Cutting insert

Abstract

To suppress wear or chipping of a side face at a tip of a cutting insert.SOLUTION: A cutting blade section 6 has a circular arc shaped cutting blade section 61 having a convex circular arc shape in a plan view of a cutting insert 1 from a direction opposite to a rake face 2. A ridge line section 7 has a first tip ridge line section 71 extending in a direction crossing the tip 61a of the circular arc shaped cutting blade section 61 at an obtuse angle in the plan view and a second tip ridge line section 72 having a convex circular arc shape having a radius of curvature smaller than that of the circular arc shaped cutting blade section 61 in the plan view. Both ends of the second tip ridge line section 72 are connected to the tip 61a of the circular arc cutting blade section 61 and the first tip ridge line section 71. A side face 5 has a circular arc blade flank 51 connected to the circular arc shaped cutting blade 61, a chamfer 53 which is connected to the first tip ridge line section 71 and has a polygonal surface shape having the first tip ridge line section 71 as one side, and a convex curved surface 54 connected to the second tip ridge line section 72. The convex curved surface 54 is positioned between the circular arc blade flank 51 and the chamfer 53.SELECTED DRAWING: Figure 6

Description

Technical Field

[0001] The present invention relates to a cutting insert.

Background Art

[0002] Conventionally, a cutting insert used for a replaceable-tip ball end mill has been known (for example, Patent Document 1). The cutting insert is detachably attached to an insert mounting seat disposed at the tip of a holder.

[0003] The throwaway tip (cutting insert) described in Patent Document 1 has a tip body formed of a hard material such as cemented carbide and having a substantially elliptical flat plate shape. The upper surface thereof is a rake face, the lower surface is a seating face, and the side surface serving as a relief face is inclined inward of the tip as it goes toward the lower surface side, and a relief angle is provided. Further, a mounting hole for mounting the tip is formed so as to penetrate the tip body in the tip thickness direction from the center of the tip in plan view of the upper surface. And, on the outer peripheral edge portion of the upper surface, a pair of arc-shaped cutting edges are formed so as to be located on opposite sides of each other with the mounting hole interposed therebetween in plan view. Further, a small cutting edge is formed at one end of these arc-shaped cutting edges, and a linear cutting edge is formed at the other end, and these cutting edges are formed so as to be point-symmetrical with respect to the center of the mounting hole in plan view, and it is designed so that one tip can be used twice.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] This type of ball end mill with replaceable cutting edges (hereinafter sometimes simply referred to as a ball end mill, a tool, etc.) may be used for modifying or repairing the shape of a mold. When modifying or repairing the shape of a mold, welding is performed on the mold to build up a welding material, and the surface of the workpiece including the periphery of the built-up welding material is machined (cutting) along a tool path along the concave curved surface of the mold or the like so as to have a desired shape by the ball end mill.

[0006] The surface of the workpiece including the built-up welding material generally has large irregularities. When machining along a tool path along the concave curved surface of the mold or the like, while descending or ascending the inclined surface of the mold, the axial cutting depth and the radial cutting depth are likely to vary, so the cutting load tends to increase. As a result, there is a risk of chipping occurring particularly at the tip portion and the arc-shaped cutting edge portion of the cutting insert.

[0007] An object of the present invention is to provide a cutting insert capable of suppressing chipping at the tip portion and the arc-shaped cutting edge portion of the cutting insert.

Means for Solving the Problems

[0008] In order to solve the above problems, the present invention provides the following means.

[0009] 〔Aspect 1 of the Present Invention〕 A cutting insert centered on an insert central axis, comprising a rake face facing one side in the insert axis direction, a seating face facing the other side in the insert axis direction, a side face facing the outside in the insert diameter direction and extending in the insert circumferential direction, and a cutting edge portion and a ridge line portion disposed on a ridge line where the rake face and the side face are connected. The cutting edge portion has an arc-shaped cutting edge portion that forms a convex arc shape in a plan view when the cutting insert is viewed from a direction facing the rake face. The ridge line portion has a first tip ridge line portion that extends in a direction intersecting at an obtuse angle with respect to a tip portion located at a corner of the rake face among both end portions of the arc-shaped cutting edge portion in the plan view, and a second tip ridge line portion that forms a convex arc shape with a smaller radius of curvature than the arc-shaped cutting edge portion in the plan view. Both end portions of the second tip ridge line portion are connected to the tip portion of the arc-shaped cutting edge portion and the first tip ridge line portion. The side face has an arc-shaped flank face continuous with the arc-shaped cutting edge portion, a chamfer having a polygonal face shape with the first tip ridge line portion as one side and continuous with the first tip ridge line portion, and a convex curved surface continuous with the second tip ridge line portion. The convex curved surface is located between the arc-shaped flank face and the chamfer. The cutting insert is as described above.

[0010] 〔Aspect 2 of the present invention〕 In the cutting insert according to Aspect 1, a portion of the convex curved surface located on the one side in the insert axis direction with respect to an extension line extending the edge on the other side in the insert axis direction of the arc-shaped flank face toward the chamfer is adjacent to the chamfer over the entire length in the insert axis direction.

[0011] 〔Aspect 3 of the present invention〕 Let the dimension along the insert axis direction from the connection point between the first tip ridge line portion and the second tip ridge line portion to the seating face be H1, and let the dimension along the insert axis direction from the vertex located most on the other side in the insert axis direction among the plurality of vertices of the polygonal face of the chamfer to the seating face be H2. The cutting insert according to Aspect 1 or 2 satisfies the relationship of [1 / 3 ≦ H2 / H1 ≦ 9 / 10].

[0012] 〔Aspect 4 of the present invention〕 In the plan view, with the radius of curvature of the arc-shaped cutting edge portion being R1 and the radius of curvature of the second tip ridge line portion being R2, the cutting insert according to any one of Aspects 1 to 3, which satisfies the relationship of [R1 / R2≤12].

