Cutting tools

Abstract

The present invention provides a cutting tool that suppresses chip elongation even at low depths of cut, thereby stably improving chip breaking performance. [Solution] The cutting edge comprises a rake face 1, a relief face 2, a cutting edge 3 that forms a V shape in a plan view when the rake face 1 is viewed from the front, and projections 5 positioned on the rake face 1 and protruding from the rake face 1. The cutting edge 3 has a corner blade 3a and a pair of straight blades 3b. In a plan view, the direction in which the bisector B of the pair of straight blades 3b extends is defined as the front-back direction, the direction perpendicular to the bisector B in a plan view is defined as the left-right direction, and the direction perpendicular to the front-back direction and the left-right direction is defined as the up-down direction. Multiple projections 5 are provided spaced apart from each other in the blade length direction in which the cutting edge 3 extends. Each projection 5 has a chip contact surface 5a that extends upward as it moves radially inward from the corner blade 3a. The amount of projection of the chip contact surface 5a upward from the cutting edge 3 is greater for the projections 5 that are positioned further away from the bisector B in the blade length direction.

Description

Technical Field

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

Background Art

[0002] Conventionally, cutting tools such as cutting inserts used for turning (turning) a workpiece made of metal or the like are known (for example, Patent Documents 1 and 2). This type of cutting tool includes a rake face, a flank face, a cutting edge that is arranged at a ridge line portion where the rake face and the flank face are connected and forms a V shape in a plan view when the rake face is viewed from the front, and a protrusion that is arranged on the rake face and protrudes from the rake face.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] In a conventional cutting tool, when the depth of cut (ap) is small, for example, 0.3 mm or less, chips tend to elongate during turning. When the chips elongate, it is not preferable because they may get caught in the chuck of a lathe that holds the workpiece. Therefore, there is room for improvement particularly in stably improving chip breaking performance during low depth of cut.

[0005] An object of the present invention is to provide a cutting tool capable of suppressing elongation of chips even during low depth of cut and stably improving chip breaking performance.

Means for Solving the Problems

[0006] In order to solve the above problems, the present invention provides the following means.

[0007] [Aspect 1 of the present invention] The cutting edge comprises a rake face, a relief face, a cutting edge positioned on the ridge where the rake face and the relief face are connected and forming a V-shape in a plan view with the rake face facing forward, and a projection positioned on the rake face and protruding from the rake face, wherein the cutting edge has a convex curved corner blade and a pair of straight blades connected to both ends of the corner blade and each extending in a straight line, wherein the direction in which the bisector of the pair of straight blades extends in the plan view is the front-to-back direction, and the bisector and A cutting tool wherein, with the orthogonal directions defined as the left-right direction and the directions orthogonal to the front-rear direction and the left-right direction defined as the up-down direction, the projections are provided in multiples spaced apart from each other in the blade length direction in which the cutting edge extends, each projection has a chip contact surface that extends upward as it moves radially inward from the corner cutting edge, and the amount of projection of the chip contact surface that protrudes upward from the cutting edge is greater for the projections that are located further away from the bisector in the blade length direction among the multiple projections.

[0008] The cutting tool of the present invention is, for example, a cutting insert for an indexable cutting tool used in turning operations. This cutting tool has multiple protrusions on its rake face. These protrusions are spaced apart from each other in the direction of the cutting edge's blade length. The chip contact surface of each protrusion protrudes above the cutting edge and extends upward as it moves radially inward from the corner edge (i.e., as it approaches the center of the corner edge's radius of curvature). The amount of projection of the chip contact surface above the cutting edge increases as the protrusion is positioned further away from the bisector in the direction of the blade length.

[0009] When turning a workpiece using this cutting tool, the chips generated by the cutting edge come into contact with projections on the rake face. Specifically, the chips come into contact with the chip contact surface of the projections, and as a result, the shape of the projections is transferred to the chips, giving them a pseudo-thickness. In other words, the cross-section of the chips becomes curved, which effectively increases the overall thickness of the chips.

[0010] Here, as shown in equation (1) below, it is generally known that as the chip thickness increases, the chip fracture strain (which contributes to chip fragmentation) also increases. ε C <(1 / R0-1 / R C ) × h / 2 …(1) In the above equation (1), ε C R is the chip fracture strain, R0 is the chip curl diameter (end time), R C represents the chip curl diameter (initial), and h represents the chip thickness.

[0011] According to the present invention, even when the depth of cut (ap) is small, for example, 0.3 mm or less, the chip fragmentation performance can be improved by transferring a protruding shape to the chip and giving it a pseudo-thickness. Furthermore, by transferring the protruding shape, tensile stress is generated in the free surface (the surface that does not contact the tool) and the side surface (the edge of the chip) of the chip, making it easier for cracks to propagate. This also changes the fracture strain of the chip and lowers the chip fragmentation threshold, thereby improving chip fragmentation performance.

[0012] More specifically, in turning operations where the depth of cut is significantly smaller than 0.3 mm, thin chips are brought into contact with large protrusions positioned away from the bisector. This ensures that the protrusion shape is stably transferred to the chip, while simultaneously imparting a pseudo-chip thickness and improving chip breakability.

[0013] Furthermore, in turning operations where the depth of cut is close to 0.3 mm, for example, the chips are simultaneously brought into contact with multiple protrusions on the chip contact surface that have different protrusion amounts. In this case, the chips are given appropriate protrusion shapes to enhance their fragmentation ability, and the chips as a whole are released in a spiral twisting (curling) manner away from the machined surface of the workpiece. This suppresses contact between the chips and the machined surface and improves chip evacuation.

[0014] As described above, according to the present invention, even when the cutting depth is small, such as 0.3 mm or less, the elongation of the chip can be suppressed, and the chip breakability can be stably improved.

[0015] 〔Aspect 2 of the present invention〕 The cutting tool according to Aspect 1, wherein in a longitudinal cross-sectional view perpendicular to the cutting edge, the chip contact surface is linear.

[0016] In this case, the chip contact surface has a planar shape or a convex curved surface shape (conical surface shape) that gently curves along the cutting edge length direction, and has a simple structure. Therefore, when manufacturing the cutting tool, it is easy to form the chip contact surface by laser processing or the like. In addition, since there are no steps or the like provided on the chip contact surface, during turning, it is possible to suppress the chip that comes into contact with the chip contact surface from getting caught, and the above-described functions and effects according to the present invention are stably achieved.

[0017] 〔Aspect 3 of the present invention〕 The cutting tool according to Aspect 1 or 2, wherein in a longitudinal cross-sectional view perpendicular to the cutting edge, the angle at which the chip contact surface is inclined with respect to a virtual plane passing through the cutting edge and perpendicular to the vertical direction is 15° or more and 35° or less.

[0018] When the angle at which the chip contact surface is inclined is 15° or more, the protrusion shape can be stably transferred to the chip that contacts the chip contact surface. In addition, when the angle at which the chip contact surface is inclined is 35° or less, while suppressing the cutting resistance from becoming excessive and maintaining the sharpness of the cutting edge, the functions (functions and effects) by the protrusions are stably achieved.

