JP7473835B2 - Cutting inserts and indexable cutting tools - Google Patents

Description

The present invention relates to a cutting insert in which mounting holes are formed on the front and back polygonal surfaces of an insert body formed in the shape of a polygonal plate, the mounting holes penetrating the insert body centered on the insert center line, and the ridges of the polygonal surfaces are formed with a convex arc-shaped corner edge, a main cutting edge extending linearly in the tangent direction of the corner edge, and a minor cutting edge receding relative to the extension line of the main cutting edge, when viewed in a plan view from the insert center line direction; and to a cutting tool in which such a cutting insert is removably attached to an insert mounting seat formed on the outer periphery of the tip of a tool body which is rotated in the tool rotation direction around an axis.
This application claims priority based on Japanese Patent Application No. 2020-56759, filed on March 26, 2020, the contents of which are incorporated herein by reference.

As such a cutting insert, for example, Patent Document 1 describes a cutting insert that has a first end face, a second end face facing in the opposite direction to the first end face, a peripheral side face connecting the first end face and the second end face and including a first peripheral side face facing in a first direction, a second peripheral side face facing in a second direction perpendicular to the first direction, a third peripheral side face facing in a third direction perpendicular to the second direction, and a fourth peripheral side face facing in a fourth direction perpendicular to the third direction, and a cutting edge formed on at least a portion of the connection between the first end face and the first peripheral side face, and that cuts the workpiece with the cutting edge by rotating relative to the workpiece on a predetermined rotation axis.

Here, the connection portion between the first end face and the first peripheral side surface portion, in an end view from a direction facing the first end face, includes a first connection portion that inclines so as to proceed in the first direction as it moves away from the second peripheral side surface portion and approaches the fourth peripheral side surface portion, and a second connection portion that is connected to a central point that is one end of the first connection portion and inclines so as to proceed in the third direction as it moves away from the second peripheral side surface portion and approaches the fourth peripheral side surface portion.

The cutting edge is provided with a first cutting edge portion that is convex in a side view from a direction facing the first peripheral side portion, has a first radius of curvature, is parallel to the first direction and the third direction, is perpendicular to the second direction and the fourth direction, and is formed on the first connecting portion a first distance away from an imaginary plane including the center point; a second cutting edge portion that is concave in a side view from a direction facing the first peripheral side portion, has a second radius of curvature smaller than the first radius of curvature, and is formed on the second connecting portion a second distance away from the imaginary plane that is greater than the first distance; and a bottom cutting edge portion that is formed across the first connecting portion and the second connecting portion to connect the first cutting edge portion and the second cutting edge portion.

A through hole is formed through the first end face and the second end face, and the imaginary plane includes the center axis of the through hole (insert center line), and the distance between a second imaginary plane that is perpendicular to the imaginary plane and passes through the first peripheral side portion, the second peripheral side portion, the third peripheral side portion, and the fourth peripheral side portion and the first cutting edge portion, the bottom cutting edge portion, and the second cutting edge portion becomes smaller as the distance from the second peripheral side portion increases and the distance from the fourth peripheral side portion decreases.

Japanese Patent No. 6507355 (B)

Incidentally, in cutting inserts such as the cutting insert described in Patent Document 1, a boss surface perpendicular to the insert center line of the through hole is formed around the opening of the through hole in the first and second end faces, and the cutting edge is usually formed at a position protruding further in the direction of the insert center line than this boss surface.

However, in such a cutting insert, as described in Patent Document 1, if the distance between the second imaginary plane and the first cutting edge portion, the bottom cutting edge portion and the second cutting edge portion is formed to become smaller as it moves away from the second circumferential side surface portion and closer to the fourth circumferential side surface portion, in other words, if the distance between the first cutting edge portion, the bottom cutting edge portion and the second cutting edge portion and the second imaginary plane is formed to become larger from the fourth circumferential surface portion toward the second circumferential surface portion, the amount by which the cutting edge protrudes from the boss surface on the second circumferential surface portion side becomes too large, and the strength of the cutting edge is impaired.

For this reason, when cutting a workpiece with a high hardness, such as HRC 50 to 65, or when cutting intermittently, such as when cutting a workpiece with many holes, the cutting edge is prone to chipping.

The present invention has been made against this background, and aims to provide a cutting insert capable of preventing chipping of the cutting edge when cutting a high-hardness workpiece material or when intermittent cutting is performed, and an indexable cutting tool to which such a cutting insert is removably attached.

In order to solve the above problems and achieve the above object, a cutting insert according to one embodiment of the present invention (hereinafter referred to as "the cutting insert of the present invention") has an insert body formed in a polygonal plate shape, and a mounting hole is opened on the front and back polygonal surfaces of the insert body, centered on the insert center line, and penetrating the insert body, and in a plan view seen from the insert center line direction, a corner blade is formed at the corner edge of the polygonal surface, the corner blade having a convex arc shape centered on a corner blade center line parallel to the insert center line, and a main cutting blade is formed from a first end of the corner blade, extending linearly in a tangential direction of the corner blade, and a minor cutting blade is formed from a first end of the main cutting blade opposite to the first end of the corner blade with respect to an extension line of the main cutting blade toward the first end of the main cutting blade. a first minor cutting edge having a convex arc shape with a radius larger than a radius of the corner edge contacting the main cutting edge at a first end of the main cutting edge in the plan view, and a second minor cutting edge extending linearly from a minor cutting edge first end of the first minor cutting edge opposite to the first end of the main cutting edge in a tangential direction of the first minor cutting edge, the main cutting edge and the first minor cutting edge being located on a parallel region extending along a direction parallel to a reference plane passing through the first end of the corner edge and perpendicular to the insert center line, and the second minor cutting edge having an inclined region inclined so as to gradually retreat toward the insert center line direction toward a second end of the minor cutting edge opposite to the first end of the minor cutting edge, and the polygonal surface has a corner edge, a main cutting edge, and a second minor cutting edge extending linearly from a first end of the minor cutting edge opposite to the first end of the main cutting edge in a tangential direction of the first minor cutting edge, the corner edge, the main cutting edge, and the second minor cutting edge having an inclined region inclined so as to gradually retreat toward the insert center line direction toward the second end of the minor cutting edge opposite to the first end of the minor cutting edge, and the polygonal surface has a corner edge, a main cutting edge, and a second minor cutting edge extending linearly from a first end of the minor cutting edge opposite to the first end of the minor cutting edge in a tangential direction of the first minor cutting edge. and a land portion is formed which gradually protrudes in the direction of the insert center line from the minor cutting edge toward the inside of the polygonal surface, and a rake face portion is formed on the inside of the polygonal surface from the land portion, which gradually recedes in the direction of the insert center line toward the inside of the polygonal surface, and the land portion has an inclination angle with respect to the reference plane in a cross section perpendicular to the first minor cutting edge on the parallel region, and a convex curved apex is formed between the land portion and the rake face portion, which is tangent to the land portion and the rake face portion in a cross section along the corner edge center line and a cross section perpendicular to the main cutting edge and the minor cutting edge, and the land portion of the corner edge is convex curved in the direction of the insert center line in a cross section along the corner edge center line, and the land portion of the first minor cutting edge has a convex curved shape that is convex in the insert centerline direction in a cross section perpendicular to the first minor cutting edge on the parallel region, ...

