Cutting insert and cutting tool

Abstract

A cutting insert according to the present application includes a rake face, a flank face, and a leading cutting edge. The leading cutting edge is formed by the ridge between the rake face and the flank face. The flank face includes a first flank face portion, a second flank face portion, a third flank face portion, and a fourth flank face portion. The third flank face portion is positioned opposite from the first flank face portion. The fourth flank face portion is positioned opposite from the second flank face portion. The leading cutting edge includes a first cutting edge portion. The first cutting edge portion is formed by the ridge between the rake face and the first flank face portion. The first cutting edge portion is linear. In the first cutting edge portion, the angle formed between the first flank face portion and the rake face exceeds 89° but is less than 91°. The angle formed between the second flank face portion and the rake face is less than 90°. The angle formed between the third flank face portion and the rake face exceeds 90°. The angle formed between the fourth flank face portion and the rake face exceeds 89° but is less than 91°.

Description

Cutting Insert and Cutting Tool

[0001] The present disclosure relates to a cutting insert and a cutting tool.

[0002] International Publication No. 2019 / 087496 (Patent Document 1) discloses a cutting insert having a rake face, a flank face, and a chamfer disposed between the rake face and the flank face.

[0003] International Publication No. 2019 / 087496

[0004] The cutting insert according to the present disclosure includes a rake face, a flank face, and a front cutting edge. The front cutting edge is formed by a ridge line between the rake face and the flank face. The flank face includes a first flank face portion, a second flank face portion, a third flank face portion, and a fourth flank face portion. The third flank face portion is located opposite to the first flank face portion. The fourth flank face portion is located opposite to the second flank face portion. The front cutting edge includes a first cutting edge portion. The first cutting edge portion is formed by a ridge line between the rake face and the first flank face portion. The first cutting edge portion is linear. In the first cutting edge portion, the angle formed by the first flank face portion with respect to the rake face is more than 89° and less than 91°. The angle formed by the second flank face portion with respect to the rake face is less than 90°. The angle formed by the third flank face portion with respect to the rake face is more than 90°. The angle formed by the fourth flank face portion with respect to the rake face is more than 89° and less than 91°.

[0005] Figure 1 is a schematic perspective view showing the configuration of a cutting insert according to the first embodiment. Figure 2 is a schematic plan view showing the configuration of a cutting insert according to the first embodiment. Figure 3 is a schematic perspective view showing the configuration of a cutting insert according to the first embodiment. Figure 4 is a schematic view showing a cross-section perpendicular to the tangent of the first cutting edge. Figure 5 is a schematic view showing a cross-section perpendicular to the tangent of the second cutting edge. Figure 6 is a schematic view showing a cross-section perpendicular to the tangent of the third edge. Figure 7 is a schematic view showing a cross-section perpendicular to the tangent of the fourth edge. Figure 8 is a schematic perspective view showing the configuration of a cutting tool according to the second embodiment. Figure 9 is a partially enlarged schematic plan view showing the configuration of a cutting tool according to the second embodiment. Figure 10 is a schematic front view showing the configuration of a cutting tool according to the second embodiment. Figure 11 is a partially enlarged schematic side view showing the configuration of a cutting tool according to the second embodiment. Figure 12 is a schematic view showing a machining method using the cutting tool according to the second embodiment. Figure 13 is a schematic perspective view showing the configuration of a cutting insert according to the third embodiment. Figure 14 is a schematic plan view showing the configuration of a cutting insert according to the third embodiment. Figure 15 is a schematic perspective view showing the configuration of a cutting tool according to the fourth embodiment. Figure 16 is a partially enlarged schematic plan view showing the configuration of a cutting tool according to the fourth embodiment. Figure 17 is a schematic front view showing the configuration of a cutting tool according to the fourth embodiment. Figure 18 is a partially enlarged schematic side view showing the configuration of a cutting tool according to the fourth embodiment. Figure 19 is a schematic diagram showing a machining method using the cutting tool according to the fourth embodiment. Figure 20 is a schematic plan view showing measurement points in the holder and the cutting insert, respectively.

[0006] [Problems this disclosure aims to solve] When performing a pull machining process, if the cutting resistance is high, there is a risk of chipping of the cutting edge. In addition, rotation of the cutting insert or lifting from the holder may occur, and there is a risk that the cutting insert may shift relative to the holder.

[0007] The object of this disclosure is to provide a cutting insert that reduces displacement relative to the holder while reducing defects. [Effects of this disclosure] According to this disclosure, it is possible to provide a cutting insert that reduces displacement relative to the holder while reducing defects. [Description of embodiments of this disclosure] First, embodiments of this disclosure will be listed and described.

[0008] (1) The cutting insert according to the present disclosure includes a rake face, a flank face, and a front cutting edge. The front cutting edge is formed by the ridge line between the rake face and the flank face. The flank face includes a first flank portion, a second flank portion, a third flank portion, and a fourth flank portion. The third flank portion is located opposite the first flank portion. The fourth flank portion is located opposite the second flank portion. The front cutting edge includes a first cutting edge portion. The first cutting edge portion is formed by the ridge line between the rake face and the first flank portion. The first cutting edge portion is linear. In the first cutting edge portion, the angle between the first flank portion and the rake face is greater than 89° and less than 91°. The angle between the second flank portion and the rake face is less than 90°. The angle between the third flank portion and the rake face is greater than 90°. The angle between the fourth flank face and the rake face is greater than 89° and less than 91°. This improves the strength of the cutting insert, and therefore reduces the loss of the front cutting edge when machining a workpiece using a cutting tool equipped with this cutting insert. In addition, rotation and lifting of the cutting insert from the holder are suppressed, and displacement from the holder is reduced.

[0009] (2) In the cutting insert according to (1) above, the front cutting edge may include a corner cutting edge portion, a raking edge portion, and a second cutting edge portion. The second cutting edge portion may be connected to the corner cutting edge portion. The second cutting edge portion may be composed of the ridge line between the rake face and the second relief face portion. The corner cutting edge portion may be curved. The raking edge portion may be positioned between the first cutting edge portion and the corner cutting edge portion. In this way, the surface roughness of the finished surface can be greatly improved during the drawing process. Therefore, a stable and good surface roughness can be obtained even in high-efficiency machining.

[0010] (3) The cutting insert according to (1) or (2) above may include a first bottom surface located opposite the rake face. The angle between the fourth flank surface and the first bottom surface may be the same as the angle between the first flank surface and the rake face. The angle between the third flank surface and the first bottom surface may be the same as the angle between the second flank surface and the rake face. The angle between the second flank surface and the first bottom surface may be the same as the angle between the third flank surface and the rake face. The angle between the first flank surface and the first bottom surface may be the same as the angle between the fourth flank surface and the rake face. In this way, the cutting insert can be used upside down.

[0011] (4) The cutting insert according to (3) above may include a rear cutting edge formed by the ridge line between the first bottom surface and the flank surface. In this way, the workpiece can be cut using not only the cutting edge members that make up the front cutting edge, but also the cutting edge members that make up the rear cutting edge, so that an economical cutting insert can be obtained.

[0012] (5) The cutting tool according to the present disclosure may comprise the cutting insert according to (2) above and a holder. The holder may be provided with a recess for restraining the cutting insert. The cutting insert may include a first bottom surface located opposite the rake face. The recess may have a second bottom surface facing the first bottom surface.

[0013] (6) In the cutting tool described in (5) above, the reference plane may be a plane that is parallel to the longitudinal direction of the holder and passes through the corner cutting edge portion. When viewed from the longitudinal direction, the first cutting edge portion may be positioned between the reference plane and the second bottom plane. When viewed from a direction perpendicular to the longitudinal direction, the second cutting edge portion may be positioned further from the second bottom plane than the reference plane when viewed from the second bottom plane. In this way, the cutting tool can be used to perform a pull operation on the outer circumferential surface of the workpiece.