[0013] 〔Aspect 5 of the present invention〕 The cutting edge portion is linear in the plan view and has a linear cutting edge portion connected to the rear end portion different from the tip end portion among both end portions of the arc-shaped cutting edge portion. The side surface has a linear cutting edge relief surface continuous with the linear cutting edge portion. The cutting insert has a shape that is rotationally symmetric by 180° about the insert central axis. The chamfer is located between the linear cutting edge relief surface and the convex curved surface. The cutting insert according to any one of Aspects 1 to 4.

[0014] 〔Aspect 6 of the present invention〕 In the plan view, the angle of the obtuse angle formed between the first tip ridge line portion and the linear cutting edge portion is larger than the angle of the obtuse angle formed between the first tip ridge line portion and the second tip ridge line portion. The cutting insert according to Aspect 5.

[0015] 〔Aspect 7 of the present invention〕 The angle formed by the chamfer and the seating surface is substantially perpendicular. The cutting insert according to any one of Aspects 1 to 6.

Advantages of the Invention

[0016] According to the cutting insert of the above aspect of the present invention, it is possible to suppress chipping at the tip end portion and the arc-shaped cutting edge portion of the cutting insert.

Brief Description of the Drawings

[0017]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

[0018] The cutting insert 1 according to an embodiment of the present invention will be described with reference to the drawings. The cutting insert 1 of the present embodiment is used for a ball end mill with replaceable cutting edges (not shown). The ball end mill with replaceable cutting edges is a cutting tool for performing milling (rotary cutting) on a workpiece such as a mold.

[0019] Specifically, this ball end mill with replaceable cutting edges is used for modifying or repairing the shape of a mold. More specifically, welding is performed on the mold to build up a welding material, and the surface of the workpiece including the built-up welding material is machined to follow a desired shape by the ball end mill with replaceable cutting edges. In the present embodiment, the cutting insert 1 and the ball end mill with replaceable cutting edges may be simply referred to as tools or the like.

[0020] As shown in FIGS. 1 to 4, the cutting insert 1 has a plate shape centered on the insert central axis C, and specifically, has a substantially parallelogram plate shape. Although not particularly shown, the ball end mill with replaceable cutting edges has a substantially cylindrical shape centered on the tool central axis O (for the overall shape of the ball end mill with replaceable cutting edges, refer to, for example, Japanese Patent Application Laid-Open No. 7-276128).

[0021] The ball end mill with replaceable cutting edges includes a holder (not shown), a cutting insert 1 detachably attached to the holder, and a fastening member such as a clamp screw (not shown) for fixing the cutting insert 1 to the holder. A plurality of cutting inserts 1 and fastening members are provided on the holder, and in the present embodiment, a pair of each is provided.

[0022] In the present embodiment, the direction in which the insert central axis C of the cutting insert 1 extends is referred to as the insert axis direction. The cutting insert 1 has a pair of plate surfaces facing opposite sides in the insert axis direction. Among the pair of plate surfaces, a rake face 2 is disposed on one plate surface, and a seating face 3 is disposed on the other plate surface.

[0023] In the present embodiment, the direction from the other plate surface (seating face 3) to one plate surface (rake face 2) along the insert axis direction is referred to as one side of the insert axis direction, and the direction from one plate surface (rake face 2) to the other plate surface (seating face 3) is referred to as the other side of the insert axis direction. Note that one side of the insert axis direction may also be referred to as the front surface side in the insert axis direction or simply the front surface side. The other side of the insert axis direction may also be referred to as the back surface side in the insert axis direction or simply the back surface side. Further, the insert axis direction may also be referred to as the thickness direction of the cutting insert 1.

[0024] Also, the direction orthogonal to the insert central axis C is referred to as the insert diameter direction. Among the insert diameter directions, the direction approaching the insert central axis C is referred to as the inner side of the insert diameter direction, and the direction away from the insert central axis C is referred to as the outer side of the insert diameter direction. Also, the direction of orbiting around the insert central axis C is referred to as the insert circumferential direction.

[0025] The dashed-dotted line indicated by the symbol O in FIG. 1 represents the tool central axis O. The tool central axis O is the central axis of the holder and is also the central axis of the replaceable ball end mill. In the present embodiment, the direction in which the tool central axis O extends is referred to as the tool axis direction.

[0026] Although not particularly shown, the holder has a shank and a body (cutting edge portion) arranged side by side in the tool axis direction. The shank is detachably attached to a spindle of a machine tool or the like. The cutting insert 1 is disposed on the body. Among the tool axis directions, the direction from the shank to the body is referred to as the tip side, and the direction from the body to the shank is referred to as the rear end side.

[0027] Also, the direction orthogonal to the tool center axis O is called the tool diameter direction. Among the tool diameter directions, the direction approaching the tool center axis O is called the inner side of the tool diameter direction, and the direction away from the tool center axis O is called the outer side of the tool diameter direction.

[0028] Also, the direction of rotation around the tool center axis O is called the tool circumferential direction. Among the tool circumferential directions, the direction in which the cutting edge exchange type ball end mill is rotated by the spindle of the machine tool or the like during cutting is called the end mill rotation direction T, and the rotation direction opposite to this is called the opposite side of the end mill rotation direction T or the reverse end mill rotation direction.

[0029] First, the holder will be described. The holder is made of metal such as steel, for example. The holder is substantially cylindrical with the tool center axis O as the center. The holder has a shank and a body disposed on the tip side of the shank in the tool axis direction. The shank and the body are integrally formed by a single member, for example.

[0030] The shank is rotated in the end mill rotation direction T around the tool center axis O by the spindle of the machine tool or the like. Also, during cutting, the shank is fed in the tool diameter direction and the tool axis direction by the spindle of the machine tool. In this way, by rotating the shank and applying feed, the cutting edge portions 6 of the plurality of cutting inserts 1 attached to the body cut into the workpiece, and profiling is performed.