[0019] 〔Aspect 4 of the present invention〕 The cutting tool according to any one of Aspects 1 to 3, wherein the plurality of protrusions include at least one radially extending protrusion along the radial direction of the corner edge in the plan view. <00​In this case, among the plurality of protrusions arranged in the blade length direction on the rake face, at least one radial protrusion is included. Since the radial protrusion extends in a direction perpendicular to the blade length direction of the corner blade in plan view (that is, the radial direction of the corner blade), the chip generated by the corner blade flows out along the radial protrusion. Thereby, the protrusion shape can be more stably transferred to the chip.

[0021] 〔Aspect 5 of the present invention〕 The cutting tool according to any one of Aspects 1 to 4, wherein the plurality of the protrusions include at least one inclined protrusion that extends inclined with respect to the radial direction of the corner blade in the plan view.

[0022] In this case, among the plurality of protrusions arranged in the blade length direction on the rake face, at least one inclined protrusion is included. With this inclined protrusion, for example, it becomes possible to control the outflow direction (discharge direction) of the chip, control the flow velocity and supply position of the coolant, and the like.

[0023] 〔Aspect 6 of the present invention〕 The cutting tool according to Aspect 5, wherein, in the plan view, the angle at which the inclined protrusion is inclined with respect to the radial direction of the corner blade is 30° or less.

[0024] When the angle at which the inclined protrusion is inclined is 30° or less, the temperature rise of the chip in contact with the inclined protrusion is suppressed. Since the temperature of the generated chip is kept low, the load acting on the cutting edge can be kept small, and the cutting edge rigidity can be maintained well.

[0025] 〔Aspect 7 of the present invention〕 The cutting tool according to any one of Aspects 1 to 6, wherein the distance between a predetermined pair of the protrusions adjacent to each other in the blade length direction among the plurality of the protrusions becomes smaller as it goes toward the outside in the radial direction of the corner blade.

[0026] In the above configuration, the distance between a predetermined pair of protrusions decreases as it moves radially outward from the corner cutting edge. When supplying coolant from the rake face toward the corner cutting edge, it becomes possible to increase the flow velocity of the coolant flowing radially outward between the protrusions as it approaches the corner cutting edge. For example, by positioning a portion of the corner cutting edge used for cutting, especially when the depth of cut is small (such as near the end of the corner cutting edge in the direction of its cutting edge), radially outward from the protrusions, the chip removal performance can be stably improved by the increased flow velocity of the coolant.

[0027] [Aspect 8 of the present invention] A cutting tool according to any one of embodiments 1 to 7, wherein the width dimension of the projection along the blade length direction is greater than the height dimension of the projection protruding upward from the cutting edge.

[0028] In this case, the width dimension of the projection along the blade length direction is greater than the height dimension of the projection protruding upward from the cutting edge, thus ensuring stable rigidity of the projection that comes into contact with the chips. Since damage to the projection is suppressed, the effects of the present invention described above are consistently achieved.

[0029] [Aspect 9 of the present invention] A cutting tool according to any one of embodiments 1 to 8, wherein the height dimension of the projection protruding upward from the cutting edge is greater than 0.05 mm and less than or equal to 0.15 mm.

[0030] If the height dimension of the protrusion is greater than 0.05 mm, the function (effect) of the protrusion can be obtained stably, and the shape of the protrusion can be stably imparted to the chips that come into contact with the protrusion. Furthermore, if the height dimension of the protrusion is 0.15 mm or less, problems such as chips that come into contact with the protrusion being unintentionally bounced off by the protrusion are suppressed. In other words, if the height dimension of the protrusion exceeds 0.15 mm, the protrusion functions as a simple wall surface, the chips are bounced off by the protrusion, and it may be difficult to transfer the protrusion shape to the chips. By setting the height dimension of the protrusion to 0.15 mm or less as in the above configuration, the protrusion shape can be stably imparted to chips that come into contact with the protrusion.

[0031] [Aspect 10 of the present invention] A cutting tool according to any one of embodiments 1 to 9, further comprising a first wall surface disposed on the rake face and protruding from the rake face, wherein the first wall surface is positioned radially inward of the projection on the rake face, and the distance from the cutting edge decreases as it moves away from the bisector in the blade length direction.

[0032] In this case, the first wall surface is positioned closer to the cutting edge as it moves away from the bisector along the blade length direction. Therefore, for example, during turning operations with a depth of cut of less than 0.3 mm, thin chips are brought into contact with large protrusions positioned away from the bisector before easily coming into contact with the first wall surface. Particularly at low depths of cut, chips with the shape of the protrusions transferred onto them can be stably brought into contact with the first wall surface, curled, and broken. This stably improves chip breaking performance.

[0033] [Aspect 11 of the present invention] The cutting tool according to embodiment 10, wherein the first wall surface has a protruding portion located at the left-right end of the first wall surface and inserted between a predetermined pair of adjacent protrusions in the blade length direction.

[0034] In this case, especially at low cutting depths, the chips with the imprinted protrusion shape can be stably brought into contact with the protruding portion of the first wall surface, curled, and then broken apart.

[0035] [Aspect 12 of the present invention] The cutting tool according to embodiment 10 or 11, further comprising a second wall surface adjacent to the first wall surface and positioned on the opposite side of the first wall surface from the cutting edge, wherein the second wall surface protrudes upward from the first wall surface and has a front wall facing forward.

[0036] In this case, for example, during turning with a depth of cut close to 0.3 mm, the chip is simultaneously brought into contact with multiple protrusions on the chip contact surface that have different protrusion amounts, and then overcomes the first wall surface and comes into contact with the front wall of the second wall surface. That is, the chip, with the shape of the protrusions transferred onto it, can be stably brought into contact with the second wall surface, curled, and broken apart. This makes it possible to stably improve chip breaking performance.

[0037] [Aspect 13 of the present invention] A cutting tool according to any one of embodiments 1 to 12, wherein the radius of curvature of the corner cutting edge in the plan view is 1.0 mm or less.

[0038] In the above configuration, since the radius of curvature of the corner blade is 1.0 mm or less, the effects of the present invention described above are more stably achieved when the depth of cut is small, for example, 0.3 mm or less.

[0039] [Aspect 14 of the present invention] A cutting tool according to any one of embodiments 1 to 13, comprising a cutting edge portion on which the rake face, the relief face, the cutting edge, and the projection are arranged, wherein the cutting edge portion is made of a cBN sintered body or a diamond sintered body.

[0040] In this case, the hardness of the blade is sufficiently increased, which suppresses wear and damage to the cutting edge and projections, allowing the desired turning process to be performed stably over a long period of time. [Effects of the Invention]

[0041] According to the above-mentioned aspect of the present invention, a cutting tool is provided that can suppress chip elongation even at low cutting depths and stably improve chip breaking performance. [Brief explanation of the drawing]

[0042] [Figure 1] Figure 1 is a perspective view showing the cutting tool of this embodiment. [Figure 2] Figure 2 is a perspective view showing a portion of a cutting tool (near the cutting edge). [Figure 3]Figure 3 is a plan view (top view) showing a part of the cutting tool (near the cutting edge). [Figure 4] Figure 4 is a front view showing a part of the cutting tool (near the cutting edge). [Figure 5] Figure 5 is a side view showing a part of the cutting tool (near the cutting edge). [Figure 6] Figure 6 is a cross-sectional view (a vertical cross-sectional view along the left-right direction) showing the VI-VI section of Figure 3. [Figure 7] Figure 7 is a cross-sectional view (a longitudinal cross-sectional view along the front-to-back direction) showing the VII-VII section of Figure 3. [Figure 8] Figure 8 is an image showing the shape of the chips generated by turning using the cutting tool of the embodiment. [Modes for carrying out the invention]

[0043] A cutting tool 10 according to one embodiment of the present invention will be described with reference to Figures 1 to 7. The cutting tool 10 of this embodiment is a cutting insert used in an indexable cutting tool for turning (cutting) a workpiece such as metal. In this embodiment, the cutting tool 10 may be simply referred to as an insert or tool.

