Cutting inserts, tool bodies, and replaceable tip rotary cutting tools

Abstract

A rake face of a cutting insert according to the present disclosure is formed with a first plane parallel to a seating surface. The outer periphery of the first plane includes a plurality of curved portions having different radii of curvature, and the outer periphery of the first plane near the corners is formed so as to protrude toward the side of the cutting insert near the corners. The rake face is equipped with a breaker around the entire circumference of the cutting insert between a cutting edge section and the first plane. The relationship L11 > L12 > L13 is satisfied for the entire circumference of the cutting edge, where L11 is the distance from the seating surface to the tip of the cutting edge section in the thickness direction, L12 is the distance from the seating surface to the first plane in the thickness direction, and L13 is the distance from the seating surface to the deepest part of the breaker in the thickness direction.

Description

Technical Field

[0001] The present invention relates to a cutting insert, a tool body, and a tip-exchangeable rotary cutting tool. This application claims priority based on Japanese Patent Application No. 2022-035460 filed in Japan on March 8, 2022, and incorporates its content herein by reference.

Background Art

[0002] By forming a breaker (referred to as an "inclined surface" in Patent Document 1) from the cutting edge toward the inside of the rake face on the rake face and setting the rake angle of the cutting edge to be positive, it is possible to reduce the cutting resistance, reduce the cutting load in high-efficiency machining such as rough machining, and as a result, reduce the burden on the cutting tool and the machine tool.

[0003] Further, Patent Document 1 discloses a configuration in which a land is formed in contact with the main cutting edge of the rake face. Further, the breaker connecting to the land is inclined so as to be lower toward the inside of the rake face. This breaker is formed so that the inclination becomes steeper as it moves away from the corner portion, and the inclination length is the longest at the central portion of each side edge of the main cutting edge. That is, the width of the breaker is the widest at the central portion of the main cutting edge. Therefore, the inclination length is the longest at the central portion of each side edge of the main cutting edge. Thereby, Patent Document 1 describes that it does not give unreasonable deformation to the chip during deep cutting, and suppresses an increase in cutting resistance caused by chip clogging and chip deformation. Further, Patent Document 1 describes that in machining such as face milling, since the frequency of cutting edge breakage is high at the corner portion where the main cutting edge and the sub-cutting edge intersect, increasing the land width enhances the breakage resistance.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

[0005] However, in the first embodiment of Patent Document 1 (Figures 1-5 of Patent Document 1), the breaker along the main cutting edge is formed as a continuous, integrated surface in which the rake angle gradually increases towards the center of the main cutting edge. As a result, the outflow velocity of the chips within the width of the cutting edge changes depending on the depth of cut, and the direction of chip discharge changes depending on the depth of cut. Therefore, in shape machining using rotary cutting tools other than face milling cutters assumed in Patent Document 1, particularly high-feed tools, there was a risk that the chips would be discharged toward the machined wall surface, potentially damaging the machined wall surface.

[0006] Furthermore, the second embodiment of Patent Document 1 discloses a configuration in which a breaker wall is provided between the breaker and the surface around the mounting hole (boss surface). In other words, the deepest part of the breaker wall (deepest part of the breaker) is not the boss surface. However, Patent Document 1 only illustrates the position of the deepest part of the breaker and does not specifically mention the detailed positional relationship. Therefore, if the position of the breaker wall is too low compared to the cutting edge, the chips will not come into contact with the breaker wall and will grow long, potentially damaging the unused cutting edge portion of the cutting insert.

[0007] Furthermore, Patent Document 1 does not mention the positional relationship of the surfaces around the mounting hole due to the provision of a breaker in all embodiments. Since the thickness of the insert decreases relative to the cutting edge height from the bottom surface of the insert when a breaker is provided, there is a risk that the strength of the insert itself will decrease if the breaker is formed deeply. Therefore, in the case of high-efficiency machining such as high-feed machining, the effect of the decrease in insert strength may be stronger than the effect of suppressing the increase in cutting resistance, and there is a risk that the insert will be damaged prematurely.

[0008] The present invention has been made in view of these circumstances, and provides a cutting insert that can improve the chip evacuation performance of a cutting insert attached to a rotating tool body and has increased strength of the cutting edge portion, a tool body equipped with such a cutting insert, and an interchangeable tip rotary cutting tool. [Means for solving the problem]

[0009] A cutting insert according to one aspect of the present invention is a positive-type cutting insert in the shape of a polygonal plate that is attached to a tool body that rotates around a rotation axis and is rotationally symmetrical with respect to a center line extending in the thickness direction, comprising: a rake face constituting one of a pair of polygonal faces; a seating face constituting the other of a pair of polygonal faces; a side surface connecting the rake face and the seating face; a cutting edge portion including a main cutting edge formed on the intersecting ridge line of the rake face and the side surface and located on the edge of the rake face; a secondary cutting edge connected to one end of the main cutting edge; and a corner cutting edge connected to the end of the secondary cutting edge opposite to the main cutting edge and located on the corner of the rake face; and a mounting hole that penetrates in the thickness direction and is attached to the tool body, wherein the rake face has a cutting edge on the seating surface A parallel first plane is formed, the outer circumference of the first plane includes a plurality of curved portions with different radii of curvature, and the outer circumference of the first plane near the corner portion is formed to protrude toward the side surface of the cutting insert near the corner portion, the rake face is provided with a breaker including a first inclined surface and a second inclined surface around the entire circumference of the cutting insert between the cutting edge portion and the first plane, and if the distance from the seating surface to the tip of the cutting edge portion in the thickness direction is L11, the distance from the seating surface to the first plane in the thickness direction is L12, and the distance from the seating surface to the deepest part of the breaker in the thickness direction is L13, then the relationship L11 > L12 > L13 is satisfied around the entire circumference of the cutting edge.

[0010] With this configuration, chip evacuation is ensured by the breaker provided around the entire circumference of the cutting insert, thus preventing chips generated at the cutting edge during use from contacting the unused cutting edge and damaging it. Furthermore, because chip evacuation is efficient, the increase in cutting resistance caused by chip clogging and chip deformation can be suppressed. In addition, since the outer circumference of the first plane near the corner is formed to protrude toward the side surface of the cutting insert near the corner, the wall thickness at the corner can be ensured even with a configuration that includes a breaker. Moreover, in the thickness direction of the cutting insert, the distance L12 from the seating surface to the first plane is smaller than the distance L11 from the seating surface to the tip of the cutting edge, and larger than the distance L13 from the seating surface to the deepest part of the breaker. By using a shape with such distance relationships, sufficient wall thickness of the cutting insert 1 can be ensured even with a breaker on the rake face side, thereby increasing the strength of the cutting insert 1. Furthermore, it is possible to prevent damage to the unused cutting edge by generated chips while ensuring chip evacuation by the breaker. This results in a cutting insert that can fully demonstrate the effect of reducing cutting resistance. In addition, while equipped with a breaker, it can suppress chip clogging not only in face milling but also in shape machining and other processes with complex shapes, enabling highly efficient machining.

[0011] In one embodiment of the present invention, the difference between distance L11 and distance L12 may be in the range of 0.01 mm or more and less than 0.15 mm, and the difference between distance L11 and distance L13 may be in the range of 0.15 mm or more and 0.25 mm or less.