[0014] (7) In the cutting tool described in (5) above, the reference plane may be a plane that is parallel to the longitudinal direction of the holder and passes through the corner cutting edge portion. When viewed from a direction perpendicular to the longitudinal direction, the first cutting edge portion may be positioned between the reference plane and the second bottom plane. When viewed from the longitudinal direction, the second cutting edge portion may be positioned further from the reference plane than the second bottom plane. In this way, the cutting tool can be used to perform a pull operation on the end face of the workpiece.

[0015] (8) In the case of a cutting tool according to any of (5) to (7) above, the recess may have a first restraining surface and a second restraining surface. The first restraining surface may be in contact with the third flank surface. The second restraining surface may be in contact with the fourth flank surface. The first restraining surface may be along the third flank surface. The second restraining surface may be along the fourth flank surface. In this way, rotation of the cutting insert and lifting from the holder are suppressed, and displacement relative to the holder is reduced.

[0016] (9) In the case of a cutting tool according to any of (5) to (8) above, the cutting insert may include a blade member and a base metal. The blade member may be attached to the base metal by brazing material. The blade member may be made of a cBN-based sintered body. The base metal may be made of cemented carbide.

[0017] (10) In the case of a cutting tool according to any of (5) to (9) above, the holder may be made of steel.

[0018] (11) A cutting tool relating to any of (5) to (10) above may be provided with a base plate. The base plate may be placed between the second bottom surface and the cutting insert. The base plate may be made of cemented carbide.

[0019] (12) In the case of a cutting tool according to any of (5) to (11) above, the cutting insert may be for turning. [Details of Embodiments of the Disclosure] A specific example of a cutting insert according to one embodiment of the Disclosure will be described below with reference to the drawings. In the following drawings, the same or corresponding parts will be given the same reference numerals, and their descriptions will not be repeated.

[0020] (First Embodiment) <Configuration of Cutting Insert> Figure 1 is a schematic perspective view showing the configuration of a cutting insert 100 according to the first embodiment. As shown in Figure 1, the cutting insert 100 according to the first embodiment has two blade members 1a and 1b and a base metal 2. The blade members 1a and 1b are attached to the base metal 2. Each of the blade members 1a and 1b is involved in cutting. The plan view shape of the base metal 2 is not particularly limited, but for example it is rhombic. The blade members 1a and 1b are joined to the acute corner portions of the base metal 2. The base metal 2 is made of, for example, cemented carbide or cermet. In the cutting insert 100 according to the first embodiment, the blade members 1a and 1b are joined to the acute corner portions of the base metal 2, but the entire cutting insert 100 may be formed from blade members.

[0021] A counterbore portion 4a is formed at the acute-angled corner of the base metal 2, where a part of the upper surface (second rake face portion 12) is partially recessed. The blade member 1a is attached to the base metal 2 at the counterbore portion 4a by a joining means such as brazing material.

[0022] The blade members 1a and 1b may be composed of a cBN-based sintered body, or of any of the following: a diamond-based sintered body, ceramics, cermet, or cemented carbide. The cBN-based sintered body is a sintered body containing 10 percent to 100 percent by volume of cBN (cubic boron nitride). The diamond-based sintered body is a sintered body containing 10 percent to 100 percent by volume of diamond. Ceramics include, for example, alumina (Al ２ O ３ ), silicon nitride (Si ３ N ４ ), or titanium carbide (TiC) ceramics. The cermet may be, for example, a nitride-based cermet or a carbide-based cermet.

[0023] The cutting insert 100 according to the first embodiment includes a rake face 10, a flank face 20, a first bottom face 30, and a front cutting edge 40. The first bottom face 30 is located opposite the rake face 10. The flank face 20 connects the rake face 10 and the first bottom face 30. The front cutting edge 40 is formed by the ridge line 50 between the rake face 10 and the flank face 20. The front cutting edge 40 is a part of the ridge line 50.

[0024] The ridge line 50 includes the front cutting edge 40, the first ridge line section 51, the second ridge line section 52, the third ridge line section 53, and the fourth ridge line section 54. The front cutting edge 40 includes the first cutting edge section 41, the second cutting edge section 42, the corner cutting edge section 43, and the sweeping edge section 44. The front cutting edge 40 is made from a blade member 1a. The first ridge line section 51, the second ridge line section 52, the third ridge line section 53, and the fourth ridge line section 54 are made from a base metal 2.

[0025] As shown in Figure 1, the first cutting edge portion 41 connects the scraping edge portion 44 and the first ridge portion 51. The second cutting edge portion 42 connects the corner cutting edge portion 43 and the second ridge portion 52. The corner cutting edge portion 43 connects the second cutting edge portion 42 and the scraping edge portion 44. The scraping edge portion 44 connects the first cutting edge portion 41 and the corner cutting edge portion 43. The scraping edge portion 44 is positioned between the first cutting edge portion 41 and the corner cutting edge portion 43.

[0026] The first ridge section 51 connects the first cutting edge section 41 and the fourth ridge section 54. The second ridge section 52 connects the second cutting edge section 42 and the third ridge section 53. The third ridge section 53 connects the second ridge section 52 and the fourth ridge section 54. The fourth ridge section 54 connects the first ridge section 51 and the third ridge section 53.

[0027] The scoop face 10 has a first scoop face portion 11 and a second scoop face portion 12. The first scoop face portion 11 is made of a blade member 1a. The second scoop face portion 12 is made of a base metal 2. A through hole 5 is formed in the second scoop face portion 12.

[0028] The relief surface 20 includes a first relief surface portion 21, a second relief surface portion 22, a third relief surface portion 23, a fourth relief surface portion 24, a corner relief surface portion 25, and a sweep relief surface portion 26. The third relief surface portion 23 is located opposite the first relief surface portion 21. The fourth relief surface portion 24 is located opposite the second relief surface portion 22.

[0029] The first relief surface 21 includes the first blade relief surface 21a and the first base metal relief surface 21b. The second relief surface 22 includes the second blade relief surface 22a and the second base metal relief surface 22b. The first blade relief surface 21a, the second blade relief surface 22a, the corner relief surface 25, and the trimming relief surface 26 are made from the blade member 1a. The first base metal relief surface 21b, the second base metal relief surface 22b, the third relief surface 23, and the fourth relief surface 24 are made from the base metal 2.

[0030] The first cutting edge portion 41 is formed by the ridge line 50 between the first rake face portion 11 of the rake face 10 and the first relief surface portion 21a of the first relief surface portion 21. The second cutting edge portion 42 is formed by the ridge line 50 between the first rake face portion 11 of the rake face 10 and the second relief surface portion 22a of the second relief surface portion 22. The corner cutting edge portion 43 is formed by the ridge line 50 between the first rake face portion 11 of the rake face 10 and the corner relief surface portion 25. The scraping edge portion 44 is formed by the ridge line 50 between the first rake face portion 11 of the rake face 10 and the scraping relief surface portion 26.

[0031] The first ridge section 51 is formed by the ridge 50 between the second rake face section 12 of the rake face 10 and the first base metal relief face section 21b of the first relief face section 21. The second ridge section 52 is formed by the ridge 50 between the second rake face section 12 of the rake face 10 and the second base metal relief face section 22b of the second relief face section 22. The third ridge section 53 is formed by the ridge 50 between the second rake face section 12 of the rake face 10 and the third relief face section 23. The fourth ridge section 54 is formed by the ridge 50 between the second rake face section 12 of the rake face 10 and the fourth relief face section 24.