[0031] The body has insert mounting seats. The insert mounting seats are arranged on the outer peripheral portion of the tip of the body. The insert mounting seats are formed by notching the outer peripheral portion of the tip of the body in a concave shape. A plurality of insert mounting seats are provided on the body at intervals in the tool circumferential direction, and a pair is provided in this embodiment.

[0032] The insert mounting seat has a bottom surface facing the end mill rotation direction T, a side wall surface protruding in the end mill rotation direction T from the inner end portion in the tool diameter direction of the bottom surface, and a rear wall surface protruding in the end mill rotation direction T from the rear end portion in the tool axis direction of the bottom surface. Further, the bottom surface has a screw hole and a pair of rib portions disposed on the tip side and the rear end side in the tool axis direction of the screw hole.

[0033] Next, the cutting insert 1 will be described. The cutting insert 1 is made of, for example, cemented carbide. As shown in FIGS. 1 to 4, the cutting insert 1 of the present embodiment has a shape that is rotationally symmetric by 180° about the insert central axis C. Further, the cutting insert 1 does not have a shape that is symmetric with respect to front-back inversion. The cutting insert 1 of the present embodiment is a so-called one-sided type positive insert.

[0034] FIG. 1 shows the posture when the cutting insert 1 is mounted on the insert mounting seat of the holder. In a state where the cutting insert 1 is attached to the insert mounting seat, the insert central axis C and the tool central axis O are in a twisted position with respect to each other.

[0035] The cutting insert 1 includes a rake face 2, a seating face 3, a boss face 4, a side face 5, a cutting edge portion 6, a ridge line portion 7, a through hole 8, and a groove portion 9.

[0036] The rake face 2 is disposed on one of the pair of plate surfaces (front surface) facing the insert axis direction of the cutting insert 1. The rake face 2 faces one side in the insert axis direction. The rake face 2 is disposed at least on the outer peripheral portion of one of the plate surfaces. The outer shape of the rake face 2 is substantially parallelogram-shaped. In a state where the cutting insert 1 is attached to the insert mounting seat, one of the plate surfaces and its rake face 2 face the end mill rotation direction T.

[0037] The rake face 2 has a convex corner 2a that protrudes outward in the insert radial direction. The corner 2a is located on the outermost side in the insert radial direction of the rake face 2. In other words, the corner 2a is the farthest from the insert central axis C among the rake face 2. When the rake face 2 is regarded as a parallelogram, the corner 2a is disposed at the end of the rake face 2 in the direction (longitudinal direction) in which the longer diagonal of the two diagonals extends.

[0038] A pair of corners 2a are provided on the rake face 2. The pair of corners 2a are disposed at both longitudinal ends of the rake face 2. As shown in Fig. 1, in the state where the cutting insert 1 is attached to the insert mounting seat, one of the pair of corners 2a is disposed at the tip end of the cutting insert 1 in the tool axis direction and also at the tip end of the ball end mill with replaceable cutting edge in the tool axis direction. The other corner 2a is located on the tool center axis O. The other of the pair of corners 2a is disposed at the rear end of the cutting insert 1 in the tool axis direction.

[0039] Further, the rake face 2 has a breaker groove 21. The breaker groove 21 is a groove that depresses from the rake face 2 to the other side in the insert axis direction. As shown in Fig. 1, in a plan view of the cutting insert 1 viewed from one side in the insert axis direction, the breaker groove 21 forms an annular shape surrounding the insert central axis C. Specifically, the breaker groove 21 extends along the outer shape of the rake face 2 and forms a substantially parallelogram shape.

[0040] As shown in Figs. 2 to 4, the seating surface 3 is disposed on the other plate surface (rear surface) of the pair of plate surfaces facing the insert axis direction of the cutting insert 1. The seating surface 3 faces the other side in the insert axis direction. The seating surface 3 is planar and extends in a direction perpendicular to the insert central axis C. In the state where the cutting insert 1 is attached to the insert mounting seat, the other plate surface and its seating surface 3 face the side opposite to the end mill rotation direction T, that is, the reverse end mill rotation direction. The seating surface 3 contacts the bottom surface of the insert mounting seat.

[0041] As shown in FIGS. 1 to 4, the boss surface 4 is disposed on one of the pair of plate surfaces (the front surface) facing the insert axial direction of the cutting insert 1. The boss surface 4 is disposed inside the insert diameter direction relative to the rake surface 2. The boss surface 4 protrudes on one side in the insert axial direction relative to the rake surface 2. The boss surface 4 has a planar shape extending in a direction perpendicular to the insert central axis C. The boss surface 4 and the seating surface 3 are parallel to each other. In the plan view shown in FIG. 1, the boss surface 4 has a substantially rhomboid shape.

[0042] As shown in FIGS. 2 to 4, the side surface 5 faces the outside in the insert diameter direction and is annular extending in the insert circumferential direction. The side surface 5 constitutes the outer peripheral surface of the cutting insert 1. One end in the insert axial direction of the side surface 5 is connected to the outer peripheral portion of the rake surface 2. The other end in the insert axial direction of the side surface 5 is connected to the outer peripheral portion of the seating surface 3.

[0043] The side surface 5 extends inward in the insert diameter direction as it goes toward the other side in the insert axial direction from the ridge line where the side surface 5 and the rake surface 2 are connected. Thereby, in a state where the cutting insert 1 is attached to the insert mounting seat, it becomes easy to provide a clearance angle between the machined surface of the workpiece and the side surface 5 during cutting, and the degree of freedom in the mounting posture of the cutting insert 1 to the holder increases. Each component provided on the side surface 5 will be described separately later.

[0044] The cutting edge portion 6 is disposed on the ridge line where the rake surface 2 and the side surface 5 are connected. The cutting edge portion 6 is located at the outer peripheral edge of the rake surface 2 and extends between the pair of corner portions 2a, 2a, and in the plan view shown in FIG. 1, it has a substantially J shape.

