Cutting insert and indexable rotary cutting tool

Abstract

To provide a cutting insert that can suppress increase in cutting resistance due to collisions of chips, even during high-efficiency processing, and a blade edge replaceable cutting tool comprising such a cutting insert.SOLUTION: The cutting insert according to the present invention satisfies a relational expression of L1<L2, where a shortest distance from a boundary between a first cutting blade and a second cutting blade which are arranged adjacent to each other in a circumferential direction to a protrusion part on a first plane in a direction orthogonal to the first cutting blade, in a planar view which is viewed from a direction opposing to the first plane which is parallel to a seating surface is defined as L1 and a shortest distance from a boundary between a corner blade and the first cutting blade to the first plane in the direction orthogonal to the first cutting blade is defined as L2. A rake face comprises a breaker including a first inclined surface and a second inclined surface over the whole circumference of the insert, between a cutting blade part and the first plane, where the first inclined surface is inclined toward the seating surface as going from the cutting blade part side toward a center line and the second inclined surface is formed between the first inclined surface and the first plane and is inclined toward the opposite side of the seating surface side as going from the first inclined surface side toward the center line.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to a cutting insert and a replaceable tip rotary cutting tool.

Background Art

[0002] In such a cutting insert, it is known that the machining efficiency is improved by increasing the depth of cut and the width of cut during cutting. However, the greater the depth of cut and the width of cut, the greater the thickness and width of the chips generated by the cutting edge, resulting in higher cutting resistance. Furthermore, when large chips are not discharged outside the tool and hit the cutting insert, a large impact is applied to the cutting insert, which also increases the cutting resistance.

[0003] Therefore, Patent Document 1 discloses a configuration in which a breaker is formed between the main cutting edge and the seating surface on the rake face side in order to suppress the cutting resistance during machining with a cutting insert. This breaker is composed of a concave curved portion, a first inclined surface and a second inclined surface that slope upward in the central direction of the rake face. It is also described that the chip dischargeability is improved by forming the width of the breaker to be narrow during light cutting and wide during deep cutting.

[0004] Furthermore, Patent Document 1 discloses that the linear main cutting edge is inclined downward on the lower surface side in a direction away from the sub-cutting edge located at the corner portion, and the height of the seating surface on the rake face side is made lower than the height of the main cutting edge. It is described that this configuration makes it difficult for chips to become clogged and reduces the cutting load.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] However, in the case of Patent Document 1, the area of the inclined surface that rises in the central direction of the scooping surface formed by combining the first inclined surface and the second inclined surface is larger than the area of the inclined surface that descends in the central direction of the scooping surface formed by the concave curved portion of the breaker. In addition, the seating surface and the concave curved portion are formed substantially parallel (FIG. 6). Therefore, when chips are caused to follow the breaker during cutting, the effect of the guiding curved portion is low, and the chips immediately hit the inclined surface that rises in the central direction of the scooping surface, causing the chips to collide with the cutting insert forcefully and imparting a large impact, which may damage the cutting insert.

[0007] Also, although there are a scooping surface and a breaker between the seating surface and the main cutting edge on the scooping surface side, there is no breaker between the seating surface and the sub-cutting edge on the scooping surface side. For this reason, chips generated by the sub-cutting edge during cutting contact the seating surface on the scooping surface side without passing through the breaker, which may inhibit the discharge of the chips, damage the cutting insert, or increase the cutting resistance due to the collision between the chips and the cutting insert.

[0008] Furthermore, since the region where both the first inclined surface and the second inclined surface are used exists on the deep cutting side, the chips generated so as to follow the inclined surface may be distorted due to the change in the angle between the first inclined surface and the second inclined surface. Then, since the seating surface height on the scooping surface side of the cutting insert described in Patent Document 1 is lower than that of the main cutting edge, there is a risk that the distorted chips may get caught between the cutting edge and the workpiece or clog the clamp screw head.

[0009] The present invention has been made in view of such circumstances, and an object thereof is to provide a cutting insert capable of suppressing an increase in cutting resistance caused by chip collision even during high-efficiency machining, and a tip-exchangeable cutting tool equipped with such a cutting insert.