Another aspect of the indexable cutting tool of the present invention (hereinafter referred to as "the indexable cutting tool of the present invention") is characterized in that such a cutting insert is removably attached to an insert mounting seat formed on the outer periphery of the tip of a tool body that is rotated in the tool rotation direction around an axis, with one of the polygonal faces facing the tool rotation direction, the corner blade formed at the corner portion of this one polygonal face facing the outer periphery of the tip of the tool body, and the main cutting edge extending from a first end of the corner blade facing the inner periphery of the tool body, by screwing a clamp screw inserted into the mounting hole into a bottom surface of the insert mounting seat facing the tool rotation direction.
Another aspect of the tool body of the present invention (hereinafter referred to as "the tool body of the present invention") is a tool body for an indexable cutting tool, characterized in that the cutting insert of the present invention is removably attached to an insert mounting seat formed on the outer periphery of the tip of the tool body which is rotated in the tool rotation direction around an axis, with one of the polygonal faces facing the tool rotation direction, the corner blade formed on the corner portion of this one polygonal face facing the outer periphery of the tip of the tool body, and the main cutting edge extending from the first end of the corner blade facing the inner periphery of the tool body, by screwing a clamp screw inserted into the mounting hole into a bottom surface of the insert mounting seat facing the tool rotation direction.

In a cutting insert of the above configuration, of the main cutting edge and the minor cutting edge, only the inclined region provided on the second minor cutting edge of the minor cutting edge protrudes toward the insert center line as it moves toward the corner edge, and the portions of the main cutting edge and the minor cutting edge other than the inclined region are located on a parallel region that passes through the first end of the corner edge, which is the point of contact between the main cutting edge and the corner edge, and extends along a direction parallel to a reference plane perpendicular to the insert center line.

Therefore, when a boss surface is formed around the opening of the mounting hole of the polygonal surface, it is possible to prevent the main cutting edge and minor cutting edge located in the parallel region from protruding too much from this boss surface in the direction of the insert center line, thereby ensuring the cutting edge strength of these cutting edges and improving their resistance to chipping.

Therefore, the cutting insert and indexable cutting tool configured in this way can perform stable cutting for a long period of time, even when cutting a hard workpiece or when cutting intermittently. The parallel region does not have to be strictly parallel to a reference plane perpendicular to the center line of the insert, and may have an angle error of within 0.5° with respect to the reference plane within the range of manufacturing error.

On the other hand, in the cutting insert of the above configuration, the second minor cutting edge connected to the first minor cutting edge has an inclined region that gradually retreats toward the insert centerline direction toward the second end of the minor cutting edge opposite the first end of the minor cutting edge. Here, this second minor cutting edge is slightly inclined toward the rear end as it approaches the inner periphery of the tool body when the insert body is attached to the insert mounting seat, and is used exclusively when performing oblique cutting processing in which the tool body is fed obliquely with respect to the axis. Therefore, with the cutting insert and indexable cutting tool of the above configuration, the chipping resistance of the second minor cutting edge can be improved even in such oblique cutting processing.

Here, the second minor cutting edge may be entirely made into an inclined region, but the portion of the second minor cutting edge toward the first end of the minor cutting edge is located on the parallel region, and the portion of the second minor cutting edge toward the second end of the minor cutting edge is made into an inclined region that gradually retreats toward the center line of the insert as it moves from the parallel region toward the second end of the minor cutting edge. This makes it possible to increase the portion located on the parallel region and improve chipping resistance even when the feed rate per blade is large.

Furthermore, by making the width of the inclined region of the second minor cutting edge in a direction perpendicular to the insert center line when viewed from the direction facing the clearance face of the minor cutting edge larger than the width of the parallel region of the second minor cutting edge in a direction perpendicular to the insert center line, the chipping resistance of the second minor cutting edge can be more reliably ensured even when the cutting depth is large in the inclined cutting process as described above.

On the other hand, when a land portion is formed on the polygonal surface which gradually protrudes in the direction of the insert center line from the corner blade and the main cutting edge toward the inside of the polygonal surface, it is desirable that in a cross section taken along the corner blade center line, the inclination angle of the land portion at the first end of the corner blade relative to the reference plane be within the range of 15° to 25°.

By forming such a land portion, it is possible to more reliably ensure the cutting edge strength of the corner blade and main cutting edge, further improving chipping resistance, while preventing an increase in cutting resistance. In other words, if the inclination angle of the land portion at the first end of the corner blade is less than 15°, the cutting tool angle becomes small and it may be difficult to ensure chipping resistance in cutting hard work materials. On the other hand, if the inclination angle of the land portion at the first end of the corner blade exceeds 25°, the land portion 7 may rise too high, causing an increase in cutting resistance.

Similarly, when a land portion is formed on the polygonal surface that gradually protrudes in the direction of the insert centerline from the corner edge and the main cutting edge toward the inside of the polygonal surface, it is desirable that the width of the land portion at the corner edge first end in the direction perpendicular to the corner edge centerline in a cross section along the corner edge centerline is within a range of 0.35 mm to 0.45 mm. This configuration also makes it possible to maintain chipping resistance while reducing cutting resistance at the corner edge first end, which is the boundary between the corner edge and the main cutting edge.

That is, if the width of the land portion at the first end of the corner blade is less than 0.35 mm, the land portion becomes narrow and it may be difficult to ensure chipping resistance in cutting hard work materials, etc. On the other hand, if the width of the land portion at the first end of the corner blade exceeds 0.45 mm, the land portion becomes long and there is a risk of increased cutting resistance due to contact with chips.

Furthermore, the polygonal surface may be formed with a land portion that gradually protrudes in the direction of the insert centerline from the minor cutting edge toward the inside of the polygonal surface, in which case the cutting edge strength of the minor cutting edge can be ensured and chipping resistance can be improved. When a land portion is thus formed from the minor cutting edge to the inside of the polygonal surface, it is desirable that the inclination angle of the land portion with respect to the reference plane be within a range of 15° to 35° in a cross section perpendicular to the minor cutting edge at the first end of the minor cutting edge.

That is, if the inclination angle of the land portion at the first end of the minor cutting edge relative to the reference plane falls below 15°, the cutting angle of the minor cutting edge becomes small, making it more likely to chip when cutting a hard workpiece, etc. On the other hand, if the inclination angle of the land portion at the first end of the minor cutting edge relative to the reference plane exceeds 35°, the land portion of the minor cutting edge may rise too high, resulting in increased cutting resistance.

Similarly, when a land portion is formed on the polygonal surface which gradually protrudes in the direction of the insert center line from the minor cutting edge toward the inside of the polygonal surface, it is desirable that the width of the land portion in a direction parallel to the reference surface in a cross section perpendicular to the minor cutting edge at the first end of the corner blade is within the range of 0.15 mm to 0.45 mm.

That is, if the width of the land portion at the first end of the minor cutting edge is less than 0.15 mm, the land portion becomes too short and is prone to chipping when cutting a hard workpiece, etc. On the other hand, if the width of the land portion at the first end of the minor cutting edge is more than 0.45 mm, the land portion of the minor cutting edge becomes too long, which may increase cutting resistance due to contact with chips.

Furthermore, by forming the polygonal surface as a rectangular surface formed with 180° rotational symmetry around the insert centerline, forming the corner blades at the corner portions where two corners located on one diagonal of the rectangular surface are located, and forming the main cutting edge and the minor cutting edge at the short side portion of the rectangular surface connected to the corner blades, it is possible to use two corner blades, two main cutting edges, and two minor cutting edges on one polygonal surface, which is efficient and economical. In particular, in this case, by making the insert body symmetrical in front and back, it is possible to use four sets of corner blades, two main cutting edges, and two minor cutting edges on one insert body, which is even more efficient and economical.