[0045] A pair of cutting edge portions 6 are provided on the ridge line (the outer peripheral edge of the rake surface 2). In a state where the cutting insert 1 is attached to the insert mounting seat, one of the pair of cutting edge portions 6 is disposed on the outer peripheral portion of the tip of the indexable ball end mill and serves as a cutting edge that cuts into the workpiece during cutting.

[0046] As shown in Fig. 1, the cutting edge portion 6 has an arcuate cutting edge portion 61 that forms a convex arc shape and a linear cutting edge portion 62 that forms a linear shape in a plan view when the cutting insert 1 is viewed from the direction facing the rake face 2.

[0047] The arcuate cutting edge portion 61 forms an arc shape that is convex toward the outside in the insert diameter direction in the plan view shown in Fig. 1. In this plan view, the radius of curvature R1 of the arcuate cutting edge portion 61 is larger than the outer dimension (width dimension) of the rake face 2 along the direction in which the shorter diagonal of the two diagonals extends (the short side direction) when the rake face 2 is regarded as a parallelogram. The center P of the radius of curvature R1 of the arcuate cutting edge portion 61 is located outside the rake face 2 in the insert diameter direction.

[0048] Also, in the state where the cutting insert 1 is attached to the insert mounting seat, the center P of the radius of curvature R1 of the arcuate cutting edge portion 61 of one of the pair of cutting edge portions 6 that is used for cutting is arranged on the tool center axis O.

[0049] Of the two ends of the arcuate cutting edge portion 61, one end 61a (the tip end 61a) is located at the corner portion 2a of the rake face 2. Of the two ends of the arcuate cutting edge portion 61, the other end 61b (the rear end 61b) is located in the middle portion between the corner portion 2a and the insert center axis C in the longitudinal direction of the rake face 2.

[0050] Of the two ends of the arcuate cutting edge portion 61 of one of the cutting edge portions 6, the tip end 61a is arranged on the tip side in the tool axis direction from the center P and is located on or near the tool center axis O. Also, of the two ends of the arcuate cutting edge portion 61 of one of the cutting edge portions 6, the rear end 61b is arranged away from the tool center axis O to the outside in the tool diameter direction. In the present embodiment, the rear end 61b and the center P are arranged at substantially the same position in the tool axis direction.

[0051] When the indexable ball end mill rotates around the tool center axis O, the rotation locus of the arcuate cutting edge portion 61 of one of the cutting edge portions 6 that is used for cutting forms a hemispherical shape centered on the center P. Also, as shown in FIGS. 2 and 3, when viewing the cutting insert 1 from the outside in the insert radial direction, the arc-shaped cutting edge portion 61 forms a curved shape that bulges toward one side in the insert axial direction.

[0052] As shown in FIG. 1, the linear cutting edge portion 62 is connected to the rear end portion 61b, which is different from the tip end portion 61a among both end portions of the arc-shaped cutting edge portion 61, so as to be in smooth contact. As shown in FIGS. 2 to 4, the linear cutting edge portion 62 extends toward the other side in the insert axial direction as it moves away from the connection point Q with the arc-shaped cutting edge portion 61 in the insert circumferential direction. Also, the blade length dimension of the linear cutting edge portion 62 is shorter than the blade length dimension of the arc-shaped cutting edge portion 61.

[0053] Also, in the state where the cutting insert 1 is attached to the insert mounting seat as shown in FIG. 1, among the pair of cutting edge portions 6, the linear cutting edge portion 62 of one of the cutting edge portions 6 used for cutting is arranged away from the tool center axis O toward the outside in the tool radial direction. This linear cutting edge portion 62 is located on the rear end side in the tool axial direction with respect to the center P.

[0054] When the insert tip exchangeable ball end mill rotates around the tool center axis O, the rotation locus of the linear cutting edge portion 62 of one of the cutting edge portions 6 used for cutting forms a cylindrical surface centered on the tool center axis O.

[0055] The ridge line portion 7 is arranged on the ridge line where the rake face 2 and the flank 5 are connected. The ridge line portion 7 is located at the corner portion 2a of the outer peripheral edge of the rake face 2. The ridge line portion 7 may be referred to as a small cutting edge or the like.

[0056] A pair of ridge line portions 7 are provided on the ridge line (outer peripheral edge of the rake face 2). The pair of ridge line portions 7 are arranged at the pair of corner portions 2a. In the state where the cutting insert 1 is attached to the insert mounting seat, one of the pair of ridge line portions 7 is arranged at the tip end portion of the cutting insert 1 in the tool axial direction and is also arranged at the tip end portion of the insert tip exchangeable ball end mill in the tool axial direction. The other of the pair of ridge line portions 7 is arranged at the rear end portion of the cutting insert 1 in the tool axial direction.

[0057] As shown in Fig. 5, in a plan view of the cutting insert 1 seen from the direction facing the scooping surface 2, the ridge line portion 7 has a first tip ridge line portion 71 that extends in a direction intersecting the tip portion 61a of the arc-shaped cutting edge portion 61 at an obtuse angle, and a second tip ridge line portion 72 that forms a convex arc shape with a smaller radius of curvature than the arc-shaped cutting edge portion 61 in this plan view.

[0058] The first tip ridge line portion 71 extends linearly in the plan view shown in Fig. 5. Also, as shown in Fig. 6, when the cutting insert 1 is viewed from the outside in the insert diameter direction, the first tip ridge line portion 71 has a convex shape that bulges toward one side in the insert axis direction.

[0059] Both end portions of the second tip ridge line portion 72 are connected to the tip portion 61a of the arc-shaped cutting edge portion 61 and the first tip ridge line portion 71. Specifically, the second tip ridge line portion 72 and the tip portion 61a of the arc-shaped cutting edge portion 61 are connected so as to be in smooth contact. Also, the second tip ridge line portion 72 and the first tip ridge line portion 71 are connected so as to form an obtuse angle with each other in the plan view shown in Fig. 5. Further, the length of the second tip ridge line portion 72 (corresponding to the cutting edge length dimension) is shorter than the length of the first tip ridge line portion 71.

