Cutting inserts and cutting tools

Abstract

Provided is a cutting insert, wherein even if one cutting portion is damaged, a tool body can fully hold the cutting insert. The cutting insert 10 has two side surfaces 20, 21 opposite to each other, a fixing hole 22 penetrating the centers of the two side surfaces 20, 21, and an outer peripheral surface 23 disposed between and connected to the outer peripheral edges of the two side surfaces 20, 21. The outer peripheral surface 23 has four cutting portions 50 to 53, a first outer peripheral surface portion 60 disposed between the first cutting portion 50 and the second cutting portion 51, and a second outer peripheral surface portion 61 opposed to the first outer peripheral surface portion 60 and disposed between the third cutting portion 52 and the fourth cutting portion 63. When the side surfaces 20, 21 are observed from the axial direction of the fixing hole 22, the first outer peripheral surface portion 60 and the second outer peripheral surface portion 61 have a shape with a central depression to approach the fixing hole 22, and an imaginary arc A1 having a diameter equal to a diameter D1 of a circumscribed circle A2 of the cutting insert 10 abuts against each outer peripheral surface portion 60, 61 at two locations.

Description

Technical Field

[0001] The invention relates to a cutting insert and a cutting tool. Background Art

[0002] In a cutting tool for turning a workpiece and grooving the inner peripheral surface of the workpiece, a tool body generally holds a cutting insert at its front end. As such a cutting tool, Patent Document 1 discloses a cutting insert having four cutting portions and corrugated projections and depressions formed on the outer peripheral surface forming the four cutting portions. The advantage of such a cutting insert is that four cutting portions can be used.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: (International Patent Application Entering Japan) Japanese Patent Application No. 2017-510469

[0006] Technical issues

[0007] However, in the above-mentioned cutting tool, the tool body contacts the cutting portion of the cutting blade to keep the cutting blade. Therefore, for example, if there is a cutting portion damaged, the tool body may not fully keep the cutting blade, and as a result, even if there is an unused cutting portion, the cutting blade may not be used.

[0008] The present invention has been made in view of this point, and an object of the present invention is to provide a cutting insert and a cutting tool in which a tool body can sufficiently hold the cutting insert even if one cutting portion is damaged. Summary of the invention

[0009] The cutting blade involved in one aspect of the present invention has two side surfaces opposite to each other, a fixing hole passing through the centers of the two side surfaces, and an outer peripheral surface arranged between and connected to the outer peripheral edges of the two side surfaces, the outer peripheral surface having four cutting parts, a first outer peripheral surface part arranged between a first cutting part and a second cutting part adjacent to each other among the four cutting parts, and a second outer peripheral surface part opposite to the first peripheral surface part and arranged between a third cutting part and a fourth cutting part adjacent to each other among the four cutting parts. When the side surfaces are observed from the axial direction of the fixing hole, the first outer peripheral surface part and the second outer peripheral surface part have a shape in which the center is recessed to approach the fixing hole, and an imaginary circular arc with a diameter the same as that of the circumscribed circle of the cutting blade abuts against each outer peripheral surface part at two locations.

[0010] According to the above aspect, the tool body can hold the cutting insert by contacting the contact portion other than the cutting portion of the cutting insert. As a result, even if one cutting portion is damaged, the tool body can still sufficiently hold the cutting insert.

[0011] In the above aspect, when the side surface is viewed from the axial direction of the fixing hole, the first outer peripheral surface portion and the second outer peripheral surface portion may be substantially V-shaped.

[0012] In the above aspect, the first outer peripheral surface portion and the second outer peripheral surface portion may have an opening angle of 130 degrees or more and 179 degrees or less.

[0013] In the above aspect, when two imaginary arcs with the same diameter as the circumscribed circle of the cutting blade are arranged to abut the first peripheral surface and the second peripheral surface respectively, the distance between the centers of the two imaginary arcs can be less than 150% of the diameter of the circumscribed circle of the cutting blade.

[0014] In the above aspect, the hole diameter of the fixing hole may be 30% or less of the diameter of the circumscribed circle of the cutting insert.

[0015] In the above aspect, the length of the cutting blade in the direction connecting the cutting edge of the first cutting part and the cutting edge of the fourth cutting part can be less than 70% of the diameter of the circumscribed circle of the cutting blade, and the length of the cutting blade in the direction connecting the cutting edge of the first cutting part and the cutting edge of the second cutting part can be less than 95% of the diameter of the circumscribed circle of the cutting blade.

[0016] In the above aspect, the clearance angle of the cutting portion may be 10 degrees or more.

[0017] In the above aspect, the side surface has a first part and a second part, the first part includes the side surface of the four cutting portions, the second part is located on the fixing hole side of the first part and protrudes to be relatively higher than the first part, the second part has an outer peripheral surface forming a second back cutting edge, and the back angle of the second back cutting edge can be greater than 5 degrees.

[0018] A cutting tool according to one aspect of the present invention includes the above-mentioned cutting insert and a tool body to which the cutting insert is fixed.

