2 This is a plan view of the cutting blade of this embodiment viewed from the blade axis.

[0048] Figure 3 This is a side view of the cutting blade of this embodiment, viewed from the left and right sides.

[0049] Figure 4 This is a front view (rear view) of the cutting blade of this embodiment viewed from the front-back direction.

[0050] Figure 5 This is a perspective view showing a portion of the tool holder according to this embodiment.

[0051] Figure 6 This is a perspective view showing a portion of the tool holder according to this embodiment.

[0052] Figure 7 This is a perspective view showing a portion of the indexable insert end mill of this embodiment.

[0053] Figure 8 This is a perspective view showing a portion of the indexable insert end mill of this embodiment.

[0054] Figure 9 This is a side view of a portion of the indexable insert end mill of this embodiment, viewed radially from the tool.

[0055] Figure 10 This is a side view of a portion of the indexable insert end mill of this embodiment, viewed radially from the tool.

[0056] Figure 11 This is a bottom view of the indexable insert end mill of this embodiment, viewed from the front end side along the tool axis.

[0057] Figure 12 It is shown in magnification Figure 9 Side view of part XII. Detailed Implementation

[0058] The cutting insert 1 and indexable insert end mill 10 of one embodiment of the present invention will be described with reference to the accompanying drawings. The indexable insert end mill 10 of this embodiment is, for example, a turning tool (cutting tool) for milling (turning) workpieces such as metal. In this embodiment, the cutting insert 1 and the indexable insert end mill 10 are sometimes simply referred to as tools, etc.

[0059] like Figures 1-4 As shown, the cutting insert 1 is a quadrilateral plate centered on the insert's central axis C; specifically, it is a rectangular plate or a parallelogram plate. Furthermore, as... Figures 7-11 As shown, the indexable insert end mill 10 is roughly cylindrical with the tool center axis O as its center.

[0060] The indexable insert end mill 10 includes a tool holder 2, cutting inserts 1 detachably mounted on the tool holder 2, and fastening components 3 for fixing the cutting inserts 1 to the tool holder 2. Multiple cutting inserts 1 and fastening components 3 are respectively provided on the tool holder 2. The multiple cutting inserts 1 are common components having the same shape as each other.

[0061] [Definition of direction]

[0062] In this embodiment, Figures 1-4 The XYZ orthogonal coordinate system (three-dimensional orthogonal coordinate system) is appropriately set in each figure, and the constituent elements of the cutting tool 1 are explained.

[0063] In this embodiment, the direction in which the cutting insert 1 extends along its central axis C is referred to as the insert axial direction. Figures 1-4 In the figures, the insert axis corresponds to the Z-axis direction. The cutting insert 1 has a pair of quadrilateral faces 11 and 12 facing the insert axis. One quadrilateral face 11 faces one side of the insert axis (+Z side), and the other quadrilateral face 12 faces the other side of the insert axis (-Z side). One quadrilateral face 11 can also be referred to as the front face 11, and the other quadrilateral face 12 can also be referred to as the back face 12. One side of the insert axis can also be referred to as the front face side of the insert axis or simply the front face side. The other side of the insert axis can also be referred to as the back face side of the insert axis or simply the back face side. Furthermore, the insert axis (Z-axis direction) can also be referred to as the thickness direction of the cutting insert 1.

[0064] In the figures, the Y-axis direction is the front-to-back direction orthogonal to the blade axis (Z-axis direction). In this embodiment, the -Y side in the front-to-back direction (Y-axis direction) is called the front side, and the +Y side is called the rear side.

[0065] Furthermore, the X-axis direction is a left-right direction orthogonal to the blade axis (Z-axis direction) and the front-back direction (Y-axis direction). In this embodiment, the -X side in the left-right direction (X-axis direction) is called the left side, and the +X side is called the right side. The direction in the left-right direction closest to the blade's central axis C is called the blade's central side or inner side in the left-right direction. The direction in the left-right direction furthest from the blade's central axis C is called the blade's outer side in the left-right direction.

[0066] Furthermore, the direction orthogonal to the blade's central axis C is called the blade radial direction. Within the blade radial direction, the direction closer to the blade's central axis C is called the inner side of the blade radial direction, and the direction farther from the blade's central axis C is called the outer side of the blade radial direction.

[0067] Furthermore, the direction of rotation around the central axis C of the blade is called the circumferential direction of the blade.

[0068] exist Figures 7-11 In this context, the direction in which the tool's central axis O extends is called the tool axis. The tool holder 2 has a shank 2a and a body 2b arranged side by side along the tool axis. In the tool axis, the direction from the shank 2a toward the body 2b is called the front end side, and the direction from the body 2b toward the shank 2a is called the rear end side. In addition, the body 2b is the part of the tool holder 2 where the cutting insert 1 is mounted, and therefore can also be called the cutting edge 2b, etc.

[0069] The direction orthogonal to the tool's central axis O is called the tool radial direction. Within the tool radial direction, the direction closer to the tool's central axis O is called the inner side of the tool radial direction, and the direction farther from the tool's central axis O is called the outer side of the tool radial direction.

[0070] The direction of rotation around the tool's central axis O is called the tool's circumferential direction. Within the tool's circumferential direction, the direction in which the indexable end mill 10 rotates during cutting is called the end mill rotation direction T, and the opposite rotation direction is called the side opposite to the end mill rotation direction T or the opposite direction of the end mill rotation.

[0071] [Cutting blade]

[0072] The cutting insert 1 is, for example, made of cemented carbide, etc. Figures 1-4 As shown, the cutting insert 1 of this embodiment has a shape that is 180° rotationally symmetrical about the insert's central axis C. Furthermore, the cutting insert 1 is not a reverse-symmetrical shape. The cutting insert 1 of this embodiment is a so-called single-sided positive-shaped insert.