[0060] In the plan view shown in Fig. 5, the symbol R2 represents the radius of curvature R2 of the second tip ridge line portion 72. In this plan view, the radius of curvature R1 of the arc-shaped cutting edge portion 61 and the radius of curvature R2 of the second tip ridge line portion 72 satisfy the relationship [R1 / R2 ≦ 12]. Note that the radius of curvature R1 of the arc-shaped cutting edge portion 61 may be read as the radius of curvature of the rotation locus of the arc-shaped cutting edge portion 61 when the cutting insert 1 is attached to a holder and rotated about the tool center axis O.

[0061] Further, among both end portions of the first tip ridge line portion 71, the other end portion 71b different from one end portion 71a connected to the second tip ridge line portion 72 is connected to the linear cutting edge portion 62. Specifically, the first tip ridge line portion 71 and the linear cutting edge portion 62 are connected so as to form an obtuse angle with each other in a plan view shown in FIG. 5. In this plan view, the angle θ of the obtuse angle formed between the first tip ridge line portion 71 and the linear cutting edge portion 62 is larger than the angle of the obtuse angle formed between the first tip ridge line portion 71 and the second tip ridge line portion 72. Specifically, in this plan view, the angle θ is, for example, 95° or more.

[0062] As shown in FIG. 1, the through hole 8 penetrates the cutting insert 1 in the insert axis direction. The through hole 8 extends in the insert axis direction inside the cutting insert 1 and opens to a pair of plate surfaces (front surface and back surface). Specifically, both end portions in the insert axis direction of the through hole 8 open to the boss surface 4 and the seating surface 3. The through hole 8 has a circular cross section perpendicular to the insert center axis C. The central axis of the through hole 8 is arranged coaxially with the insert center axis C.

[0063] A fastening member such as a clamp screw (not shown) is inserted into the through hole 8, and the male screw of this fastening member is screwed into the female screw of the screw hole of the insert mounting seat, so that the cutting insert 1 is detachably fixed to the insert mounting seat.

[0064] As shown in FIGS. 2 to 4, the groove portion 9 has a groove shape that is recessed from the seating surface 3 to one side in the insert axis direction. A pair of groove portions 9 are provided on the cutting insert 1. Although not particularly shown, in a plan view of the cutting insert 1 viewed from the direction facing the seating surface 3, the pair of groove portions 9 are arranged at positions opposite to each other with the through hole 8 interposed therebetween. In a state where the cutting insert 1 is attached to the insert mounting seat, a pair of rib portions of the insert mounting seat are inserted into the pair of groove portions 9.

[0065] Here, the components included in the side surface 5 will be described. The side surface 5 has an arc-shaped flank surface 51 continuous with the arc-shaped cutting edge portion 61, a straight-line flank surface 52 continuous with the straight-line cutting edge portion 62, a chamfer 53 continuous with the first tip ridge line portion 71, a convex curved surface 54 continuous with the second tip ridge line portion 72, a restraining surface 55, and a flat surface portion 56.

[0066] The arc-shaped flank surface 51 is disposed at one end of the side surface 5 in the insert axis direction and extends in the insert circumferential direction along the arc-shaped cutting edge portion 61. The arc-shaped flank surface 51 has a curved surface shape that is convex toward the outside in the insert diameter direction. Specifically, the arc-shaped flank surface 51 has a shape in which a cross section perpendicular to the insert central axis C is a curved line that is convex toward the outside in the insert diameter direction. In the present embodiment, since a pair of arc-shaped cutting edge portions 61 are provided on the cutting insert 1, a pair of arc-shaped flank surfaces 51 are also provided.

[0067] The straight-line flank surface 52 is disposed on the side surface 5 over the entire length in the insert axis direction. The straight-line flank surface 52 has a planar shape facing the outside in the insert diameter direction. In the present embodiment, since a pair of straight-line cutting edge portions 62 are provided on the cutting insert 1, a pair of straight-line flank surfaces 52 are also provided.

[0068] In a state where the cutting insert 1 is attached to the insert mounting seat, among the pair of straight-line flank surfaces 52, one straight-line flank surface 52 continuous with the straight-line cutting edge portion 62 of one cutting edge portion 6 to be used for cutting faces the outside in the tool diameter direction. Also, among the pair of straight-line flank surfaces 52, the other straight-line flank surface 52 continuous with the straight-line cutting edge portion 62 of the other cutting edge portion 6 not to be used for cutting contacts the side wall surface of the insert mounting seat.

[0069] As shown in FIGS. 4 and 6, the chamfer 53 is disposed at an end of at least one side in the insert axis direction among the sides 5. The chamfer 53 has a planar shape facing the outside in the insert diameter direction. Specifically, the chamfer 53 has a polygonal surface shape with the first tip ridge line portion 71 as one side. In the present embodiment, the chamfer 53 has a substantially inverted triangular surface shape with the first tip ridge line portion 71 as one side. The chamfer 53 decreases in dimension in the insert circumferential direction as it goes toward the other side in the insert axis direction.

[0070] In the present embodiment, the dimension H1 along the insert axis direction from the connection point S between the first tip ridge line portion 71 and the second tip ridge line portion 72 to the seating surface 3, and among the plurality of vertices of the polygonal surface of the chamfer 53, the dimension H2 along the insert axis direction from the vertex 53a located most on the other side in the insert axis direction to the seating surface 3 satisfy the relationship of [1 / 3 ≦ H2 / H1 ≦ 9 / 10].

[0071] The chamfer 53 is located between the straight cutting edge relief surface 52 and the convex curved surface 54 in the insert circumferential direction. Both ends of the chamfer 53 in the insert circumferential direction are connected to the straight cutting edge relief surface 52 and the convex curved surface 54 via ridge lines 57 and 58 described later.