[0019] In the above aspect, the tool body may include a first holding portion and a second holding portion, wherein the first holding portion abuts against two locations of one of the first peripheral surface and the second peripheral surface, and the second holding portion abuts against one location of the other of the first peripheral surface and the second peripheral surface.

[0020] In the above aspect, the first holding portion may have a convex arc surface on the second holding portion side.

[0021] In the above aspect, the second holding portion may have a convex arc surface on the first holding portion side.

[0022] In the above aspect, the tool body has a threaded hole, and the cutting blade is fixed to the tool body by inserting a screw into the fixing hole and the threaded hole. When the front end of the cutting tool is observed from the axial front of the tool body, the center of the threaded hole of the tool body deviates from the center of the fixing hole of the cutting blade. The cutting blade can be fixed to the tool body by a screw. When the cutting edge of a cutting portion of the cutting blade in use and the center of the fixing hole are located on a horizontal line, the direction in which the center of the threaded hole of the tool body deviates from the center of the fixing hole of the cutting blade is 0 degrees relative to the vertical downward direction, or the direction in which the center of the threaded hole of the tool body deviates from the center of the fixing hole of the cutting blade can be a direction inclined toward the center side of the tool body within a range of less than 45 degrees.

[0023] In the above aspect, when the front end of the cutting tool is observed from the axial front side of the tool body, the cutting insert can be fixed to the tool body in the following manner, that is, the virtual straight line connecting the cutting edges of two diagonally located cutting parts among the four cutting parts is horizontal. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a perspective view showing an example of the cutting tool according to the present embodiment.

[0025] Figure 2 This is an enlarged view of the front end of the cutting tool.

[0026] Figure 3 It is a three-dimensional diagram of a cutting blade.

[0027] Figure 4 This is a side view as viewed from the axial direction of the fixing hole of the cutting insert.

[0028] Figure 5 This is a front view of the first peripheral surface portion or the second peripheral surface portion of the cutting insert.

[0029] Figure 6 This is a front view of the third peripheral surface portion or the fourth peripheral surface portion of the cutting insert.

[0030] Figure 7 It is a side view for explaining the distances L3 and L4 as seen from the axial direction of the fixing hole of the cutting insert.

[0031] Figure 8 It is a side view for explaining the angles α2 and α3, as seen from the axial direction of the fixing hole of the cutting insert.

[0032] Fig. 9It is a perspective view showing a fixing portion of a tool body.

[0033] Fig.10 This is the front view of the tool body.

[0034] Fig.11 This is a front view of a cutting tool in which a cutting insert is mounted on a tool body.

[0035] Fig.12 This is a front view of the cutting tool when in use.

[0036] Main component symbols

[0037] Cutting tools 1

[0038] Cutting blade 10

[0039] Tool body 11

[0040] Side 20, 21

[0041] Fixing hole 22

[0042] Outer surface 23

[0043] The first cutting part 50

[0044] Second cutting part 51

[0045] The third cutting part 52

[0046] Fourth cutting part 53

[0047] First peripheral surface 60

[0048] Second outer peripheral surface portion 61

[0049] Length direction X

[0050] Width direction Y

[0051] Axis Z

[0052] Imaginary arc A1

[0053] Abutment portion B DETAILED DESCRIPTION

[0054] Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings.

[0055] Figure 1 is a perspective view of an example of a cutting tool 1 according to the present embodiment. Figure 21 is an enlarged view of the front end of the cutting tool 1. For example, the cutting tool 1 is a tool for turning with replaceable inserts. The cutting tool 1 includes a cutting insert 10 and a tool body (holder) 11 to which the cutting insert 10 is fixed. The cutting insert 10 is fixed to the tool body 11 by a screw 12.

[0056] <Cutting inserts>

[0057] Figure 3 is a perspective view of the cutting insert 10 . Figure 4 It is a side view as viewed from the axial direction of the fixing hole of the cutting insert 10 . Figure 5 It is a front view of the first outer peripheral surface portion or the second outer peripheral surface portion of the cutting insert 10 . Figure 6 It is a front view of the third outer peripheral surface portion or the fourth outer peripheral surface portion of the cutting insert 10 .

[0058] like Figure 3 As shown, the cutting insert 10 has a three-dimensional shape, is generally rectangular and has thickness. The cutting insert 10 has two side surfaces 20, 21 opposite to each other, a fixing hole 22 penetrating the centers of the two side surfaces 20, 21, and an outer peripheral surface 23 disposed between and connected to the outer peripheral edges of the two side surfaces 20, 21.

[0059] The side surface 20 is substantially rectangular, and a circular fixing hole 22 is formed in the center thereof. Cutting portions 50 to 53 to be described later are located at the four corners of the side surface 20 .