[0073] The cutting insert 1 has a pair of quadrilateral surfaces 11 and 12 (front 11 and back 12) facing the insert axis, an outer peripheral surface 13 facing the outer side of the insert radially and extending along the insert circumferential direction, a cutting edge 14, and a through hole 15.

[0074] One quadrilateral surface 11 is quadrilateral in shape, and in this embodiment it is rectangular or parallelogram-shaped. For example... Figure 2 As shown, the long side of a quadrilateral surface 11 corresponds to the front-back direction (Y-axis direction). The short side corresponds to the left-right direction (X-axis direction). The four sides disposed on the outer periphery of a quadrilateral surface 11 include a pair of long sides extending in the front-back direction and a pair of short sides extending in a direction intersecting the long sides. In this embodiment, the long side of a quadrilateral surface 11 is sometimes referred to as the first side, and the short side as the second side. Cutting edges 14 are disposed on the four sides of a quadrilateral surface (front) 11.

[0075] A quadrilateral surface 11 has a rake face 11a. That is, the cutting insert 1 has a rake face 11a. The rake face 11a is disposed at least on the outer periphery of the quadrilateral surface 11. The rake face 11a is disposed along the long side and the short side of the quadrilateral surface 11. The rake face 11a extends along the cutting edge 14. The rake face 11a is disposed adjacent to the cutting edge 14 on the radially inner side of the insert. The rake face 11a is connected to the cutting edge 14.

[0076] The rake face 11a extends from the inner side of the cutting edge 14 toward the radial direction of the insert and toward the other side (back side) of the insert axis. That is, when the XY plane is used as the reference plane, the rake angle of the rake face 11a is set as a positive rake angle.

[0077] Although not specifically illustrated, the other quadrilateral face 12 is quadrilateral in shape, and in this embodiment, it is rectangular or parallelogram-shaped. The surface area of ​​the other quadrilateral face (back side) 12 is smaller than the surface area of ​​the quadrilateral face (front side) 11.

[0078] like Figure 3 and Figure 4 As shown, another quadrilateral surface 12 has a sitting surface 12a. The sitting surface 12a is a plane perpendicular to the central axis C of the blade. That is, the sitting surface 12a is a plane that extends parallel to the XY plane.

[0079] like Figures 1-4 As shown, the outer peripheral surface 13 is annular, extending around the central axis C of the blade. The outer peripheral surface 13 has a pair of side surfaces (front and rear sides) facing the front-to-back direction and a pair of side surfaces (left and right sides) facing the left-to-right direction. One end of the outer peripheral surface 13 along the blade axial direction (front side) is connected to the outer periphery of a quadrilateral surface (front) 11. The other end of the outer peripheral surface 13 along the blade axial direction (back side) is connected to the outer periphery of another quadrilateral surface (back side) 12.

[0080] The outer peripheral surface 13 has a flank face 16. That is, the cutting insert 1 has a flank face 16. The flank face 16 is disposed on the side facing the front-back direction and the side facing the left-right direction of the outer peripheral surface 13. The flank face 16 is disposed at least on one end of the outer peripheral surface 13 in the insert axial direction. The flank face 16 is disposed along the long side and the short side of a quadrilateral surface 11. The flank face 16 extends along the cutting edge 14. The flank face 16 is disposed adjacent to the cutting edge 14 on the other side of the insert axial direction. The flank face 16 is connected to the cutting edge 14.

[0081] The flank face 16 extends radially inward from the cutting edge 14 toward the other side of the insert axially. As a result, during machining, it is easy to impart a clearance angle between the machined surface of the workpiece and the flank face 16, increasing the freedom of the mounting posture of the cutting insert 1 on the tool holder 2.

[0082] The specific components of the back face 16 will be described separately later.

[0083] The cutting edge 14 is disposed at the edge where the rake face 11a and the flank face 16 connect. The cutting edge 14 is disposed over the long and short sides of a quadrilateral face 11, and in this embodiment, it is approximately L-shaped.

[0084] Multiple cutting edges 14 are provided on the cutting insert 1. In this embodiment, the cutting insert 1 is a single-sided positive angle insert with a shape that is 180° rotationally symmetrical about the insert's central axis C, and two (two sets) of cutting edges 14 are provided at positions that are 180° rotationally symmetrical about each other with the insert's central axis C as the center. The two cutting edges 14 have a common structure. Hereinafter, one of the two cutting edges 14 will be described.

[0085] The cutting edge 14 has a main cutting edge 17, a secondary cutting edge 18, a cutting angle 19, and an inner cutting edge 20.

[0086] The main cutting edge 17 is disposed on the first side (the long side in this embodiment) of a quadrilateral surface 11, which extends in the front-back direction. Figure 2 As shown, when viewing the cutting insert 1 from the insert axis (Z-axis direction), the main cutting edge 17 is a roughly straight line extending in the front-to-back direction. More specifically, the main cutting edge 17 is a convex curve with a large radius of curvature (large R) bulging outwards from the insert in the left-to-right direction.

[0087] And, as Figure 3 As shown, in the side view of the cutting insert 1 viewed from the left-right direction (X-axis direction), the main cutting edge 17 extends in a straight line towards the front (-Y side) and towards one side of the insert axis (+Z side). During cutting, the main cutting edge 17 functions as the outer peripheral cutting edge of the indexable insert end mill 10.