As described above, according to the present invention, it is possible to impart high cutting edge strength to the first of the main and minor cutting edges, thereby improving the chipping resistance of these main and first minor cutting edges, and enabling stable cutting to be performed over a long period of time even when cutting a high-hardness workpiece or when intermittent cutting is performed on a workpiece containing a large number of holes.

1 is a perspective view showing a first embodiment of a cutting insert of the present invention. FIG. FIG. 2 is a plan view of the embodiment shown in FIG. 1 as viewed from the center line direction of the insert. FIG. 3 is a side view taken in the direction of the arrow V in FIG. 2 . FIG. 3 is a side view taken in the direction of the arrow W in FIG. 2 . FIG. 3 is an enlarged cross-sectional view of FIG. 2 taken along the line CX. FIG. 3 is an enlarged cross-sectional view of CY in FIG. 2 . FIG. 3 is an enlarged cross-sectional view of CZ in FIG. 2 . FIG. 2 is a perspective view of a tool body of an indexable cutting tool to which the embodiment shown in FIG. 1 is attached. FIG. 9 is a side view of the tool body shown in FIG. 8 . 9 is a perspective view showing an embodiment of an indexable cutting tool of the present invention in which the cutting insert of the embodiment shown in FIG. 1 is attached to the tool body shown in FIG. 8 . FIG. 11 is a side view of the embodiment shown in FIG. FIG. 2 is a perspective view showing a second embodiment of the cutting insert of the present invention. FIG. 13 is a plan view of the embodiment shown in FIG. 12 as viewed from the insert centerline direction. FIG. 14 is a side view taken in the direction of the arrow V in FIG. 13 . FIG. 14 is a side view taken in the direction of the arrow W in FIG. 13 . FIG. 14 is an enlarged cross-sectional view of FIG. 13 along the line CX. FIG. 14 is an enlarged cross-sectional view of CY in FIG. 13 . FIG. 14 is an enlarged cross-sectional view of CZ in FIG. 13 . FIG. 11 is a perspective view showing a third embodiment of the cutting insert of the present invention. FIG. 20 is a plan view of the embodiment shown in FIG. 19 as viewed from the insert centerline direction. 21 is a side view taken in the direction of the arrow V in FIG. 20 . 21 is a side view taken in the direction of the arrow W in FIG. 20. 21 is an enlarged cross-sectional view of FIG. 20 along the line CX. 21 is an enlarged cross-sectional view of CY in FIG. 20 . FIG. 21 is an enlarged cross-sectional view of CZ in FIG. 20 . FIG. 11 is a perspective view showing a fourth embodiment of the cutting insert of the present invention. FIG. 27 is a plan view of the embodiment shown in FIG. 26 as viewed from the insert centerline direction. 28 is a side view taken in the direction of the arrow V in FIG. 27. 28 is a side view taken in the direction of the arrow W in FIG. 27. 28 is an enlarged cross-sectional view of FIG. 27 along the line CX. FIG. 28 is an enlarged cross-sectional view of CY in FIG. 27 . FIG. 28 is an enlarged cross-sectional view of CZ in FIG. 27 .

Figures 1 to 7 show a first embodiment of the cutting insert of the present invention. Figures 8 and 9 show a tool body of an indexable cutting tool to which the cutting insert of this first embodiment is removably attached, and Figures 10 and 11 show one embodiment of the indexable cutting tool of the present invention in which the cutting insert of the first embodiment shown in Figures 1 to 7 is attached to the tool body.

The cutting insert of this embodiment has an insert body 1 formed into a polygonal plate shape from a hard material such as cemented carbide, and in this embodiment, the polygonal surface 2 of this insert body 1 is formed into a roughly rectangular surface centered on the insert center line L. The insert center line L is a line parallel to the thickness direction of the insert body that passes through the center of the polygonal surface 2. A mounting hole 1A with a circular cross section centered on the insert center line L is formed in the insert body 1 so as to penetrate the insert body 1 and opens into the center of the polygonal surfaces 2 on the front and back.

2, in a plan view seen from the insert center line L direction, a corner blade 3 is formed at the corner of the polygonal surface 2 of the insert body 1, forming a convex arc shape with the corner blade center line C parallel to the insert center line L. A main cutting edge 4 extending linearly in the tangent direction of the corner blade 3 is formed from the first corner blade end 3a of the corner blade 3 (the end of the corner blade 3 on the short side of the rectangle formed by the polygonal surface 2).

Furthermore, a minor cutting edge 5 is formed from the main cutting edge first end 4a opposite the corner edge first end 3a of the main cutting edge 4, receding toward the inside of the polygonal surface 2 with respect to the extension line toward the main cutting edge first end 4a of the main cutting edge 4. In this embodiment, the minor cutting edge 5 is provided with a first minor cutting edge 5A that is convexly arcuate with a larger radius than the corner edge 3 and contacts the main cutting edge 4 at the main cutting edge first end 4a in the plan view, and a second minor cutting edge 5B that contacts the first minor cutting edge 5A at the minor cutting edge first end 5a opposite the main cutting edge first end 4a of the first minor cutting edge 5A and extends in a straight line.

In this embodiment, the rectangular surface formed by the polygonal surfaces 2 on the front and back is formed with 180° rotational symmetry around the insert center line L, and corner edges 3 are formed at the corners (the lower right and upper left corners in FIG. 2) where two corners located on one diagonal of this rectangular surface are located. In addition, the main cutting edge 4 and the minor cutting edge 5 are formed on the short sides of the rectangular surface connected to this corner edge 3. Furthermore, the insert body 1 of this embodiment is formed with a shape that is inverted symmetrical on the front and back, and therefore four sets of corner edges 3, main cutting edges 4 and minor cutting edges 5 are formed on one insert body 1.

Here, a clearance surface 6 that connects to the corner edge 3, the main cutting edge 4, and the minor cutting edge 5 is formed on the side of the insert body 1 that extends between the front and rear polygonal faces 2. The side of the insert body 1, including this clearance surface 6, extends parallel to the insert center line L, and the cutting insert of this embodiment is a negative type cutting insert. Of this clearance surface 6, the portion that connects to the first minor cutting edge 5A of the minor cutting edge 5 is made into a common clearance surface 6 between the first minor cutting edges 5A formed on the same short side of the front and rear polygonal faces 2.

On the other hand, the polygonal surface 2 has land portions 7 formed along the entire length of the corner edges 3, major cutting edges 4, and minor cutting edges 5, which gradually protrude toward the outside of the insert body 1 in the direction of the insert center line L as they move toward the inside of the polygonal surface 2, as shown in Figures 5 to 7, and a rake surface portion 8 is formed on the inside of the polygonal surface 2 more than the land portions 7, which gradually recedes toward the inside of the insert body 1 in the direction of the insert center line L as they move toward the inside of the polygonal surface 2. In addition, between the land portions 7 and the rake surface portion 8, a convex curved apex 9 is formed that contacts the land portions 7 and the rake surface portion 8 in a cross section along the corner edge center line C and in a cross section perpendicular to the major cutting edges 4 and minor cutting edges 5.