[0044] Although not specifically shown in the diagram, the replaceable tip cutting tool comprises a holder, a cutting tool (cutting insert) 10, and fastening members. The holder has a concave insert mounting seat located at the tip of the holder. The cutting tool 10 is detachably attached to the insert mounting seat by fastening members such as a clamp piece, clamp lever, or clamp screw.

[0045] As shown in Figure 1, the cutting tool 10 is plate-shaped. In this embodiment, the cutting tool 10 is polygonal plate-shaped, specifically, a rectangular plate-shaped such as a rhombic plate-shaped one. More specifically, the cutting tool 10 in this embodiment is, for example, a rhombic insert (cutting insert) with a shape conforming to ISO standards. However, it is not limited to this, and the cutting tool 10 may be polygonal plate-shaped such as a triangular plate-shaped, pentagonal plate-shaped, or hexagonal plate-shaped one.

[0046] The cutting tool 10 is a polygonal plate shape centered on the insert central axis C, and its pair of plate surfaces (front and back surfaces) face the direction in which the insert central axis C extends (insert axis direction). In this specification, the direction perpendicular to the insert central axis C is sometimes called the insert radial direction, and the direction that circles around the insert central axis C is sometimes called the insert circumferential direction. Of the insert radial directions, the direction approaching the insert central axis C is the inside of the insert radial direction, and the direction away from the insert central axis C is the outside of the insert radial direction.

[0047] The cutting tool 10 comprises a blade portion 12 and a base metal portion 11 to which the blade portion 12 is fixed. The base metal portion 11 is made of, for example, cemented carbide. The base metal portion 11 is in the shape of a polygonal plate, and in this embodiment it is in the shape of a rectangular plate such as a rhombic plate. The base metal portion 11 has a blade mounting portion 11a and a mounting hole 11b.

[0048] The blade mounting portion 11a is concave, recessed from the outer surface of the base metal portion 11. The blade mounting portion 11a is formed by recessing from one of the pair of plate surfaces (front and back) of the base metal portion 11 (front surface) and the outer peripheral surface. The blade mounting portion 11a is positioned at a predetermined corner among the multiple corners of the base metal portion 11. In the illustrated example, the blade mounting portion 11a is provided at each of the two acute corners (i.e., a pair) of the four corners of the base metal portion 11. In this embodiment, the blade mounting portion 11a has a triangular concave shape.

[0049] The mounting hole 11b penetrates the base metal portion 11 in the direction of the insert axis and opens into a pair of plate surfaces (front and back surfaces) of the base metal portion 11. The mounting hole 11b is a circular hole centered on the insert's central axis C. A fastening member for fixing the cutting tool 10 to the insert mounting seat of the holder is inserted into the mounting hole 11b.

[0050] The blade portion 12 is fixed (joined) to the blade portion mounting portion 11a by a joining means such as brazing. The blade portion 12 is positioned at a predetermined corner among the multiple corners of the cutting tool 10. In the illustrated example, the blade portion 12 is provided at two acute corners (i.e., a pair) among the four corners of the cutting tool 10. However, the configuration is not limited to this; the base metal portion 11 may have only one blade portion mounting portion 11a, and only one blade portion 12 may be provided at this blade portion mounting portion 11a.

[0051] The blade portion 12 is composed of a cBN (cubic boron nitride) sintered body or a diamond sintered body (polycrystalline diamond, PCD). The cBN sintered body is a hard sintered body containing cBN and a binder. The diamond sintered body is a hard sintered body containing diamond and a binder.

[0052] When the blade portion 12 is made of a cBN sintered body, the cBN content of the blade portion 12 is, for example, 20% by volume or more and 80% by volume or less. Preferably, the cBN content of the blade portion 12 is 40% by volume or more. As a binder, a binder can be used that has a composition consisting of at least one selected from the group consisting of nitrides, carbides, borides, oxides and solid solutions thereof of elements of groups 4, 5, and 6 of the periodic table, and at least one selected from the group consisting of nitrides, borides, oxides and solid solutions thereof of aluminum. If the blade portion 12 is made of a diamond sintered body, the diamond content of the blade portion 12 is, for example, 80 volume percent or more.

[0053] The blade portion 12 is polygonal plate-shaped, and in this embodiment, it is triangular plate-shaped. As shown in Figure 2, the blade portion 12 has a rake face 1, a relief face 2, a cutting edge 3 positioned on the ridge where the rake face 1 and the relief face 2 are connected, a chamfer honing 4 extending along the cutting edge 3, a projection 5, a first wall surface 6, and a second wall surface 7. That is, the blade portion 12 has a rake face 1, a relief face 2, a cutting edge 3, a chamfer honing 4, a projection 5, a first wall surface 6, and a second wall surface 7. Therefore, the cutting tool 10 is equipped with a rake face 1, a relief face 2, a cutting edge 3, a chamfer honing 4, a projection 5, a first wall surface 6, and a second wall surface 7.

[0054] Figure 3 shows a plan view (top view) of the vicinity of the cutting edge 12 of the cutting tool 10, viewed from the insert axis direction. As shown in Figure 3, in a plan view with the rake face 1 facing forward, the cutting edge 3 has a V-shape. Specifically, the cutting edge 3 has a convex curved corner edge 3a and a pair of straight edges 3b connected to both ends of the corner edge 3a, each extending in a straight line. More specifically, the corner edge 3a has a convex arc shape with a constant radius of curvature.

[0055] [Definition of direction] In this embodiment, an XYZ Cartesian coordinate system (3D Cartesian coordinate system) is appropriately set in each figure, and each component will be described. In a plan view of the vicinity of the cutting edge 12 of the cutting tool 10 shown in Figure 3, the direction in which the bisector B of the pair of straight blades 3b extends is called the front-to-back direction. The front-to-back direction corresponds to the Y-axis direction in each figure. In this embodiment, the bisector B is perpendicular to the insert central axis C. That is, the bisector B extends along a predetermined insert radial direction. Of the front-to-back directions, the direction from the insert central axis C toward the corner blade 3a is called the front side (-Y side), and the direction from the corner blade 3a toward the insert central axis C is called the rear side (+Y side).

[0056] Furthermore, in the plan view shown in Figure 3, the direction perpendicular to the bisector B is called the left-right direction. The left-right direction corresponds to the X-axis direction in each figure. Of the left-right directions, as shown in Figure 3, when viewing the rake face 1 from the front, the direction to the left of the bisector B is called the left side (-X side), and the direction to the right of the bisector B is called the right side (+X side). Also, in the left-right direction, the direction approaching the bisector B is called the inward (center side), and the direction moving away from the bisector B is called the outward.