[0012] This configuration allows for an increase in the cross-sectional area of ​​the cutting insert while still incorporating a breaker, thus achieving both a reduction in cutting resistance and an improvement in the strength of the cutting insert.

[0013] In one embodiment of the present invention, the side surface is composed of two relief surfaces divided in the thickness direction. When the relief surface closer to the first plane among the two relief surfaces is defined as the upper relief surface, in a side view seen from a direction intersecting the thickness direction, the distance from the lower end of the upper relief surface to the tip of the cutting edge portion may be configured such that the distance L14 in a cross section passing through the center of the corner blade is maximum.

[0014] According to this configuration, it is possible to sufficiently secure the wall thickness at the corner portion where the cutting resistance tends to be large.

[0015] In one embodiment of the present invention, the first inclined surface may have a multi-stage configuration having a plurality of angles. In one embodiment of the present invention, the first plane has an outer periphery composed of linear portions and protrusions arranged alternately around the axis of the center line. In a plan view seen from the direction facing the first plane, when the shortest distance from the boundary between the main cutting edge and the sub-cutting edge adjacent in the circumferential direction to the first plane is L1, and the shortest distance from the boundary between the corner blade and the main cutting edge to the first plane is L2, a configuration satisfying the relationship L1 < L2 may be employed. In one embodiment of the present invention, when the diameter of the inscribed circle of the rake face is D, a configuration satisfying the relationship 3.0 ≦ D / L2 ≦ 6.5 between D and L2 may be employed. In one embodiment of the present invention, in a plan view seen from the direction facing the first plane, a configuration may be adopted in which the width of the first inclined surface is wider than the width of the second inclined surface. In one embodiment of the present invention, when viewed from a direction perpendicular to the first plane, the line connecting the intersection of the extensions of adjacent main cutting edges and the center line is defined as the first line, and the point where the first line passes through the corner cutting edge is defined as the first vertex. In this case, the shape formed by connecting the first vertices of the multiple corner cutting edges forms a regular polygon, and when the vertex of the projection furthest from the mounting hole is defined as the second vertex, the shape formed by connecting the multiple second vertices also forms a regular polygon. A phase difference occurs around the center line between the regular polygon formed by connecting the first vertices and the regular polygon formed by connecting the second vertices, and the first line and the second line, which is parallel to the first plane and passes through the center line to connect the second vertices, may intersect at the center line at an angle θ3.

[0016] The tool body of the present invention is a tool body that rotates around the axis of the tool rotation shaft, and is characterized in that the tip of the tool body is provided with an insert mounting seat to which the above-mentioned cutting insert is detachably attached.

[0017] This configuration ensures the reduction of cutting resistance by the breaker while also providing a cutting insert that suppresses damage to unused cutting edges, thus enabling highly efficient cutting over the long term.

[0018] The replaceable-tip rotary cutting tool of the present invention comprises the above-described cutting insert and the above-described tool body, and is characterized in that when the cutting insert is mounted to the tool body such that the seating surface of the cutting insert contacts the insert mounting seat of the tool body, the cutting angle of the main cutting edge with respect to the workpiece is less than 45°. [Effects of the Invention]

[0019] According to the present invention, it is possible to provide a cutting insert that improves the chip evacuation performance of a cutting insert attached to a rotating tool body, as well as increasing the cutting edge strength, and an indexable rotary cutting tool equipped with such a cutting insert. [Brief explanation of the drawing]

[0020] [Figure 1] Figure 1 is a plan view showing an embodiment of the cutting insert 1. [Figure 2] Figure 2 is a side view showing the configuration of the cutting insert 1 shown in Figure 1. [Figure 3] Figure 3 is a cross-sectional view taken along line III-III shown in Figure 1. [Figure 4] Figure 4 is a cross-sectional view taken along line IV-IV shown in Figure 1. [Figure 5] Figure 5 is a cross-sectional view taken along line V-V shown in Figure 1. [Figure 6] Figure 6 is a plan view of the cutting insert shown in Figure 1. [Figure 7] Figure 7 is a perspective view showing the configuration of a tip-exchangeable rotary cutting tool including a plurality of cutting inserts and a tool body. [Figure 8] Figure 8 is a perspective view showing the configuration of the tool body 31 in the tip-exchangeable rotary cutting tool 30 shown in Figure 7. [Figure 9A] Figure 9A is a photograph showing the chips generated in the example in Test 1 (axial depth of cut ap = 2.0 mm). [Figure 9B] Figure 9B is a photograph showing the chips generated in the comparative example in Test 1 (axial depth of cut ap = 2.0 mm). [Figure 10A] Figure 1OA is a photograph showing the chips generated in the example in Test 2 (axial depth of cut ap = 2.5 mm). [Figure 10B] Figure 1OB is a photograph showing the chips generated in the comparative example in Test 2 (axial depth of cut ap = 2.5 mm). [Figure 11A] Figure 11A is a photograph showing the chips generated in the example in Test 3 (axial depth of cut ap = 3.0 mm). [Figure 11B] Figure 11B is a photograph showing the chips generated in the comparative example in Test 3 (axial depth of cut ap = 3.0 mm).

Embodiments for Carrying Out the Invention

[0021] Embodiments to which the present invention is applied will be described in detail below with reference to the drawings. Note that, in order to make the characteristic parts easier to understand, non-characteristic parts may be omitted from the drawings in the following description.

[0022] <Cutting inserts> Figure 1 is a plan view showing one embodiment of the cutting insert 1. Figure 2 is a side view showing the configuration of the cutting insert 1 shown in Figure 1. Figure 3 is a cross-sectional view along the line III-III shown in Figure 1. Figure 4 is a cross-sectional view along the line IV-IV shown in Figure 1. Figure 5 is a cross-sectional view along the line VV shown in Figure 1. Figure 6 is a plan view of the cutting insert 1, which will be used to explain various parameters in the following paragraphs. Figure 7 is a perspective view showing the configuration of an indexable rotary cutting tool 30 comprising a plurality of cutting inserts 1 and a tool body 31. Figure 8 is a perspective view showing the configuration of the tool body 31 in the indexable rotary cutting tool 30 shown in Figure 7.

[0023] As shown in Figure 1, the cutting insert 1 has a polygonal plate shape (a rectangular plate shape in this embodiment) that is rotationally symmetric with respect to the center line CO extending in the thickness direction. In the following description, the direction along the center line CO may be simply referred to as the "thickness direction." Similarly, the direction perpendicular to the center line CO may be simply referred to as the "radial direction." Likewise, the circumferential direction around the axis centered on the center line CO may be simply referred to as the "circumferential direction."

[0024] As shown in Figures 1 and 2, the cutting insert 1 comprises a rake face 2 that constitutes one of a pair of polygonal faces, a seating face 3 that constitutes the other of the pair of polygonal faces, a side surface 10 (Figure 2) connecting the rake face 2 and the seating face 3, a plurality of cutting edges 20 formed on the intersecting ridge line of the rake face 2 and the side surface 10, and a mounting hole 7 for attaching the cutting insert 1 to the tool body 31.