Means for Solving the Problems

[0010] 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 rotationally symmetric with respect to a center line extending in the thickness direction and is attached to a tool body that rotates around a rotation axis. The cutting insert includes a rake face that constitutes one of a pair of polygonal faces, a seating face that constitutes the other of the pair of polygonal faces, a side face that connects between the rake face and the seating face, a first cutting edge formed at an intersection ridge line between the rake face and the side face and located at a side portion of the rake face, a second cutting edge continuous with one end side of the first cutting edge, and a corner edge continuous with an end portion of the second cutting edge on the side opposite to the first cutting edge side and located at a corner portion of the rake face. The cutting insert further includes a mounting hole that penetrates in the thickness direction and is for mounting to the tool body. A first plane parallel to the seating face is formed on the rake face. The first plane has an outer periphery composed of linear portions and protrusions that are alternately arranged around the axis of the center line. In a plan view seen from a direction facing the first plane, the shortest distance L1 from the boundary between the first cutting edge and the second cutting edge adjacent in the circumferential direction to the protrusion of the first plane in a direction orthogonal to the first cutting edge, and the shortest distance L2 from the boundary between the corner edge and the first cutting edge to the first plane in a direction orthogonal to the first cutting edge satisfy the relationship L1 < L2. The rake face is provided with a breaker including a first inclined surface and a second inclined surface on the entire circumference of the insert between the cutting edge portion and the first plane. The first inclined surface is inclined toward the seating face side as it goes from the cutting edge portion side toward the center line side, and the second inclined surface is formed between the first inclined surface and the first plane and is inclined toward the side opposite to the seating face side as it goes from the first inclined surface side toward the center line side.

[0011] According to the above configuration, by providing the first plane such that "the shortest distance L2 from the boundary between the corner edge and the first cutting edge to the first plane" is greater than "the shortest distance L1 from the boundary between the first cutting edge and the second cutting edge adjacent in the circumferential direction to the protrusion of the first plane in a direction orthogonal to the center line", it is possible to avoid the chips from contacting the first plane, and thus it is possible to prevent an increase in cutting resistance due to the collision between the chips and the cutting insert.

[0012] Further, by forming most of the outer periphery of the first plane as a linear portion facing the first cutting edge and forming the vicinity of the corner portion as a protruding portion, it is possible to achieve both coping with chip collision and taking a wide reference surface during insert manufacturing, thereby facilitating obtaining the dimensional accuracy of the cutting insert. In the present invention, the farther the distance between the cutting edge portion and the first plane, the less likely the chips are to hit the cutting insert. On the other hand, in order to solve the problem that the smaller the area of the first plane, the smaller the reference surface also becomes, while ensuring a sufficient distance between the first cutting edge and the first plane to prevent the chips generated from the first cutting edge, which is frequently used during cutting, from colliding with the first plane, a protruding portion is formed near the corner portion to increase the area of the reference surface in a balanced manner.

[0013] Furthermore, the first plane is farther from the seating surface than the entire cutting edge portion in the direction along the center line. Therefore, even if the chips are not discharged outside the tool by any chance, the possibility that the chips are caught between the cutting edge and the work material or clogged in the clamp screw head can be reduced.

[0014] Also, according to the above-described configuration, although the cutting edge portion and the cutting edge length used during cutting vary depending on processing conditions such as the cutting depth, since the breaker is formed on the entire circumference of the cutting insert in the present invention, the chips are discharged through the breaker under any processing conditions, so that the cutting resistance can be suppressed.

[0015] In the cutting insert according to one aspect of the present invention, when the diameter of the inscribed circle of the rake face is D, the D and the L2 may be configured to satisfy the relationship of 3.0 ≤ D / L2 ≤ 6.5.

[0016] According to the above configuration, when D / L2 is less than 3.0, the length of L2 is not sufficient for the size of the cutting insert, so there is a high risk that chips will collide with the first plane during cutting. On the other hand, when D / L2 is greater than 6.5, the area of the first plane around the mounting hole is too small, so the reference area during the manufacture of the cutting insert becomes insufficient, making it difficult to ensure dimensional accuracy.

[0017] In the cutting insert according to one aspect of the present invention, in a plan view seen from the direction facing the first plane, the width of the first inclined surface may be wider than the width of the second inclined surface, and the angle θ1 of the first inclined surface may be smaller than the angle θ2 of the second inclined surface.

[0018] According to the above configuration, the chips can be guided along the gentle and wide first inclined surface after leaving the cutting edge. Therefore, the chips can be discharged while suppressing the resistance due to the impact between the breaker surface and the chips. Also, by narrowing the width of the second inclined surface, it is possible to ensure both the width of the first inclined surface and the area of the first plane. Furthermore, by increasing the angle of the second inclined surface with respect to the first plane, it becomes easier to form the first plane at a position higher than the cutting edge portion.

[0019] In the cutting insert according to one aspect of the present invention, when viewed from a direction perpendicular to the first plane, a straight line connecting the intersection of the extension lines of adjacent first cutting edges and the center line is defined as a first straight line, and when a point where the first straight line passes through the corner blade is defined as a first vertex, the shape formed by connecting the first vertices of a plurality of the corner blades forms a regular polygon. When a vertex of the protrusion farthest from the mounting hole is defined as a second vertex, the shape formed by connecting a plurality of the second vertices also forms a regular polygon. There is a phase shift around the center line between the regular polygon formed by connecting the first vertices and the regular polygon formed by connecting the second vertices. The first straight line and a second straight line that is parallel to the first plane and passes through the center line to connect the second vertex may intersect at an angle θ3 on the center line.