[0072] Specifically, in the present embodiment, the chamfer 53 has a triangular surface shape and the chamfer 53 has three vertices (53a, 53b, S). The chamfer 53 is connected to the straight cutting edge relief surface 52 via a ridge line 57 connecting the vertex 53b located at the connection point between the first tip ridge line portion 71 and the linear cutting edge portion 62 and the vertex 53a.

[0073] The chamfer 53 is also connected to the convex curved surface 54 via a ridge line 58 connecting the vertex S located at the connection point between the first tip ridge line portion 71 and the second tip ridge line portion 72 and the vertex 53a.

[0074] In the present embodiment, along with the provision of a pair of first tip edge portions 71 on the cutting insert 1, a pair of chamfers 53 are also provided. In a state where the cutting insert 1 is attached to the insert mounting seat, one of the pair of chamfers 53 is disposed at the tip portion of the cutting insert 1 in the tool axis direction and is also disposed at the tip portion of the indexable ball end mill in the tool axis direction. The other of the pair of chamfers 53 is disposed at the rear end portion of the cutting insert 1 in the tool axis direction.

[0075] The convex curved surface 54 is disposed on the side surface 5 over the entire length in the insert axis direction. That is, the other end portion of the convex curved surface 54 in the insert axis direction reaches the ridge line where the side surface 5 and the seating surface 3 are connected. The convex curved surface 54 is formed to extend in the insert axis direction.

[0076] The convex curved surface 54 has a curved surface shape that is convex toward the outside in the insert diameter direction. Specifically, the convex curved surface 54 has a shape in which the cross-section perpendicular to the insert central axis C is a curved line that is convex toward the outside in the insert diameter direction.

[0077] The convex curved surface 54 is located between the arc edge relief surface 51 and the chamfer 53 in the insert circumferential direction. Both end portions of the convex curved surface 54 in the insert circumferential direction are connected to the arc edge relief surface 51 and the chamfer 53.

[0078] As shown in FIG. 6, among the convex curved surface 54, the portion (one-side portion) 54a located on the one-side in the insert axis direction with respect to the extension line EL obtained by extending the other end edge of the arc edge relief surface 51 in the insert axis direction toward the chamfer 53 is adjacent to the arc edge relief surface 51 and the chamfer 53 over the entire length in the insert axis direction. The one-side portion 54a of the convex curved surface 54 increases in dimension along the insert circumferential direction as it goes from the second tip edge portion 72 toward the other side in the insert axis direction.

[0079] Further, among the convex curved surfaces 54, the portion (the other-side portion) 54b located on the other side in the insert axis direction from the extension line EL has a dimension along the insert circumferential direction that decreases as it goes toward the other side in the insert axis direction from the extension line EL.

[0080] In the present embodiment, along with the provision of a pair of second tip ridge line portions 72 on the cutting insert 1, a pair of convex curved surfaces 54 are also provided. With the cutting insert 1 attached to the insert mounting seat, one of the pair of convex curved surfaces 54 is disposed at the tip portion of the cutting insert 1 in the tool axis direction and is also disposed at the tip portion of the indexable ball end mill in the tool axis direction. The other of the pair of convex curved surfaces 54 is disposed at the rear end portion of the cutting insert 1 in the tool axis direction.

[0081] As shown in FIG. 3, the restraining surface 55 is disposed at the end portion on the other side in the insert axis direction of the side surface 5. The restraining surface 55 is disposed on the other side in the insert axis direction of the arc-edge relief surface 51, and specifically, it is disposed adjacent to the other side in the insert axis direction of one end portion connected to the convex curved surface 54 among both end portions in the insert circumferential direction of the arc-edge relief surface 51. The restraining surface 55 has a planar shape facing the outside in the insert radial direction. A pair of restraining surfaces 55 are provided on the side surface 5.

[0082] With the cutting insert 1 attached to the insert mounting seat, one of the pair of restraining surfaces 55 faces the tip side in the tool axis direction of the indexable ball end mill. The other of the pair of restraining surfaces 55 contacts the rear wall surface of the insert mounting seat.

[0083] As shown in FIGS. 4 and 6, the flat portion 56 is disposed at the end portion on the other side in the insert axis direction of the side surface 5. The flat portion 56 is disposed adjacent to the chamfer 53 on the other side in the insert axis direction of the chamfer 53. Further, the flat portion 56 is disposed adjacent to the convex curved surface 54 (the other-side portion 54b thereof) in the insert circumferential direction. The flat portion 56 has a planar shape facing the outside in the insert radial direction. The flat portion 56 extends in the insert axis direction and has a rectangular shape elongated in the insert axis direction in the present embodiment.

[0084] The flat portion 56 is continuous with the end portion on the other side in the insert axis direction of the ridge line 58 that constitutes one of the three sides (71, 57, 58) of the chamfer 53. That is, the flat portion 56 is connected to the chamfer 53 via the ridge line 58. A pair of flat portions 56 are provided on the side surface 5.

[0085] In a state where the cutting insert 1 is attached to the insert mounting seat, one of the pair of flat portions 56 is disposed at the tip portion of the cutting insert 1 in the tool axis direction and is also disposed at the tip portion of the indexable ball end mill in the tool axis direction. The other of the pair of flat portions 56 is disposed at the rear end portion of the cutting insert 1 in the tool axis direction.

[0086] When a pair of cutting inserts are attached to the pair of insert mounting seats of the holder, one of the pair of cutting inserts functions as a parent cutting edge, and the other functions as a sub cutting edge. The tip portion 61a of the arc-shaped cutting edge portion 61 of the parent cutting edge is disposed near the tool center axis O. The tip portion 61a of the arc-shaped cutting edge portion 61 of the sub cutting edge is disposed away from the tool center axis O to the outside in the tool diameter direction.

[0087] The cutting insert 1 of the present embodiment is, for example, the one of the cutting inserts that functions as a parent cutting edge. Also, the other cutting insert that functions as a sub cutting edge has a configuration different from that of the cutting insert 1 of the present embodiment.