[0060] The side surface 20 has a first portion 30 and a second portion 31. The first portion 30 is close to the four corners, and the second portion 31 is on the fixing hole 22 side of the first portion 30 and is located around the fixing hole 22. The second portion 31 protrudes to be relatively higher than the first portion 30. The second portion 31 is roughly rhombus-shaped, and its outer edge has four peripheral surfaces 40. Each peripheral surface 40 is a vertical surface that stands slightly perpendicular to the second portion 31 (along the axial direction Z of the fixing hole 22). In addition, in the direction perpendicular to the axial direction Z of the fixing hole 22, each peripheral surface 40 faces the cutting portion 50 to 53 side to be described later. The surface of the second portion 31 is, for example, a flat surface perpendicular to the axial direction Z of the fixing hole 22, and when the cutting insert 10 is mounted on the tool body 11, it abuts against the fixing bottom surface 100 of the tool body 11 to be described later.

[0061] The side surface 21 on the rear side of the side surface 20 has the same structure as the side surface 20. That is, the side surface 21 has a first portion 30 and a second portion 31 having four outer peripheral surfaces 40, similarly to the side surface 20.

[0062] The outer peripheral surface 23 has four cutting portions 50, 51, 52, 53 and four outer peripheral surface portions 60, 61, 62, 63. Figure 4As shown, the outer peripheral surface 23 has a shape that is symmetrical relative to the center line K1 and the center line K2, respectively, the center line K1 extends along the width direction Y passing through the center of the length direction X of the cutting blade 10 (the center C1 of the fixing hole 22), and the center line K2 extends along the length direction X passing through the center of the width direction Y of the cutting blade 10 (the center C1 of the fixing hole 22).

[0063] like Figure 3 and Figure 4 As shown, the outer peripheral surface 23 is around the central axis C1 of the fixing hole 22 ( Figure 3 and Figure 4 The first cutting portion 50 and the second cutting portion 51, the third cutting portion 52 and the fourth cutting portion 53 are adjacent to each other in the length direction X, and the second cutting portion 51 and the third cutting portion 52, the first cutting portion 50 and the fourth cutting portion 53 are adjacent to each other in the width direction Y.

[0064] The first cutting portion 50 has a rake face 70-1, a flank face 71-1, and a cutting edge 72-1, wherein a cross ridge is formed between the rake face 70-1 and the flank face 71-1, and the cutting edge 72-1 is formed on the cross ridge between the rake face 70-1 and the flank face 71-1. Furthermore, a cross ridge is formed between the side surface of the first cutting portion 50 and the rake face 70-1, and a cross ridge is formed between the side surface of the first cutting portion 50 and the flank face 71-1, and this part of the side surface of the first cutting portion 50 is the first part 30 of the side surfaces 20, 21.

[0065] Similar to the first cutting portion 50, the second cutting portion 51 has a rake face 70-2, a flank face 71-2, and a cutting edge 72-2. The cutting edge 72-1 of the first cutting portion 50 and the cutting edge 72-2 of the second cutting portion 51 are opposite to each other. That is, the rake face 70-1 of the first cutting portion 50 and the rake face 70-2 of the second cutting portion 51 are located on a surface facing the same direction (approximately the width direction Y), and the flank face 71-1 of the first cutting portion 50 and the flank face 71-2 of the second cutting portion 51 are located on a surface facing the opposite direction (approximately the length direction X).

[0066] The third cutting portion 52 has a rake face 70-3, a flank face 71-3, and a cutting edge 72-3, similarly to the first cutting portion 50. The fourth cutting portion 53 has a rake face 70-4, a flank face 71-4, and a cutting edge 72-4, similarly to the first cutting portion 50. The cutting edge 72-3 of the third cutting portion 52 and the cutting edge 72-4 of the fourth cutting portion 53 are opposite to each other. That is, the rake face 70-3 of the third cutting portion 52 and the rake face 70-4 of the fourth cutting portion 53 are located on a surface facing the same direction (approximately the width direction Y), and the flank face 71-3 of the third cutting portion 52 and the flank face 71-4 of the fourth cutting portion 53 are located on a surface facing the opposite direction (approximately the length direction X).

[0067] like Figures 3 to 5 As shown, the first peripheral surface 60 is located between the first cutting portion 50 and the second cutting portion 51 adjacent to each other in the length direction X, the second peripheral surface 61 is opposite to the first peripheral surface 60, and the second peripheral surface 61 is located between the third cutting portion 52 and the fourth cutting portion 53 adjacent to each other in the length direction X. Figure 3 , Figure 4 , Figure 6 As shown, the third outer peripheral surface 62 is located between the second cutting portion 51 and the third cutting portion 52 adjacent to each other in the width direction, and the fourth outer peripheral surface 63 is opposite to the third outer peripheral surface 62. The fourth outer peripheral surface 63 is located between the first cutting portion 50 and the fourth cutting portion 53 adjacent to each other in the width direction.