[0025] The cutting insert 1 of this embodiment is detachably attached to the tip of the tool body 31 shown in Figure 7 using a clamp screw (fixing member) 38 as shown in Figure 7. Therefore, as shown in Figure 1, a mounting hole 7 is formed in the center of the cutting insert 1 through which the clamp screw 38 is inserted. The mounting hole 7 is coaxial with the center line CO and extends along the center line CO, opening into the first plane 4 and the seating surface 3. In other words, the mounting hole 7 penetrates through the thickness direction of the cutting insert 1.

[0026] (Seat surface) The seating surface 3 is formed in a roughly square shape when viewed from the direction along the center line CO. The seating surface 3 is contained within the projection area of ​​the scoop surface 2 in the thickness direction.

[0027] (Scooping surface) The scoop face 2 is formed in a roughly square shape when viewed from the direction along the center line CO. The outer shape of the scoop face 2 is larger than the outer shape of the seating surface 3. As shown in Figure 1, in this embodiment, the rake face 2 has a first plane 4 provided around the entire perimeter of the mounting hole 7, and a breaker 5 located between the first plane 4 and the cutting edge portion 20 (land 6).

[0028] As shown in Figure 3, the first plane 4 is a plane parallel to the seating surface 3, and in the thickness direction of the cutting insert 1 (along the center line CO), its distance from the seating surface 3 is smaller than that of the cutting edge portion 20, and it is a plane that is recessed compared to the cutting edge portion 20. The first plane 4 is not connected to the cutting edge portion 20 (land 6), and its entire outer circumference is separated from the cutting edge portion 20 (land 6) toward the center line CO.

[0029] As shown in Figure 1, the breaker 5 is provided around the entire perimeter of the first plane 4. The breaker 5 is connected to the land 6 formed on the cutting edge of the cutting edge portion 20. As shown in Figure 3, the breaker 5 has a first inclined surface 5a that slopes toward the seating surface 3 as it moves toward the center line CO from the cutting edge portion 20, a second inclined surface 5b that slopes toward the opposite direction from the seating surface 3 (towards the scooping surface 2) as it moves toward the center line CO, and a connecting portion 5c that connects the first inclined surface 5a and the second inclined surface 5b. The second inclined surface 5b is formed between the first inclined surface 5a and the first plane 4.

[0030] The first inclined surface 5a of the breaker 5 in this embodiment is configured to be connected to four cutting edge portions 20 (lands 6), and as it approaches the inside of the rake face 2 (towards the center line CO), it slopes gently toward the seating surface 3, and then slopes sharply so as to protrude toward the first plane 4 and connects to the outer edge of the first plane 4.

[0031] The cutting edge portion 20 and the length of the cutting edge used during cutting vary depending on the machining conditions such as the depth of cut. However, in this embodiment, since the breaker 5 is formed around the entire circumference of the cutting insert 1, chips are discharged via the breaker 5 regardless of the machining conditions under which the cutting insert 1 is used, thus suppressing cutting resistance.

[0032] Furthermore, as shown in Figures 1 and 3 to 5, the end of the first inclined surface 5a on the land 6 side has a multi-stage configuration, but this configuration is optional, and for example, it may be a single-stage inclined surface. When the first inclined surface 5a has a multi-stage surface 8 as shown in Figures 1 and 3 to 5, the angle θ1 formed by the multi-stage surface 8 and the first plane 4 is always smaller on the cutting edge side. For example, in Figure 3, where the multi-stage surface 8 consists of two stages, the angle θ1B formed by the multi-stage surface 8 on the cutting edge side and the first plane 4 is 5°, and the angle θ1A formed by the multi-stage surface 8 on the first plane 4 side and the first plane 4 is 10°. Note that the angle θ1 is constant around the entire circumference of the cutting insert 1. This is also true when the first inclined surface 5a consists of a multi-stage surface 8. For example, when angle θ1B is 5° and angle θ1A is 10°, angle θ1B will be 5° and angle θ1A will be 10° in any cross-section of the cutting insert 1. In other words, the angle relationship in Figure 3 also applies to Figures 4 and 5.

[0033] As shown in Figures 3 to 5, in any cross-section of the cutting insert 1, it is preferable that the width of the first inclined surface 5a in the radial direction of the breaker 5 in this embodiment (the sum of the first width W5a1 and the second width W5a2) is greater than the second width W5a2 of the second inclined surface 5b. Also, similar to the angle relationship described above, the width of the first inclined surface 5a is constant around the entire circumference of the cutting insert 1.

[0034] As a result, the chips can be guided along the gently sloping and wide first inclined surface 5a after they leave the cutting edge. Therefore, the chips can be discharged while suppressing resistance caused by collision between the breaker surface and the chips. In addition, by narrowing the width of the second inclined surface 5b in the radial direction, it is possible to achieve both "securing the width of the first inclined surface 5a (the sum of the first width W5a1 and the second width W5a2)" and "securing the area of ​​the first plane 4".

[0035] Furthermore, the angle θ1 formed between the first inclined surface 5a and the first plane 4 of the breaker 5, and the angle θ2 formed between the second inclined surface 5b and the first plane 4, may be formed to be equal. Also, if the first inclined surface 5a has a multi-stage configuration, the angle formed between the first inclined surface 5a closest to the deepest part S and the first plane 4 (angle θ1A in Figures 3 to 5) and angle θ2 may be formed to be equal.

[0036] (Cutting edge) The intersecting ridge between the rake face 2 and the side surface 10 is formed by a plurality of cutting edge sections 20, each comprising a plurality of main cutting edges 21, a plurality of secondary cutting edges 22, and a plurality of corner edges 23. As shown in Figure 1, the cutting edge section 20 includes a main cutting edge 21, a secondary cutting edge 22 connected to one end of the main cutting edge 21, and a corner edge 23 connected to the end of the secondary cutting edge 22 opposite to the main cutting edge 21. The main cutting edges 21, secondary cutting edges 22, and corner edges 23 are arranged in this order in a clockwise direction in a plan view of the rake face 2.

[0037] In the cutting insert 1 of this embodiment, the cutting edge portion 20, which consists of a main cutting edge 21, a secondary cutting edge 22, and a corner cutting edge 23, is provided in four locations at 90° intervals in the circumferential direction around the center line CO. The four cutting edge portions 20 are arranged in a rotationally symmetrical manner around the center line CO. The four cutting edges 20, arranged along the circumferential direction, are continuous with each other.

[0038] The main cutting edge 21 is located on the edge of the rake face 2 and extends in a straight line in a plan view of the rake face 2. The main cutting edge 21 constitutes the majority of the cutting edge portion 20. When the cutting insert 1 is attached to the tool body 31 (see Figure 7), the main cutting edge 21 faces the rotational direction TD of the tool body 31 and faces the workpiece.

[0039] The corner blade 23 is located at the corner of the rake face 2. The corner blade 23 has an arc shape in the plan view shown in Figure 1. On the other hand, the main cutting edge 21 and the secondary cutting edge 22 extend in a straight line. Therefore, the boundary between the corner blade 23 and the main cutting edge 21 and the secondary cutting edge 22 is determined by the boundary between the straight-shaped portion and the arc-shaped portion of the cutting edge portion 20.

[0040] The secondary cutting edge 22 is located between the main cutting edge 21 and the corner cutting edge 23. The secondary cutting edge 22 extends linearly between the main cutting edge 21 and the corner cutting edge 23. The secondary cutting edge 22 extends at an inclination relative to the direction of extension of the main cutting edge 21, approaching the center line CO as it moves from the main cutting edge 21 to the corner cutting edge 23. Therefore, the boundary portion between the main cutting edge 21 and the secondary cutting edge 22 has a shape that protrudes slightly outward.