[0057] Furthermore, the direction perpendicular to the front-back and left-right directions is called the up-down direction. In each figure, the up-down direction corresponds to the Z-axis direction. Of the up-down directions, the direction in which the rake face 1 faces is called the upper side (+Z side), and the opposite direction is called the lower side (-Z side). In this embodiment, the up-down direction corresponds to the insert axis direction. That is, the up-down direction is the direction extending along the insert central axis C.

[0058] In this embodiment, the terms front, rear, left, right, top, and bottom are merely names (designations) used to describe the relative positional relationship of each part, and the actual arrangement when using tools, etc., may be different from the arrangements indicated by these names.

[0059] Furthermore, the symbol O shown in Figure 3 represents the center O of the radius of curvature of the corner blade 3a. In the plan view shown in Figure 3, the direction connecting any point on the corner blade 3a to the center O is called the radial direction of the corner blade 3a or simply the radial direction. Of the radial directions of the corner blade 3a, the direction approaching the center O (the direction from the corner blade 3a toward the center O) is called the radially inward direction, and the direction moving away from the center O (the direction from the center O toward the corner blade 3a) is called the radially outward direction.

[0060] Furthermore, the direction in which the cutting edge 3 extends is called the blade length direction. Specifically, the blade length direction in which the corner cutting edge 3a extends is the curved direction along the corner cutting edge 3a (this is the direction in which the arc centered at the center O of the radius of curvature of the corner cutting edge 3a extends, and corresponds to the direction around center O). Also, the blade length direction in which the straight cutting edges 3b extend is the straight direction along each straight cutting edge 3b.

[0061] In this embodiment, as shown in Figure 3, the YZ plane, which includes the bisector B and is perpendicular to the left-right direction (X-axis direction), is used as the reference plane (plane of symmetry), and the blade portion 12 and the cutting tool 10 are symmetrical (mirror-image symmetrical shape, mirror-surface symmetrical shape).

[0062] [Scooping surface] As shown in Figures 2, 3, and 7, the rake face 1 is positioned on one of the pair of plate surfaces (front and back) of the blade portion 12, the one facing upwards (front surface). The rake face 1 is positioned adjacent to the cutting edge 3, on the inside in the insert diameter direction of the cutting edge 3. The rake face 1 has a corner rake face 1a positioned at the front end of the rake face 1, and a pair of straight rake faces 1b positioned on both the left and right outer sides and rear of the corner rake face 1a.

[0063] The corner rake face 1a is the portion of the rake face 1 that is connected to the corner blade 3a. The corner rake face 1a extends downward as it moves radially inward from the corner blade 3a. In this embodiment, as shown in Figure 7, the angle γ at which the corner rake face 1a is inclined with respect to a virtual plane (XY plane) VS perpendicular to the vertical direction in a vertical cross-sectional view perpendicular to the corner blade 3a (cutting edge 3) is, for example, about 20°.

[0064] As shown in Figures 2, 3, and 6, the linear rake face 1b is the portion of the rake face 1 that is connected to the linear blade 3b. In this embodiment, as shown in Figure 6, the linear rake face 1b extends along the plane direction (XY plane direction) of the virtual plane VS perpendicular to the vertical direction (Z axis direction). Although not specifically shown, the linear rake face 1b may extend downward as it moves inward and towards the rear in the left-right direction from the linear blade 3b.

[0065] [Fleeing face] As shown in Figure 2, the relief surface 2 is positioned on the front, left, and right sides of the outer circumferential surface of the blade portion 12. The relief surface 2 is positioned below the cutting edge 3 and adjacent to the cutting edge 3. The relief surface 2 extends in the circumferential direction of the insert. In this embodiment, the relief surface 2 is a surface parallel to the insert's central axis C. Although not specifically shown, the relief surface 2 may extend inward in the radial direction of the insert as it moves downward from the cutting edge 3.

[0066] The relief surface 2 has a corner relief surface 21 and a pair of straight relief surfaces 22 connected to both ends of the corner relief surface 21 in the insert circumferential direction. The corner relief surface 21 is the portion of the relief surface 2 that is connected to the corner blade 3a. The corner relief surface 21 is located at the front end of the relief surface 2 and has a curved (cylindrical) shape that is convex toward the front. The straight relief surfaces 22 are the portions of the relief surface 2 that are connected to the straight blades 3b. Each straight relief surface 22 is connected to each straight blade 3b. Each straight relief surface 22 has a planar shape and extends along each straight blade 3b.

[0067] [Cutting edge] As shown in Figures 4 and 5, in this embodiment, the cutting edge 3 extends along the plane direction perpendicular to the vertical direction (Z-axis direction) (the direction in which the XY plane expands). More specifically, the entire cutting edge 3 is contained within the XY plane. The cutting edge 3 has a corner blade 3a and a pair of straight blades 3b.

[0068] As shown in Figures 2 and 3, the corner blade 3a has a curved shape that is convex toward the front (-Y side), and in this embodiment, it has a circular arc shape that is convex toward the front. In the plan view shown in Figure 3, the radius of curvature R (nose R) of the corner blade 3a is, for example, 1.0 mm or less, and in this embodiment it is about 0.8 mm.

[0069] A pair of straight blades 3b are connected to both ends of the corner blade 3a in the direction of its blade length, so as to be in smooth contact with each other without any steps. Specifically, each straight blade 3b extends linearly along each tangent line passing through both ends of the corner blade 3a. Each straight blade 3b extends outward in the left-right direction as it moves towards the rear (+Y side) from the connection point with the corner blade 3a.

[0070] [Chamfer honing] The chamfer honing 4 is positioned adjacent to the cutting edge 3 on the rake face 1 side of the cutting edge 3. As shown in Figure 7, in a vertical cross-sectional view perpendicular to the cutting edge 3, the honing width D of the chamfer honing 4 (honing width dimension in the plane direction perpendicular to the vertical direction (the direction in which the virtual plane VS expands)) is, for example, 0.03 mm or more and smaller than 0.05 mm. Because the honing width D of the chamfer honing 4 is small as described above, it can be said that the chamfer honing 4 constitutes a part of the cutting edge 3. Alternatively, it can be said that the chamfer honing 4 constitutes a part of the rake face 1.

[0071] In the longitudinal section view of Figure 7, the chamfer honing 4 extends upward as it moves radially inward from the cutting edge 3. In this longitudinal section view, the chamfer honing 4 is linear. In this longitudinal section view, the angle α at which the chamfer honing 4 is inclined with respect to the virtual plane VS (XY plane) is, for example, between 15° and 35°. In this embodiment, the angle α is approximately 30°.

[0072] As shown in Figures 2 and 3, the portion of the chamfer honing 4 adjacent to the corner cutting edge 3a has a curved shape that is convex toward the front. Specifically, the portion of the chamfer honing 4 adjacent to the corner cutting edge 3a has a curved shape that is convex toward the front. In addition, the portions of the chamfer honing 4 adjacent to the pair of straight cutting edges 3b are each straight. The portions of the chamfer honing 4 adjacent to each straight cutting edge 3b extend toward the rear as they are directed outward in the left-right direction.