[0020] According to the above configuration, between the first plane and the scooping surface, since the shape has a phase shift around the center line, among the first plane, the protrusion located at the corner portion is the farthest from the cutting edge portion, and it is possible to avoid the chips generated by the first cutting edge from contacting the first plane. Thereby, the cutting resistance can be suppressed.

[0021] In the cutting insert according to one aspect of the present invention, the angle θ3 may be configured to be within the range of 3° < θ3 < 15°.

[0022] According to the above configuration, since the amount of phase shift (the above angle θ3) is within the above range, while securing the restraint region when attaching to the tool body, it is possible to prevent the chips generated by the first cutting edge from contacting the first plane (protrusion).

[0023] Further, a tip-exchangeable rotary cutting tool according to one aspect of the present invention includes the above cutting insert and the tool body to which the cutting insert is detachably attached and rotates around a rotation axis.

[0024] According to the tip-exchangeable rotary cutting tool of the present invention, the effects obtained from the above cutting insert are exhibited.

[0025] Also, in the tip-exchangeable rotary cutting tool described above, the cutting insert may be configured to be attached to the tool body such that the rake angle in the radial direction of the cutting edge portion is a negative angle.

[0026] According to the above configuration, even when the rake angle in the radial direction of the cutting edge portion is a negative angle, it is possible to provide a tip-exchangeable rotary cutting tool that sufficiently secures the clearance of the cutting edge portion.

Effects of the Invention

[0027] According to the present invention, it is possible to provide a cutting insert that can prevent chips from colliding with the cutting insert even under machining conditions that achieve high machining efficiency such as increasing the cutting depth, and a tip-exchangeable cutting tool equipped with such a cutting insert.

Brief Description of the Drawings

[0028]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Embodiments for Carrying Out the Invention

[0029] Hereinafter, embodiments to which the present invention is applied will be described in detail with reference to the drawings. Note that the drawings used in the following description may sometimes show only the characteristic parts for easy understanding, omitting parts that are not characteristic for convenience.

[0030] FIG. 1 is a plan view showing one embodiment of the cutting insert 1. FIG. 2 is a side view showing the configuration of the cutting insert 1 shown in FIG. 1. FIG. 3 is a cross-sectional view taken along line I-I in a direction perpendicular to the first cutting edge 21 of FIG. 1. FIG. 4 is a plan view showing the configuration on the rake face 2 side of the cutting insert 1.

[0031] As shown in Fig. 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. Also, the direction orthogonal to the center line CO may be simply referred to as the radial direction. Similarly, the circumferential direction around the axis centered on the center line CO may be simply referred to as the circumferential direction.

[0032] The cutting insert 1 includes 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, and a side face 10 that connects between the rake face 2 and the seating face 3. As shown in Fig. 2, the rake face 2 and the seating face 3 are formed in a substantially square shape. The seating face 3 is included inside the projection area of the rake face 2 in the thickness direction.

[0033] As shown in Fig. 1, the rake face 2 is provided with a breaker 5 between the cutting edge portion 20 and the first plane 4. The breaker 5 is formed around the entire circumference of the insert and is connected to the honing 6 formed at the cutting edge of the cutting edge portion 20. As shown in Fig. 3, the breaker 5 includes a first inclined face 5a that inclines toward the seating face 3 (Fig. 2) side as it goes from the cutting edge portion 20 toward the center line CO side, and a second inclined face 5b that inclines in the direction opposite to the seating face 3 (Fig. 2) side (rake face 2 side) as it goes toward the center line CO side. The second inclined face 5b is formed between the first inclined face 5a and the first plane 4.

[0034] Although the cutting edge portion 20 and the cutting edge length used during cutting vary depending on machining conditions such as the cutting depth, in this embodiment, since the breaker 5 is formed around the entire circumference of the cutting insert 1, no matter what machining conditions the cutting insert 1 is used under, the chips are discharged through the breaker 5, so that the cutting resistance can be suppressed.

[0035] As shown in Fig. 3, the angle θ1 formed between the first inclined surface 5a of the breaker 5 and the first flat surface 4 is 10°. Also, the angle θ2 formed between the second inclined surface 5b of the breaker 5 and the first flat surface 4 is 30°. The breaker 5 shown in Fig. 3 has a shape in which the first inclined surface 5a and the second inclined surface 5b are connected by an arc, but it is not limited to an arc as long as the first inclined surface 5a and the second inclined surface 5b are smoothly connected.

[0036] Also, the end on the honing 6 side of the first inclined surface 5a has a multi-step configuration, but this configuration may or may not be present. When the multi-step surface 8 is provided, the angle θ4 formed between the multi-step surface 8 and the first flat surface 4 shall be smaller than the angle θ1 formed between the first inclined surface 5a and the first flat surface 4. In Fig. 3, the angle θ4 formed between the multi-step surface 8 and the first flat surface 4 is 5° or less.