[0032] The first blade relief surface 21a is connected to the scraping relief surface 26 and the first base metal relief surface 21b. The scraping relief surface 26 is connected to the first blade relief surface 21a and the corner relief surface 25. The corner relief surface 25 is connected to the scraping relief surface 26 and the second blade relief surface 22a. The second blade relief surface 22a is connected to the corner relief surface 25 and the second base metal relief surface 22b. The third relief surface 23 is connected to the second base metal relief surface 22b and the fourth relief surface 24. The fourth relief surface 24 is connected to the 23rd relief surface 23 and the first base metal relief surface 21b.

[0033] Figure 2 is a schematic plan view showing the configuration of the cutting insert 100 according to the first embodiment. The schematic plan view shown in Figure 2 shows the rake face 10 as viewed along a straight line perpendicular to the rake face 10.

[0034] As shown in Figure 2, the corner cutting edge portion 43 is curved when viewed along a straight line perpendicular to the rake face 10. The corner cutting edge portion 43 is curved so as to be convex outward. When viewed along a straight line perpendicular to the rake face 10, the radius of curvature of the corner cutting edge portion 43 is 0.2 mm or more and 2.4 mm or less. The radius of curvature of the corner cutting edge portion 43 may be 0.3 mm or more and 2.2 mm or less, 0.4 mm or more and 2.0 mm or less, or 0.6 mm or more and 1.8 mm or less.

[0035] As shown in Figure 2, when viewed along a straight line perpendicular to the scoop face 10, the shape of the scraping blade portion 44 is straight. When viewed along a straight line perpendicular to the scoop face 10, the shape of the scraping blade portion 44 may be curved. When the shape of the scraping blade portion 44 is curved, when viewed along a straight line perpendicular to the scoop face 10, the radius of curvature of the scraping blade portion 44 may be 10 mm or more and 100 mm or less, 20 mm or more and 90 mm or less, or 30 mm or more and 80 mm or less. On the other hand, if the radius of curvature of the scraping blade portion 44 is less than 5 mm, the surface roughness of the finished surface will not be significantly improved.

[0036] As shown in Figure 2, when viewed along a straight line perpendicular to the rake face 10, the shapes of the first cutting edge portion 41 and the second cutting edge portion 42 are straight. The length of the first cutting edge portion 41 is greater than the length of the second cutting edge portion 42. The length of the first cutting edge portion 41 may be 1.5 times or more the length of the second cutting edge portion 42, or it may be 2 times or more.

[0037] As shown in Figure 2, the shapes of the first ridge section 51, the second ridge section 52, the third ridge section 53, and the fourth ridge section 54 are all straight lines. The length of the first ridge section 51 is less than the length of the second ridge section 52. The length of the third ridge section 53 is the same as the length of the fourth ridge section 54. The length of the second ridge section 52 is less than the length of both the third ridge section 53 and the fourth ridge section 54.

[0038] A through hole 5 is formed in the second scoop face portion 12. The through hole 5 penetrates the base metal 2. The through hole 5 opens into both the scoop face 10 and the first bottom surface 30.

[0039] Figure 3 is a schematic perspective view showing the configuration of a cutting insert 100 according to the first embodiment. The schematic perspective view shown in Figure 3 shows the third relief surface 23 and the fourth relief surface 24 viewed from the opposite side of the blade member 1a as seen from the base metal 2. As shown in Figure 3, a counterbore 4b may be formed at the opposite position of the counterbore 4a (acute corner portion of the base metal 2) where the blade member 1a is located, by partially recessing a part of the lower surface (first bottom surface 30). The blade member 1b is located in the counterbore 4b. The blade member 1b is attached to the base metal 2 in the counterbore 4b by a joining means such as brazing material.

[0040] The blade member 1b includes the same configuration as the blade member 1a. Specifically, the cutting insert 100 according to the first embodiment includes a rear cutting edge 60. The rear cutting edge 60 is made of the blade member 1b. The rear cutting edge 60 includes a first cutting edge portion 61, a second cutting edge portion 62, a corner cutting edge portion 63, and a sweeping edge portion 64. The rear cutting edge 60 is made up of the ridge line between the first bottom surface 30 and the relief surface 20. The rear cutting edge 60 is part of the ridge line between the first bottom surface 30 and the relief surface 20.

[0041] The blade member 1b may be attached to the base metal 2 so that the cutting insert 100 is mirror-symmetrical. Specifically, when viewed along a straight line perpendicular to the rake face 10, a line passing through the center of the through-hole 5 and perpendicular to a line passing through a pair of acute-angle corner portions is defined as line segment A (see FIG. 2). When viewed along a straight line perpendicular to the rake face 10, the blade member 1a disposed in the chamfer portion 4a and the blade member 1b disposed in the chamfer portion 4b are arranged to be mirror-symmetrical with respect to the line segment A. In this way, not only the blade member 1a constituting the front cutting edge 40 but also the blade member 1b constituting the rear cutting edge 60 can be used to cut the workpiece 300. As a result, a cutting insert 100 with excellent economy can be attached to the holder 101.

[0042] In the cutting insert 100 according to the first embodiment, the number of blade members (number of corners) is 2, but it may be 1. That is, the blade member 1b may not be disposed in the chamfer portion 4b, and only the blade member 1a may be disposed in the chamfer portion 4a.

[0043] FIG. 4 is a schematic view showing a cross-section perpendicular to the tangent line of the first cutting edge portion 41. As shown in FIG. 4, the first relief face portion 21 extends along a direction perpendicular to the rake face 10. Specifically, in the first cutting edge portion 41, the angle (first angle θ1) formed by the first relief face portion 21 with respect to the rake face 10 is 90°. In the first cutting edge portion 41, the angle formed by the first relief face portion 21 with respect to the rake face 10 may be more than 89° and less than 91°, or may be 89.5° or more and 90.5° or less.

[0044] In the first relief face portion 21, the first blade relief face portion 21a and the first base metal relief face portion 21b are arranged on the same plane. Therefore, in the first ridge line portion 51, the angle formed by the first relief face portion 21 with respect to the rake face 10 is 90°.

[0045] FIG. 5 is a schematic view showing a cross-section perpendicular to the tangent line of the second cutting edge portion 42. As shown in FIG. 5, the second relief surface portion 22 is inclined inward with respect to a plane perpendicular to the rake face 10. Specifically, in the second cutting edge portion 42, the angle (second angle θ2) formed by the second relief surface portion 22 with respect to the rake face 10 is less than 90°. In the second cutting edge portion 42, the angle formed by the second relief surface portion 22 with respect to the rake face 10 may be 85° or less, or may be 80° or less.

[0046] In the second relief surface portion 22, the second blade relief surface portion 22a and the second base metal relief surface portion 22b are arranged on the same plane. Therefore, in the second ridge line portion 52, the angle (first angle θ1) formed by the second relief surface portion 21 with respect to the rake face 10 is less than 90°.

[0047] FIG. 6 is a schematic view showing a cross-section perpendicular to the tangent line of the third ridge line portion 53. As shown in FIG. 6, the third relief surface portion 23 is inclined outward with respect to a plane perpendicular to the rake face 10. Specifically, the angle (third angle θ3) formed by the third relief surface portion 23 with respect to the rake face 10 is greater than 90°. The angle formed by the third relief surface portion 23 with respect to the rake face 10 may be 95° or more, or may be 100° or more. The second angle θ2 and the third angle θ3 may be determined such that the value obtained by adding the third angle θ3 to the second angle θ2 is 180°.

[0048] FIG. 7 is a schematic view showing a cross-section perpendicular to the tangent line of the fourth ridge line portion 54. As shown in FIG. 7, the fourth relief surface portion 24 is along the direction perpendicular to the rake face 10. Specifically, the angle (fourth angle θ4) formed by the fourth relief surface portion 24 with respect to the rake face 10 is 90°. The angle formed by the fourth relief surface portion 24 with respect to the rake face 10 may be greater than 89° and less than 91°, or may be 89.5° or more and 90.5° or less.