[0068] like Figures 3 to 5 As shown, the first outer peripheral surface portion 60 is formed between the rake face 70-1 of the first cutting portion 50 and the rake face 70-2 of the second cutting portion 51. Figure 3 and Figure 4 As shown, the first outer peripheral surface portion 60 has a shape in which the center of the length direction X is recessed to be close to the fixing hole 22. Figure 4 As shown, when the side surface 20 is viewed from the axial direction Z of the fixing hole 22, the first outer peripheral surface 60 is substantially V-shaped. The first outer peripheral surface 60 is configured so that when the imaginary arc A1 abuts against the first outer peripheral surface 60, there are two abutting portions B.

[0069] like Figures 3 to 5 As shown, the second outer peripheral surface portion 61 is formed between the rake face 70-3 of the third cutting portion 52 and the rake face 70-4 of the fourth cutting portion 53. Figure 3 and Figure 4 As shown, similar to the first peripheral surface 60, the second peripheral surface 61 has a shape in which the center of the longitudinal direction X is recessed to be close to the fixing hole 22, and is generally V-shaped. Figure 4As shown, the second outer peripheral surface 61 is configured so that when the imaginary arc A1 abuts the second outer peripheral surface 61, there will be two abutment portions B. The diameter of the imaginary arc A1 is the same as the diameter D1 of the circumscribed circle (the circle passing through the cutting edges of each cutting portion 50 to 53) A2 of the cutting insert 10. The imaginary arc A1 abuts against the concave surfaces of the first outer peripheral surface 60 and the second outer peripheral surface 61. The abutment portions B are closer to the center side than the outer ends 61 of the first outer peripheral surface 60 and the second outer peripheral surface 61.

[0070] The first outer peripheral surface portion 60 and the second outer peripheral surface portion 61 have an opening angle α1 of 130 degrees or more and 179 degrees or less. The opening angle α1 is preferably 140 degrees or more and 150 degrees or less.

[0071] Assuming that the diameter of the imaginary arc A1 is the same as the diameter D1 of the circumscribed circle (circle passing through the cutting edges of each cutting portion 50 to 53) A2 of the cutting insert 10, when the two imaginary arcs A1 abut against the first outer peripheral surface 60 and the second outer peripheral surface 61, respectively, the distance L1 between the centers O1 and O2 of the two imaginary arcs A1 is 150% or less of the diameter D1 of the circumscribed circle A2 of the cutting insert 10. Furthermore, the distance L1 is preferably 150% or less and 140% or more of the diameter D1 of the circumscribed circle A2, and more preferably 147% or less and 143% or more.

[0072] like Figure 3 , Figure 4 , Figure 6 As shown, the third outer peripheral surface 62 is formed between the flank surface 71-2 of the second cutting portion 51 and the flank surface 71-3 of the third cutting portion 52. For example, the third outer peripheral surface 62 has a flat surface 75 located at the center of the width direction Y, and an inclined surface 76 connecting the flank surfaces 71-2 and 71-3 from both ends of the flat surface 75. The fourth outer peripheral surface 63 is formed between the flank surface 71-1 of the first cutting portion 50 and the flank surface 71-4 of the fourth cutting portion 53. For example, the fourth outer peripheral surface 63 has a flat surface 75 located at the center of the width direction Y, and an inclined surface 76 connecting the flank surfaces 71-1 and 71-4 from both ends of the flat surface 75.

[0073] like Figure 7 As shown, the length L3 of the cutting insert 10 in the direction (width direction Y) connecting the cutting edge 72-1 of the first cutting portion 50 and the cutting edge 72-4 of the fourth cutting portion 53 is more than 70% and less than 75% of the length L4 of the cutting insert 10 in the direction (length direction X) connecting the cutting edge 72-1 of the first cutting portion 50 and the cutting edge 72-2 of the second cutting portion 51. Furthermore, the length L3 is also the distance between the cutting edge 72-1 of the first cutting portion 50 and the cutting edge 72-4 of the fourth cutting portion 53.

[0074] In addition, the length L4 of the length direction X of the cutting insert 10 is less than 95% of the diameter D1 of the circumscribed circle A2 of the cutting insert 10, preferably less than 95% and more than 85%. The length L3 of the width direction Y of the cutting insert 10 is less than 70% of the diameter D1 of the circumscribed circle A2 of the cutting insert 10, preferably less than 70% and more than 65%.

[0075] The hole diameter D2 of the fixing hole 22 is 30% or less of the diameter D1 of the circumscribed circle A2 of the cutting insert 10. The hole diameter D2 is preferably 28% or less and 20% or more of the diameter D1 of the circumscribed circle A2.

[0076] In addition, if Figure 8 As shown, the clearance angle α2 of the clearance surfaces 71-1, 71-2, 71-3, and 71-4 of the cutting portions 50 to 53 is not less than 10 degrees, and preferably not less than 10 degrees and not more than 15 degrees.

[0077] When the cutting edges of the cutting portions 50 to 53 enter the workpiece, the outer peripheral surface 40 of the second portion 31 of the side surfaces 20 and 21 can abut against the workpiece, thereby forming a second clearance face. The clearance angle α3 of the second clearance face of the outer peripheral surface 40 is greater than 5 degrees. The clearance angle α3 of the second clearance face is preferably greater than 5 degrees and less than 10 degrees.