[0037] As shown in Fig. 1, in the breaker 5 of the present embodiment, in a plan view seen from the direction facing the first flat surface 4, the width W5a of the first inclined surface 5a in the radial direction is wider than the width W5b of the second inclined surface 5b (see also Fig. 3). Also, as shown in Fig. 3, it is preferable that the angle θ1 of the first inclined surface 5a is smaller than the angle θ2 of the second inclined surface 5b.

[0038] Thereby, the chips can be guided along the gentle and wide first inclined surface 5a after leaving the cutting edge. Therefore, the chips can be discharged while suppressing the resistance due to the collision between the breaker surface and the chips. Also, by narrowing the width of the second inclined surface 5b in the radial direction, it is possible to achieve both "ensuring the width W5a of the first inclined surface 5a" and "ensuring the area of the first flat surface 4". Furthermore, by increasing the angle of the second inclined surface 5b with respect to the first flat surface 4, it becomes easier to form the first flat surface 4 at a position higher than the cutting edge portion 20.

[0039] The cutting insert 1 is detachably attached to the tip of the tool body 31 shown in Fig. 5 by a clamp screw (fixing member) 38. As shown in Fig. 1, a mounting hole 7 through which the clamp screw 38 is inserted penetrates the center of the cutting insert 1. The mounting hole 7 is coaxial with the center line CO and extends along the center line CO.

[0040] On the intersecting ridge line between the rake face 2 and the side face 10, a cutting edge portion 20 is provided. The cutting edge portion 20 includes a first cutting edge 21, a second cutting edge 22 continuous with one end side of the first cutting edge 21, and a corner edge 23 continuous with the end portion of the second cutting edge 22 on the side opposite to the first cutting edge 21 side. The first cutting edge 21, the second cutting edge 22, and the corner edge 23 are arranged in this order clockwise in the plan view of the rake face 2.

[0041] In the cutting insert 1 of the present embodiment, four cutting edge portions 20 composed of the first cutting edge 21, the second cutting edge 22, and the corner edge 23 are provided at every 90° in the circumferential direction centered on the center line CO. The four cutting edge portions 20 are arranged rotationally symmetrically about the center line CO. The four cutting edge portions 20 arranged along the circumferential direction are continuous with each other.

[0042] The first cutting edge 21 is located at the side portion of the rake face 2 and extends linearly in the plan view of the rake face 2. The first cutting edge 21 constitutes most of the cutting edge portion 20. The first cutting edge 21 faces the work material toward the rotation direction TD side of the tool body 31 in a state where the cutting insert 1 is attached to the tool body 31 (see FIG. 5).

[0043] The corner edge 23 is located at the corner portion of the rake face 2. The corner edge 23 has an arc shape in the plan view shown in FIG. 1. On the other hand, the first cutting edge 21 and the second cutting edge 22 extend linearly. Therefore, the boundary between the corner edge 23 and the first cutting edge 21 and the second cutting edge 22 is determined by the boundary between the linear portion and the arc-shaped portion in the cutting edge portion 20.

[0044] The second cutting edge 22 is located between the first cutting edge 21 and the corner edge 23. The second cutting edge 22 extends linearly between the first cutting edge 21 and the corner edge 23. The second cutting edge 22 extends inclined so as to approach the center line CO as it goes from the first cutting edge 21 to the corner edge 23 with respect to the extending direction of the first cutting edge 21. Therefore, the boundary portion between the first cutting edge 21 and the second cutting edge 22 has a shape that slightly protrudes outward.

[0045] In this embodiment, a tip treatment for maintaining the strength of the cutting edge portion 20 is performed, and a honing 6 is formed at the tip of the cutting edge of the cutting edge portion 20. The honing 6 is formed at the tip of each of the cutting edges of the four cutting edge portions 20 and exists on the entire outer periphery of the rake face 2. In this embodiment, as the shape of the honing 6, a chamfered negative honing is formed, but other honing-treated shapes such as a round-shaped round honing or a horizontal-shaped flat honing may be used. The honing amount is appropriately set in consideration of the desired cutting edge strength, rake face wear amount, cutting resistance, etc.

[0046] As shown in FIG. 1, in this embodiment, the rake face 2 has a first plane 4 provided over the entire periphery of the mounting hole 7 and a breaker 5 existing between the first plane 4 and the cutting edge portion 20 (honing 6). The first plane 4 is not connected to the cutting edge portion 20 (honing 6), and the entire outer periphery thereof is separated from the cutting edge portion 20 toward the center line CO side.

[0047] As shown in FIG. 2, the first plane 4 is a plane parallel to the seating surface 3, and in the thickness direction of the cutting insert 1 (the direction along the center line CO), the distance from the seating surface 3 is larger than that of the cutting edge portion 20 and it is a surface protruding more than the cutting edge portion 20.

[0048] As shown in FIG. 1, the breaker 5 is provided over the entire periphery of the first plane 4 and has a first inclined surface 5a that inclines toward the seating surface 3 as it goes from the cutting edge portion 20 toward the center line CO. The first inclined surface 5a of the breaker 5 in this embodiment is configured to be continuous with the four cutting edge portions 20 (honing 6), gently inclines toward the seating surface 3 as it goes toward the inside (center line CO side) of the rake face 2, and then suddenly inclines so as to protrude toward the first plane 4 and is continuous with the outer peripheral edge of the first plane 4. The mounting hole 7 opens to the first plane 4 and the seating surface 3.