[0049] The cutting insert 100 according to the first embodiment is configured to be mirror symmetric. From a different perspective, the fourth flank surface 24 as viewed from the first bottom surface 30 corresponds to the first flank surface 21 as viewed from the rake face 10. That is, the angle made by the fourth flank surface 24 with respect to the first bottom surface 30 is the same as the first angle θ1 (the angle made by the first flank surface 21 with respect to the rake face 10). The third flank surface 23 as viewed from the first bottom surface 30 corresponds to the second flank surface 22 as viewed from the rake face 10. That is, the angle made by the third flank surface 23 with respect to the first bottom surface 30 is the same as the second angle θ2 (the angle made by the second flank surface 22 with respect to the rake face 10). The second flank surface 22 as viewed from the first bottom surface 30 corresponds to the third flank surface 23 as viewed from the rake face 10. In other words, the angle between the second flank surface 22 and the first base surface 30 is the same as the third angle θ3 (the angle between the third flank surface portion 23 and the rake face 10). The first flank surface portion 21 as seen from the first base surface 30 corresponds to the fourth flank surface portion 24 as seen from the rake face 10. In other words, the angle between the first flank surface 21 and the first base surface 30 is the same as the fourth angle θ4 (the angle between the fourth flank surface portion 24 and the rake face 10).

[0050] (Second Embodiment) <Configuration of the Cutting Tool> Next, the cutting tool 200 according to the second embodiment will be described.

[0051] Figure 8 is a schematic perspective view showing the configuration of a cutting tool 200 according to the second embodiment. The cutting tool 200 according to the second embodiment includes a cutting insert 100 according to the first embodiment 1, a holder 101, a base plate 102, a pressing member 110, and a fastening screw 120. The holder 101 may be cylindrical or rectangular. The holder 101 is attached to the turret of a machine tool. The holder 101 may be made of steel such as chromium-molybdenum steel or die steel. The base plate 102 may be made of cemented carbide.

[0052] As shown in Figure 8, when the holder 101 is rectangular, the holder 101 has a first side surface 101a, a second side surface 101b, a third side surface 101c, a fourth side surface 101d, a first end surface 101e, and a second end surface 101f. The direction perpendicular to the first end surface 101e is defined as the X direction. The direction perpendicular to the first side surface 101a is defined as the Y direction. The direction perpendicular to the X and Y directions is defined as the Z direction. The longitudinal direction of the holder 101 is the X direction. The second end surface 101f is located opposite the first end surface 101e in the longitudinal direction (X direction) of the holder 101.

[0053] The first side surface 101a has a first upper surface region 101a1 and a second upper surface region 101a2. Viewed from the third side surface 101c, the second upper surface region 101a2 is located further away from the first upper surface region 101a1 in the Y direction. The second upper surface region 101a2 is connected to the second end surface 101f.

[0054] The second side surface 101b has a first side surface region 101b1 and a second side surface region 101b2. Viewed from the fourth side surface 101d, the second side surface region 101b2 is located further away in the Z direction than the first side surface region 101b1. The second side surface region 101b2 is connected to the second end surface 101f.

[0055] Recesses 103 are provided at the boundaries of the second end face 101f, the second upper surface region 101a2, and the second side surface region 101b2 to restrain the cutting insert 100. The cutting insert 100 and the base plate 102 are placed in the recesses 103. The cutting inserts 100 are stacked on top of the base plate 102.

[0056] Figure 9 is a partially enlarged schematic plan view showing the configuration of the cutting tool 200 according to the second embodiment. The partially enlarged schematic plan view shown in Figure 9 shows the cutting insert 100 viewed along a straight line (Y direction) perpendicular to the first side surface 101a. The cutting insert 100 is attached to the holder 101 using a retaining member 110. The retaining member 110 has a main body portion 112 and an insertion portion 111. The insertion portion 111 is inserted into the through hole 5 of the cutting insert 100. A mounting hole 113 is formed in the main body portion 112. A fastening screw 120 is inserted into the mounting hole 113. In this way, the retaining member 110 is fixed to the holder 101.

[0057] The first relief surface portion 21 is positioned along the second end face 101f. In other words, the first cutting edge portion 41 is positioned along the second end face 101f. The second relief surface portion 22 is positioned along the second side region 101b2. In other words, the second cutting edge portion 42 is positioned along the second side region 101b2.

[0058] Figure 10 is a schematic front view showing the configuration of the cutting tool 200 according to the second embodiment. The schematic front view shown in Figure 10 shows the cutting insert 100 as viewed along the longitudinal direction (X direction) of the holder 101. Figure 11 is a schematic side view showing a partially enlarged portion of the configuration of the cutting tool 200 according to the second embodiment. The schematic side view shown in Figure 11 shows the cutting insert 100 as viewed along the Z direction.

[0059] The recess 103 has a second bottom surface 103a, a first restraining surface 103b (see Figure 11), and a second restraining surface 103c (see Figure 10). The recess 103 is composed of the second bottom surface 103a, the first restraining surface 103b, and the second restraining surface 103c. The second bottom surface 103a is the surface facing the first bottom surface 30. The first restraining surface 103b is the surface in contact with the third relief surface 23. The first restraining surface 103b is connected to the second upper surface region 101a2, the second side surface region 101b2, the second bottom surface 103a, and the second restraining surface 103c. The second restraining surface 103c is the surface in contact with the fourth relief surface 24. The second restraining surface 103c is connected to the second upper surface region 101a2, the second end surface 101f, the second bottom surface 103a, and the second restraining surface 103c.

[0060] As shown in Figures 10 and 11, the cutting insert 100 is positioned in the recess 103 such that the first bottom surface 30 faces the second bottom surface 103a. A base plate 102 may be placed between the second bottom surface 103a and the first bottom surface 30.

[0061] As shown in Figure 11, the cutting insert 100 is positioned in the recess 103 such that the third relief surface 23 faces the first restraint surface 103b. In other words, when the cutting insert 100 is positioned in the recess 103, the first restraint surface 103b is aligned with the third relief surface 23. The angle (third angle θ3) between the third relief surface 23 and the rake face 10 is greater than 90°. Therefore, the angle between the first restraint surface 103b and the second upper surface region 101a2 may be less than 90°.

[0062] As shown in Figure 10, the cutting insert 100 is positioned in the recess 103 such that the fourth relief surface 24 faces the second restraint surface 103c. In other words, when the cutting insert 100 is positioned in the recess 103, the second restraint surface 103c is aligned with the fourth relief surface 24. The angle (fourth angle θ4) of the third relief surface 23 with respect to the rake face 10 is greater than 89° and less than 91°. Therefore, the angle of the second restraint surface 103c with respect to the second upper surface region 101a2 may be greater than 89° and less than 91°. If the fourth angle θ4 is 90°, the angle of the second restraint surface 103c with respect to the second upper surface region 101a2 may be 90°.

[0063] As shown in Figures 10 and 11, the reference plane A1 is a plane that is parallel to the longitudinal direction (X direction) of the holder 101 and passes through the corner cutting edge portion 43. The reference plane A1 may also be a plane perpendicular to the first end face 101e. As shown in Figure 10, when viewed from the X direction, the first cutting edge portion 41 is inclined inward. From a different viewpoint, when the cutting insert 100 is viewed from the longitudinal direction (X direction), the first cutting edge portion 41 is positioned between the reference plane A1 and the second bottom face 103a in the Y direction. When viewed from the X direction, the angle (fifth angle θ5) made by the first cutting edge portion 41 with respect to the reference plane A1 may be 5° or more, 7° or more, or 10° or more.