Furthermore, as shown in Figures 5 to 7 in a cross section along the corner blade centerline C, a rear wall surface 10 is formed on the inside of the polygonal surface 2 relative to an extension line M of the scooping surface 8 toward the inside of the polygonal surface 2, and gradually retreats in the direction of the insert centerline L as it moves toward the inside of the polygonal surface 2. Also, on the inside of the polygonal surface 2 relative to the rear wall surface 10, a boss surface 2A is formed, which is a plane perpendicular to the insert centerline L that extends toward the inside of the polygonal surface 2 and forms the opening of the mounting hole 1A.

Here, the land portion 7 may be formed straight in a cross section along the corner blade center line C and in a cross section perpendicular to the major cutting edge 4 and the minor cutting edge 5, but in this embodiment, it is formed in a convex curve that is slightly convex in the direction of the corner blade center line C as shown in Figures 5 to 7. The rake surface portion 8 may also be formed straight in a cross section along the corner blade center line C and in a cross section perpendicular to the major cutting edge 4 and the minor cutting edge 5, but in this embodiment, it is formed in a convex curve that is slightly convex in the direction of the corner blade center line C as shown in Figures 5 to 7.

Furthermore, as shown in Figures 5 to 7 in a cross section along the corner blade center line C, in this embodiment, the rear wall surface portion 10 is formed so that, relative to the extension line M of the scooping surface portion 8 which is linear as described later, it forms a convex curve as it moves toward the inside of the polygonal surface 2, retreats in the direction of the insert center line L, and then forms a concave curve tangent to this convex curve, retreats in the direction of the insert center line L, and becomes tangent to the boss surface 2A.

Furthermore, within a range of 40° from the corner blade first end 3a of the corner blade 3 along the corner blade 3 toward the corner blade second end 3b opposite the corner blade first end 3a, the inclination angle θ1 of the land portion 7 with respect to a reference plane P perpendicular to the insert center line L is set to be equal to or greater than the inclination angle θ2 of the rake face portion 8 with respect to a reference plane P perpendicular to the insert center line L, as shown in Figures 5 to 7 in a cross section taken along the corner blade center line C. Note that in Figures 5 to 7, the position of the reference plane P perpendicular to the insert center line L is aligned with the position of the boss surface 2A.

In addition, in a cross section along the corner blade center line C, the inclination angle θ1 of the land portion 7 connected to the corner blade 3 shown in Figures 5 to 7 is preferably within the range of 15° to 25°, and in this embodiment is constant at 20° over the entire length of the corner blade 3.

In contrast, in a cross section along the corner blade center line C, the inclination angle θ2 of the rake face portion 8 at the corner blade first end 3a shown in Figure 7 is 17.1°, the inclination angle θ2 of the rake face portion 8 at a position that is 40° around the corner blade center line C from the corner blade first end 3a toward the corner blade second end 3b shown in Figure 6 and that is also 40° around the corner blade center line C from the corner blade second end 3b toward the corner blade first end 3a is 16.4°, and the inclination angle θ2 of the rake face portion 8 at the corner blade second end 3b of the corner blade 3 shown in Figure 5 is 14.4°. That is, in this embodiment, even within a range of 40° from the corner blade center line C along the corner blade 3 from the corner blade second end 3b on the opposite side to the corner blade first end 3a to the corner blade first end 3a, in a cross section along the corner blade center line C, the inclination angle θ1 of the land portion 7 with respect to a reference plane P perpendicular to the insert center line L is set to be equal to or larger than the inclination angle θ2 of the rake face portion 8 with respect to a reference plane P perpendicular to the insert center line L, and the inclination angle θ1 of the land portion 7 is set to be equal to or larger than the inclination angle θ2 of the rake face portion 8 over the entire length of the corner blade 3, and in particular the inclination angle θ1 is set to be larger than the inclination angle θ2. Note that the inclination angle θ2 of the rake face portion 8 connected to the corner blade 3 via the land portion 7 and the apex 9 is preferably set to be within a range of 5° to 20°.

Here, in this embodiment, since the cross section of the land portion 7 taken along the corner blade center line C has a slightly convex curved shape as described above, the inclination angle θ1 of this land portion 7 is the inclination angle of the straight line N connecting the corner blade 3 and the apex 9a of the apex 9 that protrudes most in the direction of the insert center line L, relative to the reference plane P, in the cross section taken along the corner blade center line C as shown in Figures 5 to 7. However, if the land portion 7 is formed in a straight line as described above in the cross section taken along the corner blade center line C, the inclination angle θ1 of the land portion 7 may be the inclination angle of this straight line, relative to the reference plane P.

In addition, in this embodiment, the cross section of the scooping surface portion 8 along the corner blade center line C also has a slightly convex curved shape as described above, so the inclination angle θ2 of this scooping surface portion 8 is the inclination angle, relative to the reference plane P, of a straight line connecting the vertex 9a of the apex 9 and the contact point 8a with the rear wall surface portion 10 of the scooping surface portion 8 where the rear wall surface portion 10 begins to retreat from the scooping surface portion 8 in the direction of the insert center line L, as shown in Figures 5 to 7, in the cross section along the corner blade center line C, i.e., the intersection angle between the extension line M of this straight line toward the inside of the polygonal surface 2 and the reference plane P (boss surface 2A).

However, when the cutting surface portion 8 is also linear as described above in the cross section along the corner blade center line C, the inclination angle θ2 of the cutting surface portion 8 may be the inclination angle of this straight line with respect to the reference plane P, i.e., the intersection angle between the extension line M of the straight line formed by the cutting surface portion 8 in the cross section along the corner blade center line C toward the inside of the polygonal surface 2 and the reference plane P.

Furthermore, in this embodiment, within a range of 40° around the corner blade center line C along the corner blade 3 from the corner blade first end 3a to the corner blade second end 3b, as shown in Figures 5 to 7 in the cross section along the corner blade center line C, the distance H1 in the direction perpendicular to the corner blade center line C from the corner blade 3 to the vertex 9a of the apex 9 in the direction of the insert center line L is less than or equal to the distance H2 in the direction perpendicular to the corner blade center line C from the vertex 9a of the apex 9 to the intersection 2a between the extension line M toward the inside of the polygonal surface 2 of the scooping surface portion 8 and the boss surface 2A.

However, as in this embodiment, when the cutting surface portion 8 is also formed in a convex curve that is slightly convexly curved in the direction of the corner blade center line C in a cross section along the corner blade center line C, the extension line of the cutting surface portion 8 to the inside of the polygonal face 2 also becomes a convex curve that is slightly convexly curved in the direction of the corner blade center line C.

Therefore, in such a case, the distance H2 may be determined as the distance perpendicular to the corner cutting edge center line C from the vertex 9a of the apex 9 to the intersection with the boss surface 2A of the extension line M of the straight line connecting the tangential point 8a between the scooping surface portion 8 and the rear wall surface portion 10 where the rear wall surface portion 10 begins to retreat from the scooping surface portion 8 in the direction of the insert center line L, and the vertex 9a of the apex 9, as shown in Figures 5 to 7.

Furthermore, in this embodiment, within a range of 40° from the corner blade center line C along the corner blade 3 from the corner blade first end 3a to the corner blade second end 3b, as shown in Figures 5 to 7 in a cross section along the corner blade center line C, the ratio H3/H2 of the distance H3 in a direction perpendicular to the corner blade center line C from the vertex 9a of the top 9 to the contact point or intersection (contact point 10a in this embodiment) with the boss surface 2A of the rear wall surface portion 10, and the distance H2 in a direction perpendicular to the corner blade center line C from the vertex 9a of the top 9 to the intersection point 2a between the extension line M toward the inside of the polygonal surface 2 of the scooping surface portion 8 and the boss surface 2A, is within a range of 0.45 to 0.75.