[0041] In this embodiment, the cutting edge portion 20 is treated to maintain its strength, and a strip-shaped land 6 is provided at the tip of the cutting edge portion 20. Multiple lands 6 are continuous with each other and are present around the entire outer circumference of the rake face 2.

[0042] Alternatively, honing may be formed instead of the land 6. In this case, since the breaker 5 is provided around the entire circumference of the cutting insert 1 across multiple cutting edge portions 20, it is preferable that the honing is also provided on multiple cutting edge portions 20 so that it is present around the entire circumference of the cutting insert 1.

[0043] Furthermore, the honing shape may be any shape that has been treated with other honing processes, such as flat honing, chamfered negative honing, round honing, or horizontal flat honing. In this embodiment, it is preferable to form R-honing after forming negative honing at the tip of the cutting edge portion 20. This is because applying both negative honing and R-honing improves the strength of the tip of the cutting edge portion 20, and by increasing the tool angle at the tip of the cutting edge portion 20, damage to the cutting edge portion 20 when it bites into the workpiece can be suppressed. The amount of honing is set appropriately considering the desired cutting edge strength, rake face wear, cutting resistance, etc.

[0044] (side) In this embodiment, the cutting insert 1 is a positive-type cutting insert, and as shown in Figure 2, the upper relief surface 11 and the lower relief surface 15 that constitute the side surface 10 are inclined surfaces that are approximately aligned with the relief angle. In this embodiment, when the cutting insert 1 is attached to the tool body 31, the first cutting angle with respect to the workpiece is less than 45°.

[0045] A boundary portion 14 is located between the upper relief surface 11 and the lower relief surface 15. That is, the side surface 10 is composed of two relief surfaces 11 and 15 that are separated in the thickness direction, and the boundary portion 14 divides it into the upper relief surface 11 and the lower relief surface 15. The upper relief surface 11 and the lower relief surface 15 are adjacent to each other in the direction (thickness direction) along the center line CO of the cutting insert 1.

[0046] The upper relief surface 11 is located on the side surface 10, closer to the rake face 2 than the boundary portion 14. The lower relief surface 15 is located on the side surface 10, closer to the seating surface 3 than the boundary portion 14. Of the two relief surfaces 11 and 15, the distance from the lower end of the upper relief surface 11, which is closer to the first plane 4, to the tip of the cutting edge portion 20 satisfies the relationship L14 ≥ L15 between the distance L14 in the cross-section passing through the normal to the corner blade 23 and the distance L15 in the cross-section passing through the main cutting edge 21, as shown in Figures 3 and 4. In other words, the side surface corresponding to the corner portion has the boundary portion 14 positioned closer to the seating surface. As shown in Figure 5, the distance L16 in the cross-section passing through the secondary cutting edge 22 is shorter than L14 and L15. However, as shown in Figure 2, the boundary portion 14 of the secondary cutting edge 22 has a shape that is convex upward from the main cutting edge 21 side to the corner cutting edge 23 side.

[0047] The upper relief surface 11 is divided into a first region 11A connected to the main cutting edge 21, a second region 11B connected to the secondary cutting edge 22, and a third region 11C connected to the corner edge. The first region 11A, the second region 11B, and the third region 11C are aligned along the circumferential direction of the centerline CO.

[0048] The boundary portion 14 extends along the circumferential direction of the center line CO on the side surface 10, curving in the thickness direction. The boundary portion 14 includes a first section 14a extending along the main cutting edge 21, a second section 14b extending along the secondary cutting edge 22, and a third section 14c extending along the corner cutting edge 23. On the side surface 10, the first section 14a separates the lower relief surface 15 from the first region 11A of the upper relief surface 11, the second section 14b separates the lower relief surface 15 from the second region 11B, and the third section 14c separates the lower relief surface 15 from the third region 11C. As shown in Figure 2, the second section 14b is located on the scuff surface 2 side of the first section 14a. Also, the third section 14c is located on the seating surface 3 side of the first section 14a.

[0049] In this embodiment, the side surface 10 of the cutting insert 1 is composed of two relief surfaces 11 and 15 that are separated in the thickness direction. This increases the degree of freedom of the cutting edge shape of the cutting edge portion 20 and also increases the area of ​​the seating surface 3.

[0050] The cross-sectional shape shown in Figure 3 is the cross-section of the cutting edge portion 20 in Figure 1 that passes through the center of the main cutting edge 21 in the longitudinal direction, and is the cross-sectional shape along the line III-III in Figure 1. In the thickness direction at this position, the distance from the lower end of the upper relief surface 11 to the tip of the cutting edge portion 20 is defined as L15.

[0051] The cross-sectional shape shown in Figure 4 is the cross-section of the cutting edge portion 20 in Figure 1 that passes through the normal to the corner blade 23, and is the cross-sectional shape along the line IV-IV in Figure 1. In the thickness direction at this position, the distance from the lower end of the upper relief surface 11 to the tip of the cutting edge portion 20 is defined as L14.

[0052] The cross-sectional shape shown in Figure 5 is a cross-section that passes through the center of the length of the secondary cutting edge 22, which is a secondary cutting edge of the cutting edge portion 20 in Figure 1, and is a cross-sectional shape that follows the VV line in Figure 1. In the thickness direction at this position, the distance from the lower end of the upper relief surface 11 to the tip of the cutting edge portion 20 is defined as L16.

[0053] In this embodiment, the corner cutting edge 23 of the cutting edge portion 20 is located furthest from the tool rotation axis when the cutting insert 1 is attached to the tool body 31. Therefore, as shown in Figure 4, in a cross-section passing through the normal to the corner cutting edge 23, by setting the relationship between the distance L14 from the lower end of the upper relief surface 11 located on the rake face 2 side in the thickness direction of the side surface 10 to the cutting edge of the cutting edge portion 20 and the distance L15 in the cross-section passing through the main cutting edge 21 to L14 ≥ L15, sufficient wall thickness on the cutting edge side of the corner portion can be secured. This makes it possible to increase the cutting edge strength of the corner portion of the cutting insert 1, where the cutting load tends to be large. Furthermore, by satisfying the relationship L14 ≥ L15, friction between the corner portion and the workpiece caused by the rotation trajectory approaching the bottom surface side of the corner portion during cutting can be suppressed.

[0054] When attaching the cutting insert 1 to the tool body 31, as shown in Figure 7, the cutting insert 1 can be attached to the tool body 31 by tightening the clamp screw 38 against the tool body 31. When the clamp screw 38 is tightened, the seating surface 3 of the cutting insert 1 is pressed against the insert mounting seat 33 of the tool body 31, and the upper relief surface 11 located on the rake face 2 side of the side surface 10 comes into contact with the tool body 31, thereby restraining the cutting insert 1 to the tool body 31.

[0055] This positions the cutting insert 1 around the axis and radially within the tool body 31. By constraining the first region 11A of the upper relief surface 11, which is close to the cutting edge portion 20, to the tool body 31, it becomes possible to sufficiently and firmly restrain the cutting insert 1 against the cutting force applied to the cutting edge portion 20.