[0088] like Figure 1 and Figure 2 As shown, the secondary cutting edge 18 is disposed on the second side (in this embodiment, the short side) of a quadrilateral surface 11, which extends in the direction intersecting the first side. During cutting, the secondary cutting edge 18 functions as the bottom cutting edge of the indexable insert end mill 10.

[0089] The secondary cutting edge 18 has a curved cutting edge 18a connected to the cutting edge angle 19 and a straight cutting edge 18b connected to the curved cutting edge 18a.

[0090] The curved cutting edge 18a is connected tangentially to the end of the blade at the center side in the left-right direction of the cutting angle 19. In this embodiment, "connected tangentially" means that two adjacent cutting edges are smoothly connected in such a way that they have a common tangent at the connection points (the ends of the cutting edges).

[0091] Here, Figure 12 This shows a side view, viewed radially from the tool, near the tool tip of the indexable insert end mill 10, in which the cutting insert 1 is mounted on the tool holder 2. Furthermore, Figure 12 This is a view taken from the axial direction of the cutting blade 1 near the cutting edge 14 of the cutting blade 1 mounted on the tool holder 2.

[0092] like Figure 2 and Figure 12 As shown, when the cutting insert 1 is viewed from the insert axis (Z-axis direction), the curved cutting edge 18a is a curved shape that bulges forward (towards the front end of the tool axis). In detail, the curved cutting edge 18a is a convex curve with a large radius of curvature (large R) that bulges forward.

[0093] When viewed from the axial direction of the blade, the radius of curvature of the curved cutting edge 18a is, for example, R50mm or more and R200mm or less. The curved cutting edge 18a can be composed of a single circular arc with a constant radius of curvature, or it can be composed of multiple circular arcs with different radii of curvature.

[0094] In this embodiment, the curved cutting edge 18a extends rearward in the left-right direction toward the side opposite to the cutting edge 19 (moving away from the cutting edge 19) from the connection point P where the curved cutting edge 18a is located. Specifically, the curved cutting edge 18a extends rearward gradually to the left from the connection point P where it is located at the foremost side. Furthermore, the dimension (width dimension) of the curved cutting edge 18a in the left-right direction is, for example, 0.2 mm or more and 1.5 mm or less.

[0095] And, as Figure 4As shown, when the cutting insert 1 is viewed from the front-to-back direction (Y-axis direction), the curved cutting edge 18a appears as a straight line. The curved cutting edge 18a extends towards the opposite side of the insert axis (-Z side) in the left-to-right direction (X-axis direction) towards the side opposite to the cutting angle 19.

[0096] The straight cutting edge 18b is connected tangentially to the curved cutting edge 18a at the end of the blade on the central side in the left-right direction. For example... Figure 2 and Figure 12 As shown, when the cutting insert 1 is viewed from the insert axis, the straight cutting edge 18b extends in a straight line toward the side opposite to the curved cutting edge 18a in the left-right direction (as it moves away from the curved cutting edge 18a) toward the rear (rear end side in the tool axis). Specifically, the straight cutting edge 18b gradually extends toward the rear from the connection point with the curved cutting edge 18a located at the foremost side of the straight cutting edge 18b toward the left.

[0097] like Figure 2 As shown, when viewed from the insert's axial direction, the secondary cutting edge clearance angle θ formed between the imaginary straight line VL extending in the left-right direction and the straight cutting edge 18b can, for example, be 0.2° or more and 5.0° or less, 0.3° or more and 4.5° or less, or 0.5° or more and 4.0° or less. Figure 12 As shown, when the cutting insert 1 is mounted on the tool holder 2, when viewed from the insert axis, the clearance angle θ of the secondary cutting edge is equivalent to the angle formed between the imaginary plane VS perpendicular to the tool center axis O and the straight cutting edge 18b.

[0098] Furthermore, the width of the straight cutting edge 18b in the left-right direction is, for example, 1.0 mm or more and 3.0 mm or less. The width of the straight cutting edge 18b in the left-right direction is greater than the width of the curved cutting edge 18a in the left-right direction. Additionally, in this embodiment, the widths of the curved cutting edge 18a and the straight cutting edge 18b in the left-right direction can also be referred to as the cutting edge length. That is, the cutting edge length of the straight cutting edge 18b is greater than the cutting edge length of the curved cutting edge 18a.

[0099] And, as Figure 4 As shown, when viewing the cutting insert 1 from the front-to-back direction, the straight cutting edge 18b extends in a straight line towards the opposite side (-Z side) of the insert axis in the left-to-right direction, opposite to the curved cutting edge 18a. In this embodiment, in Figure 4 In the front view of the blade shown, the curved cutting edge 18a and the straight cutting edge 18b are arranged side by side on a straight line in a manner that forms a single straight line.

[0100] like Figures 1-4As shown, the cutting edge 19 is located at the corner between the first side (the long side in this embodiment) and the second side (the short side in this embodiment) of a quadrilateral surface 11, and connects to the main cutting edge 17 and the secondary cutting edge 18. In this embodiment, the cutting edge 19 is a curved shape that convexes outward and forward towards the blade in the left-right direction. Figure 12 As shown, when the cutting insert 1 is mounted on the tool holder 2, the cutting angle 19 is a curved shape that bulges outward in the radial direction of the tool and towards the front end in the axial direction of the tool.

[0101] like Figure 2 As shown, one end of the cutting edge 19 is connected to the front end of the main cutting edge 17. One end of the cutting edge 19 is connected tangentially to the front end of the main cutting edge 17. The other end of the cutting edge 19 is connected to the end of the secondary cutting edge 18 on the outer side of the insert in the left-right direction (opposite to the insert's central axis C). Specifically, the other end of the cutting edge 19 is connected to the right end of the curved cutting edge 18a at connection point P. The other end of the cutting edge 19 is connected tangentially to the right end of the curved cutting edge 18a (secondary cutting edge 18). The cutting edge 19 extends from the end connected to the main cutting edge 17 towards the front and towards the central side of the insert in the left-right direction (the side of the insert's central axis C).