In particular, it is desirable that the distance H1 at the first end 3a of the corner blade be within the range of 0.35 mm to 0.45 mm, and in this embodiment, the distance H1 is constant at 0.4 mm over the entire length of the corner blade 3. In contrast, the distance H2 at the first end 3a of the corner blade shown in Figure 7 is 1.1 mm, and the distance H3 is 0.8 mm, while the distance H2 at the position 40° around the corner blade center line C from the first end 3a of the corner blade to the second end 3b of the corner blade shown in Figure 6 is 1.2 mm, and the distance H3 is 0.7 mm, and the distance H2 at the second end 3b of the corner blade 3 shown in Figure 5 is 0.7 mm, and the distance H3 is 0.4 mm.

That is, in this embodiment, even within a range of 40° from the corner blade centerline C from the corner blade second end 3b to the corner blade first end 3a along the corner blade 3, the distance H1 is set to be equal to or less than the distance H2, and the distance H1 is set to be equal to or less than the distance H2 over the entire length of the corner blade 3. Also, within a range of 40° from the corner blade centerline C from the corner blade first end 3a to the corner blade second end 3b along the corner blade 3, the ratio H3/H2 is set to be within a range of 0.45 to 0.75, and also within a range of 40° from the corner blade centerline C from the corner blade second end 3b to the corner blade first end 3a along the corner blade 3, the ratio H3/H2 is set to be within a range of 0.45 to 0.75.

Furthermore, in this embodiment, within a range of 40° from the corner blade centerline C along the corner blade 3 from the corner blade second end 3b to the corner blade first end 3a, the tangent or intersection line between the rear wall surface portion 10 and the boss surface 2A (in this embodiment, tangent line Q) is formed in an arc shape in the plan view as shown in Figure 2. In this plan view, the ratio G2/G1 of the radius G2 of the arc of the tangent line Q between the rear wall surface portion 10 and the boss surface 2A to the radius G1 of the arc of the corner blade 3 is within a range of 0.23 to 0.87 in this embodiment.

On the other hand, in this embodiment, the corner blade 3 is formed with a parallel region A extending along a direction parallel to a reference plane P perpendicular to the insert center line L. Here, in this embodiment, the corner blade 3 is located at a position close to the boss surface 2A in the insert center line L direction at the corner blade second end 3b as shown in FIG.

As shown in FIG. 4, the corner blade 3 gradually protrudes in the direction of the insert center line L from the corner blade second end 3b toward the corner blade first end 3a, and then reaches the parallel region A extending along a direction parallel to the reference plane P perpendicular to the insert center line L at a position 40° before the corner blade second end 3b around the corner blade center line C. After reaching the parallel region A, the corner blade 3 extends in a direction parallel to the reference plane P, reaches the corner blade first end 3a, and continues to the main cutting edge 4.

Furthermore, in this embodiment, the main cutting edge 4 to which the corner edge 3 is connected, and the first minor cutting edge 5A on the main cutting edge 4 side of the minor cutting edge 5 connected to this main cutting edge 4 are also located on a parallel region A that passes through the corner edge first end 3a and extends in a direction parallel to a reference plane P perpendicular to the insert center line L, as shown in Figure 3. On the other hand, the second minor cutting edge 5B connected to this first minor cutting edge 5A has an inclined region B that gradually retreats toward the insert center line L direction as it approaches the minor cutting edge second end 5b opposite the minor cutting edge first end 5a in this embodiment.

Here, in this embodiment, as shown in Figure 3, the portion of the second minor cutting edge 5B on the minor cutting edge first end 5a side is a parallel region A extending along a direction parallel to a reference plane P perpendicular to the insert center line L. The portion on the minor cutting edge second end 5b side of this parallel region A is an inclined region B which retreats in the direction of the insert center line L while tracing a convex curve that becomes convex in the direction of the insert center line L as it approaches the minor cutting edge second end 5b side, and then gradually retreats in the direction of the insert center line L at a constant inclination angle.

Furthermore, as shown in Figure 3 when viewed from the direction facing the clearance face 6 of the minor cutting edge 5, in this embodiment, the width W1 of the inclined region B of the second minor cutting edge 5B in a direction perpendicular to the insert center line L is made larger than the width W2 of the parallel region A of the second minor cutting edge 5B in a direction perpendicular to the insert center line L.

Furthermore, although not shown, at the minor cutting edge first end 5a, the inclination angle of the land portion 7 with respect to the reference plane P in a cross section perpendicular to the minor cutting edge 5 is preferably within a range of 15° to 35°, and is set to 20° in this embodiment. Similarly, at the minor cutting edge first end 5a, the width of the land portion 7 in a direction parallel to the reference plane P in a cross section perpendicular to the minor cutting edge 5 is preferably within a range of 0.15 mm to 0.45 mm, and is set to 0.4 mm in this embodiment.

Here, the insert body 1 of the cutting insert formed from such a hard material such as cemented carbide is manufactured according to the basic process of powder metallurgy technology. That is, when the insert body 1 is made of cemented carbide, powder press molding is performed using a die using granular granulated powder containing tungsten carbide powder and cobalt powder as the main components, with chromium, tantalum, etc. as secondary components as necessary.

The press-molded body thus obtained can be sintered for a prescribed time in a sintering furnace with appropriate atmosphere and temperature control to produce a sintered body that will become the insert body 1. The basic shape of the insert body 1 is reflected by the design of the mold, and the detailed shape of the insert body 1 is obtained by mold molding. Furthermore, to improve the precision of the cutting edge shape of the insert body 1, grinding processing may be performed using a grinding wheel as necessary.

A cutting insert of this configuration is removably attached to an insert mounting seat 12 formed on the outer periphery of the tip of the tool body 11 of the indexable cutting tool shown in Figures 8 and 9, constituting one embodiment of the indexable cutting tool of the present invention shown in Figures 10 and 11. The cutting insert attached to the insert mounting seat 12 in this manner cuts the workpiece with the corner blade 3, main cutting blade 4, and minor cutting blade 5 as the tool body 11 is rotated around the axis O in the tool rotation direction T and fed in a direction intersecting the axis O.

The tool body 11 is integrally formed from a metal material such as steel into a roughly cylindrical shaft shape centered on the axis O, with the rear end (upper part in Figs. 8 to 11) being the shank portion 11A that remains cylindrical, and the tip portion (lower part in Figs. 8 to 11) being the cutting edge portion 11B that has a smaller diameter than the shank portion 11A, and the insert mounting seat 12 is formed on this cutting edge portion 11B. In addition, a tapered neck portion 11C that decreases in diameter toward the tip side of the tool body 11 is formed between the shank portion 11A and the cutting edge portion 11B.

A plurality of groove-shaped chip pockets 13 (four evenly spaced in the circumferential direction in this embodiment) are formed on the outer periphery of the cutting edge portion 11B of the tool body 11, and the insert mounting seat 12 is formed as a recess that is recessed on the opposite side to the tool rotation direction T at the tip of the wall surface of the chip pockets 13 facing the tool rotation direction T. The coolant hole 11a formed in the tool body 11 opens on the wall surface of the chip pocket 13 facing the opposite side to the tool rotation direction T.