[0056] The cutting insert 1 in this embodiment is a four-corner type insert. When the cutting edges 20, which are arranged rotationally, reach a predetermined amount of wear, the cutting insert 1 is rotated 90° around the center line CO and reattached to the tool body 31 so that the other cutting edges 20 face the workpiece.

[0057] Next, the shape of the rake face 2 side of the cutting insert 1 in this embodiment will be described in detail. As shown in Figure 1, in this embodiment, the rake face 2 has a first plane 4 parallel to the seating surface 3 around the entire perimeter of the mounting hole 7. As shown in Figures 3, 4, and 5, the first plane 4 is located at a shorter distance from the seating surface 3 than the cutting edge portion 20 and is recessed inward from the cutting edge portion 20.

[0058] The first plane 4 has an outer circumference consisting of alternating linear portions 4a and projections 4b arranged around the axis of the center line CO. The linear portions 4a and projections 4b that constitute the outer circumference of the first plane 4 are provided in groups of four, at 90° intervals in the circumferential direction centered on the center line CO. The four linear portions 4a are identical in shape to each other, and the four projections 4b are also identical in shape to each other.

[0059] The linear portions 4a and projections 4b are arranged alternately in the circumferential direction and are continuous with respect to each other. In the radial direction intersecting the center line CO, each linear portion 4a faces each main cutting edge 21, and each projection 4b faces each secondary cutting edge 22 and corner cutting edge 23.

[0060] As shown in Figure 6, when viewed from an axial direction perpendicular to the first plane 4, the linear portion 4a is generally linear, but the central part in the longitudinal direction is slightly curved outward (towards the main cutting edge 21). The protruding portion 4b has an arc shape centered on one or more virtual center points located on the side of the mounting hole 7, and is a portion that protrudes radially outward from the linear portion 4a toward the sub cutting edge 22 and the corner edge 23.

[0061] Further, the protruding portion 4b has a pair of connection end portions 4b1 respectively connected to a pair of linear portions 4a adjacent to each other on both sides in the circumferential direction. These pair of connection end portions 4b1 have an arc shape centered on one or more virtual center points located on the side of the main cutting edge 21, and are portions that are slightly recessed inward from the linear portion 4a toward the mounting hole 7 side.

[0062] In the present embodiment, the protruding portion 4b may have an arc shape composed of a plurality of curvatures, or may have an arc shape composed of one curvature. Further, it may have an arc shape in which short straight lines are mixed in part. In the present embodiment, for example, a straight portion 4b2 exists at the apex (apex q2 described later) of the protruding portion 4b.

[0063] In the radial direction of the mounting hole 7, the maximum width W2 between the mounting hole 7 and the protruding portion 4b (apex q2) is larger than the maximum width W1 between the mounting hole 7 and the linear portion 4a facing the main cutting edge 21, satisfying the relationship W1 < W2.

[0064] If the width W1 on the side of the linear portion 4a facing the main cutting edge 21 in the first plane 4 is increased, most of the chips generated by the main cutting edge 21 during cutting of the workpiece may contact the linear portion 4a. Therefore, it is preferable that the linear portion 4a is away from the main cutting edge 21.

[0065] As shown by the broken line in FIG. 6, the shape connecting the intersection points (intersection point Q) of the extension lines of adjacent main cutting edges 21 is a regular polygon 20T. Further, the first plane 4 has a regular polygon 4T in which the shape connecting the apexes q2 of the four protruding portions 4b is smaller than the outer shape of the rake face 2. In the present embodiment, a "phase shift" is provided around the center line CO between the outer shape of the rake face 2 and the outer shape of the first plane 4.

[0066] Here, "phase shift" refers to the amount of displacement around the axis between the two regular polygons 20T and 4T shown in Figure 6. Specifically, when viewed from a direction perpendicular to the first plane 4, if the line connecting the intersection point Q of the extensions of adjacent main cutting edges 21 and the center line CO is called the first line M1, and the line connecting vertex q2 and the center line CO is called the second line M2, then the angle θ3 between the first line M1 and the second line M2 is the amount of displacement around the axis. When the point where the first line M1 passes through the corner cutting edge 23 is called vertex q1, the shape formed by connecting the vertices q1 of multiple corner cutting edges 23 is the regular polygon 20T.

[0067] Furthermore, if we define vertex q2 as the vertex of the projection 4b furthest from the mounting hole 7 on the first plane 4, the shape formed by connecting all vertices q2 is a regular polygon 4T. In other words, the shape of all projections 4b is formed to be identical.

[0068] A phase difference exists around the center line CO between the regular polygon 20T formed by connecting all vertices q1 and the regular polygon 4T formed by connecting all vertices q2, and the first line M1 and the second line M2 intersect at the center line CO at an angle θ3.

[0069] The angle θ3, which is the amount of displacement, is preferably within the range of 3° < θ3 < 15°, and more preferably within the range of 5° < θ3 < 10°.

[0070] Therefore, the vertex q1 of the corner blade 23 on the rake face 2 (cutting edge portion 20) side and the vertex q2 of the projection 4b of the first plane 4 do not face each other in the radial direction of the mounting hole 7. In this way, due to the phase difference between the rake face 2 and the first plane 4 around the center line CO, the distance between the first plane 4 and the cutting edge portion 20 is not constant, and there are positions in the circumferential direction where they are closest and furthest apart from each other.

[0071] As shown in Fig. 6, in the direction orthogonal to the center line CO, when the shortest distance from the boundary A between the main cutting edge 21 and the sub-cutting edge 22 adjacent in the circumferential direction to the first plane 4 is defined as L1, and the shortest distance from the boundary B between the main cutting edge 21 and the corner edge 23 to the first plane 4 is defined as L2, the relationship L1 < L2 is satisfied.

[0072] Also, in the present embodiment, as shown in Fig. 6, when the diameter of the inscribed circle 100 of the rake face 2 is D, it is preferable that the diameter D and the shortest distance L2 satisfy the relationship 3.0 ≤ D / L2 ≤ 6.5.

[0073] In order to obtain a preferable chip shape and a reduction effect of cutting resistance during cutting, a certain breaker distance is required. In the vicinity of the corner edge 23 where the chip becomes large, it is necessary to secure the length of the shortest distance L2. However, when D / L2 is larger than 6.5, the length of the shortest distance L2 is not sufficient with respect to the size of the cutting insert 1, so it is difficult to obtain the effect of an appropriate breaker. On the other hand, when D / L2 is smaller than 3.0, the area of the first plane 4 around the mounting hole 7 is too small, so the cutting edge strength of the cutting edge portion 20 decreases.