[0049] Since the cutting insert 1 in the present embodiment is a positive-type cutting insert, as shown in FIG. 2, the relief surface 11 and the connecting surface 15 that constitute the side surface 10 are inclined surfaces along a substantially relief angle. A boundary line 14 is located between the relief surface 11 and the connecting surface 15. That is, the side surface 10 is partitioned into the relief surface 11 and the connecting surface 15 by the boundary line 14.

[0050] The relief surface 11 and the connecting surface 15 are adjacent to each other in the direction along the center line CO of the cutting insert 1. The relief surface 11 is located on the rake face 2 side of the boundary line 14 on the side surface 10. Also, the connecting surface 15 is located on the seating surface 3 side of the boundary line 14 on the side surface 10.

[0051] The relief surface 11 is partitioned into a first region 11A continuous with the first cutting edge 21, a second region 11B continuous with the second cutting edge 22, and 11C continuous with the corner edge. The first region 11A, the second region 11B, and the third region 11C are arranged along the circumferential direction of the center line CO.

[0052] The boundary line 14 extends along the circumferential direction of the center line CO while curving in the thickness direction on the side surface 10. The boundary line 14 includes a first section 14a extending along the first cutting edge 21, a second section 14b extending along the second cutting edge 22, and a third section 14c extending along the corner edge 23. On the side surface 10, the first section 14a partitions the connecting surface 15 and the first region 11A of the relief surface 11, the second section 14b partitions the connecting surface 15 and the second region 11B, and the third section 14c partitions the connecting surface 15 and the third region 11C. As shown in FIG. 2, the second section 14b is located on the rake face 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.

[0053] As shown in FIG. 5, the cutting insert 1 is attached to the tool body 31 by tightening the clamp screw 38. When attaching the cutting insert 1 to the tool body 31, the first region 11A of the flank face 11 and the seating surface 3 function as a restraining portion that contacts the insert mounting seat 33. The cutting insert 1 is restrained by the tool body 31 when the seating surface 3 is pressed against the insert mounting seat 33 of the tool body 31 by tightening the clamp screw 38 and the first region 11A (see FIG. 2) located on the rake face 2 side of the flank face 11 contacts the tool body 31. Thereby, the cutting insert 1 is positioned in the tool body 31 in the axial direction and the radial direction. By restraining the first region 11A of the flank face 11 close to the cutting edge portion 20 by the tool body 31, it becomes possible to sufficiently firmly restrain the cutting insert 1 against the cutting force applied to the cutting edge portion 20.

[0054] On the other hand, the tool body 31 is provided with a clamp piece (not shown) that presses the rake face 2 of the cutting insert 1. The clamp piece faces the insert mounting seat 33 (FIG. 6) on the tool body 31 side via the cutting insert 1 and presses the cutting insert 1 toward the insert mounting seat 33. In the present embodiment, the clamp piece presses the first flat surface 4 existing on the rake face 2. The clamp piece can suppress the lifting of the cutting insert 1 during cutting.

[0055] The cutting insert 1 of the present embodiment is an insert having a four-corner type shape. When the cutting edge portion 20 arranged rotationally symmetrically reaches a predetermined wear amount, the cutting insert 1 is rotated 90° around the center line CO and remounted on the tool body 31 so that the other cutting edge portion 20 faces the workpiece.

[0056] Next, the shape on the rake face 2 side of the cutting insert 1 in the present embodiment will be described in detail. As shown in FIG. 1, on the rake face 2 of the present embodiment, a first flat surface 4 parallel to the seating surface 3 exists throughout the circumference of the mounting hole 7. As shown in FIG. 2, the first flat surface 4 is at a greater distance from the seating surface 3 than the cutting edge portion 20 and protrudes outward from the cutting edge portion 20.

[0057] The first plane 4 has an outer periphery composed of linear portions 4a and protruding portions 4b that are alternately arranged around the axis of the center line CO. The linear portions 4a and the protruding portions 4b that constitute the outer periphery of the first plane 4 are provided in groups of four at intervals of 90° in the circumferential direction centered on the center line CO. The four linear portions 4a have the same shape as each other, and the four protruding portions 4b also have the same shape as each other.

[0058] The linear portions 4a and the protruding portions 4b are alternately arranged in the circumferential direction and are continuous with each other. In the direction intersecting the center line CO, each linear portion 4a faces each first cutting edge 21, and each protruding portion 4b faces each second cutting edge 22 and the corner edge 23, respectively.

[0059] As shown in FIG. 1, when viewed from a direction perpendicular to the first plane 4, the linear portion 4a is generally linear, but the central portion in the length direction is slightly curved outward (toward the first 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 outward from the linear portion 4a toward the second cutting edge 22 and the corner edge 23.