The insert mounting seat 12 has a bottom surface 12a facing the tool rotation direction T, a wall surface 12b extending from the inner periphery of the bottom surface 12a in the tool rotation direction T and facing the outer periphery, and a wall surface 12c extending from the rear end of the bottom surface 12a in the tool body 11 in the tool rotation direction T and facing the tip side. In addition, a groove-shaped relief portion 12d is formed at a corner where the bottom surface 12a and the wall surfaces 12b and 12c intersect and at a corner where the wall surfaces 12b and 12c intersect.

The bottom surface 12a is formed in a flat shape that is slightly smaller than the boss surface 2A of the polygonal surface 2 in the insert body 1 of the cutting insert, and is slightly inclined toward the tool rotation direction T as it approaches the rear end side of the tool body 11. In addition, a screw hole 12e is formed perpendicular to the center of the bottom surface 12a.

The cutting insert of the embodiment is seated on such an insert mounting seat 12 with one polygonal surface 2 of the insert body 1 facing the tool rotation direction T and the boss surface 2A of the other polygonal surface 2 in close contact with the bottom surface 12a, with the corner blade 3 formed on one corner of the one polygonal surface 2 facing the outer periphery of the tip of the tool body 11 and the main cutting edge 4 extending from the first end 3a of the corner blade 3 facing the inner periphery of the tool body 11. At this time, the two side surfaces of the insert body 1 that intersect with the other corner located diagonally on the one polygonal surface 2 from the one corner are abutted against the wall surfaces 12b, 12c.

The cutting insert thus seated is then removably attached to the insert mounting seat 12 by a clamp screw 14 inserted into the mounting hole 1A from the tool rotation direction T side and screwed into the screw hole 12e in the bottom surface 12a, whereby the boss surface 2A of the other polygonal surface 2 is pressed against the bottom surface 12a and the two side surfaces intersecting the other corner portion of the one polygonal surface 2 are pressed against the wall surfaces 12b, 12c.

Because the cutting insert attached to the insert mounting seat 12 in this manner has an inclined bottom surface 12a as described above, the insert center line L is slightly inclined toward the rear end of the tool body 11 as it moves in the opposite direction to the tool rotation direction T, thereby providing a clearance angle to the corner edge 3 facing the outer periphery of the tip of the tool body 11 and to the clearance faces 6 of the main cutting edge 4 and minor cutting edge 5 extending from this corner edge 3 toward the inner periphery of the tool body 11.

The main cutting edge 4 extending from the corner edge 3 facing the outer periphery of the tip of the tool body 11 to the inner periphery of the tool body 11 is slightly inclined toward the tip of the tool body 11 as it approaches the inner periphery. In other words, the indexable cutting tool of this embodiment is an indexable radius end mill. Furthermore, the minor cutting edge 5 connected to the main cutting edge 4 is disposed so that the straight line connecting the first end 4a of the main cutting edge and the first end 5a of the minor cutting edge is located on a plane perpendicular to the axis O of the tool body 11.

In the cutting insert of the above configuration thus attached to the tool body 11 of the indexable cutting tool, the main cutting edge 4, the first minor cutting edge 5A of the minor cutting edge 5, and the portion of the second minor cutting edge 5B other than the inclined region B are located on a parallel region A which passes through the corner edge first end 3a, which is the contact point between the main cutting edge 4 and the corner edge 3, and extends along a direction parallel to a reference plane P perpendicular to the insert center line L.

Therefore, when a boss surface 2A perpendicular to the insert center line L is formed around the opening of the mounting hole 1A of the polygonal surface 2 as in this embodiment, it is possible to prevent the main cutting edge 4 and the minor cutting edge 5 located in the parallel area A from protruding too much in the direction of the insert center line L from the boss surface 2A, and it is possible to ensure the strength of these cutting edges and improve their chipping resistance. Therefore, with the cutting insert and the indexable cutting tool configured in this way, it is possible to perform stable cutting over a long period of time, even when cutting a high-hardness workpiece or when cutting an intermittent cutting such as cutting a workpiece with many holes.

In particular, in this embodiment, the portion of the corner edge 3 on the side of the first end 3a of the corner edge, which is the contact point with the main cutting edge 4, is located on a parallel region A extending along a direction parallel to the reference plane P perpendicular to the insert center line L, like the first minor cutting edge 5A of the main cutting edge 4 and the minor cutting edge 5, which passes through the first end 3a of the corner edge 3, so that the cutting edge strength can be secured over a wider range from the corner edge 3 through the main cutting edge 4 to the minor cutting edge 5, thereby improving the chipping resistance. Note that this parallel region A does not have to be strictly parallel to the reference plane perpendicular to the insert center line, and may have an angle error of within 0.5° with respect to the reference plane within the range of manufacturing error, for example.

On the other hand, in the cutting insert of the above configuration, the second minor cutting edge 5B connected to the first minor cutting edge 5A in the minor cutting edge 5 is provided with an inclined region B that gradually retreats in the direction of the insert center line L as it approaches the second minor cutting edge end 5b opposite the first minor cutting edge end 5a. Here, this second minor cutting edge 5B extends in a straight line tangent to the convex curved first minor cutting edge 5A at the first minor cutting edge end 5a, and is slightly inclined toward the rear end as it approaches the inner periphery of the tool body 11 when the insert body 1 is attached to the insert mounting seat 12 so that the straight line connecting the first main cutting edge end 4a and the first minor cutting edge end 5a is located on a plane perpendicular to the axis O of the tool body 11 as described above.

The second minor cutting edge 5B inclined in this manner is used exclusively when performing oblique cutting in which the tool body 11 is fed obliquely with respect to the axis O. Therefore, with the cutting insert and indexable cutting tool configured as described above, even in the case of such oblique cutting, the cutting edge strength of the second minor cutting edge 5B can be ensured and chipping resistance can be improved.

Here, the entire second minor cutting edge 5B may be inclined region B, but in this embodiment, the portion of the second minor cutting edge 5B on the minor cutting edge first end 5a side is located on the parallel region A as described above, and the portion of the second minor cutting edge 5B on the minor cutting edge second end 5b side is inclined region B that gradually retreats toward the insert center line L as it approaches the minor cutting edge second end 5b. Therefore, in this embodiment, the portion of the minor cutting edge 5 located on the parallel region A can be made larger, making it possible to improve chipping resistance even when the feed rate per blade is large.

On the other hand, in this embodiment, when viewed from the direction facing the clearance face 6 of the minor cutting edge 5, the width W1 in the direction perpendicular to the insert center line L of the inclined region B of the second minor cutting edge 5B is made larger than the width W2 in the direction perpendicular to the insert center line L of the parallel region A of the second minor cutting edge 5B. Therefore, even when the cutting depth is large in the inclined cutting process as described above, the chipping resistance of the second minor cutting edge 5B can be more reliably ensured.

In addition, in this embodiment, the polygonal surface 2 is formed with a land portion 7 that gradually protrudes in the direction of the insert center line L from the corner edge 3 and the main cutting edge 4 toward the inside of the polygonal surface 2, and this land portion 7 makes it possible to increase the thickness of the insert body 1 on the polygonal surface 2 connected to the corner edge 3 and the main cutting edge 4, thereby providing high cutting edge strength. This further improves the chipping resistance of the corner edge 3 and the main cutting edge 4, making it possible to perform more stable cutting over a longer period of time, even when cutting a high-hardness workpiece or when cutting intermittently.

Furthermore, in this embodiment, in a cross section taken along the corner blade center line C, the inclination angle θ1 of the land portion 7 connected to the corner blade 3 is within a range of 15° to 25°, and this is also the case for the corner blade first end portion 3a which is the boundary between the corner blade 3 and the main cutting edge 4. Therefore, at the corner blade first end portion 3a which is the boundary between the corner blade 3 and the main cutting edge 4, it is possible to maintain chipping resistance while reducing cutting resistance.