[0102] like Figures 1-4 As shown, the inner cutting edge 20 is located on the second side (the shorter side in this embodiment) of a quadrilateral surface 11. The inner cutting edge 20 is positioned in the left-right direction on the side of the secondary cutting edge 18 opposite to the cutting angle 19. In this embodiment, the inner cutting edge 20 is positioned adjacent to the secondary cutting edge 18 on its left side. The inner cutting edge 20 sometimes functions as a cutting edge, for example, during bevel milling. Alternatively, the inner cutting edge 20 may not function as a cutting edge.

[0103] like Figure 2 As shown, when viewing the cutting insert 1 from the insert axis, the inner cutting edge 20 extends rearward in the left-right direction toward the side opposite to the secondary cutting edge 18 (as it moves away from the secondary cutting edge 18). Figure 12 As shown, with the cutting insert 1 mounted on the tool holder 2, the inner cutting edge 20 extends toward the rear end of the tool along the tool axis as it moves toward the inner side of the tool in the radial direction.

[0104] like Figure 2 and Figure 12 As shown, when viewing the cutting insert 1 from the insert axis, the inner cutting edge 20 has a curved shape that is concave towards the rear (rear end side in the tool axis). Furthermore, as... Figure 4 As shown, when the cutting insert 1 is viewed from the front and back direction, the inner cutting edge 20 is a curved shape that is concave towards the other side (-Z side) of the insert axis.

[0105] Here, the constituent elements of the back face 16 will be explained.

[0106] like Figure 1 , Figure 3 and Figure 4 As shown, the back face 16 has a main back face 16a, a first secondary back face 16b, a second secondary back face 16c, a corner back face 16d, and an inner cutting back face 16e.

[0107] The main relief face 16a is disposed on the side (right side) of the outer peripheral surface 13 of the cutting insert 1, facing left and right, on one side (+Z side) of the insert axial direction. The main relief face 16a is connected to the main cutting edge 17. The main relief face 16a extends along the main cutting edge 17 in the front-back direction. The main relief face 16a is a curved surface convex outward of the insert facing left and right. Specifically, the cross-section of the main relief face 16a perpendicular to the insert's central axis C is a curved shape convex outward of the insert facing left and right.

[0108] The main relief face 16a extends from the main cutting edge 17 toward the other side (-Z side) of the insert axis toward the center side (left side) of the insert in the left-right direction. As a result, during cutting, it is easy to impart a clearance angle between the machined surface (side wall) of the workpiece and the main relief face 16a.

[0109] A supported surface 16f is provided on the outer side of the cutting insert 13, facing left and right, on the side opposite to the main relief face 16a along the insert axis. The supported surface 16f is planar and extends in the front-back direction.

[0110] The first secondary flank face 16b and the second secondary flank face 16c constitute the flank face (secondary flank face) of the secondary cutting edge 18. The first secondary flank face 16b and the second secondary flank face 16c are disposed on the front side (front side) of the outer peripheral surface 13 of the cutting insert 1 in the front-rear direction. In this embodiment, the first secondary flank face 16b and the second secondary flank face 16c are disposed on the front side of the outer peripheral surface 13 of the cutting insert 1, covering the entire axial length of the insert.

[0111] The first secondary flank face 16b and the second secondary flank face 16c extend toward the rearward side from the secondary cutting edge 18 toward the other side (-Z side) of the insert axis. As a result, during cutting, it is easy to impart a clearance angle between the workpiece's machined surface (finished surface) and the secondary flank faces (the first secondary flank face 16b and the second secondary flank face 16c).

[0112] The first flank face 16b is connected to the curved cutting edge 18a. The first flank face 16b is a curved surface that convexes towards the front. Specifically, the cross-section of the first flank face 16b perpendicular to the central axis C of the insert is a curved shape that convexes towards the front.

[0113] The second secondary flank face 16c is connected to the straight cutting edge 18b. The second secondary flank face 16c is planar. The center of the second secondary flank face 16c in the left-right direction is located on the right side (near the main cutting edge 17) compared to the center of the cutting insert 1 in the left-right direction. In this embodiment, the entire second secondary flank face 16c is located on the right side (near the main cutting edge 17) compared to the center of the cutting insert 1 in the left-right direction. In other words, the entire secondary flank face of the secondary cutting edge 18 (the first secondary flank face 16b and the second secondary flank face 16c) is positioned on the side (near the main cutting edge 17) compared to the center of the insert in the left-right direction.

[0114] Furthermore, in this embodiment, the dimension of the second set of back face 16c in the left-right direction is greater than the dimension of the first set of back face 16b in the left-right direction.

[0115] The corner relief face 16d is located at the corner of the outer peripheral surface 13 of the cutting insert 1, between the side facing left and right and the side facing front and back. The corner relief face 16d is connected to the cutting edge angle 19. The corner relief face 16d is a curved surface that convexes outward in the radial direction of the insert. Specifically, the cross-section of the corner relief face 16d perpendicular to the central axis C of the insert is a curved shape that convexes outward in the radial direction of the insert.

[0116] The corner relief face 16d extends radially inward from the cutting angle 19 toward the other side (-Z side) of the insert axis. Thus, during cutting, it is easy to impart a clearance angle between the machined surface of the workpiece and the corner relief face 16d.