[0064] As shown in Figure 11, when viewed from the Z direction, the second cutting edge portion 42 is inclined outward. From a different perspective, when the cutting insert 100 is viewed from a direction perpendicular to the longitudinal direction (X direction) (Z direction), the second cutting edge portion 42 is positioned further away from the reference plane A1 in the Y direction when viewed from the second bottom surface 103a. When viewed from the Z direction, the angle (sixth angle θ6) made by the second cutting edge portion 42 with respect to the reference plane A1 may be 5° or more, 7° or more, or 10° or more.

[0065] Next, a machining method using the cutting tool 200 according to the second embodiment will be described. Figure 12 is a schematic diagram showing a machining method using the cutting tool 200 according to the second embodiment.

[0066] A cutting tool 200 to which a cutting insert 100 according to the first embodiment is attached is capable of pull machining on the outer circumferential surface 301 of the workpiece 300. The workpiece 300 has an outer circumferential surface 301. Pull machining according to the second embodiment is performed while moving the cutting insert 100 in a first feed direction D1. The first feed direction D1 is the direction toward the -Z direction. In pull machining, the workpiece 300 is machined using the first cutting edge portion 41. The outer circumferential surface 301 is parallel to the rotation axis X1 of the workpiece 300. That is, the first feed direction D1 is parallel to the rotation axis X1 of the workpiece 300. The workpiece 300 rotates around the rotation axis X1 in the rotation direction R1. Thus, the cutting insert 100 may also be for turning.

[0067] The first angle θ1 is 90°. Therefore, the strength of the cutting insert 100 during the pulling process is sufficiently ensured. In other words, even when machining the workpiece 300 using the cutting tool 200 to which the cutting insert 100 is attached, the chipping of the front cutting edge 40 as a cutting edge is reduced. Also, the third angle θ3 is greater than 90°. Therefore, even if the cutting resistance in the Y direction increases during the pulling process, the cutting insert 100 does not lift off the holder 101. Also, the fourth angle θ4 is 90°. In other words, when viewed from the Y direction, the fourth relief surface 24 is aligned perpendicular to the rotational direction of the cutting insert 100. Therefore, even if the cutting resistance increases during the pulling process, the cutting insert 100 does not rotate within the plane of the reference surface A1. In this way, the displacement of the cutting insert 100 relative to the holder 101 is reduced. Also, the second angle θ2 is less than 90°. Therefore, the second relief surface 22 is inclined inward with respect to a plane perpendicular to the rake face 10. As a result, the second relief surface 22 does not interfere with the end face 302 (see Figure 19) of the workpiece 300 when machining it. Also, when viewed from the X direction, the first cutting edge 41 is inclined inward. Therefore, the first cutting edge 41 can be brought into contact with the workpiece 300 for efficient pull machining.

[0068] The cutting insert 100 may be used to perform a pressing operation on the outer circumferential surface 301 of the workpiece 300. Pressing is a machining operation performed while moving the cutting insert 100 in the opposite direction to the first feed direction D1 (towards the Z direction). In pressing, the workpiece 300 is machined using the second cutting edge portion 42. When viewed from the Z direction, the second cutting edge portion 42 is inclined outward. Therefore, the second cutting edge portion 42 can be brought into contact with the workpiece 300 to perform pressing efficiently.

[0069] (Third Embodiment) <Configuration of the Cutting Tool> Next, the cutting insert 100 according to the third embodiment will be described. The cutting insert 100 according to the third embodiment differs from the cutting insert 100 according to the first embodiment mainly in that it is configured to be mirror-symmetric with respect to the cutting insert 100 according to the first embodiment, and is the same as the cutting insert 100 according to the first embodiment in other respects. The following description will focus on the configuration that differs from the cutting insert 100 according to the first embodiment.

[0070] Figure 13 is a schematic perspective view showing the configuration of the cutting insert 100 according to the third embodiment. The schematic perspective view shown in Figure 13 is mirror-symmetric with respect to the schematic perspective view of the cutting insert 100 shown in Figure 1. Figure 14 is a schematic plan view showing the configuration of the cutting insert 100 according to the third embodiment. The schematic plan view shown in Figure 14 is mirror-symmetric with respect to the schematic plan view of the cutting insert 100 shown in Figure 2.

[0071] Specifically, the cutting insert 100 according to the third embodiment is configured such that, when viewed along a straight line perpendicular to the rake face 10 in the cutting insert 100 according to the first embodiment, it is a surface that passes through a pair of acute-angled corners and is mirror-symmetric with respect to the surface that passes through the center of the through hole 5.

[0072] The relative magnitudes of the first angle θ1, second angle θ2, third angle θ3, and fourth angle θ4 in the third embodiment are the same as the relative magnitudes of the first angle θ1, second angle θ2, third angle θ3, and fourth angle θ4 in the first embodiment.

[0073] (Fourth Embodiment) <Configuration of the Cutting Tool> Next, the cutting tool 200 according to the fourth embodiment will be described. The cutting tool 200 according to the fourth embodiment differs from the cutting tool 200 according to the second embodiment mainly in that the cutting insert 100 according to the third embodiment is attached to the holder 101, and in other respects it is the same as the cutting tool 200 according to the second embodiment. The following description will focus on the configuration that differs from the cutting tool 200 according to the fourth embodiment.

[0074] Figure 15 is a schematic perspective view showing the configuration of a cutting tool 200 according to the fourth embodiment. The cutting tool 200 according to the fourth embodiment includes a cutting insert 100 according to the second embodiment 1, a holder 101, a base plate 102, a pressing member 110, and fastening screws 120.

[0075] Figure 16 is a partially enlarged schematic plan view showing the configuration of the cutting tool 200 according to the fourth embodiment. The partially enlarged schematic plan view shown in Figure 16 shows the cutting insert 100 as viewed along a straight line (Y direction) perpendicular to the first side surface 101a.

[0076] As shown in Figure 16, the first relief surface 21 is positioned along the second side region 101b2. In other words, the first cutting edge 41 is positioned along the second side region 101b2. The second relief surface 22 is positioned along the second end face 101f. In other words, the second cutting edge 42 is positioned along the second end face 101f.

[0077] Figure 17 is a schematic front view showing the configuration of the cutting tool 200 according to the fourth embodiment. The schematic front view shown in Figure 17 shows the cutting insert 100 as viewed along the longitudinal direction (X direction) of the holder 101. Figure 18 is a schematic side view showing a partially enlarged portion of the configuration of the cutting tool 200 according to the fourth embodiment. The schematic side view shown in Figure 18 shows the cutting insert 100 as viewed along the Z direction.

[0078] As shown in Figure 18, in the cutting tool 200 according to the fourth embodiment, the first restraining surface 103b is a surface that contacts the fourth relief surface 24. As shown in Figure 17, in the cutting tool 200 according to the fourth embodiment, the second restraining surface 103c is a surface that contacts the third relief surface 23.

[0079] In other words, as shown in Figure 18, the cutting insert 100 is positioned in the recess 103 such that the fourth relief surface 24 faces the first restraint surface 103b. When the cutting insert 100 is positioned in the recess 103, the first restraint surface 103b is aligned with the fourth relief surface 24. The angle (fourth angle θ4) that the fourth relief surface 24 makes with respect to the rake face 10 is greater than 89° and less than 91°. Therefore, the angle that the first restraint surface 103b makes with respect to the second upper surface region 101a2 may be greater than 89° and less than 91°. If the fourth angle θ4 is 90°, the angle that the first restraint surface 103b makes with respect to the second upper surface region 101a2 may be 90°.