[0074] Also, when the cutting insert 1 is attached to the tool body 31, regardless of the presence or absence of the breaker 5, the corner portion is located on the outermost peripheral side. Also, in the case of a shape having the breaker 5 on the rake face 2 side, it is likely to be affected by the reduction of the wall thickness. That is, the cutting load at the corner portion during cutting is likely to increase. In contrast, in the rake face 2 of the present embodiment, a protrusion 4b is provided on the first plane 4 so as to protrude toward the cutting edge portion 20 in the vicinity of the corner portion, and the width of the breaker 5 at the corner portion is partially narrowed, so that while securing the width of the breaker necessary to obtain a preferable chip shape and a reduction effect of cutting resistance, the wall thickness of the cutting insert 1 at the corner portion can be sufficiently secured. Thereby, while ensuring the chip discharge property and the reduction effect of cutting resistance by the breaker 5, it is possible to make it difficult to be affected by the reduction of the wall thickness by the breaker 5. Similarly, the secondary cutting edge 22 receives a large impact from the workpiece because it includes the lowest point of the tool that first contacts the workpiece during cutting. However, in the rake face 2 of this embodiment, the width of the breaker 5 is partially narrowed in the first plane 4 near the secondary cutting edge 22. As a result, the cutting edge strength of the secondary cutting edge 22 is ensured, and the shape is designed to provide impact resistance. On the other hand, since the chip thickness generated by the secondary cutting edge 22 is thinner than the chip thickness generated by the main cutting edge 21 and the corner cutting edge 23, the shortest distance L1 can be made smaller than the shortest distance L2.

[0075] Next, the shape of the breaker 5 of the cutting insert 1 in this embodiment will be described in detail. As shown in Figures 3, 4, and 5, the breaker 5 of this embodiment is composed of a first inclined surface 5a, a second inclined surface 5b, and a connecting portion 5c that connects the first inclined surface 5a and the second inclined surface 5b.

[0076] As shown in Figure 3, the connecting portion 5c of the breaker 5 is shaped like an arc connecting the first inclined surface 5a and the second inclined surface 5b, but it is not limited to an arc shape as long as the first inclined surface 5a and the second inclined surface 5b are smoothly connected. For example, it may be a straight line. Here, the point of the connecting portion 5c that is closest to the seating surface 3 is called the "deepest part S".

[0077] As shown in Figure 3, in the thickness direction of the cutting insert 1, the distance from the seating surface 3 to the tip of the cutting edge portion 20 is defined as L11. Here, the tip of the cutting edge portion 20 refers to the part of the cutting edge portion 20 that is furthest from the seating surface 3. Therefore, if negative honing is formed on the tip of the cutting edge portion 20, the distance from the corner furthest from the seating surface 3 among the two corners formed by the negative honing to the seating surface 3 is L11. Similarly, if R-honing is applied to the tip of the cutting edge portion 20, the distance from the apex of the R-honing, that is, the point furthest from the seating surface 3 in the R-arc shape to the seating surface 3 is L11.

[0078] In the thickness direction of the cutting insert 1, the distance from the seating surface 3 to the first plane 4 is defined as L12. The first plane 4 is formed as a plane perpendicular to the center line CO around the mounting hole 7. Since the first plane 4 is parallel to the seating surface 3, the distance L12 to the seating surface 3 is the same at any point on the first plane 4.

[0079] In the thickness direction of the cutting insert 1, the distance from the seating surface 3 to the deepest part S of the breaker 5 is defined as L13. The two inclined surfaces (first inclined surface 5a and second inclined surface 5b) that make up the breaker 5 are connected by a connecting part 5c. The deepest part S of the breaker 5 refers to the lowest point of the connecting part 5c. Therefore, if the connecting part 5c is arc-shaped, the distance from the deepest part S (lowest point) of the connecting part 5c to the seating surface 3 is L13. Similarly, if the connecting part 5c is straight and parallel to the seating surface 3, the distance between the connecting part 5c and the seating surface 3 is L13, and the distance L13 to the seating surface 3 is the same at any point on the connecting part 5c. Furthermore, if the connecting portion 5c consists of an inclined surface, one of the connecting portions 5c, either the side connected to the first inclined surface 5a or the side connected to the second inclined surface 5b, will be closer to the seating surface 3 than the other. Therefore, the distance from one end of the connecting portion 5c in the longitudinal direction to the seating surface 3 will be L13.

[0080] In the cutting insert 1, in the thickness direction along the center line CO, the distance L11 from the seating surface 3 to the tip of the cutting edge portion 20, the distance L12 from the seating surface 3 to the first plane 4, and the distance L13 from the seating surface 3 to the deepest part S of the breaker 5 are in the relationship L11 > L12 > L13.

[0081] As shown in Figure 5, the difference between the distance L11 from the seating surface 3 to the tip of the cutting edge portion 20 and the distance L12 from the seating surface 3 to the first plane 4 is within the range of 0.01 mm or more and less than 0.15 mm.

[0082] In a configuration where a breaker 5 is provided around the entire circumference of the cutting insert 1 on the rake face 2 side, the effect of reducing cutting can be obtained regardless of which cutting edge portion 20 is used. However, at the same time, there was a risk of reduced strength due to the reduction in the thickness of the cutting insert 1. In contrast, in this embodiment, by setting the difference between the distance L11 and the distance L12 within the range of 0.01 mm to 0.15 mm, it is possible to increase the cross-sectional area of ​​the cutting insert 1 even with a configuration equipped with a breaker 5. Therefore, it is possible to ensure chip evacuation with the breaker 5 while ensuring the strength of the cutting insert 1 due to the increase in thickness. As a result, cutting resistance can be reduced even when using harsh cutting conditions, especially in high-efficiency machining, so that high-efficiency machining can be performed.

[0083] Furthermore, the difference between the distance L11 from the seating surface 3 to the tip of the cutting edge portion 20 and the distance L13 from the seating surface 3 to the deepest part S of the breaker 5 is within the range of 0.15 mm to 0.25 mm. If the difference between distance L11 and distance L13 is 0.25 mm or more, the adverse effects of insufficient strength of the cutting insert 1 outweigh the effect of reducing cutting resistance, resulting in bending or cracking at the base of the chip. Therefore, by keeping the difference between distance L11 and distance L13 within the above range, the effect of reducing cutting resistance, chip evacuation, and maintaining the strength of the cutting insert 1 can be sufficiently ensured.

[0084] (Configuration of a rotary cutting tool with replaceable cutting edges) Figure 7 is a perspective view showing the configuration of an interchangeable-tip rotary cutting tool 30 having a plurality of cutting inserts 1 and a tool body 31 to which these cutting inserts 1 are detachably attached. Figure 8 is a perspective view showing the configuration of the tool body 31 in the replaceable tip rotary cutting tool 30 shown in Figure 7.

[0085] As shown in Figures 7 and 8, the replaceable-tip rotary cutting tool 30 performs milling by rotating the tool body 31 in the rotational direction TD around the tool rotation axis JO. As shown in Figure 7, the replaceable-tip rotary cutting tool 30 has a tool body 31 that rotates around the axis of the tool rotation axis JO, and five cutting inserts 1 attached to the tool body 31.

[0086] As shown in Figures 7 and 8, the tip of the tool body 31 is provided with four insert mounting seats 33. The number of insert mounting seats 33 increases or decreases depending on the tool diameter of the replaceable-tip rotary cutting tool. Therefore, the number of insert mounting seats 33 decreases when the tool diameter is small, and conversely, the number of insert mounting seats 33 increases when the tool diameter is large. Each insert mounting seat 33 has a mounting seat bottom surface 33a and a pair of mounting seat wall surfaces 33b.

[0087] As shown in Figure 8, the mounting base surface 33a is square in shape with an area approximately equal to that of the seating surface 3 of the cutting insert 1 and faces the rotational direction TD. A pair of mounting base wall surfaces 33b extend from two sides of the mounting base surface 33a toward the rotational direction TD. A screw hole 33c is formed approximately in the center of the mounting base surface 33a.