[0078] <Tool body>

[0079] like Figure 1 As shown, the tool body 11 has a substantially cylindrical shape that is long in one direction, and a fixing portion 80 to which the cutting insert 10 is fixed is formed at the front end portion thereof.

[0080] Fig. 9 It is a perspective view showing the fixing portion 80 of the tool body 11 in a state where the cutting insert 10 is removed. Fig.10 This is a front view of the fixing portion 80 of the tool body 11 in a state where the cutting insert 10 is removed, as viewed from the axial direction Z1. Fig.10 The tool body 11 is the posture when it is fixed to the cutting machine tool during use. The up, down, left, and right in this specification are Fig.10 The posture of the tool body 11 shown is a reference.

[0081] like Fig. 9 and Fig.10 As shown, the fixing portion 80 of the tool body 11 includes, for example, a fixing bottom surface 100 that contacts the side surface 20 or the side surface 21 of the cutting insert 10 , and a first holding portion 101 and a second holding portion 102 that hold the outer peripheral surface 23 of the cutting insert 10 .

[0082] The fixing bottom surface 100 is, for example, a flat surface perpendicular to the axial direction Z1 (the direction of the central axis C2) of the tool body 11. The fixing bottom surface 100 is formed with a threaded hole 110 extending along the axial direction Z1 for screwing the screw 12. Fig.10 As shown, when observing the tool body 11 from the axial direction Z1, the threaded hole 110 is arranged at a position where its center C3 is located in the same horizontal plane (for example, slightly downward) as the center C2 of the tool body 11 in the vertical direction M and is offset to the right from the center C2 in the horizontal direction N.

[0083] like Fig. 9 and Fig.10 As shown, the first holding portion 101 and the second holding portion 102 protrude from the fixed bottom surface 100 toward the front end side. Fig.10 As shown, the first holding portion 101 is arranged on the lower side of the fixed bottom surface 100. The first holding portion 101 has an arc surface 111 which is slightly vertically erected relative to the fixed bottom surface 100 on the upper side of the fixed bottom surface 100. The arc surface 111 is convexly curved toward the upper right side of the fixed bottom surface 100. The arc surface 111 has a curved surface that is longer than the first peripheral surface portion 60 or the second peripheral surface portion 61 of the cutting insert 10.

[0084] The second holding portion 102 is disposed on the upper side of the fixed bottom surface 100. The second holding portion 102 has an arc surface 112 which is erected slightly perpendicularly to the fixed bottom surface 100 on the lower side of the fixed bottom surface 100. The arc surface 112 is convexly curved toward the oblique lower left side of the fixed bottom surface 100. The arc surface 112 has a curved surface which is shorter than the arc surface 111 of the first holding portion 101 and has a length of about half of the first outer peripheral surface portion 60 or the second outer peripheral surface portion 61 of the cutting insert 10.

[0085] <Cutting Tools>

[0086] Fig.11 It is a front view of the cutting tool 1 in a state where the cutting insert 10 is attached to the tool body 11 .

[0087] like Figure 2 and Fig.11 As shown, the cutting insert 10 is fixed to the tool body 11 by means of a screw 12 inserted into the fixing hole 22 and the threaded hole 110. In this example, the second cutting portion 51 of the four cutting portions 50 to 53 is used during cutting.

[0088] For example, the side surface 21 of the cutting insert 10 abuts against the fixed bottom surface 100 of the tool body 11, and the side surface 20 is exposed to the front. Fig.11As shown, the second peripheral surface 61 of the cutting insert 10 abuts against the arc surface 111 of the first holding portion 101 at two locations. At this time, the abutting portions of the second peripheral surface 61 are a portion P1 closer to the third cutting portion 52 side than the center of the second peripheral surface 61 in the longitudinal direction X and a portion P2 closer to the fourth cutting portion 53 side than the center of the longitudinal direction X. The rake face 70-3 of the third cutting portion 52 and the rake face 70-4 of the fourth cutting portion 53 near the center of the longitudinal direction X of the second peripheral surface 61 do not abut against the arc surface 111.

[0089] The first outer peripheral surface 60 of the cutting insert 10 abuts against the arc surface 112 of the second holding portion 102 at one place. At this time, the abutting portion of the first outer peripheral surface 60 is a portion P3 closer to the first cutting portion 50 than the center of the first outer peripheral surface 60 in the longitudinal direction X. The rake face 70-1 of the first cutting portion 50, the portion near the center of the first outer peripheral surface 60 in the longitudinal direction X and closer to the second cutting portion 51, and the rake face 70-2 of the second cutting portion 51 do not abut against the arc surface 112.