[0080] As shown in Figure 17, the cutting insert 100 is positioned in the recess 103 such that the third relief surface 23 faces the second restraint surface 103c. In other words, when the cutting insert 100 is positioned in the recess 103, the second restraint surface 103c is aligned with the third relief surface 23. The angle (third angle θ3) between the third relief surface 23 and the rake face 10 is greater than 90°. Therefore, the angle between the second restraint surface 103c and the second upper surface region 101a2 may be less than 90°.

[0081] As shown in Figures 17 and 18, the reference plane A2 is a plane that is parallel to the longitudinal direction (X direction) of the holder 101 and passes through the corner cutting edge portion 43. The reference plane A2 may also be a plane perpendicular to the first end face 101e. As shown in Figure 18, when viewed from the Z direction, the first cutting edge portion 41 is inclined inward. From a different perspective, when viewing the cutting insert 100 along the direction perpendicular to the longitudinal direction (X direction) (Z direction), the first cutting edge portion 41 is positioned between the reference plane A2 and the second bottom face 103a in the Y direction. When viewed from the Z direction, the angle (seventh angle θ7) made by the first cutting edge portion 41 with respect to the reference plane A2 may be 5° or more, 7° or more, or 10° or more.

[0082] As shown in Figure 17, when viewed from the X direction, the second cutting edge portion 42 is inclined outward. From a different perspective, when viewing the cutting insert 100 along the longitudinal direction (X direction), the second cutting edge portion 42 is positioned further away from the reference plane A2 in the Y direction when viewed from the second bottom surface 103a. When viewed from the X direction, the angle (eighth angle θ8) made by the second cutting edge portion 42 with respect to the reference plane A2 may be 5° or more, 7° or more, or 10° or more.

[0083] Next, a machining method using the cutting tool 200 according to the fourth embodiment will be described. Figure 19 is a schematic diagram showing a machining method using the cutting tool 200 according to the fourth embodiment.

[0084] A cutting tool 200 to which a cutting insert 100 according to the fourth embodiment is attached is capable of pull machining on the end face 302 of the workpiece 300. The workpiece 300 has an end face 302. The pull machining according to the fourth embodiment is performed while moving the cutting insert 100 in a second feed direction D2. The second feed direction D2 is the direction toward the -X direction. In the pull machining, the workpiece 300 is machined using the first cutting edge portion 41. The end face 302 is perpendicular to the rotation axis X2 of the workpiece 300. Therefore, the second feed direction D2 is perpendicular to the rotation axis X2 of the workpiece 300. The workpiece 300 rotates around the rotation axis X2 in the rotation direction R2. Thus, the cutting insert 100 may be configured to enable pull machining on the end face 302 of the workpiece 300.

[0085] Next, the effects of the cutting insert 100 and cutting tool 200 according to this embodiment will be described.

[0086] The cutting insert 100 according to this embodiment includes a rake face 10, a flank face 20, and a front cutting edge 40. The front cutting edge 40 is formed by the ridge line 50 between the rake face 10 and the flank face 20. The flank face 20 includes a first flank portion 21, a second flank portion 22, a third flank portion 23, and a fourth flank portion 24. The third flank portion 23 is located opposite the first flank portion 21. The fourth flank portion 24 is located opposite the second flank portion 22. The front cutting edge 40 includes a first cutting edge portion 41. The first cutting edge portion 41 is formed by the ridge line 50 between the rake face 10 and the first flank portion 21. The first cutting edge portion 41 is linear. At the first cutting edge portion 41, the angle (first angle θ1) between the first flank portion 21 and the rake face 10 is greater than 89° and less than 91°. The angle (second angle θ2) between the second flank portion 22 and the rake face 10 is less than 90°. The angle (third angle θ3) between the third flank portion 23 and the rake face 10 is greater than 90°. The angle (fourth angle θ4) between the fourth flank portion 24 and the rake face 10 is greater than 89° and less than 91°. In this way, the strength of the cutting insert 100 is improved, and even when machining the workpiece 300 using a cutting tool 200 to which the cutting insert 100 is attached, the chipping of the front cutting edge 40 as a cutting edge is reduced. In addition, rotation of the cutting insert 100 and lifting from the holder 101 are suppressed, and displacement from the holder 101 is reduced.

[0087] According to the cutting insert 100 of this embodiment, the front cutting edge 40 includes a corner cutting edge portion 43, a scavenging edge portion 44, and a second cutting edge portion 42. The second cutting edge portion 42 is connected to the corner cutting edge portion 43. The second cutting edge portion 42 is composed of a ridge line 50 between the rake face 10 and the second relief face portion 22. The corner cutting edge portion 43 is curved. The scavenging edge portion 44 is positioned between the first cutting edge portion 41 and the corner cutting edge portion 43. In this way, the surface roughness of the finished surface can be greatly improved during the drawing process.

[0088] The cutting insert 100 according to this embodiment includes a first bottom surface 30 located opposite the rake face 10. The angle between the fourth flank surface 24 and the first bottom surface 30 is the same as the angle between the first flank surface 21 and the rake face 10 (first angle θ1). The angle between the third flank surface 23 and the first bottom surface 30 is the same as the angle between the second flank surface 22 and the rake face 10 (second angle θ2). The angle between the second flank surface 22 and the first bottom surface 30 is the same as the angle between the third flank surface 23 and the rake face 10 (third angle θ3). The angle between the first flank surface 21 and the first bottom surface 30 is the same as the angle between the fourth flank surface 24 and the rake face 10 (fourth angle θ4). In this way, the cutting insert 100 can be used upside down.

[0089] The cutting insert 100 according to this embodiment includes a rear cutting edge 60 formed by the ridge line between the first bottom surface 30 and the relief surface 20. In this way, the workpiece 300 can be cut not only using the cutting member 1a that constitutes the front cutting edge 40, but also using the cutting member 1b that constitutes the rear cutting edge 60, thus providing an economical cutting insert 100.

[0090] According to the cutting tool 200 of this embodiment, the reference surface A1 is a surface that is parallel to the longitudinal direction (X direction) of the holder 101 and passes through the corner cutting edge portion 43. When viewed from the longitudinal direction (X direction), the first cutting edge portion 41 is positioned between the reference surface A1 and the second bottom surface 103a. When viewed from a direction perpendicular to the longitudinal direction (Z direction), the second cutting edge portion 42 is positioned further away from the reference surface A1 than the second bottom surface 103a. In this way, the cutting tool 200 can be used to perform a pull operation on the outer circumferential surface 301 of the workpiece 300.

[0091] According to the cutting tool 200 of this embodiment, the reference plane A2 is a surface that is parallel to the longitudinal direction (X direction) of the holder 101 and passes through the corner cutting edge portion 43. When viewed from a direction perpendicular to the longitudinal direction (Z direction), the first cutting edge portion 41 is positioned between the reference plane A2 and the second bottom surface 103a. When viewed from the longitudinal direction (X direction), the second cutting edge portion 42 is positioned further away from the reference plane A2 than the second bottom surface 103a. In this way, the cutting tool 200 can be used to perform a pull operation on the end face 302 of the workpiece 300.

[0092] According to the cutting tool 200 of this embodiment, the recess 103 has a first restraining surface 103b and a second restraining surface 103c. The first restraining surface 103b is in contact with the third relief surface 23. The second restraining surface 103c is in contact with the fourth relief surface 24. The first restraining surface 103b is along the third relief surface 23. The second restraining surface 103c is along the fourth relief surface 24. In this way, rotation of the cutting insert 100 and lifting from the holder 101 are suppressed, and displacement relative to the holder 101 is reduced.

[0093] <Examples> (Sample Preparation) Cutting inserts 100 (Samples 1 to 43) having the shapes described in Tables 1 to 4 were prototyped and cut evaluations were performed under the following conditions. In Tables 1 and 2, the first angle θ1, second angle θ2, third angle θ3, and fourth angle θ4 are shown from left to right.