[0073] 〔protrusion〕 The projections 5 are positioned on the rake face 1 and protrude from the rake face 1. Specifically, the projections 5 are rib-shaped and protrude upward from the rake face 1, extending in the radial direction of the corner blade 3a or in a direction inclined with respect to the radial direction. Multiple projections 5 are provided at intervals from each other in the blade length direction along which the cutting edge 3 extends. The number of projections 5 provided is a natural number between 2 and 5R in the left or right region of the bisector B of the rake face 1 (i.e., on one side in the left-right direction centered on the bisector B). Hereinafter, R refers to the radius of curvature R of the corner blade 3a described above. For example, in this embodiment, the radius of curvature R of the corner blade 3a is approximately 0.8 mm, and the number of projections 5 is between 2 and 4 (5 × 0.8 mm) on one side in the left-right direction of the rake face 1.

[0074] As shown in Figures 2, 4, 5, and 7, each projection 5 has a chip contact surface 5a that extends upward as it moves radially inward from the corner cutting edge 3a. The chip contact surface 5a is the surface of each projection 5 that faces the cutting edge 3 side and upward. In this embodiment, as shown in Figure 7, in a vertical cross-sectional view perpendicular to the cutting edge 3, the chip contact surface 5a is linear. In this vertical cross-sectional view, the angle α at which the chip contact surface 5a is inclined with respect to a virtual plane VS perpendicular to the vertical direction passing through the cutting edge 3 is, for example, 15° to 35°, and in this embodiment it is about 30°. During turning, the chips generated by the cutting edge 3 come into contact with the chip contact surface 5a.

[0075] In this embodiment, in the longitudinal cross-sectional view shown in Figure 7, the chip contact surface 5a of the projection 5 is located on a virtual straight line VL that extends the chamfer honing 4. Specifically, the chip contact surface 5a is formed continuously with the chamfer honing 4. That is, the chip contact surface 5a is formed integrally with the surface that forms the chamfer honing 4. Although not specifically shown, the chip contact surface 5a may be formed with a gap between it and the chamfer honing 4. That is, the chip contact surface 5a may be formed separately from the surface that forms the chamfer honing 4.

[0076] Furthermore, the chip contact surface 5a is not limited to being configured to coincide with a virtual straight line VL that extends the chamfer honing 4 in this longitudinal cross-sectional view. For example, the chip contact surface 5a may be positioned offset by a predetermined dimension from this virtual straight line VL radially inward of the corner cutting edge 3a.

[0077] Furthermore, in each projection 5, the upper end of the chip contact surface 5a corresponds to the upper end of the projection 5. Therefore, as shown in Figure 7, the amount of projection H of the chip contact surface 5a protruding upward from the cutting edge 3 corresponds to the amount of projection (height dimension) of the projection 5 protruding upward from the cutting edge 3. And, as shown in Figures 2 to 5, the amount of projection H of the chip contact surface 5a protruding upward from the cutting edge 3 is larger for the projections 5 that are positioned further away from the bisector B in the cutting edge length direction of the cutting edge 3.

[0078] Furthermore, as shown in Figures 3 and 7, the width dimension W of the projection 5 along the blade length direction is greater than the height dimension (projection amount) H of the projection 5 protruding upward from the cutting edge 3. The height dimension H of the projection 5 protruding upward from the cutting edge 3 is, for example, greater than 0.05 mm and less than or equal to 0.15 mm.

[0079] More specifically, in this embodiment, the multiple protrusions 5 include a first protrusion 51 positioned furthest from the bisector B in the plan view shown in Figure 3, a second protrusion 52 positioned between the first protrusion 51 and the bisector B in the blade length direction of the cutting edge 3, and a third protrusion 53 positioned on the bisector B. The first protrusions 51 are provided in pairs at positions symmetrical to each other with respect to the bisector B in this plan view, the second protrusions 52 are provided in pairs at positions symmetrical to each other with respect to the bisector B in this plan view, and the third protrusion 53 is provided as a single unit on the bisector B. In other words, in this embodiment, a total of five protrusions 5 are provided on the blade portion 12.

[0080] As shown in Figures 4 and 5, the amount of protrusion H of the chip contact surface 51a (5a) of the first projection 51, the chip contact surface 52a (5a) of the second projection 52, and the chip contact surface 53a (5a) of the third projection 53, respectively, which protrude upward from the cutting edge 3, increases in proportion to the distance away from the bisector B in the direction of the cutting edge length. Specifically, the amount of protrusion H of the chip contact surface 5a of each projection 5 is increased in the order of the chip contact surface 53a of the third projection 53, the chip contact surface 52a of the second projection 52, and the chip contact surface 51a of the first projection 51.

[0081] As shown in Figure 3, the radial dimensions of the chip contact surfaces 51a of the first projection 51, 52a of the second projection 52, and 53a of the third projection 53 increase as they move further away from the bisector B in the blade length direction. Specifically, the radial dimensions of the chip contact surfaces 5a of each projection 5 increase in the order of chip contact surface 53a of the third projection 53, chip contact surface 52a of the second projection 52, and chip contact surface 51a of the first projection 51. Furthermore, the radial dimensions of the projections 5 as a whole also increase in the order of the third projection 53, second projection 52, and first projection 51.

[0082] Furthermore, the width dimension W along the blade length direction of the first projection 51, the second projection 52, and the third projection 53 increases as they move further away from the bisector B in the blade length direction. Specifically, the width dimension W along the blade length direction of each projection 5 increases in the order of the third projection 53, the second projection 52, and the first projection 51.

[0083] Furthermore, in the plan view of Figure 3, the multiple protrusions 5 include at least one radial protrusion that extends along the radial direction of the corner blade 3a. In this embodiment, the first protrusion 51 and the third protrusion 53 among the multiple protrusions 5 are radial protrusions that extend along the radial direction.

[0084] Furthermore, the multiple protrusions 5 include at least one inclined protrusion that extends inclined with respect to the radial direction of the corner blade 3a in the plan view of Figure 3. In this embodiment, the second protrusion 52 among the multiple protrusions 5 is an inclined protrusion that extends inclined with respect to the radial direction. In this plan view, the angle β at which the inclined protrusion (second protrusion 52) is inclined with respect to the radial direction of the corner blade 3a is, for example, greater than 0° and 30° or less.

[0085] Furthermore, because the second projection 52 is an inclined projection, the distance between the second projection 52 and the first projection 51 decreases as it moves radially outward from the corner blade 3a. In other words, in this embodiment, among the multiple projections 5, the distance between a predetermined pair of adjacent projections 5 (the second projection 52 and the first projection 51) in the direction of the blade length decreases as it moves radially outward from the corner blade 3a.

[0086] The structure of each projection 5 will be explained in more detail. The first projection 51 is positioned between the corner rake face 1a and the straight rake face 1b in the direction of the blade length. The width dimension of the chip contact surface 51a of the first projection 51 decreases along the direction of the blade length as it moves radially inward. As shown in Figures 4 and 5, the portion of the first projection 51 located radially inward from the chip contact surface 51a has a height dimension in the vertical direction that is approximately constant along the radial direction.