That is, if the inclination angle θ1 of the land portion 7 at the corner blade first end 3a is less than 15°, the cutting tool angle becomes small and it may be difficult to ensure chipping resistance in cutting a hard workpiece. On the other hand, if the inclination angle θ1 of the land portion 7 at the corner blade first end 3a is more than 25°, the land portion 7 may rise too high, which may increase the cutting resistance.

Furthermore, in this embodiment, when a land portion 7 is formed on the polygonal surface 2, which gradually protrudes in the direction of the insert center line L from the corner edge 3 and the main cutting edge 4 toward the inside of the polygonal surface 2, the width of the land portion 7 at the corner edge first end 3a in the direction perpendicular to the corner edge center line C is within the range of 0.35 mm to 0.45 mm.

Here, in this embodiment, the width of the land portion 7 at the corner edge first end 3a is the distance H1 in the direction perpendicular to the corner edge center line C from the corner edge 3 to the apex 9a in the direction of the insert center line L of the apex 9, as shown in Figure 7. Therefore, according to this embodiment, it is possible to maintain chipping resistance while reducing cutting resistance at the corner edge first end 3a, which is the boundary between the corner edge 3 and the main cutting edge 4.

That is, if the width (distance H1) of the land portion 7 at the corner blade first end 3a is less than 0.35 mm, the land portion 7 becomes narrow and it may be difficult to ensure chipping resistance in cutting of high-hardness workpieces or in cutting that involves intermittent cutting. On the other hand, if the width (distance H1) of the land portion 7 at the corner blade first end 3a exceeds 0.45 mm, the land portion 7 becomes too long and there is a risk of increased cutting resistance due to friction caused by long contact with the chips.

Furthermore, in this embodiment, the land portion 7 is formed on the inside of the polygonal surface 2 even from the main cutting edge to the minor cutting edge 5, thereby ensuring the cutting edge strength of the minor cutting edge 5 and improving chipping resistance. In particular, in this embodiment, at the minor cutting edge first end 5a, which is the boundary between the first minor cutting edge 5A and the second minor cutting edge 5B of the minor cutting edge 5, the inclination angle of the land portion 7 with respect to the reference plane P in the cross section perpendicular to the minor cutting edge 5 is within the range of 15° to 35°, so that even at this corner edge first end 3a, it is possible to reliably improve chipping resistance and promote reduction in cutting resistance.

That is, if the inclination angle θ1 of the land portion 7 at the first end 5a of the minor cutting edge is less than 15°, the cutting angle of the minor cutting edge 5 becomes small, making it easier for chipping to occur when cutting a hard workpiece. On the other hand, if the inclination angle θ1 of the land portion 7 at the first end 5a of the minor cutting edge exceeds 35°, the land portion 7 of the minor cutting edge 5 may rise too high, resulting in increased cutting resistance.

In addition, in this embodiment, at the first end 5a of the minor cutting edge, the distance in a direction parallel to the reference plane P of the land portion 7 in a cross section perpendicular to the minor cutting edge 5 is within the range of 0.15 mm to 0.45 mm, which also improves the resistance to chipping at the first end 3a of the corner edge and promotes a reduction in cutting resistance.

That is, if the width of the land portion 7 at the first end 5a of the minor cutting edge in the direction parallel to the reference plane P falls below 0.15 mm, the land portion 7 becomes short and is prone to chipping when cutting a hard workpiece or when performing intermittent cutting. On the other hand, if the width of the land portion 7 at the first end 5a of the minor cutting edge in the direction parallel to the reference plane P exceeds 0.45 mm, the land portion 7 of the minor cutting edge 5 becomes too long, which may increase the cutting resistance due to friction caused by long contact with the chip.

In addition, if the land portion 7 formed on the inside of the polygonal surface 2 of the minor cutting edge 5 has a convex curved shape that is convex in the direction of the insert center line L in a cross section perpendicular to the minor cutting edge 5, like the land portion 7 formed on the inside of the polygonal surface 2 of the corner edge 3 and the main cutting edge 4, then, like the corner edge 3, in the cross section, the inclination angle θ1 of the land portion 7 can be the inclination angle θ1 of the straight line N connecting the minor cutting edge 5 and the vertex 9a of the apex 9, and the width of the land portion 7 can be the width in a direction parallel to the reference plane P between the minor cutting edge 5 and the vertex 9a of the apex 9 (corresponding to the distance H1 in Figures 5 to 7).

On the other hand, in this embodiment, as described above, the polygonal surface 2 is formed with a land portion 7 that gradually protrudes in the direction of the insert center line L as it moves from the corner edge 3 toward the inside of the polygonal surface 2, and a scooping surface portion 8 that gradually recedes in the direction of the insert center line L as it moves toward the inside of the polygonal surface 2 beyond this land portion 7.

And within a range of 40° from the corner blade first end 3a to the corner blade second end 3b along the corner blade 3 around the corner blade center line C, in a cross section along the corner blade center line C, the inclination angle θ1 of the land portion 7 with respect to a reference plane P perpendicular to the insert center line L is greater than or equal to the inclination angle θ2 of the rake face portion 8 with respect to a reference plane P perpendicular to the insert center line L.

Therefore, in the cutting insert and replaceable cutting tool configured as described above, the cross-sectional area of the cross section along the corner blade center line C of the insert body 1 on the polygonal surface 2 connected to the corner blade 3 can be secured to be large, particularly on the corner blade 3 side, within a range of 40° around the corner blade center line C from the corner blade first end 3a to the corner blade second end 3b of the corner blade 3 used exclusively for cutting processing.

Therefore, even on the polygonal surface 2 connected to the corner blade 3, the thickness of the insert body 1 can be increased to provide high cutting edge strength, improving the chipping resistance of the corner blade 3, and stable cutting can be performed over a long period of time even when cutting a high-hardness workpiece or when cutting is interrupted. In particular, in this embodiment, the inclination angle θ1 is set to be equal to or greater than the inclination angle θ2 even within a range of 40° around the corner blade center line C from the corner blade second end 3b to the corner blade first end 3a along the corner blade 3, that is, the inclination angle θ1 is set to be equal to or greater than the inclination angle θ2 over the entire length of the corner blade 3, so that the chipping resistance of the corner blade 3 can be improved even when the entire length of the corner blade 3 is used.

In this embodiment, a convex curved apex 9 is formed between the land portion 7 and the scooping surface portion 8, which is tangent to the land portion 7 and the scooping surface portion 8 in a cross section along the corner blade center line C, and further inward from the scooping surface portion 8 into the polygonal surface 2, a rear wall surface portion 10 is formed which gradually retreats in the direction of the insert center line L as it moves inward toward the polygonal surface 2 with respect to an extension line M of the scooping surface portion 8 toward the inside of the polygonal surface 2 in a cross section along the corner blade center line C, and a boss surface 2A which is a plane P perpendicular to the insert center line L extending from the rear wall surface portion 10 into the inside of the polygonal surface 2 to form the opening of the mounting hole 1A.

Within the above-mentioned range of 40° around the corner blade center line C along the corner blade 3 from the corner blade first end 3a to the corner blade second end 3b, in a cross section along the corner blade center line C, the distance H1 in a direction perpendicular to the corner blade center line C from the corner blade 3 to the vertex 9a of the apex 9 in the direction of the insert center line L is less than or equal to the distance H2 in a direction perpendicular to the corner blade center line C from the vertex 9a of the apex 9 to the intersection 2a between the extension line M toward the inside of the polygonal surface 2 of the scooping surface portion 8 and the boss surface 2A.