[0060] Further, the protruding portion 4b has a pair of connection end portions 4b1 that are respectively connected to a pair of adjacent linear portions 4a 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 first cutting edge 21, and are portions that slightly protrude inward from the linear portion 4a toward the mounting hole 7 side.

[0061] 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 line portion 4b2 exists at the apex (second apex q2 described later) of the protruding portion 4b.

[0062] In this embodiment, by providing protruding portions 4b at the four corners of the first plane 4, it is possible to secure an area (the area where the clamping piece contacts) that is pressed by a clamping piece (not shown), that is, a so-called restraint area. In the radial direction of the mounting hole 7, the maximum width W2 between the mounting hole 7 and the protruding portion 4b (the second vertex q2) is larger than the maximum width W1 between the mounting hole 7 and the linear portion 4a facing the first cutting edge 21, satisfying the relationship W1 < W2.

[0063] If the width W1 on the side of the linear portion 4a facing the first cutting edge 21 in the first plane 4 is increased, most of the chips generated by the first cutting edge 21 during cutting of the workpiece to be machined may contact the linear portion 4a. Therefore, it is preferable that the linear portion 4a is away from the first cutting edge 21. On the other hand, since the protruding portion 4b side is an area pressed by the clamping piece, a wide pressing area is required. In this embodiment, in order to secure the pressing area by the clamping piece and prevent the chips from contacting in the first plane 4, the first plane 4 having a polygonal shape smaller than the scooping surface 2 is in a positional relationship shifted around the center line CO with respect to the polygonal scooping surface 2.

[0064] As shown by the broken line in FIG. 4, the first plane 4 has a shape in which the second vertices q2 of the four protruding portions 4b are connected to form a regular polygon. In this embodiment, a "phase shift" is provided around the center line CO between the outer shape of the scooping surface 2 and the outer shape of the first plane 4.

[0065] Here, the "phase shift" is the amount of shift around the axis between the two regular polygons 20T and 4T shown in FIG. 4. Specifically, when viewed from a direction perpendicular to the first plane 4, a straight line connecting the intersection Q of the extension lines of adjacent first cutting edges 21 and the center line CO is defined as the first straight line M1, and the point where the first straight line M1 passes through the corner blade 23 is defined as the first vertex q1, the shape formed by connecting the first vertices q1 of the plurality of corner blades 23 is a regular polygon 20T. Also, when the vertex of the protruding portion 4b farthest from the mounting hole 7 in the first plane 4 is defined as the second vertex q2, the shape formed by connecting the four second vertices q2 is a regular polygon 4T. There is a phase shift around the center line CO between the regular polygon 20T formed by connecting four first vertices q1 and the regular polygon 4T formed by connecting four second vertices q2, and the first straight line M1 and the second straight line M2 intersect at the center line CO at an angle θ3.

[0066] The angle θ3, which is the amount of shift, is preferably in the range of 3° < θ3 < 15°, and more preferably in the range of 5° < θ3 < 10°.

[0067] Therefore, the first vertex q1 of the corner blade 23 on the scooping surface 2 (cutting edge portion 20) side and the second vertex q2 of the protrusion 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 shift between the scooping surface 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 closest to each other and farthest apart in the circumferential direction.

[0068] As shown in FIG. 4, in the direction orthogonal to the center line CO, let the shortest distance from the boundary A between the first cutting edge 21 and the second cutting edge 22 adjacent in the circumferential direction to the protrusion 4b of the first plane 4 be L1, and the shortest distance from the boundary B between the corner blade 23 and the first cutting edge 21 to the protrusion 4b of the first plane 4 be L2. Then, the relationship L1 < L2 is satisfied.

[0069] That is, due to the above-mentioned phase shift, the first plane 4 is closest to the cutting edge portion 20 at the boundary A between the first cutting edge 21 and the second cutting edge 22, and the first plane 4 is farthest from the cutting edge portion 20 at the boundary B between the corner blade 23 and the first cutting edge 21.

[0070] In this way, among the first plane 4, the protrusion 4b located at the corner blade 23 is farthest from the cutting edge portion 20, and it is possible to avoid the chips generated by the first cutting edge 21 during cutting from contacting the first plane 4. Thereby, the cutting resistance can be suppressed.

[0071] In this embodiment, as shown in FIG. 4, assuming that 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 of 3.0 ≦ D / L2 ≦ 6.5. When D / L2 is less than 3.0, the length of the shortest distance L2 is not sufficient with respect to the size of the cutting insert 1, so there is a high risk that the chips will collide with the first plane 4 during cutting. On the other hand, when D / L2 is greater than 6.5, the area of the first plane 4 around the mounting hole 7 is too small, so the reference area during the manufacture of the cutting insert 1 becomes insufficient, and it becomes difficult to ensure the dimensional accuracy of the cutting insert 1.