[0087] As shown in Figure 3, the second projection 52 is positioned on the corner rake face 1a. The width dimension of the chip contact surface 52a of the second projection 52 decreases along the blade length direction as it moves radially inward. On the other hand, the overall width dimension of the second projection 52 along the blade length direction increases as it moves radially inward. As shown in Figures 4, 5, and 7, the portion of the second projection 52 located radially inward from the chip contact surface 52a has a height dimension that protrudes upward from the corner rake face 1a (rake face 1) as it moves radially inward.

[0088] As shown in Figure 3, the third projection 53 is positioned on the corner rake face 1a. The chip contact surface 53a of the third projection 53 has a width dimension along the blade length direction that is constant along the radial direction. The width dimension of the third projection 53 as a whole along the blade length direction is also constant along the radial direction. As shown in Figures 5 and 7, the portion of the third projection 53 located radially inward from the chip contact surface 53a has a height dimension that protrudes upward from the corner rake face 1a (rake face 1) as it moves radially inward.

[0089] [First wall] As shown in Figures 2 to 4, the first wall surface 6 is positioned on the rake face 1 and protrudes from the rake face 1. Specifically, the first wall surface 6 is positioned radially inward from the projection 5 on the rake face 1 (corner rake face 1a) and protrudes upward from the rake face 1, forming a pedestal shape that extends in the vertical and perpendicular plane directions (XY plane directions). Also, in the plan view shown in Figure 3, the first wall surface 6 extends in the left-right direction. As the first wall surface 6 moves away from the bisector B in the blade length direction, the distance from the cutting edge 3 decreases.

[0090] As shown in Figure 4, the first wall surface 6 protrudes above the cutting edge 3. The height dimension of the first wall surface 6 protruding above the cutting edge 3 is smaller than the height dimension of the first projection 51, and larger than the respective height dimensions of the second projection 52 and the third projection 53.

[0091] As shown in Figures 2 to 4, 6 and 7, the first wall surface 6 has an upward-facing top surface 61 and protruding portions 62 located at the left and right ends of the first wall surface 6. The vertex 61 extends downwards as it approaches the front. Furthermore, the vertex 61 extends downwards as it approaches the inside in the left-right direction (i.e., the center in the left-right direction, and the side of the bisector B).

[0092] A pair of overhangs 62 are provided at both outer ends in the left-right direction of the first wall surface 6 (i.e., both ends in the left-right direction). The width dimension of each overhang 62 decreases along the blade length direction as it extends radially outward. Also, the height dimension of each overhang 62 decreases vertically as it extends radially outward. The overhangs 62 are inserted from the radially inward side between adjacent first projections 51 and second projections 52 in the blade length direction. That is, the overhangs 62 are inserted between a predetermined pair of adjacent projections 5 (between the first projection 51 and the second projection 52) in the blade length direction.

[0093] [Second wall] As shown in Figures 2 to 7, the second wall surface 7 is adjacent to the first wall surface 6 and positioned on the opposite side of the first wall surface 6 from the cutting edge 3. Specifically, the second wall surface 7 is positioned behind the first wall surface 6 and adjacent to it. The second wall surface 7 protrudes above the cutting edge 3. The height dimension of the second wall surface 7 protruding above the cutting edge 3 is greater than the height dimensions of the first to third projections 51 to 53, and greater than the height dimension of the first wall surface 6.

[0094] The second wall surface 7 has a front wall 71 that protrudes upward from the first wall surface 6 and faces forward, and a side wall 72 that is outward in the left-right direction and also faces forward. The front wall 71 is planar and extends upward towards the rear. In the longitudinal section view shown in Figure 7, the angle at which the front wall 71 is inclined with respect to the virtual plane VS is, for example, about 60°. The lower end of the front wall 71 is connected to the rear end of the top surface 61 of the first wall surface 6.

[0095] The side walls 72 are provided in pairs, positioned on both the left and right outer sides of the front wall 71. Each pair of side walls 72 is planar in shape. Each side wall 72 extends upward as it moves inward in the left-right direction. Each side wall 72 is positioned behind each first projection 51.

[0096] [Effects of this embodiment] In the cutting tool 10 of this embodiment described above, a plurality of protrusions 5 are provided on the rake face 1. These protrusions 5 are spaced apart from each other in the direction of the cutting edge length of the cutting edge 3. Furthermore, the chip contact surface 5a of each protrusion 5 protrudes upward from the cutting edge 3 and extends upward as it moves radially inward from the corner edge 3a (i.e., as it approaches the center O of the radius of curvature of the corner edge 3a). The amount H of projection of the chip contact surface 5a upward from the cutting edge 3 is larger for each of the plurality of protrusions 5 that is located further away from the bisector B in the direction of the cutting edge length.

[0097] When turning a workpiece using this cutting tool 10, the chips generated by the cutting edge 3 are brought into contact with the projection 5 on the rake face 1. Specifically, the chips come into contact with the chip contact surface 5a of the projection 5, and as a result, the shape of the projection 5 is transferred to the chips, thereby giving them a pseudo-thickness. In other words, the cross-section of the chips becomes curved, which makes the overall thickness of the chips appear to be increased.

[0098] Here, as shown in equation (1) below, it is generally known that as the chip thickness increases, the chip fracture strain (which contributes to chip fragmentation) also increases. ε C <(1 / R0-1 / R C ) × h / 2 …(1) In the above equation (1), ε C R is the chip fracture strain, R0 is the chip curl diameter (end time), R C represents the chip curl diameter (initial), and h represents the chip thickness.

[0099] In Figure 3, the cutting angle of the cutting tool 10 relative to the machined surface of the workpiece during turning is indicated by the symbol θ, and the depth of cut is indicated by the symbol ap. Specifically, the cutting angle θ shown in Figure 3 is, for example, 5°, and the depth of cut ap is, for example, 0.3 mm.

[0100] According to this embodiment, even when the depth of cut ap is small, for example, 0.3 mm or less, the chip fragmentation performance can be improved by transferring the shape of the protrusions 5 to the chip and giving it a pseudo-thickness. Furthermore, by transferring the shape of the protrusions 5, tensile stress is generated in the free surface (the surface that does not contact the tool) and the side surface (the edge of the chip), making it easier for cracks to propagate. This also changes the fracture strain of the chip and lowers the chip fragmentation threshold, thereby improving chip fragmentation performance.

[0101] More specifically, during turning operations where the depth of cut ap is significantly smaller than 0.3 mm, the thin chip is brought into contact with a projection 5 with a large protrusion H, which is positioned away from the bisector B. This ensures that the shape of the projection 5 is stably transferred to the chip, and also imparts a pseudo-chip thickness, thereby improving chip breakability.

[0102] Furthermore, in turning operations where the depth of cut ap is close to 0.3 mm, the chips are simultaneously brought into contact with multiple protrusions 5, each with a different protrusion H on the chip contact surface 5a. In this case, the chips are appropriately given the shape of each protrusion 5 to enhance their fragmentation, and the chips as a whole are spirally twisted (curled) and discharged away from the machined surface of the workpiece. This suppresses contact between the chips and the machined surface and improves chip discharge. In Figure 3, an example of the chip discharge direction according to this embodiment is indicated by the symbol F. Also in this embodiment, as shown in Figure 3, when turning operations where the depth of cut ap is close to 0.3 mm, the chips are brought into contact with all of the first protrusion 51, the second protrusion 52, and the third protrusion 53 (i.e., all three protrusions 5).