[0088] As shown in Figure 7, the mounting base surface 33a contacts the seating surface 3 of the cutting insert 1 opposite it. The mounting base wall surface 33b also contacts the sides 10 formed on all four sides of the cutting insert 1 opposite it. In other words, the mounting base surface 33a and the mounting base wall surface 33b of the insert mounting base 33 contact the seating surface 3 and the upper relief surface 11 of the cutting insert 1.

[0089] The cutting insert 1 is attached to the insert mounting seat 33 of the tool body 31 using a clamp screw 38 as shown in Figure 7. Specifically, the cutting insert 1 is attached to the tool body 31 by tightening the clamp screw 38, which is inserted into the mounting hole 7, into a screw hole 33c formed in the center of the bottom surface 33a of the mounting seat.

[0090] In this embodiment, the cutting insert 1 is seated by bringing its seating surface 3 into close contact with the mounting base surface 33a of the tool body 31, and by bringing its two circumferentially adjacent upper relief surfaces 11 into contact with the mounting base wall surface 33b. Furthermore, by inserting the clamp screw 38 shown in Figure 7 into the screw hole 33c shown in Figure 8, the seating surface 3 is pressed against the mounting base surface 33a, and the upper relief surfaces 11 (first region 11A) are pressed against the mounting base wall surface 33b.

[0091] In this embodiment, the cutting insert 1 is shaped to ensure sufficient wall thickness at the corner, thereby increasing the strength of the cutting insert 1 itself when attached to the rotating tool body 31. Specifically, by providing a projection 4b that extends toward the corner on the first plane 4 that constitutes the rake face 2, the cutting insert can be made less susceptible to the effects of wall thickness reduction caused by the breaker 5. Furthermore, in the cross section passing through the normal to the corner blade 23, by maximizing the distance L14 from the lower end of the upper relief surface 11 located on the rake face 2 side in the thickness direction of the side surface 10 to the tip of the cutting edge portion 20, the lower end of the upper relief surface 11 can be brought closer to the seating surface 3, thereby ensuring sufficient wall thickness at the corner. This makes it possible to reduce cutting resistance at the corners of the cutting insert 1, where the cutting load tends to be high, while simultaneously maintaining strength.

[0092] Furthermore, since the breaker 5, located lower than the cutting edge portion 20 (on the seating surface 3 side), is formed around the entire circumference of the cutting insert 1, chips are discharged via the breaker 5 regardless of the machining conditions under which the cutting insert 1 is used. Therefore, it is possible to prevent damage to the cutting edge portion 20 due to chips coming into contact with the unused cutting edge portion 20. In addition, because chip evacuation is efficient, it is possible to suppress chip clogging and the increase in cutting resistance caused by chip deformation.

[0093] Furthermore, with the cutting insert 1 having the breaker 5, chip clogging can be suppressed not only in face milling but also in shape machining and other processes with complex shapes, enabling highly efficient machining.

[0094] Furthermore, the cutting insert 1 of this embodiment has a shape in which a first plane 4 and a breaker 5 exist on the rake face 2, and a "phase shift" occurs between the rake face 2 and the first plane 4 with a displacement of the angle θ3 around the center line CO. This makes it possible to secure the wall thickness of the cutting insert 1 near the corner cutting edge 23, resulting in a shape that achieves both the effect on chips due to the breaker shape and improved strength of the cutting insert 1.

[0095] Furthermore, the breaker 5 ensures that the chips are discharged after they have curled appropriately, preventing chip jamming between the cutting insert 1 and the workpiece. This improves chip evacuation during cutting and reduces cutting resistance.

[0096] According to the cutting insert 1 of this embodiment, even when machining difficult-to-machine materials, the chip evacuation performance is high, allowing for larger cutting widths and depths. As a result, even under machining conditions that achieve high machining efficiency, it is possible to prevent chips from colliding with the cutting insert, and the cutting insert 1 can fully demonstrate its inherent performance. [Examples]

[0097] Next, we will describe the results of the cutting process performed to confirm the effects of the present invention. Using the cutting inserts described in the examples, cutting operations were performed on the workpiece under the machining conditions described in the paragraphs below and in Table 1, and the chip shape and the spindle load on the machine tool's spindle were compared.

[0098] The workpiece used was made of S50C(H) steel and had a shape consisting of a flat section and a vertical wall section connected to the flat section.

[0099] To compare the performance of the cutting insert in the example and the cutting insert in the comparative example, in [Test 1], the axial depth of cut ap was set to 2.0 mm. In [Test 2], the axial depth of cut ap was set to 2.5 mm. In [Test 3], the axial depth of cut ap was set to 3.0 mm. Furthermore, all other conditions were the same in both the examples and the comparative examples.

[0100] The cutting conditions that were the same for both the example and the comparative example are shown below. • Rotation speed n = 758 min -1 ·Cutting speed Vc=150m / min Feed rate Vf = 1516 Feed rate per tooth fz = 2.0 mm / t • Radial cutting width ae = 38 mm • Projection OH = 200 mm (Tool diameter Do relative to projection OH: OH / Do = 3.2) • No coolant

[0101] Except for the above, the tool diameter and shape of the tool body, the number of inserts, and the type of machine tool were all the same in both the examples and the comparative examples. Cutting was performed under these machining conditions.

[0102] The cutting insert of the embodiment is a cutting insert in which, in the thickness direction along the center line CO, the distance L11 from the seating surface 3 to the tip of the cutting edge portion 20, the distance L12 from the seating surface 3 to the first plane 4, and the distance L13 from the seating surface 3 to the deepest part S of the breaker 5 are in the relationship L11 > L12 > L13.

[0103] The comparative example is a cutting insert in which the distances L11, L12, and L13 in the thickness direction along the center line CO are in the relationship L12 > L11 > L13. The other shapes are the same as in the example.

[0104] Table 1 shows the results (spindle load values ​​of the machine tool spindle) when Test 1, Test 2, and Test 3 were performed using the examples and comparative examples.

[0105] Figure 9A is a photograph showing the chips generated in this embodiment during Test 1 (axial depth of cut ap = 2.0 mm). Figure 9B is a photograph showing the chips generated in the comparative example during Test 1 (axial depth of cut ap = 2.0 mm). Figure 10A is a photograph showing the chips generated in this embodiment during Test 2 (axial depth of cut ap = 2.5 mm). Figure 10B is a photograph showing the chips generated in the comparative example during Test 2 (axial depth of cut ap = 2.5 mm). Figure 11A is a photograph showing the chips generated in this embodiment during Test 3 (axial depth of cut ap = 3.0 mm). Figure 11B is a photograph showing the chips generated in the comparative example during Test 3 (axial depth of cut ap = 3.0 mm).

[0106] [Table 1]

[0107] From the spindle load values ​​of the machine tool spindles in Table 1, the spindle load values ​​of the machine tool spindles in the embodiment were approximately the same as the spindle load values ​​of the machine tool spindles in the comparative example in all of the cutting tests from Test 1 to Test 3. In other words, it is considered that there is no influence on the cutting resistance due to the positional relationship between the first plane 4, the tip of the cutting edge portion 20, and the deepest part S of the breaker 5 in the cutting insert 1. The spindle load values ​​were measured using a load logger manufactured by the machine tool manufacturer (machine tool manufacturer: OKK Corporation) used for cutting.