[0088] However, it is not limited to this, and the pair of cutting inserts (parent cutting edge, sub cutting edge) attached to the holder may be common products having the same shape as each other. In this case, each cutting insert does not have to be a 180° rotationally symmetric shape about the insert center axis C.

[0089] The cutting insert 1 of the present embodiment described above is disposed at the tip portion in the tool axis direction of a ball end mill with replaceable cutting edges, in a state of being attached to the insert mounting seat of the holder. The chamfer 53 and the convex curved surface 54 on the side surface 5 of the cutting insert 1 face the tip side in the tool axis direction. When machining the periphery of the surface of the workpiece including the built-up weld material along a tool path along a concave curved surface of a mold or the like by this ball end mill while descending or ascending the inclined surface of the mold, the axial cutting depth and the radial cutting depth are likely to vary, and thus the cutting load may increase. As a result, there is a tendency that chipping is likely to occur particularly at the tip portion of the cutting insert 1. However, according to the cutting insert 1 of the present embodiment, the following excellent effects can be obtained.

[0090] That is, in the present embodiment, a chamfer 53 is formed at the portion of the side surface 5 of the cutting insert 1 that is located at the foremost end in the tool axis direction. By this chamfer 53, it is possible to suppress defects and the like that are likely to occur in the edge portion and the like of the side surface in a conventional cutting insert.

[0091] Further, a convex curved surface 54 is formed at the portion of the side surface 5 of the cutting insert 1 that is located at the foremost end in the tool axis direction. This convex curved surface 54 is located between the arc-shaped flank face 51 and the chamfer 53. Further, the second tip ridge line portion 72 continuous with the convex curved surface 54 is disposed between the tip portion 61a of the arc-shaped cutting edge portion 61 continuous with the arc-shaped flank face 51 and the first tip ridge line portion 71 continuous with the chamfer 53, and connects these.

[0092] For example, different from the present embodiment, when the tip portion 61a of the arc-shaped cutting edge portion 61 and the first tip ridge line portion 71 are directly connected, a sharp edge portion is likely to be formed at the connection boundary between the arc-shaped flank face 51 and the chamfer 53, and there is a risk that the side surface 5 is likely to be chipped. On the one hand, in the present embodiment, a second leading edge line portion 72 is disposed between the tip portion 61a of the arc-shaped cutting edge portion 61 and the first leading edge line portion 71, and a convex curved surface 54 is interposed between the arc-shaped flank 51 and the chamfer 53. Therefore, due to the convex curved surface 54, the arc-shaped flank 51 adjacent to the convex curved surface 54 and the chamfer 53 are smoothly connected, so that sharp edge portions are less likely to be formed at the connection boundary between the arc-shaped flank 51 and the chamfer 53, and chipping of the arc-shaped cutting edge portion 61 can be suppressed.

[0093] Note that the side surface 5 including the convex curved surface 54 is preferably a ground surface rather than a sintered surface (unfinished surface). By making the convex curved surface 54 a ground surface, it becomes possible to more smoothly connect the arc-shaped flank 51 and the chamfer 53, and chipping of the arc-shaped cutting edge portion 61 can be suppressed.

[0094] As described above, according to the present embodiment, the chamfer 53 and the convex curved surface 54 provided on the side surface 5 of the cutting insert 1 can suppress the chipping that was likely to occur at the tip portion and the arc-shaped cutting edge portion 61 of the cutting insert 1 during cutting in the prior art.

[0095] Also, in the present embodiment, a portion 54a of the convex curved surface 54, which is located on one side in the insert axis direction with respect to an extension line EL extending the edge on the other side in the insert axis direction of the arc-shaped flank 51 toward the chamfer 53, is adjacent to the chamfer 53 over the entire length in the insert axis direction. Among the side surfaces 5 of the cutting insert 1, wear, chipping, etc. are particularly likely to occur near the cutting edge (near the end on one side in the insert axis direction). According to the above configuration of the present embodiment, both of the above-described effects of the chamfer 53 and the convex curved surface 54 can be stably obtained near the cutting edge of the side surface 5.

[0096] In this embodiment, the dimension along the insert axis direction from the connection point S between the first tip ridge line portion 71 and the second tip ridge line portion 72 to the seating surface 3 is defined as H1, and among the plurality of vertices of the polygonal surface of the chamfer 53, the dimension along the insert axis direction from the vertex 53a located on the other side in the insert axis direction to the seating surface 3 is defined as H2, and the relationship of [1 / 3 ≦ H2 / H1 ≦ 9 / 10] is satisfied.

[0097] If the value of H2 / H1 is 1 / 3 or more, it is possible to suppress the chamfer 53 from extending too long on the other side in the insert axis direction. It is possible to prevent a situation where the side surface 5 is excessively cut by the chamfer 53 (the inclination of the chamfer 53 becomes too steep), making it easy to cause defects.

[0098] Also, if the value of H2 / H1 is 9 / 10 or less, the chamfer 53 can be stably formed near the cutting edge (near the first tip ridge line portion 71). The above-described effects of the chamfer 53 are stably achieved.

[0099] In this embodiment, in a plan view of the cutting insert 1 seen from the direction facing the rake face 2, the radius of curvature of the arc-shaped cutting edge portion 61 is defined as R1, and the radius of curvature of the second tip ridge line portion 72 is defined as R2, and the relationship of [R1 / R2 ≦ 12] is satisfied.

[0100] If the value of R1 / R2 is 12 or less, it is possible to suppress the radius of curvature R2 of the second tip ridge line portion 72 from becoming too small. Also, in the convex curved surface 54 continuous with the second tip ridge line portion 72, it is possible to suppress the radius of curvature of the convex curve appearing in the cross section perpendicular to the insert central axis C from becoming too small. Since the second tip ridge line portion 72 and the arc-shaped cutting edge portion 61 are smoothly connected, the defect of the arc-shaped cutting edge portion 61 is suppressed.