[0094] The cutting inserts 100 of Samples 1 to 22 are examples. As shown in Table 1, in the cutting inserts 100 of Samples 1 to 22, the first angle θ1 is 90°, the second angle θ2 is less than 90°, the third angle θ3 is greater than 90°, and the fourth angle θ4 is 90°.

[0095] The cutting inserts 100 from samples 23 to 43 are comparative examples. As shown in Table 2, the first angle θ1 is 89° or less in the cutting inserts 100 from samples 23 to 25, samples 27 to 29, and samples 38 to 42. In the cutting inserts 100 from samples 26, 31, and 43, the first angle θ1 is greater than 90°. In the cutting inserts 100 from samples 30, 32 to 37, the second angle θ2 is 90°.

[0096]

[0097]

[0098] Tables 3 and 4 show the shape of the cutting edge and the number of corners from left to right. Note that in the cutting inserts 100 of Samples 1 to 43, the fifth angle θ5 is 6°. In the cutting inserts 100 of Samples 1 to 43, the sixth angle θ6 is -6°.

[0099] The cutting inserts 100 of samples 1 to 43 are mounted on the holder 101 as shown in Figures 10 and 11. As shown in Figure 10, when viewed from the X direction, the fifth angle θ5 is positive when the first cutting edge portion 41 is inclined inward. On the other hand, when viewed from the X direction, the fifth angle θ5 is negative when the first cutting edge portion 41 is inclined outward. As shown in Figure 11, when viewed from the Z direction, the sixth angle θ6 is negative when the second cutting edge portion 42 is inclined outward. On the other hand, when viewed from the Z direction, the sixth angle θ6 is positive when the second cutting edge portion 42 is inclined inward.

[0100] In the cutting inserts 100 of Samples 1 to 7 and Samples 17 to 43, the shape of the cleaning edge portion 44 is linear. In the cutting inserts 100 of Samples 14 to 16, there is no cleaning edge portion 44. In the cutting inserts 100 of Samples 8 to 13, the shape of the cleaning edge portion 44 is curved. In the cutting inserts 100 of Samples 8 to 10, the radius of curvature of the cleaning edge portion 44 is 5 mm. In the cutting inserts 100 of Samples 11 to 13, the radius of curvature of the cleaning edge portion 44 is 40 mm.

[0101] In the cutting inserts 100 of Samples 1 to 18, 27 to 29, 31 to 13, and 38 to 43, two cutting members 1a and 1b are attached to the base metal 2, resulting in two corners (see Figure 1). In the cutting inserts 100 of Samples 17 to 26 and 34 to 37, one cutting member 1a is attached to the base metal 2, resulting in one corner. In the cutting insert 100 of Sample 30, four cutting members are attached to the base metal 2, resulting in four corners. In the cutting inserts 100 of Samples 1 to 43, the material of the cutting members is a cBN-based sintered body.

[0102]

[0103]

[0104] (Processing Condition 1) With the cutting insert 100 attached to the holder 101, the outer circumferential surface 301 of the workpiece 300 was machined by drawing. The outer circumferential surface 301 was machined using the first cutting edge portion 41. The outer circumferential surface 301 was machined under high-efficiency conditions. (Workpiece) Chromium molybdenum steel SCM415H (HRC 58-60), diameter = 100 mm, length = 300 mm (Cutting conditions) Cutting speed: Vc = 200 m / min, feed rate: f = 0.6 mm / revolution, depth of cut: ap = 0.2 mm, wet (Processing Condition 2) With the cutting insert 100 attached to the holder 101, the end face 302 of the workpiece 300 was machined by drawing. The end face 302 was machined using the second cutting edge portion 42. The end face 302 was machined under normal efficiency conditions. (Workpiece material) Chromium molybdenum steel SCM415H (HRC 58-60), diameter = 100 mm, length = 50 mm (Cutting conditions) Cutting speed: Vc = 200 m / min, feed rate: f = 0.15 mm / revolution, depth of cut: ap = 0.2 mm, wet cutting (Processing conditions 3) With the cutting insert 100 attached to the holder 101, the outer circumferential surface 301 of the workpiece 300 was cut by drawing. The outer circumferential surface 301 was processed using the first cutting edge portion 41. The outer circumferential surface 301 was processed under high-efficiency conditions. (Workpiece material) Chromium molybdenum steel SCM415H (HRC 58-60), diameter = 100 mm, length = 300 mm (Cutting conditions) Cutting speed: Vc = 150 m / min, feed rate: f = 1.4 mm / revolution, depth of cut: ap = 0.4 mm, wet cutting (Test results) Tables 5 and 6 show the machining results when drawing was performed on the outer circumferential surface 301 and when drawing was performed on the end face 302. When drawing was performed on the outer circumferential surface 301, the displacement of the cutting insert 100, the fracture resistance of the first cutting edge portion 41, and the surface finish roughness were evaluated.

[0105] Regarding the fracture resistance of the first cutting edge portion 41, the amount of cutting edge detachment of the first cutting edge portion 41 after the outer circumference of the workpiece 300 had moved 10 km was evaluated. If the amount of cutting edge detachment of the first cutting edge portion 41 is 0.2 mm or less, the fracture resistance evaluation is A. If the amount of cutting edge detachment of the first cutting edge portion 41 exceeds 0.2 mm, the fracture resistance evaluation is B.

[0106] Regarding the displacement of the cutting insert 100, the displacement of the cutting insert 100 after the outer circumference of the workpiece 300 had moved 1 km was evaluated. Figure 20 is a schematic plan view showing measurement points P1 and P2 on the holder 101 and the cutting insert 100, respectively. The amount of displacement can be measured by measuring the difference in the X direction between measurement point P1 and measurement point P2 shown in Figure 20. The displacement of the cutting insert 100 was evaluated under the machining condition 3 described above.

[0107] The measurement point P1 is a point on the rake face 10 of the cutting insert 100. Specifically, the width W1 between the measurement point P1 and the corner cutting edge portion 43 in the Z direction is 2 mm. The distance L1 between the measurement point P1 and the corner cutting edge portion 43 in the X direction is 10 mm.

[0108] The measurement point P2 is a point on the first side surface 101a of the holder 101. Specifically, the width between the measurement point P2 and the corner cutting edge portion 43 in the Z direction is the same as the width W1 between the measurement point P1 and the corner cutting edge portion 43, which is 2 mm. The distance L2 between the measurement point P2 and the corner cutting edge portion 43 in the X direction is 20 mm.

[0109] Before machining the workpiece 300, the difference in height d1 in the X direction between measurement point P1 and measurement point P2 is calculated. Next, after machining the workpiece 300 (after the outer circumference of the workpiece 300 has moved 1 km), the difference in height d2 in the X direction between measurement point P1 and measurement point P2 is calculated. Measurements at measurement points P1 and P2 can be taken using a standard dial gauge (2109A-10) manufactured by Mitutoyo.

[0110] The displacement of the cutting insert 100 can be evaluated by the difference d3 in height between the difference d1 and the difference d2. If the difference d3 is less than 2 μm, the evaluation of the displacement of the cutting insert 100 is A. If the difference d3 is 2 μm or more, the evaluation of the displacement of the cutting insert 100 is B.

[0111] Regarding surface finish roughness, the surface roughness of the outer surface 301 of the workpiece 300 was evaluated after the outer circumference of the workpiece 300 had moved 0.1 km. Surface roughness was evaluated using the maximum height Rz. If the maximum height Rz is 10 μm or less, the surface finish roughness is evaluated as A. If the maximum height Rz exceeds 10 μm, the surface finish roughness is evaluated as B.