[0108] Furthermore, the test results showed that in Test 1, the curl diameter φ1 of the chips generated in the example was 14.4 mm, and the curl diameter φ2 of the chips generated in the comparative example was 14.8 mm, indicating that they were of similar quality.

[0109] Furthermore, in Test 2, the curl diameter φ1 of the chips generated in the Example was 13.3 mm, while the curl diameter φ2 of the chips generated in the Comparative Example was 10.4 mm, indicating that the chips from the Example were larger than those from the Comparative Example.

[0110] Furthermore, in Test 3, the curl diameter φ1 of the chips generated in the Example was 15.0 mm, while the curl diameter φ2 of the chips generated in the Comparative Example was 11.0 mm, indicating that the chips from the Example were larger than those from the Comparative Example.

[0111] Furthermore, as can be seen from the dashed lines in Figures 9B, 10B, and 11B, in all tests 1, 2, and 3, bending (including extreme bending) was observed at the base of the chips in the comparative example.

[0112] In contrast, no bending was observed at the base of the chips in the example, and the shape extended naturally from the curled portion of the chip. In particular, in the comparative examples of Test 2 and Test 3, not only was the base of the chip bent, but cracks also occurred. Since the shape of the chip is directly related to the ease of chip evacuation, it can be seen that the example without bending or cracking had better chip evacuation than the comparative examples.

[0113] Although embodiments of the present invention have been described above, the configurations and combinations thereof in the embodiments are merely examples, and additions, omissions, substitutions, and other modifications are possible without departing from the spirit of the present invention. Furthermore, the present invention is not limited by the embodiments. [Explanation of symbols]

[0114] 1…Cutting insert 2... Scoop surface 3…Seat surface 4...1st plane 5... Circuit breaker 5a...first slope 5b…Second slope 7…Mounting holes 10... Side 11… Upper escape face 11...Escape face (upper escape face) 15...Escape 20...Blade part 21... Main cutting edge 22…Sub-cutting edge 23...Corner blade 30… Replaceable tip rotary cutting tool 31...Tool body 33…Insert mounting seat CO…center line JO...Tool rotation axis L11, L12, L13, L14... Distances in the cross-sectional view L1, L2… Distances in the floor plan S...Deepest part θ1, θ2, θ3… angles

Claims

1. A positive-type cutting insert in the shape of a polygonal plate, which is attached to a tool body that rotates around a rotation axis and is rotationally symmetrical with respect to a center line extending in the thickness direction, A rake face that constitutes one of a pair of polygonal faces, The seating surface that constitutes the other of a pair of polygonal surfaces, A side surface connecting the scooping surface and the seating surface, A cutting edge portion including a straight main cutting edge located at the edge of the rake face, formed on the intersecting ridge line of the rake face and the side surface, a straight secondary cutting edge connected to one end of the main cutting edge, and an arc-shaped corner cutting edge connected to the end of the secondary cutting edge opposite to the main cutting edge and located at the corner of the rake face, It comprises a mounting hole that penetrates in the thickness direction and is used for attaching to the tool body, The secondary cutting edge is located between the main cutting edge and the corner cutting edge, and extends inclined so as it approaches the center line from the boundary with the main cutting edge toward the corner cutting edge. A first plane parallel to the seating surface is formed on the scooping surface. The outer periphery of the first plane has linear portions and protrusions arranged alternately around the axis of the center line, The aforementioned projection has an arc shape centered on one or more virtual center points, and protrudes radially outward from the linear portion only toward the secondary cutting edge and the corner cutting edge. The rake face is provided with a breaker including a first inclined surface and a second inclined surface around the entire circumference of the cutting insert, between the cutting edge portion and the first plane. In a cross-sectional view perpendicular to the cutting edge portion, The first inclined surface is inclined toward the seating surface side as it moves from the cutting edge toward the center line side, The second inclined surface is formed between the first inclined surface and the first plane, and is inclined in the opposite direction to the seating surface as it approaches the centerline. L11 is the distance from the seating surface to the tip of the cutting edge in the thickness direction. The distance from the seating surface to the first plane in the thickness direction is L12. If L13 is the distance from the seating surface to the deepest part of the breaker in the thickness direction, A cutting insert characterized in that the relationship L11 > L12 > L13 is satisfied around the entire circumference of the cutting edge portion.

2. The difference between the distance L11 and the distance L12 is within the range of 0.01 mm or more and less than 0.15 mm. The difference between the distance L11 and the distance L13 is within the range of 0.15 mm or more and 0.25 mm or less. The cutting insert according to claim 1.

3. The aforementioned side surface is composed of two relief surfaces that are divided in the thickness direction, If, of the two relief surfaces, the one closer to the first plane is designated as the upper relief surface, In a side view taken from a direction intersecting the aforementioned thickness direction, The distance L14 from the lower end of the upper relief surface to the tip of the cutting edge portion in the cross section passing through the corner blade, The distance L15 from the lower end of the upper relief surface to the tip of the cutting edge portion in the cross-section passing through the main cutting edge is, L14 ≥ L15. A cutting insert according to claim 1 or 2.

4. The cutting insert according to claim 1 or 2, wherein the first inclined surface has a multi-stage configuration with multiple angles.

5. The first plane is, In a plan view from a direction opposite to the first plane, if L1 is the shortest distance from the boundary between adjacent main cutting edges and sub-cutting edges in the circumferential direction to the first plane, and L2 is the shortest distance from the boundary between the corner cutting edge and the main cutting edge to the first plane, then the relationship L1 < L2 is satisfied. A cutting insert according to claim 1 or 2.

6. If D is the diameter of the inscribed circle of the rake face, The relationship between D and L2 satisfies 3.0 ≤ D / L2 ≤ 6.

5. The cutting insert according to claim 5.

7. In a plan view from a direction opposite to the first plane, the width of the first inclined surface is wider than the width of the second inclined surface. A cutting insert according to claim 1 or 2.

8. Viewed from a direction perpendicular to the first plane, When the line connecting the intersection of the extensions of adjacent main cutting edges and the center line is defined as the first line, and the point where the first line passes through the corner cutting edge is defined as the first vertex, the shape formed by connecting the first vertices of the multiple corner cutting edges forms a regular polygon. When the vertex of the projection furthest from the mounting hole is designated as the second vertex, the shape formed by connecting multiple such second vertices also forms a regular polygon. A phase difference occurs between the regular polygon formed by connecting the first vertices and the regular polygon formed by connecting the second vertices, with respect to the center line. The first straight line and the second straight line, which is parallel to the first plane and passes through the center line connecting the second vertex, intersect at the center line at an angle θ3. A cutting insert according to claim 1 or 2.

9. A tool body that rotates around the axis of the tool rotation shaft, The tool body is provided with an insert mounting seat at its tip, to which a cutting insert according to claim 1 or 2 can be detachably attached.

10. The cutting insert and, The tool body is as described in claim 9, and comprises: When the cutting insert is mounted to the tool body such that the seating surface of the cutting insert contacts the insert mounting seat of the tool body, the cutting angle of the main cutting edge with respect to the workpiece is less than 45°. A rotary cutting tool with replaceable cutting edges.

Images