[0072] (Configuration of Indexable Rotary Cutting Tool) FIG. 5 is a perspective view showing the configuration of an indexable 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. FIG. 6 is a perspective view showing the configuration of the tool body 31 in the indexable rotary cutting tool 30 shown in FIG. 5. FIG. 7 is a view showing the cutting insert in a state of being attached to the tool body shown in FIG. 6.

[0073] As shown in FIGS. 5 and 6, the indexable rotary cutting tool 30 performs milling by rotating the tool body 31 about the rotation axis JO in the rotation direction TD. As shown in FIG. 5, the indexable rotary cutting tool 30 includes a tool body 31 that rotates about the axis of the rotation axis JO and five cutting inserts 1 that are attached to the tool body 31.

[0074] As shown in FIGS. 5 and 6, four insert mounting seats 33 are provided at the tip of the tool body 31. The number of insert mounting seats 33 increases or decreases depending on the tool diameter of the indexable rotary cutting tool. For this reason, when the tool diameter is small, the number of insert mounting seats 33 decreases, and conversely, when the tool diameter is large, the number of insert mounting seats 33 increases. As shown in FIG. 5, the insert mounting seat 33 has a mounting seat bottom surface 33a and a pair of mounting seat wall surfaces 33b.

[0075] The mounting seat bottom surface 33a is square-shaped with an area approximately equal to the seating surface 3 of the cutting insert 1 and faces the rotational direction TD. The pair of mounting seat wall surfaces 33b extend from two sides of the mounting seat bottom surface 33a toward the rotational direction TD side respectively. A screw hole 33c is formed at approximately the center of the mounting seat bottom surface 33a.

[0076] The mounting seat bottom surface 33a contacts the seating surface 3 of the cutting insert 1 in an opposing manner. Also, the mounting seat wall surfaces 33b contact the side surfaces 10 formed on four sides of the cutting insert 1 in an opposing manner. That is, the mounting seat bottom surface 33a and the mounting seat wall surfaces 33b in the insert mounting seat 33 contact the seating surface 3 and the relief surface 11 of the cutting insert 1.

[0077] The cutting insert 1 is attached to the insert mounting seat 33 of the tool body 31 using a clamp screw 38. Specifically, the cutting insert 1 is attached to the tool body 31 by tightening the clamp screw 38 inserted into the mounting hole 7 to the screw hole 33c formed at the center of the mounting seat bottom surface 33a.

[0078] Also, although not shown in FIG. 5, the indexable rotary cutting tool 30 may be provided with a clamping piece for pressing the rake face 2 side of the cutting insert 1. The clamping piece suppresses the lifting of the cutting insert 1 during cutting.

[0079] The cutting insert 1 of the present embodiment has its seating surface 3 closely attached to the mounting seat bottom surface 33a of the tool body 31, and the two adjacent relief surfaces 11 in the circumferential direction are made to abut against the mounting seat wall surfaces 33b and seated. Further, by inserting the clamp screw 38 into the screw hole 33c, the seating surface 3 is pressed against the mounting seat bottom surface 33a, and the relief surface 11 (first region 11A) is pressed against the mounting seat wall surfaces 33b.

[0080] The cutting insert 1 of the present embodiment is shaped such that a first plane 4 and a breaker 5 are present on the rake face 2, and a "phase shift" occurs between the rake face 2 and the first plane 4 with a shift amount of the above angle θ3 around the center line CO. As a result, while securing a contact area (constraint area) of the clamping piece on the protrusion 4b side of the first plane 4, the distance between the cutting edge portion 20 and the first plane 4 can be partially increased. That is, among the first plane 4, the protrusion 4b located at the corner portion has a shape that is farthest from the cutting edge portion 20 (the boundary B between the first cutting edge 21 and the corner cutting edge 23).

[0081] Therefore, in the state where the cutting insert 1 is attached to the tool body 31 as shown in FIG. 5, as shown in FIG. 7, the distance between the corner cutting edge 23A (23) of each cutting insert 1 located on the outermost periphery of the indexable rotary cutting tool 30 and the machined surface 90a of the workpiece 90 becomes the largest, and it is possible to avoid the chips generated by the first cutting edge 21 from contacting the first plane 4, particularly the corner portion (protrusion 4b) during cutting. As a result, the chip discharge property is not inhibited, and it is possible to suppress the cutting resistance. Also, since the phase shift amount (the above angle θ3) is within the above range, it is possible to prevent the chips generated by the first cutting edge 21 from contacting the first plane 4 (protrusion 4b) while securing a constraint area when attaching the cutting insert 1 to the tool body 31.

[0082] Furthermore, since the breaker 5 preferably curls the chips and then discharges them, it is possible to prevent the chips from biting between the cutting insert 1 and the workpiece. As a result, the chip discharge property during cutting can be improved.