[0090] When viewed from the front in the axial direction Z1 of the tool body 11 Fig.11 When the front end of the cutting tool 1 is shown, the center C3 of the threaded hole 110 of the tool body 11 is slightly offset from the center C1 of the fixing hole 22 of the cutting insert 10. That is, the diameter of the screw 12 is slightly smaller than the diameter of the fixing hole 22, and the screw 12 is inserted into the threaded hole 110 in the fixing hole 22 from a position offset from the center C1 thereof. In a state where the cutting edge 72-2 of the second cutting portion 51 of the cutting insert 10 and the center C1 of the fixing hole 22 are located on the horizontal line H1, the direction in which the center C3 of the threaded hole 110 of the tool body 11 deviates from the center C1 of the fixing hole 22 of the cutting insert 10 is 0 degrees relative to the vertical downward direction H2, or the direction in which the center C3 of the threaded hole 110 of the tool body 11 deviates from the center C1 of the fixing hole 22 of the cutting insert 10 is a direction inclined toward the center C2 side of the tool body 11 at an angle α4 of less than 45 degrees. The angle α4 is preferably not less than 40 degrees and not more than 44 degrees.

[0091] In addition, when viewed from the front in the axial direction Z1 of the tool body 11 Fig.11 When the front end of the cutting tool 1 is shown, the cutting insert 10 can be fixed to the tool body 11 in the following manner, that is, the virtual straight line H1 connecting the cutting edges 72-2 and 72-4 of the second cutting portion 51 and the fourth cutting portion 53 located at opposite corners is horizontal (the set rake angle is 0 degrees).

[0092] The cutting tool 1 is used, for example, when grooving the inner peripheral surface of a workpiece. Fig.12As shown, when the cutting tool 1 is observed from the front, the cut piece 200 rotates clockwise around the rotation axis serving as the central axis, and the second cutting portion 51 of the cutting tool 1 advances to the right side of the horizontal direction N relative to the inner peripheral surface 201 of the cut piece 200, and the inner peripheral surface 201 of the cut piece 200 is grooved by the cutting edge 72-2.

[0093] Furthermore, when a cutting portion other than the second cutting portion 51 of the cutting insert 10 is used in a cutting process, Fig.11 The cutting insert 10 is rotated 180° around the center C1 of the fixing hole 22 and mounted on the tool body 11, so that the fourth cutting portion 53 can be used. At this time, the first peripheral surface 60 is held by the first holding portion 101 at two locations, and the second peripheral surface 61 is held by the second holding portion 102 at one location. Fig.11 The cutting insert 10 is turned over, with the side surface 21 as the surface, the first peripheral surface 60 is held by the first holding portion 101, and the second peripheral surface 61 is held by the second holding portion 102, so that the third cutting portion 52 can be used. In addition, the first cutting portion 50 can be used by rotating the cutting insert 10 by 180 degrees.

[0094] According to the present embodiment, the outer peripheral surface 23 of the cutting insert 10 has four cutting portions 50 to 53, a first outer peripheral surface 60 and a second outer peripheral surface 61, the first outer peripheral surface 60 and the second outer peripheral surface 61 have a shape with a central depression to approach the fixing hole 22, and an imaginary arc A1 having a diameter equal to the diameter D1 of the circumscribed circle A2 of the cutting insert 10 abuts at two locations with each outer peripheral surface 60, 61. Thus, the tool body 11 can abut on the abutment portion B of the portion other than the cutting portions 50 to 53 of the cutting insert 10 and hold the cutting insert 10, and as a result, even if one of the cutting portions is damaged, the tool body 11 can fully hold the cutting insert 10. In addition, the first peripheral surface portion 60 and the second peripheral surface portion 61 are constructed so that an imaginary arc A1 having a diameter equal to a diameter D1 of a circumscribed circle A2 of the cutting insert 10 abuts against each peripheral surface portion 60, 61 at two locations. This makes it easy to ensure the thickness of the cutting insert 10 in the width direction Y and the thickness of the first retaining portion 101 and the second retaining portion 102 of the tool body 11, thereby suppressing deformation and damage of the cutting insert 10 and the tool body 11.

[0095] When the side surfaces 20 and 21 are viewed from the axial direction Z of the fixing hole 22, the first outer peripheral surface 60 and the second outer peripheral surface 61 are substantially V-shaped. As a result, the tool body 11 can properly contact the contact portion B of the cutting insert 10 other than the cutting portions 50 to 53 and can be fully held.

[0096] The first peripheral surface portion 60 and the second peripheral surface portion 61 have an opening angle of greater than 130 degrees and less than 179 degrees, so it is easy to ensure the thickness of the cutting blade 10 in the width direction Y and the thickness of the first retaining portion 101 and the second retaining portion 102 of the tool body 11, thereby suppressing deformation and damage of the cutting blade 10 and the tool body 11.