[0103] Based on the above, according to this embodiment, even when the depth of cut ap is small, such as 0.3 mm or less, the elongation of the chips can be suppressed, and the chip breaking performance can be stably improved.

[0104] Furthermore, in this embodiment, the chip contact surface 5a is linear in a longitudinal cross-sectional view perpendicular to the cutting edge 3. In this case, the chip contact surface 5a is flat or a gently curved convex surface (conical surface) along the blade length direction, resulting in a simple configuration. Therefore, the chip contact surface 5a is easy to form by laser processing or the like during the manufacturing of the cutting tool 10. Furthermore, since there are no steps or other irregularities on the chip contact surface 5a, during turning, the chips that come into contact with the chip contact surface 5a are prevented from getting caught, and the effects of this embodiment described above are stably achieved.

[0105] In this embodiment, in a vertical cross-sectional view perpendicular to the cutting edge 3, the angle α at which the chip contact surface 5a is inclined with respect to a virtual plane VS that passes through the cutting edge 3 and is perpendicular in the vertical direction is 15° or more and 35° or less.

[0106] When the angle α at which the chip contact surface 5a is inclined is 15° or more, the shape of the protrusion 5 can be stably transferred to the chips that come into contact with the chip contact surface 5a. Furthermore, if the angle α at which the chip contact surface 5a is inclined is 35° or less, excessive cutting resistance is suppressed, maintaining good cutting performance of the cutting edge 3, while the function (effect) of the projection 5 is stably achieved.

[0107] In this embodiment, the multiple protrusions 5 include at least one radial protrusion (first protrusion 51, third protrusion 53) that extends along the radial direction of the corner blade 3a in the plan view shown in Figure 3.

[0108] In this case, at least one radial projection is included among the multiple projections 5 arranged in the blade length direction on the rake face 1. Since the radial projection extends in a direction perpendicular to the blade length direction of the corner blade 3a in a plan view (i.e., the radial direction of the corner blade 3a), the chips generated by the corner blade 3a flow out along the radial projection. This allows the shape of the projection 5 to be transferred to the chips more stably.

[0109] In this embodiment, the multiple protrusions 5 include at least one inclined protrusion (second protrusion 52) that extends inclined with respect to the radial direction of the corner blade 3a in the plan view shown in Figure 3.

[0110] In this case, at least one inclined projection is included among the multiple projections 5 arranged in the direction of the cutting edge length on the rake face 1. This inclined projection makes it possible to control, for example, the direction of chip outflow (discharge direction) F, or the flow velocity and supply position of the coolant.

[0111] Furthermore, in this embodiment, in the plan view shown in Figure 3, the angle β at which the inclined projection (second projection 52) is inclined with respect to the radial direction of the corner blade 3a is 30° or less. When the angle β of the inclined projection is 30° or less, the temperature rise of the chips in contact with the inclined projection is suppressed. Because the temperature of the generated chips is kept low, the load acting on the cutting edge 3 can be kept small, and the rigidity of the cutting edge is well maintained.

[0112] Furthermore, in this embodiment, the distance between a predetermined pair of adjacent protrusions 5 in the blade length direction (between the first protrusion 51 and the second protrusion 52) decreases as the corner blade 3a moves radially outward.

[0113] In the above configuration, the distance between a predetermined pair of protrusions 5 decreases as it moves radially outward from the corner cutting edge 3a. When coolant is supplied from the rake face 1 toward the corner cutting edge 3a, the flow velocity of the coolant flowing radially outward between the protrusions 5 can be increased as it approaches the corner cutting edge 3a. For example, by positioning a portion of the corner cutting edge 3a used for cutting, especially when the depth of cut ap is small (such as near the end of the corner cutting edge 3a in the cutting edge direction), radially outward from the protrusions 5, the chip removal performance can be stably improved by the increased flow velocity of the coolant.

[0114] Furthermore, in this embodiment, the width dimension W along the blade length direction of the projection 5 is greater than the height dimension H to which the projection 5 protrudes upward from the cutting edge 3, thus ensuring stable rigidity of the projection 5 that comes into contact with the chips. Since damage to the projection 5 is suppressed, the effects of this embodiment described above are consistently achieved.

[0115] In this embodiment, the height dimension H of the projection 5 protruding upward from the cutting edge 3 is greater than 0.05 mm and less than or equal to 0.15 mm.

[0116] If the height dimension H of the projection 5 is greater than 0.05 mm, the function (effect) of the projection 5 can be obtained stably, and the shape of the projection 5 can be stably imparted to the chips that come into contact with the projection 5. Furthermore, if the height dimension H of the protrusion 5 is 0.15 mm or less, problems such as chips that come into contact with the protrusion 5 being unintentionally bounced off by the protrusion 5 are suppressed. In other words, if the height dimension of the protrusion 5 exceeds 0.15 mm, the protrusion 5 functions as a simple wall surface, causing the chips to be bounced off by the protrusion 5, and making it difficult for the shape of the protrusion 5 to be transferred to the chips. By setting the height dimension H of the protrusion 5 to 0.15 mm or less, as in this embodiment, the shape of the protrusion 5 can be stably imparted to chips that come into contact with the protrusion 5.

[0117] In this embodiment, the first wall surface 6 is positioned radially inward from the projection 5 on the rake face 1, and the distance from the cutting edge 3 decreases as it moves away from the bisector B in the blade length direction.

[0118] In this case, the first wall surface 6 is positioned closer to the cutting edge 3 as it moves away from the bisector B along the blade length direction. Therefore, for example, during turning operations where the depth of cut ap is sufficiently smaller than 0.3 mm, thin chips are brought into contact with the projection 5, which has a large projection H and is positioned away from the bisector B, before easily coming into contact with the first wall surface 6. Particularly at low depths of cut, chips with the shape of the projection 5 transferred onto them can be stably brought into contact with the first wall surface 6, curl, and be broken. This stably improves chip breaking performance.

[0119] In this embodiment, the first wall surface 6 is located at the left-right end of the first wall surface 6 and has a protruding portion 62 that is inserted between a predetermined pair of adjacent protrusions 5 in the blade length direction (between the first protrusion 51 and the second protrusion 52). In this case, especially when cutting at a low depth of cut, the chips with the shape of the protrusion 5 transferred onto them can be stably brought into contact with the protruding portion 62 of the first wall surface 6, curled, and then cut.

[0120] In this embodiment, the second wall surface 7 has a front wall 71 that protrudes upward from the first wall surface 6 and faces forward.

[0121] In this case, for example, during turning with a depth of cut ap close to 0.3 mm, the chip is simultaneously brought into contact with multiple protrusions 5 on the chip contact surface 5a, each with a different protrusion amount H, and then overcomes the first wall surface 6 to come into contact with the front wall 71 of the second wall surface 7. That is, the chip, with the shape of the protrusions 5 imprinted on it, can be stably brought into contact with the second wall surface 7, curl, and be broken apart. This makes it possible to stably improve chip breaking performance.