[0112] The fracture resistance of the second cutting edge portion 42 was evaluated when the end face 302 was machined. The fracture resistance of the second cutting edge portion 42 was evaluated by the amount of cutting edge detachment of the second cutting edge portion 42 after the end face of the workpiece 300 had moved 10 km. If the amount of cutting edge detachment of the second cutting edge portion 42 was 0.2 mm or less, the fracture resistance evaluation was A. If the amount of cutting edge detachment of the second cutting edge portion 42 was more than 0.2 mm, the fracture resistance evaluation was B.

[0113]

[0114]

[0115] As shown in Tables 5 and 6, when the cutting inserts 100 of Sample 1 to Sample 22 were used to perform a drawing process on the outer circumferential surface 301, the displacement of the cutting insert 100 and the fracture resistance of the first cutting edge portion 41 were evaluated as A. On the other hand, when the cutting inserts 100 of Sample 23 to Sample 43 were used to perform a drawing process on the outer circumferential surface 301, at least one of the displacement of the cutting insert 100 and the fracture resistance of the first cutting edge portion 41 were evaluated as B.

[0116] In particular, for the cutting inserts 100 of samples 23 to 25, where the first angle θ1 is 89° or less, the fracture resistance of the first cutting edge portion 41 was evaluated as B. Also, for the cutting inserts 100 of samples 26 and 31, where the first angle θ1 is 95°, the cutting resistance was high, and the displacement of the cutting insert 100 was evaluated as B. Furthermore, for the cutting inserts 100 of samples 27 to 30, 32 and 33, where the third angle θ3 is 90° or less, the displacement of the cutting insert 100 was evaluated as B. For the cutting inserts 100 of samples 34 to 36, where the fourth angle θ4 is less than 89°, the displacement of the cutting insert 100 was evaluated as B. For the cutting inserts 100 of samples 38 to 42, where the first angle θ1 is less than 89°, the fracture resistance of the first cutting edge portion 41 was B, and the displacement of the cutting insert 100 was evaluated as B. This is thought to be because the cutting resistance applied to the cutting insert 100 has increased.

[0117] When the outer circumferential surface 301 was subjected to a drawing process using the cutting insert 100 from sample 14, which does not have a finishing blade portion 43, to sample 16, the surface roughness of the outer circumferential surface 301 was evaluated as B.

[0118] The embodiments and examples disclosed herein should be considered in all respects to be illustrative and not restrictive. The scope of this disclosure is indicated by the claims rather than the embodiments described above, and all modifications within the scope are intended to be in the sense of equivalents of the claims.

[0119] 1a, 1b Blade member, 2 Base metal, 4a, 4b Counterbore section, 5 Through hole, 10 Rake face, 11 First rake face section, 12 Second rake face section, 20 Relief face, 21 First relief face section, 21a First blade relief face section, 21b First base metal relief face section, 22 Second relief face section, 22a Second blade relief face section, 22b Second base metal relief face section, 23 Third relief face section, 24 Fourth relief face section, 25 Corner relief face section, 26 Relief relief face section, 30 First bottom surface, 40 Front cutting edge, 41 First cutting edge section, 42 Second cutting edge section, 43 Corner cutting edge section, 44 Relief edge section, 50 Ridge, 51 First ridge section, 52 Second ridge section, 53 Third ridge section, 54 Fourth ridge section, 60 Rear cutting edge, 100 Cutting insert, 101 Holder, 101a First side surface, 101a1 First upper surface area, 101a2 Second upper surface area, 101b Second side surface, 101b1 First side surface area, 101b2 Second side surface area, 101c Third side surface, 101d Fourth side surface, 101e First end surface, 101f Second end surface, 102 Base plate, 103 Recess, 103a Second bottom surface, 103b First restraining surface, 103c Second restraining surface, 110 Pressing member, 111 Insertion part, 112 Main body part, 113 Mounting hole, 120 Fastening screw, 200 Cutting tool, 300 Workpiece, 301 Outer peripheral surface, 302 End surface, A1, A2 Reference surface, D1 First feed direction, D2 Second feed direction, R1, R2 Direction of rotation: X1, X2. Axis of rotation: θ1 (1st angle), θ2 (2nd angle), θ3 (3rd angle), θ4 (4th angle), θ5 (5th angle), θ6 (6th angle), θ7 (7th angle), θ8 (8th angle).

Claims

1. A cutting insert comprising a rake face, a flank face, and a forward cutting edge formed by the ridge line between the rake face and the flank face, wherein the flank face comprises a first flank portion, a second flank portion, a third flank portion located opposite the first flank portion, and a fourth flank portion located opposite the second flank portion, the forward cutting edge comprises a linear first cutting edge portion formed by the ridge line between the rake face and the first flank portion, the angle between the first flank portion and the rake face being greater than 89° and less than 91°, the angle between the second flank portion and the rake face being less than 90°, the angle between the third flank portion and the rake face being greater than 90°, and the angle between the fourth flank portion and the rake face being greater than 89° and less than 91°.

2. The cutting insert according to claim 1, wherein the front cutting edge includes a corner cutting edge portion, a scavenging edge portion, and a second cutting edge portion connected to the corner cutting edge portion, the second cutting edge portion being composed of the ridge line between the rake face and the second relief face portion, the corner cutting edge portion being curved, and the scavenging edge portion being positioned between the first cutting edge portion and the corner cutting edge portion.

3. The cutting insert according to claim 1 or 2, wherein the cutting insert includes a first bottom surface located opposite the rake face, the angle between the fourth flank face and the first bottom surface is the same as the angle between the first flank face and the rake face, the angle between the third flank face and the first bottom surface is the same as the angle between the second flank face and the rake face, the angle between the second flank face and the first bottom surface is the same as the angle between the third flank face and the rake face, and the angle between the first flank face and the first bottom surface is the same as the angle between the fourth flank face and the rake face.

4. The cutting insert according to claim 3, wherein the cutting insert includes a rear cutting edge formed by the ridge line between the first bottom surface and the relief surface.

5. A cutting tool comprising a cutting insert according to claim 2, and a holder provided with a recess for restraining the cutting insert, wherein the cutting insert includes a first bottom surface located opposite the rake face, and the recess has a second bottom surface facing the first bottom surface.

6. The cutting tool according to claim 5, wherein, with respect to a surface parallel to the longitudinal direction of the holder and passing through the corner cutting edge portion as the reference plane, when viewed from the longitudinal direction, the first cutting edge portion is positioned between the reference plane and the second bottom surface, and when viewed from a direction perpendicular to the longitudinal direction, the second cutting edge portion is positioned further from the second bottom surface than the reference plane.

7. The cutting tool according to claim 5, wherein, with respect to a surface parallel to the longitudinal direction of the holder and passing through the corner cutting edge portion as the reference plane, when viewed from a direction perpendicular to the longitudinal direction, the first cutting edge portion is positioned between the reference plane and the second bottom surface, and when viewed from the longitudinal direction, the second cutting edge portion is positioned further away from the second bottom surface than the reference plane.

8. The cutting tool according to any one of claims 5 to 7, wherein the recess has a first restraining surface in contact with the third relief surface and a second restraining surface in contact with the fourth relief surface, the first restraining surface is along the third relief surface and the second restraining surface is along the fourth relief surface.

9. The cutting tool according to any one of claims 5 to 8, wherein the cutting insert comprises a cutting member and a base metal to which the cutting member is attached by brazing material, the cutting member is made of a cBN-based sintered body, and the base metal is made of cemented carbide.

10. The cutting tool according to any one of claims 5 to 9, wherein the holder is made of steel.

11. The cutting tool according to any one of claims 5 to 10, comprising a base plate made of cemented carbide, disposed between the second bottom surface and the cutting insert.

12. The cutting tool according to any one of claims 5 to 11, wherein the cutting insert is for turning.

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