[0117] like Figure 1 and Figure 4 As shown, the inner cutting edge flank 16e is disposed on the front-to-back side of the outer peripheral surface 13 of the cutting insert 1. The inner cutting edge flank 16e is connected to the inner cutting edge 20. The inner cutting edge flank 16e is planar. The inner cutting edge flank 16e is disposed along the entire axial length of the cutting insert on the front-to-back side of the outer peripheral surface 13 of the cutting insert 1.

[0118] The inner cutting edge relief face 16e extends toward the rearward side from the inner cutting edge 20 toward the other side (-Z side) of the insert axis. Thus, during cutting, it is easy to impart a clearance angle between the machined surface of the workpiece and the inner cutting edge relief face 16e.

[0119] The center of the inner cutting edge flank 16e in the left-right direction is located on the side opposite to the main cutting edge 17 (left side) compared to 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 side opposite to the main cutting edge 17 in the left-right direction compared to the center of the cutting insert 1 in the left-right direction.

[0120] like Figure 1 and Figure 2 As shown, the through hole 15 extends through the cutting insert 1 along the insert's axial direction. The through hole 15 extends axially within the cutting insert 1 and opens on a pair of quadrilateral surfaces 11 and 12. The cross-section of the through hole 15 perpendicular to the insert's central axis C is circular. The central axis of the through hole 15 is coaxial with the insert's central axis C.

[0121] [Knife Holder]

[0122] The tool holder 2 is made of metal, such as steel. Figure 5 and Figure 6 As shown, the tool holder 2 is cylindrical, extending axially along the tool's central axis O. Specifically, the tool holder 2 is approximately cylindrical with the tool's central axis O at its center. The tool holder 2 has a shank 2a and a body 2b disposed on the axially forward end side of the shank 2a. The shank 2a and the body 2b are arranged adjacent to each other axially and connected to each other. The shank 2a and the body 2b are formed as a single piece.

[0123] The shank 2a is cylindrical, centered on the tool's central axis O, and extends along the tool's axial direction. The shank 2a is detachably mounted on the spindle of a machine tool (not shown). The shank 2a rotates via the machine tool spindle in the end mill's rotation direction T around the tool's central axis O. Furthermore, during cutting, the shank 2a is fed radially along the tool via the machine tool spindle. Thus, by rotating the shank 2a and applying feed, the cutting edges 14 of the plurality of cutting inserts 1 mounted on the body 2b cut into the workpiece to perform milling.

[0124] The main body 2b is approximately cylindrical with the tool's central axis O at its center and extends along the tool's axial direction. In this embodiment, the outer diameter of the main body 2b is smaller than the outer diameter of the shank 2a. The main body 2b has a chip removal groove 21 and a blade mounting seat 22. That is, the tool holder 2 has a chip removal groove 21 and a blade mounting seat 22.

[0125] The chip removal groove 21 is a groove-shaped opening on the front end face 2c of the main body 2b facing the tool axis and the outer peripheral face 2d facing the radial outer side of the tool. The chip removal groove 21 extends in a spiral shape from the front end face 2c of the tool holder 2 facing the tool axis toward the rear end side toward the side opposite to the rotation direction T of the end mill in the direction around the tool central axis O.

[0126] Multiple chip removal grooves 21 are spaced apart from each other on the main body 2b along the circumferential direction of the tool. In this embodiment, two chip removal grooves 21 are provided at equal intervals in the circumferential direction of the tool. Alternatively, two (or more) chip removal grooves 21 may be arranged at unequal intervals in the circumferential direction of the tool.

[0127] The insert mount 22 is disposed in the wall portion of the chip vent 21 facing the rotation direction T of the end mill. Multiple insert mounts 22 are provided along the helical extension direction of the chip vent 21. The multiple insert mounts 22 are arranged in a stepped configuration along the chip vent 21. Specifically, two or more insert mounts 22 are provided within one chip vent 21; in this embodiment, three insert mounts 22 are provided.

[0128] like Figures 7-11 As shown, multiple cutting blades 1 of the same shape are mounted on multiple blade mounting seats 22 as common components. Each cutting blade 1 is detachably mounted on its respective blade mounting seat 22.

[0129] The plurality of insert mounts 22 include an insert mount 22A located at the foremost end in the tool axis and insert mounts 22B located further back in the tool axis than the foremost insert mount 22A. The foremost insert mount 22A may also be referred to as the first section insert mount 22A. Furthermore, the insert mounts 22B located further back in the tool axis may also be referred to as the second and subsequent sections insert mounts 22B.

[0130] like Figure 5 As shown, the foremost (first segment) insert mounting base 22A has a first wall surface 22a facing the end mill rotation direction T, a second wall surface 22b facing the radially outer side of the tool, a fourth wall surface 22c facing the axial front end side of the tool, and an internal threaded hole 22d.

[0131] The first wall surface 22a contacts the seat surface 12a of the cutting insert 1, and the seat surface 12a faces the side opposite to the rake face 11a in the axial direction of the insert. The first wall surface 22a is planar. The first wall surface 22a supports the cutting insert 1 from the side opposite to the rotation direction T of the end mill.

[0132] The second wall surface 22b contacts the left-right oriented side of the cutting insert 1. Specifically, the second wall surface 22b contacts the supported surface 16f of the left-right oriented side of the outer peripheral surface 13 of the cutting insert 1. The second wall surface 22b is planar. The second wall surface 22b supports the cutting insert 1 radially inward from the tool.