[0097] When two imaginary arcs A1 having the same diameter as the diameter D1 of the circumscribed circle A2 of the cutting insert 10 are arranged to abut against the first outer peripheral surface 60 and the second outer peripheral surface 61, respectively, the distance L1 between the centers O1 and O2 of the two imaginary arcs A1 is less than 150% of the diameter D1 of the circumscribed circle A2 of the cutting insert 10. As a result, the opening angle α1 of the first outer peripheral surface 60 and the second outer peripheral surface 61 becomes larger, so it is easy to ensure the thickness of the cutting insert 10 in the width direction Y and the thickness of the first holding portion 101 and the second holding portion 102 of the tool body 11, and deformation and damage of the cutting insert 10 and the tool body 11 can be suppressed.

[0098] The hole diameter D2 of the fixing hole 22 may be 30% or less of the diameter D1 of the circumscribed circle A2 of the cutting insert 10 , so that the wall thickness around the fixing hole 22 of the cutting insert 10 can be ensured and the strength of the cutting insert 10 can be ensured.

[0099] The length L3 of the cutting insert 10 in the direction (width direction Y) connecting the cutting edge 72-1 of the first cutting portion 50 and the cutting edge 72-4 of the fourth cutting portion 53 is 70% or less of the diameter D1 of the circumscribed circle A2 of the cutting insert 10. In addition, the length L4 of the cutting insert 10 in the direction (length direction X) connecting the cutting edge 72-1 of the first cutting portion 50 and the cutting edge 72-2 of the second cutting portion 51 is 95% or less of the diameter D1 of the circumscribed circle A2 of the cutting insert 10. As a result, the length between the cutting edges of the cutting insert 10 is appropriate, and the abutment surface with respect to the tool body 11 can be fully ensured.

[0100] The clearance angle α2 of the cutting portions 50 to 53 may be greater than 10 degrees, and thus, can be used for small-diameter machining of a workpiece.

[0101] The second portion 31 of the side surfaces 20 and 21 has an outer peripheral surface 40 forming a second clearance face, and the clearance angle α3 of the second clearance face is 5 degrees or more. At this time, since the clearance angle of the second clearance face of the outer peripheral surface 40 is large enough, when the cutting parts 50 to 53 perform deeper groove processing, the outer peripheral surface 40 is prevented from contacting the workpiece. As a result, deeper groove processing can be performed by the cutting parts 50 to 53.

[0102] In the cutting tool 1, the tool body 11 has a first holding portion 101 and a second holding portion 102. The first holding portion 101 abuts against two locations of one of the first outer peripheral surface portion 60 and the second outer peripheral surface portion 61, and the second holding portion 102 abuts against one location of the other of the first outer peripheral surface portion 60 and the second outer peripheral surface portion 61. Therefore, the tool body 11 can properly hold the cutting insert 10 at three locations other than the cutting portions 50 to 53, and even if one cutting portion is damaged, the cutting insert 10 can be fully held.

[0103] The first holding portion 101 has a convex arc surface 111 on the second holding portion 102 side, and the second holding portion 102 has a convex arc surface 112 on the first holding portion 101 side. Therefore, the tool body 11 can appropriately hold the cutting insert 10 at three locations other than the cutting portions 50 to 53 .

[0104] like Fig.11 As shown, the center C3 of the threaded hole 110 of the tool body 11 deviates from the center C1 of the fixing hole 22 of the cutting insert 10, and the cutting insert 10 can be fixed to the tool body 11 by the screw 12. In a state where the cutting edge 72-2 of one cutting portion 52 of the cutting insert 10 in use and the center C1 of the fixing hole 22 are located on the horizontal line H1, the direction in which the center C3 of the threaded hole 110 of the tool body 11 deviates from the center C1 of the fixing hole 22 of the cutting insert 10 is 0 degrees relative to the vertical downward direction H2, or the direction in which the center C3 of the threaded hole 110 of the tool body 11 deviates from the center C1 of the fixing hole 22 of the cutting insert 10 is a direction inclined toward the center C2 side of the tool body 11 at an angle α4 of less than 45 degrees. At this time, the cutting insert 10 can be pressed against the first holding portion 101 side by the screw 12 and fixed. Therefore, the load in the rotation direction of the workpiece can be fully borne by the screw 12 and the first holding portion 101, and as a result, the load applied to the second holding portion 102 can be reduced. Therefore, the thickness of the second holding portion 102 can be reduced, and as a result, the protrusion amount (groove amount) of the cutting portion 52 to be used relative to the tool body 11 can be increased.

[0105] The cutting tool 1 is configured such that the cutting insert 10 can be fixed to the tool body 11 in such a manner that the virtual straight line H1 connecting the cutting edges 72-2 and 72-4 of the two cutting portions 51 and 53 located at opposite corners is horizontal when the front end of the cutting tool 1 is viewed from the axial front of the tool body 11. Therefore, in the cutting insert 10 having four cutting portions 50 to 53, the cutting edge of the second cutting portion 51 being used is made to protrude as much as possible from the tool body 11, and the groove amount can be fully ensured.

[0106] The preferred embodiments of the present invention are described above with reference to the accompanying drawings, but the present invention is not limited to these examples. Obviously, those skilled in the art can think of various changes or modifications within the scope of the concept described in the claims, and it should be understood that these naturally also belong to the technical scope of the present invention.