[0122] Furthermore, in this embodiment, the radius of curvature R of the corner blade 3a in the plan view shown in Figure 3 is 1.0 mm or less. In the above configuration, since the radius of curvature R of the corner cutting edge 3a is set to 1.0 mm or less, the effects of this embodiment described above are more stably achieved when the depth of cut ap is small, for example, 0.3 mm or less.

[0123] In this embodiment, the blade portion 12 is made of a cBN sintered body or a diamond sintered body. In this case, the hardness of the blade portion 12 is sufficiently increased, which suppresses wear and damage to the cutting edge 3 and projection 5, allowing the desired turning process to be performed stably over a long period of time.

[0124] [Other components included in the present invention] The present invention is not limited to the embodiments described above, and modifications to the configuration, etc., are possible without departing from the spirit of the invention, as described below, for example.

[0125] In the above-described embodiment, an example was given in which the corner edge 3a of the cutting edge 3 has a convex arc shape with a constant radius of curvature R, but it is not limited to this. Although not specifically shown, the corner edge 3a may be formed in a convex curve shape by combining, for example, multiple arcs having different radii of curvature.

[0126] In the embodiments described above, an example was given in which the blade portion 12 and the cutting tool 10 are symmetrical (mirror-image symmetrical shape) with respect to the YZ plane, which includes the bisector B and is perpendicular to the left-right direction (X-axis direction), as the reference plane (plane of symmetry). However, the invention is not limited to this. That is, the cutting tool 10 is not limited to a tool for both left-handed and right-handed use, but may be, for example, a tool for left-handed use or a tool for right-handed use. Specifically, the blade portion 12 and the cutting tool 10 may be asymmetrical with respect to the YZ plane, which includes the bisector B and is perpendicular to the left-right direction (X-axis direction), as the reference plane.

[0127] The present invention may be combined in any way that does not depart from the spirit of the invention, as described in the above embodiments and modifications, and the configurations may be added, omitted, substituted, or otherwise modified. Furthermore, the present invention is not limited by the above embodiments, but is limited only by the claims. [Examples]

[0128] The present invention will be described in detail below with reference to examples. However, the present invention is not limited to these examples.

[0129] <Chip fragmentation confirmation test> As an embodiment of the present invention, the cutting insert (cutting tool) 10 of the above-described embodiment was used to perform turning on a workpiece using an indexable cutting tool with the cutting tip mounted on the insert mounting seat of the holder, and the chip breaking performance was confirmed. Chromium steel (Scr420H) was used as the workpiece. The results are shown in Figure 8.

[0130] In Figure 8, "No." represents the cutting test number, "vc" represents the cutting speed, "ap" represents the depth of cut, and "fr" represents the feed rate in the axial direction of the workpiece. Additionally, "DRY" represents turning without coolant supply, and "WET" represents turning with coolant supply.

[0131] As shown in the images in Figure 8, it was confirmed that, according to the cutting tool 10 of the embodiment of the present invention, chip elongation is suppressed and chip breaking performance is improved even under cutting conditions with a depth of cut ap of 0.3 mm or less. The circles in each image indicate good chip breaking performance. [Industrial applicability]

[0132] According to the cutting tool of the present invention, chip elongation is suppressed even at low depths of cut, and chip breaking performance can be stably improved. Therefore, it has industrial applicability. [Explanation of Symbols]

[0133] 1... Scoop surface 2…Escape 3…Cutting edge 3a...Corner blade 3b…Straight blade 5...Protrusion 5a(51a,52a,53a)...Chip contact surface 6…First wall 7…Second wall 10…Cutting insert (cutting tool) 12...Blade part 62...Protruding section 71...Front wall B…Bisector H...Protrusion amount (height dimension) R…curvature radius VS…Virtual plane W...Width dimension α, β, γ… angles

Claims

1. The scooping surface, The escape face, A cutting edge is positioned on the ridge where the rake face and the relief face are connected, and has a V-shape when viewed from above with the rake face facing forward. The scoop surface is provided with a projection that is positioned on the scoop surface and protrudes from the scoop surface, The aforementioned cutting edge is A corner blade with a convex curve shape, The corner blade is connected to both ends of the corner blade and has a pair of straight blades that extend in a straight line, In the aforementioned plan view, the direction in which the bisectors of the pair of straight blades extend is defined as the front-to-back direction, the direction perpendicular to the bisectors in the aforementioned plan view is defined as the left-to-right direction, and the direction perpendicular to the front-to-back direction and the left-to-right direction is defined as the up-and-down direction. Multiple projections are provided at intervals from each other in the direction of the cutting edge's length. Each of the aforementioned protrusions has a chip contact surface that extends upward as it moves radially inward toward the corner cutting edge, The amount by which the chip contact surface protrudes upward from the cutting edge is greater for each of the multiple protrusions that are positioned further away from the bisector in the direction of the cutting edge length. cutting tools.

2. In a longitudinal cross-sectional view perpendicular to the cutting edge, the chip contact surface is linear. The cutting tool according to claim 1.

3. In a vertical cross-sectional view perpendicular to the cutting edge, the angle at which the chip contact surface is inclined with respect to a virtual plane passing through the cutting edge and perpendicular to the vertical direction is 15° or more and 35° or less. A cutting tool according to claim 1 or 2.

4. The plurality of projections include, in the plan view, at least one radial projection extending along the radial direction of the corner blade, The cutting tool according to claim 1 or 2.

5. The plurality of projections include, in the plan view, at least one inclined projection that extends inclined with respect to the radial direction of the corner blade, A cutting tool according to claim 1 or 2.

6. In the plan view, the angle at which the inclined projection is inclined with respect to the radial direction of the corner blade is 30° or less. The cutting tool according to claim 5.

7. Of the multiple protrusions, the distance between a predetermined pair of adjacent protrusions in the direction of the blade length decreases as the corner blade extends radially outward. A cutting tool according to claim 1 or 2.

8. The width dimension of the projection along the blade length direction is greater than the height dimension of the projection protruding upward from the cutting edge. A cutting tool according to claim 1 or 2.

9. The height dimension of the projection that protrudes upward from the cutting edge is greater than 0.05 mm and less than or equal to 0.15 mm. A cutting tool according to claim 1 or 2.

10. The scoop surface is further provided with a first wall surface that is positioned on the scoop surface and protrudes from the scoop surface, The first wall surface is positioned radially inward from the projection on the rake face, and the distance from the cutting edge decreases as it moves away from the bisector in the blade length direction. A cutting tool according to claim 1 or 2.

11. The first wall surface has a protruding portion located at the left-right end of the first wall surface, which is inserted between a predetermined pair of adjacent protrusions in the blade length direction. The cutting tool according to claim 10.

12. The first wall surface is adjacent to the second wall surface and is located on the opposite side of the first wall surface from the cutting edge, The second wall surface protrudes upward from the first wall surface and has a front wall facing forward. The cutting tool according to claim 10.

13. The radius of curvature of the corner blade in the plan view is 1.0 mm or less. A cutting tool according to claim 1 or 2.

14. The blade portion comprises the scooping surface, the relief surface, the cutting edge, and the projection, The blade portion is made of a cBN sintered body or a diamond sintered body. A cutting tool according to claim 1 or 2.

Images