[0133] The fourth wall surface 22c contacts the front-to-back side of the cutting insert 1. Specifically, the fourth wall surface 22c contacts the inner cutting face 16e of the front-to-back side of the outer peripheral surface 13 of the cutting insert 1. The fourth wall surface 22c is planar. The fourth wall surface 22c supports the cutting insert 1 from the rear end side of the tool axis.

[0134] The internally threaded hole 22d opens on the first wall surface 22a. The internally threaded hole 22d is a hole extending in a direction substantially perpendicular to the direction of expansion of the first wall surface 22a. The internally threaded hole 22d has an internally threaded portion on its inner circumferential surface.

[0135] like Figure 6 As shown, the insert mounting base 22B, excluding the foremost part (from the second section onwards), has a first wall surface 22a facing the rotation direction T of the end mill, a second wall surface 22b facing the radially outward side of the tool, a third wall surface 22e facing the axial rear end side of the tool, and an internal threaded hole 22d. Furthermore, the structures of the first wall surface 22a, the second wall surface 22b, and the internal threaded hole 22d are the same as described above, therefore detailed descriptions are omitted here.

[0136] The third wall surface 22e contacts the frontal side of the cutting insert 1. Specifically, the third wall surface 22e contacts the second flank face 16c of the frontal side of the outer peripheral surface 13 of the cutting insert 1. The third wall surface 22e is planar. In this embodiment, the third wall surface 22e extends radially along the tool. The dimension of the third wall surface 22e in the circumferential direction of the tool increases with the outer direction radially towards the tool. In other words, the width dimension of the third wall surface 22e increases with the outer direction radially towards the tool. The third wall surface 22e supports the cutting insert 1 from the front end side in the tool axial direction.

[0137] [Fastening components]

[0138] like Figures 7-11 As shown, the fastening component 3 is, for example, a clamping screw. The fastening component 3 detachably fixes the cutting insert 1 to the insert mounting base 22 (22A, 22B) of the tool holder 2. Specifically, the fastening component 3 is inserted into the through hole 15 of the cutting insert 1 and screwed into the internal threaded hole 22d of the insert mounting base 22.

[0139] [Regarding the mounting posture of the cutting inserts on the tool holder, etc.]

[0140] When the cutting insert 1 is mounted on the tool holder 2, the pair of quadrilateral faces 11 and 12 (front face 11 and back face 12) of the cutting insert 1 face the circumferential direction of the tool. Specifically, one quadrilateral face 11 faces the end mill rotation direction T, and the other quadrilateral face 12 faces the opposite direction of end mill rotation. That is, the cutting insert 1 in this embodiment is a so-called chisel-edge type insert. When the cutting insert 1 is mounted on the insert mounting base 22, although not specifically illustrated, the insert center axis C of the cutting insert 1 extends toward the rear end side of the tool axis in the direction of end mill rotation T.

[0141] Furthermore, with the cutting insert 1 mounted in the insert holder 22, the cutting edge 14 protrudes radially outward from the outer peripheral surface 2d of the body 2b. The main cutting edge 17 of each cutting insert 1 mounted in the plurality of insert holders 22 extends in the opposite direction to the rotation of the end mill towards the rear end side of the tool axial direction. Moreover, the rotation trajectory of the main cutting edge 17 of each cutting insert 1 mounted in the plurality of insert holders 22 about the tool's central axis O lies on an imaginary cylindrical surface (not shown) centered on the tool's central axis O.

[0142] And, as Figure 9 and Figure 12 As shown, the cutting edge 14 of the cutting insert 1 mounted on the foremost insert mount 22A protrudes axially towards the front end of the tool body 2b from the front end face 2c. Furthermore, as... Figure 11 As shown, the radial rake angle (radial inclination angle) of the secondary cutting edge 18 of the cutting insert 1 installed in the insert mounting base 22A at the foremost end becomes a positive rake angle (positive angle).

[0143] [Based on the effects of this implementation method]

[0144] In the cutting insert 1 and indexable insert end mill 10 of this embodiment, the secondary cutting edge 18 for finishing the machined surface of the workpiece has a curved cutting edge 18a that protrudes towards the front end side (front side in the cutting insert 1) in the tool axis. Therefore, the accuracy of the finished surface can be improved by the curved cutting edge 18a. Furthermore, the secondary cutting edge 18 has a straight cutting edge 18b disposed on the inner side of the curved cutting edge 18a in the tool radial direction (in the cutting insert 1, the side of the curved cutting edge 18a opposite to the cutting angle 19 in the left-right direction). The straight cutting edge 18b extends in a straight line in the tool radial direction (left-right direction) towards the rear end side (rear side) in the tool axis as it moves towards the side opposite to the curved cutting edge 18a.

[0145] The flank face 16 has a convex curved first flank face 16b connected to the curved cutting edge 18a of the secondary cutting edge 18, and a planar second flank face 16c connected to the straight cutting edge 18b of the secondary cutting edge 18. Therefore, by making the third wall surface 22e of the insert mounting base 22B (after the second section) contact the second flank face 16c of the cutting insert 1 on the front end side (front side) facing the tool axis, this contact is a surface contact, which easily increases the contact area.

[0146] Furthermore, unlike the structure in which, for example, the third wall surface 22e contacts the inner cutting edge flank face 16e, in this embodiment, the third wall surface 22e contacts the second secondary flank face 16c (secondary flank face). Therefore, in this embodiment, the third wall surface 22e is arranged closer to the main cutting edge 17 and the cutting edge angle 19 in the tool radial direction. That is, the contact between the third wall surface 22e and the cutting insert 1 in the tool radial direction is further outward, becoming a so-called "outer contact".

[0147] Therefore, according to this embodiment, the cutting blade 1 can be stably supported by the third wall surface 22e.