[0107] For example, the structure and shape of the cutting insert 10 and the tool body 11 are not limited to the above-mentioned embodiment. For example, the shape of the first peripheral surface 60 and the second peripheral surface 61 of the cutting insert 10 is not limited to the V-shape, and may be, for example, a U-shape. The present invention is applicable not only to turning cutting tools, but also to milling cutting tools.

[0108] Industrial Applicability

[0109] The present invention is used to provide a cutting insert and a cutting tool, wherein even if one cutting portion is damaged, the tool body can fully hold the cutting insert.

Claims

1. A cutting insert, comprising two side surfaces opposite to each other, a fixing hole penetrating the centers of the two side surfaces, and an outer peripheral surface disposed between and connected to the outer peripheral edges of the two side surfaces, The outer peripheral surface comprises four cutting portions, a first outer peripheral surface portion provided between a first cutting portion and a second cutting portion adjacent to each other among the four cutting portions, and a second outer peripheral surface portion opposite to the first outer peripheral surface portion and provided between a third cutting portion and a fourth cutting portion adjacent to each other among the four cutting portions. When the side surface is observed from the axial direction of the fixing hole, the first peripheral surface and the second peripheral surface have a shape with a center recessed to approach the fixing hole, and an imaginary arc having a diameter equal to a diameter of a circumscribed circle of the cutting insert abuts against the concave surface of the first peripheral surface at two locations and abuts against the concave surface of the second peripheral surface at two locations; When two imaginary arcs having the same diameter as the circumscribed circle of the cutting insert are arranged to abut against the first peripheral surface portion and the second peripheral surface portion respectively, the distance between the centers of the two imaginary arcs is less than 150% of the diameter of the circumscribed circle of the cutting insert.

2. The cutting insert according to claim 1, wherein When the side surface is viewed from the axial direction of the fixing hole, the first outer peripheral surface portion and the second outer peripheral surface portion are substantially V-shaped.

3. The cutting insert according to claim 1 or 2, wherein: The first outer peripheral surface portion and the second outer peripheral surface portion have an opening angle of not less than 130 degrees and not more than 179 degrees.

4. The cutting insert according to claim 1 or 2, wherein: The hole diameter of the fixing hole is less than 30% of the diameter of the circumscribed circle of the cutting insert.

5. The cutting insert according to claim 1 or 2, wherein: The length of the cutting insert in the direction connecting the cutting edge of the first cutting portion and the cutting edge of the fourth cutting portion is less than 70% of the diameter of the circumscribed circle of the cutting insert. The length of the cutting insert in a direction connecting the cutting edge of the first cutting portion and the cutting edge of the second cutting portion is 95% or less of a diameter of a circumscribed circle of the cutting insert.

6. The cutting insert according to claim 1 or 2, wherein: The back angle of the cutting portion is greater than 10 degrees.

7. The cutting insert according to claim 1 or 2, wherein: The side surface has a first portion and a second portion, the first portion includes the side surface of the four cutting portions, the second portion is located at the fixing hole side of the first portion and protrudes to be relatively higher than the first portion, The second portion has an outer peripheral surface forming a second relief surface, and the relief angle of the second relief surface is 5 degrees or more. 8 . A cutting tool comprising the cutting insert according to claim 1 and a tool body to which the cutting insert is fixed.

9. The cutting tool according to claim 8, wherein: The tool body includes a first holding portion and a second holding portion. The first holding portion abuts against two locations of one of the first peripheral surface and the second peripheral surface. The second holding portion abuts against one location of the other of the first peripheral surface and the second peripheral surface.

10. The cutting tool according to claim 9, wherein: The first holding portion has a convex arc surface on the second holding portion side.

11. The cutting tool according to claim 9, wherein: The second holding portion has a convex arc surface on the first holding portion side.

12. The cutting tool according to any one of claims 8 to 11, wherein The tool body has a threaded hole, The cutting insert is fixed to the tool body by a screw inserted into the fixing hole and the threaded hole, When observing the front end of the cutting tool from the axial front side of the tool body, the center of the threaded hole of the tool body deviates from the center of the fixing hole of the cutting insert. The cutting insert is fixed to the tool body by a screw. When the cutting edge of a cutting portion of the cutting insert in use and the center of the fixing hole are on a horizontal line, the direction in which the center of the threaded hole of the tool body deviates from the center of the fixing hole of the cutting insert is 0 degrees relative to the vertical downward direction, or the direction in which the center of the threaded hole of the tool body deviates from the center of the fixing hole of the cutting insert is in a direction inclined toward the center side of the tool body within a range of less than 45 degrees.

13. The cutting tool according to any one of claims 8 to 11, wherein: The cutting insert is fixed to the tool body in such a manner that a virtual straight line connecting cutting edges of two diagonally located cutting portions among the four cutting portions is horizontal when the front end of the cutting tool is viewed from the axial front side of the tool body.

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