[0101] In this embodiment, the chamfer 53 is located between the straight cutting edge relief surface 52 and the convex curved surface 54. In this case, it becomes difficult to form a sharp edge portion such as the boundary line between the chamfer 53 and the straight cutting edge relief surface 52, and it is possible to smoothly connect the straight cutting edge relief surface 52 and the chamfer 53, suppressing the defect of the straight cutting edge portion 62.

[0102] Further, in the present embodiment, in a plan view of the cutting insert 1 viewed from the direction facing the scooping surface 2, since the angle θ formed between the first tip ridge line portion 71 and the linear cutting edge portion 62 is an obtuse angle, chipping at the tip portion of the cutting insert 1 can be suppressed. Further, the angle θ is larger than the obtuse angle formed between the first tip ridge line portion 71 and the second tip ridge line portion 72. In this case, during cutting, the strength near the connection boundary between the chamfer 53 and the linear flank 52, which is likely to be a fracture initiation point or a chipped portion, can be stably increased.

[0103] Further, in the present embodiment, the angle θ2 formed between the chamfer 53 and the seating surface 3 is substantially perpendicular. In other words, the chamfer 53 and the insert central axis C are substantially parallel. According to the present embodiment, it is possible to prevent a situation where chipping is likely to occur due to an increase in the inclination of the chamfer 53 (the chamfer 53 is greatly inclined with respect to the insert central axis C). The angle θ2 is preferably 80° or more and 100° or less, and FIG. 1 illustrates an aspect where the angle θ2 is 90°.

[0104] The present invention is not limited to the above-described embodiments. For example, as described below, modifications such as changes in configuration are possible without departing from the spirit of the present invention.

[0105] In the above-described embodiment, an example is given in which the chamfer 53 has a triangular planar shape with the first tip ridge line portion 71 as one side, but the present invention is not limited to this. Although not particularly shown, the chamfer 53 may have a polygonal planar shape with four or more sides with the first tip ridge line portion 71 as one side.

[0106] The present invention may combine the respective configurations described in the above-described embodiments and modifications without departing from the spirit of the present invention. Also, addition, omission, substitution, and other changes in configuration are possible. Further, the present invention is not limited by the above-described embodiments, etc., and is limited only by the scope of the claims.

Industrial Applicability

[0107] According to the cutting insert of the present invention, it is possible to suppress chipping at the tip and the arc-shaped cutting edge of the cutting insert. Therefore, it has industrial applicability.

Description of Signs

[0108] 1... Cutting insert, 2... Rake face, 2a... Corner, 3... Seating face, 5... Side face, 6... Cutting edge, 7... Ridge line, 51... Arc-edge relief face, 52... Straight-edge relief face, 53... Chamfer, 53a... Apex, 54... Convex curved surface, 54a... Portion, 61... Arc-shaped cutting edge, 61a... Tip, 61b... Rear end, 62... Straight-line cutting edge, 71... First tip ridge line, 72... Second tip ridge line, C... Insert center axis, EL... Extension line, H1, H2... Dimensions, P... Center of the radius of curvature of the arc-shaped cutting edge, S... Connection point, R1, R2... Radius of curvature, θ... Angle

Claims

1. A cutting insert centered on an insert central axis, a rake face facing one side in the insert axial direction; a seating surface facing the other side in the insert axial direction; A side surface facing outward in the insert radial direction and extending in the insert circumferential direction; A cutting edge portion and a ridge portion are disposed on a ridge line connecting the rake face and the side surface, The cutting edge portion has a convex arc-shaped cutting edge portion in a plan view of the cutting insert seen from a direction facing the rake face, The ridge portion is a first tip ridge portion extending in a direction intersecting at an obtuse angle with a tip portion located at a corner of the rake face among both ends of the arcuate cutting edge portion in the plan view; A second tip ridge line portion having a convex arc shape having a smaller radius of curvature than the arc-shaped cutting edge portion in the plan view, Both ends of the second tip ridgeline are connected to the tip of the arc-shaped cutting edge portion and the first tip ridgeline, The aspect is an arcuate cutting edge flank surface connected to the arcuate cutting edge portion; a chamfer connected to the first tip edge portion and having a polygonal surface shape with the first tip edge portion as one side; a convex curved surface connected to the second tip ridge portion, The convex curved surface is located between the arcuate cutting edge flank and the chamfer. Cutting insert.

2. a portion of the convex curved surface that is located on one side in the insert axial direction of the extension line of the other end edge of the arc-shaped cutting edge flank surface in the insert axial direction toward the chamfer is adjacent to the chamfer over the entire length in the insert axial direction; The cutting insert according to claim 1 .

3. a dimension along the insert axial direction from a connection point between the first tip ridge portion and the second tip ridge portion to the seating surface is defined as H1; A dimension along the insert axial direction from the apex located on the other side in the insert axial direction among the multiple apexes of the polygonal surface of the chamfer to the seating surface is defined as H2, The relationship of [1 / 3≦H2 / H1≦9 / 10] is satisfied. The cutting insert according to claim 1 or 2.

4. In the plan view, The radius of curvature of the arc-shaped cutting edge portion is R1, The radius of curvature of the second tip ridgeline portion is R2, The relationship of [R1 / R2≦12] is satisfied. The cutting insert according to claim 1 or 2.

5. The cutting edge portion has a linear shape in the plan view and includes a linear cutting edge portion connected to a rear end portion different from the tip end portion of both end portions of the arc-shaped cutting edge portion, The side surface has a straight cutting edge relief surface connected to the straight cutting edge portion, The cutting insert has a shape rotationally symmetrical by 180° about the insert central axis, The chamfer is located between the straight edge flank and the convex curved surface. The cutting insert according to claim 1 or 2.

6. In the plan view, an obtuse angle formed between the first tip ridge portion and the linear cutting edge portion is larger than an obtuse angle formed between the first tip ridge portion and the second tip ridge portion. The cutting insert according to claim 5 .

7. The angle between the chamfer and the seating surface is approximately perpendicular. The cutting insert according to claim 1 or 2.

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