[0148] Furthermore, since the third wall surface 22e contacts the secondary flank face, there is no need to provide a concave slit (gap) or the like to prevent contact between the third wall surface 22e and the secondary flank face. Therefore, chips will not enter the concave slit or the like, suppressing chip bite. Moreover, since there is no need to provide a concave slit or the like, the rigidity of the tool holder can be stably ensured.

[0149] In summary, according to this embodiment, the finishing surface accuracy can be improved by the secondary cutting edge 18, and the cutting insert 1 can be stably supported by the insert mount 22. It can suppress chip intrusion between the insert mount 22 and the cutting insert 1 and improve the tool holder rigidity.

[0150] Furthermore, in this embodiment, the curved blade 18a extends rearward from the connection point P between the curved blade 18a and the blade angle 19 in the left-right direction toward the side opposite to the blade angle 19.

[0151] In this case, such as Figure 12 As shown, when the cutting insert 1 is mounted on the foremost (first segment) insert mount 22A, the secondary cutting edge 18 extends from the connection point P with the cutting edge angle 19, towards the rear end side of the tool axis (rear side in the cutting insert 1) as it moves radially inward (in the cutting insert 1, as it moves away from the cutting edge angle 19 in the left-right direction). That is, the secondary cutting edge 18 is designed as a so-called "positive disc shape," thus tilting relative to an imaginary plane VS perpendicular to the tool's central axis O.

[0152] This reduces the contact area between the secondary cutting edge 18 and the workpiece's machined surface (equivalent to the imaginary plane VS), suppressing so-called seamless contact and thus minimizing cutting resistance. It effectively maintains the precision of the finished surface and improves cutting efficiency or extends tool life.

[0153] Furthermore, in this embodiment, as Figure 2As shown, when viewed from the axial direction of the blade, the secondary cutting edge clearance angle θ formed between the imaginary straight line VL extending in the left-right direction and the straight cutting edge 18b is 0.2° or more and 5.0° or less.

[0154] If the clearance angle θ of the secondary cutting edge is 0.2° or more, the secondary cutting edge 18 can be stably designed as a positive disc shape. Furthermore, if the clearance angle θ of the secondary cutting edge is 5.0° or less, the gap between the straight cutting edge 18b and the machined surface of the workpiece can be prevented from becoming too large, and the function of the secondary cutting edge 18 as a finishing edge is more stable.

[0155] Furthermore, the center of the second flank face 16c in the left-right direction is located closer to the main cutting edge 17 in the left-right direction compared to the center of the cutting insert 1 in the left-right direction. In this embodiment, the entire second flank face 16c is located closer to the main cutting edge 17 in the left-right direction compared to the center of the cutting insert 1 in the left-right direction.

[0156] In the above structure, when the third wall surface 22e of the insert mounting base 22B (after the second section) is brought into contact with the second flank face 16c, the third wall surface 22e is positioned closer to the main cutting edge 17 and the cutting edge angle 19 in the tool radial direction. As a result, the cutting insert 1 can be supported more stably by the third wall surface 22e.

[0157] Furthermore, in this embodiment, the fourth wall surface 22c of the foremost blade mounting base 22A contacts the inner cutting edge face 16e of the cutting blade 1.

[0158] In the above structure, by making the fourth wall surface 22c of the foremost (first segment) blade mounting seat 22A contact the inner cutting face 16e of the cutting blade 1 facing the rear end (rear side) of the tool axis, the contact is a surface contact, which easily increases the contact area.

[0159] Furthermore, the inner cutting face 16e of the cutting insert 1 facing the rear end of the tool axis is arranged radially close to the main cutting edge 17 and the cutting angle 19 of the outer periphery of the front end used for cutting. That is, the fourth wall surface 22c contacts the cutting insert 1 more outward in the radial direction of the tool, becoming a so-called "outer contact".

[0160] Therefore, according to the structure described above in this embodiment, the cutting blade 1 can be stably supported by the fourth wall surface 22c.

[0161] [Other structures included in this invention]

[0162] The present invention is not limited to the above-described embodiments. For example, as described below, structural changes can be made without departing from the spirit of the present invention.

[0163] In the above embodiments, examples are given of the cutting blade 1 being rectangular or parallelogram-shaped, but it is not limited to these. The cutting blade 1 may also be square or rhomboid in shape with the blade's central axis C as the center.

[0164] The cutting edge angle 19 of the cutting insert 1 can be a straight line that intersects the main cutting edge 17 and the secondary cutting edge 18 (curved cutting edge 18a) at an obtuse angle. That is, the cutting edge angle 19 is not limited to the rounded shape described in the above embodiment, and can also be a chamfered shape.

[0165] In the above embodiments, the secondary cutting edge 18 is designed as a positive disc shape, but it is not limited to this. For example, the curved cutting edge 18a may also extend from the connection point P with the cutting edge angle 19, gradually extending towards the left and then towards the front, and after passing the most prominent top on the front side, it gradually extends towards the left and then towards the rear.

[0166] Furthermore, although not specifically illustrated, the tool holder 2 may have cooling holes that extend inside the tool holder 2 and open toward the cutting edge 14 of each cutting blade 1 disposed in the plurality of blade mounts 22.

[0167] Furthermore, in the above embodiments, such as Figure 11 As shown, the rotation direction T of the end mill is set to be counterclockwise when viewed from the front end side along the tool axis, but it is not limited to this. The rotation direction T of the end mill can also be clockwise when viewed from the front end side along the tool axis. That is, the present invention can also be applied to cutting inserts and indexable insert end mills with cutting directions different from those in the above embodiments.