[0083] According to the cutting insert 1 of the present embodiment, since the chip discharge property is high even when machining difficult-to-cut materials, the cutting width and the cutting depth can be set large. As a result, it is possible to prevent the chips from colliding with the cutting insert even under machining conditions that achieve high machining efficiency, and it is possible to fully exhibit the original performance of the cutting insert 1.

[0084] The embodiments of the present invention have been described above. However, each configuration and their combinations in the embodiments are merely examples, and additions, omissions, substitutions, and other modifications of the configuration are possible without departing from the spirit of the present invention. Further, the present invention is not limited by the embodiments.

Description of Reference Numerals

[0085] 1... Cutting insert 2... Rake face 3... Seating surface 4... First plane 4a... Linear portion 4b... Protrusion 5... Breaker 5a... First inclined surface 5b... Second inclined surface 6... Honing 7... Mounting hole 10... Side surface 20... Cutting edge portion 21... First cutting edge 22... Second cutting edge 23(23A)... Corner edge 30... Indexable rotary cutting tool 31... Tool body A... Boundary between the first cutting edge and the second cutting edge B... Boundary between the corner edge and the first cutting edge CO... Center line JO... Rotation axis M1... First straight line M2... Second straight line q1... First vertex q2... Second vertex θ1... Angle formed by the first inclined surface 5a and the first plane 4 θ2... Angle formed by the second inclined surface 5b and the first plane 4 θ3... Angle (deviation amount)

Claims

1. A positive type cutting insert in the shape of a polygonal plate that is attached to a tool body rotating around a rotation axis and is rotationally symmetric with respect to a center line extending in the thickness direction, a rake face that constitutes one of a pair of polygonal faces, a seating face that constitutes the other of the pair of polygonal faces, a side face connecting between the rake face and the seating face, a cutting edge portion including a first cutting edge formed at an intersection ridge line between the rake face and the side face and located at an edge portion of the rake face, a second cutting edge continuous with one end side of the first cutting edge, and a corner edge continuous with an end portion of the second cutting edge on the side opposite to the first cutting edge side and located at a corner portion of the rake face, a mounting hole that penetrates in the thickness direction and is for mounting to the tool body, the cutting edge portion is provided at each of the corner portions of the rake face, the plurality of cutting edge portions are arranged rotationally symmetrically about the center line, and adjacent cutting edge portions are continuous with each other, a first plane parallel to the seating face is formed on the rake face, the first plane has an outer periphery composed of straight portions and protrusions arranged alternately around the axis of the center line, in a plan view seen from a direction facing the first plane, the shortest distance from the boundary between the first cutting edge and the second cutting edge adjacent in the circumferential direction to the protrusion of the first plane in a direction orthogonal to the first cutting edge is L1, and the shortest distance from the boundary between the corner edge and the side of the first cutting edge opposite to the second cutting edge side to the first plane in a direction orthogonal to the first cutting edge is L2. The relationship L1 < L2 is satisfied, and the rake face is provided with a breaker including a first inclined face and a second inclined face on the entire circumference of the insert between the cutting edge portion and the first plane, the first cutting edge is linear in a side view, in a cross-sectional view orthogonal to the first cutting edge, the first inclined face is inclined toward the seating face side as it goes from the cutting edge portion side toward the center line side, the second inclined face is formed between the first inclined face and the first plane and is formed to be inclined toward the side opposite to the seating face side as it goes from the first inclined face side toward the center line side. A cutting insert characterized by this.

2. When the diameter of the inscribed circle of the rake face is D, the cutting insert according to claim 1, wherein D and L2 satisfy the relationship 3.0 ≦ D / L2 ≦ 6.

5.

3. In a cross-sectional view including the center line and orthogonal to the first cutting edge, the width of the first inclined face is wider than the width of the second inclined face, and The angle θ1 formed by the first inclined surface and the first plane is smaller than the angle θ2 formed by the second inclined surface and the first plane, the cutting insert according to claim 1 or 2.

4. When viewed from a direction perpendicular to the first plane, when a straight line connecting the intersection of the extension lines of adjacent first cutting edges and the center line is defined as a first straight line and the point where the first straight line passes through the corner edge is defined as a first vertex, the shape formed by connecting the first vertices of the plurality of corner edges forms a regular polygon, when the vertex of the protrusion farthest from the mounting hole is defined as a second vertex, the shape formed by connecting the plurality of second vertices also forms a regular polygon, a phase shift 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, the cutting insert according to any one of claims 1 to 3, wherein the first straight line and a second straight line parallel to the first plane and passing through the center line and connecting the second vertex intersect at an angle θ3 on the center line.

5. the angle θ3 is within a range of 3° < θ3 < 15°, the cutting insert according to claim 4.

6. a cutting insert according to any one of claims 1 to 5, and a tool body to which the cutting insert is detachably attached and rotates around a rotation axis, a tip-exchangeable rotary cutting tool.

7. the tip-exchangeable rotary cutting tool according to claim 6, wherein the cutting insert is attached to the tool body such that the rake angle in the radial direction of the cutting edge portion is a negative angle.

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