[0168] Without departing from the spirit of the invention, the structures described in the above embodiments and variations can be combined, and additions, omissions, substitutions, or other modifications to the structures are possible. Furthermore, the invention is not limited to the above embodiments, but only to the claims.

[0169] Industrial availability

[0170] The cutting inserts and indexable insert end mills according to the present invention can improve the finishing surface accuracy through the secondary cutting edge, and can stably support the cutting inserts through the insert mount, suppressing chip intrusion between the insert mount and the cutting insert and thus preventing bite-in, and improving the tool holder rigidity. Therefore, they are industrially applicable.

[0171] Explanation of reference numerals in the attached figures

[0172] 1: Cutting blade

[0173] 2: Knife holder

[0174] 2c: Front end

[0175] 10: Indexable insert end mill

[0176] 11: A quadrilateral face (front)

[0177] 11a: Rake face

[0178] 12a: Seating surface

[0179] 14: Cutting edge

[0180] 16: Back face

[0181] 16b: First set of back face

[0182] 16c: Second back face

[0183] 16e: Back face of the inner edge

[0184] 17: Main cutting edge

[0185] 18: Secondary cutting edge

[0186] 18a: Curved cutting edge

[0187] 18b: Straight cutting edge

[0188] 19: Blade Angle

[0189] 20: Inner blade

[0190] 21: Chip Conveyor

[0191] 22: Blade Mount

[0192] 22A: The foremost (first segment) blade mount

[0193] 22B: Blade mount other than the very front end (after the second segment)

[0194] 22a: 1st wall

[0195] 22b: Second wall

[0196] 22c: 4th wall

[0197] 22e: 3rd wall

[0198] C: Blade center axis

[0199] O: Tool center axis

[0200] P: Connection point

[0201] T: End mill rotation direction

[0202] VL: Imaginary straight line

[0203] θ: Rake angle of the secondary cutting edge

Claims

1. A cutting insert, comprising: a rake surface disposed on a quadrangular surface in a direction of an insert axial line; a relief surface disposed on a side surface in a direction orthogonal to the insert axial line and a side surface in a direction orthogonal to the insert axial line and a front-rear direction; and a cutting edge disposed on a ridge line portion where the rake surface and the relief surface are connected, the cutting edge having: a main cutting edge disposed on a first side of four sides of the quadrangular surface in the front-rear direction; a sub cutting edge disposed on a second side of the four sides in a direction intersecting the first side; and a corner disposed on a corner between the first side and the second side of the quadrangular surface and connected to the main cutting edge and the sub cutting edge, the sub cutting edge having: a curved edge portion connected to the corner and protruding in a curve toward a front side; and a straight edge portion connected to the curved edge portion and extending in a straight line toward a rear side as it goes toward a side opposite the curved edge portion in a left-right direction, the relief surface having: a first sub relief surface connected to the curved edge portion and protruding in a curve toward the front side; and a second sub relief surface connected to the straight edge portion and flat.

2. The cutting insert according to claim 1, wherein the curved edge portion extends toward the rear side as it goes toward the side opposite the corner in the left-right direction from a connection point between the curved edge portion and the corner.

3. The cutting insert according to claim 2, wherein a sub cutting edge clearance angle formed between an imaginary straight line extending in the left-right direction and the straight edge portion is 0.2° or more and 5.0° or less when viewed in the insert axial line.

4. The cutting insert according to any one of claims 1 to 3, wherein a center of the second sub relief surface in the left-right direction is located on a side of the main cutting edge in the left-right direction compared to a center of the cutting insert in the left-right direction.

5. The cutting insert according to any one of claims 1 to 3, wherein an entirety of the second sub relief surface is located on the side of the main cutting edge in the left-right direction compared to the center of the cutting insert in the left-right direction.

6. An indexable insert type end mill, comprising: the cutting insert according to any one of claims 1 to 3; and a columnar holder extending in a tool axial line along a tool center axis, the holder having: a plurality of insert seats disposed in a stepped manner along the flutes, the cutting insert being provided with a plurality of, each of the cutting inserts being detachably mounted to each of the insert seats, the plurality of insert seats including: a foremost insert seat disposed on a foremost end side in the tool axial line; and an insert seat other than the foremost insert seat disposed on a position on a rear end side than the foremost insert seat in the tool axial line, the insert seat other than the foremost insert seat having: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ A chip flute extends spirally toward a side opposite to a rotation direction of the end mill in a direction around the tool center axis as it goes from a front end surface of the tool holder toward a rear end side in an axial direction of the tool; ​ ​ ​ ​ ​ ​ ​ ​ a first wall surface facing a direction of rotation of the end mill and contacting a seating surface of the cutting insert, the seating surface facing a side opposite the rake surface in the tool axial direction; a second wall surface facing an outer side in a tool radial direction orthogonal to the tool center axis and contacting a side surface of the cutting insert facing the left-right direction; and a third wall surface facing a rear end side in the tool axial direction and contacting a side surface of the cutting insert facing the front-back direction, the third wall surface contacting the second minor flank surface.

7. The indexable insert end mill according to claim 6, wherein the cutting edge has an inner edge located at the second edge and disposed on a side opposite the edge angle from the minor cutting edge in the left-right direction, the flank surface has a planar inner edge flank surface connected to the inner edge, the cutting insert has a shape that is 180° rotationally symmetrical about the insert center axis, the foremost insert seating has: the first wall surface; the second wall surface; and a fourth wall surface facing a front end side in the tool axial direction and contacting a side surface of the cutting insert facing the front-back direction, the fourth wall surface contacting the inner edge flank surface.

Images