Therefore, according to this embodiment, the distance H2 from the apex 9 arranged on the inside of the polygonal surface 2 of the land portion 7 to the extension line M along the rake surface 8 to the boss surface 2A is equal to or greater than the distance H1, which is the width of the land portion 7. This makes it possible to secure a larger cross-sectional area along the corner blade center line C of the insert body 1 on the polygonal surface 2 connected to the corner blade 3, thereby giving the corner blade 3 even higher cutting edge strength and more reliably improving chipping resistance. In this embodiment, the distance H1, which is the width of the land portion 7, is constant from the corner blade second end 3b to the main cutting edge first end 4a.

Furthermore, in this embodiment, within the above-mentioned range of 40° from the corner blade first end 3a to the corner blade second end 3b along the corner blade 3, in a cross section along the corner blade centerline C, the ratio H3/H2 of the distance H3 in a direction perpendicular to the corner blade centerline C from the vertex 9a of the apex 9 to the tangent point 10a between the rear wall surface portion 10 and the boss surface 2A and the distance H2 in a direction perpendicular to the corner blade centerline C from the vertex 9a of the apex 9 to the intersection 2a between the extension line M to the inside of the polygonal surface 2 of the scooping surface portion 8 and the boss surface 2A is within a range of 0.45 to 0.75.

This improves the discharge of chips generated by the corner edge 3, main cutting edge 4, and minor cutting edge 5 during cutting, and when the insert body 1 has an inverted symmetrical shape as in this embodiment, it is possible to ensure a large area for the boss surface 2A, which serves as the seating surface that is brought into close contact with the bottom surface 12a of the insert mounting seat 12 of the tool body 11, thereby enabling the cutting insert to be stably seated in the insert mounting seat 12.

Here, if the ratio H3/H2 is smaller than 0.45, the contact distance between the chips and the rake surface 8 becomes shorter, which may cause unstable control of the chip discharge direction. Conversely, if the ratio H3/H2 is larger than 0.75, the contact distance between the chips and the rake surface 8 becomes longer, which increases the cutting resistance due to the scraping of the chips, and the rear wall surface 10 retreats to the inside of the polygonal surface, which reduces the area of the boss surface 2A of the polygonal surface 2, which serves as the seating surface that is brought into close contact with the bottom surface 12a of the insert mounting seat 12 as described above, and may cause the seating stability of the cutting insert to be impaired.

Furthermore, in this embodiment, a tangent Q between the rear wall surface portion 10 and the boss surface 2A is formed in a concave arc shape in the plan view within a range of 40° from the corner blade centerline C from the corner blade second end portion 3b to the corner blade first end portion 3a along the corner blade 3. In the plan view, the ratio G2/G1 of the radius G2 of the concave arc of the tangent Q between the rear wall surface portion 10 and the boss surface 2A to the radius G1 of the arc formed by the corner blade 3 is within a range of 0.23 to 0.87.

This also improves the seating stability of the cutting insert and makes it easier to control the direction of chip discharge. In other words, if the ratio G2/G1 is smaller than 0.23, the rear wall surface portion 10 retreats to the inside of the polygonal surface 2, reducing the area of the boss surface 2A, which may impair the seating stability of the cutting insert. In addition, the width from the corner edge 3 to the tangent line Q between the rear wall surface portion 10 and the boss surface 2A as viewed from the direction of the corner edge center line C increases, which may increase the contact distance between the chip and the land portion 7 and the scoop surface portion 8, resulting in increased cutting resistance.

Conversely, if the ratio G2/G1 is greater than 0.87, the width from the corner blade 3 to the tangent Q between the rear wall surface portion 10 and the boss surface 2A as viewed from the direction of the corner blade center line C becomes smaller, and the contact distance between the chips and the land portion 7 and the scoop surface portion 8 becomes shorter, which may cause unstable control of the chip discharge direction.

In this embodiment, since the rear wall portion 10 is in contact with the boss surface 2A, the distance H3 and the radius G2 are based on the contact point 10a and the tangent line Q between the boss surface 2A and the rear wall portion 10. However, if the rear wall portion 10 intersects with the boss surface 2A at an angle, they may be based on the intersection point or intersection line between the boss surface 2A and the rear wall portion 10.

Furthermore, in this embodiment, the polygonal surface 2 is a rectangular surface formed with 180° rotational symmetry around the insert center line L, and a corner blade 3 is formed at a corner portion where two corners located on one diagonal line of this rectangular surface are located, and a main cutting edge 4 and a minor cutting edge 5 are formed on the short side portion of the rectangular surface connected to this corner blade 3. Therefore, two each of corner blades 3, main cutting edges 4, and minor cutting edges 5 can be used on one polygonal surface 2, which is both efficient and economical.

Moreover, in this embodiment, the insert body 1 having such a rectangular polygonal surface 2 has a shape that is inverted symmetrically from front to back, so that four sets of corner edges 3, main cutting edges 4, and minor cutting edges 5 can be used in one insert body 1, making it even more efficient and economical.

Next, Figures 12 to 18 show a second embodiment of the cutting insert of the present invention, Figures 19 to 25 show a third embodiment of the cutting insert of the present invention, and Figures 26 to 32 show a fourth embodiment of the cutting insert of the present invention. In the cutting inserts of the second to fourth embodiments, parts common to the cutting insert of the first embodiment of the present invention shown in Figures 1 to 7 are assigned the same reference numerals and descriptions thereof will be omitted.

In the cutting insert of the second embodiment shown in Figures 12 to 18, in a cross section along the corner blade center line C, the inclination angle θ2 of the rake face portion 8 at the corner blade first end 3a shown in Figure 18 is 17.0° and the distance H3 is 0.9 mm, the inclination angle θ2 of the rake face portion 8 at a position of 40° around the corner blade center line C from the corner blade first end 3a to the corner blade second end 3b shown in Figure 17 is 16.3°, the inclination angle θ2 of the rake face portion 8 at the corner blade second end 3b of the corner blade 3 shown in Figure 16 is 14.2° and the distance H2 is 0.8 mm. The other specifications are the same as those of the first embodiment.

In the cutting insert of the third embodiment shown in Figures 19 to 25, in the cross section along the corner blade center line C, the inclination angle θ1 of the land portion 7 at the corner blade first end 3a shown in Figure 25 is 20°, the inclination angle θ2 of the rake face portion 8 is 17°, and the distance H2 is 1.1 mm, the inclination angle θ2 of the rake face portion 8 at a position of 40° around the corner blade center line C from the corner blade first end 3a to the corner blade second end 3b shown in Figure 24 is 16.9°, the distance H2 is 1.1 mm, and the distance H3 is 0.8 mm, and the inclination angle θ1 of the land portion 7 at the corner blade second end 3b of the corner blade 3 shown in Figure 23 is 20°, the inclination angle θ2 of the rake face portion 8 is 9.3°, the distance H2 is 1.3 mm, and the distance H3 is 0.5 mm. The other specifications are the same as those of the first embodiment.

Furthermore, in the cutting insert of the fourth embodiment shown in Figures 26 to 32, the inclination angle θ2 of the rake face portion 8 at the corner blade first end 3a shown in Figure 32 is 16.9°, the distance H2 is 1.1 mm, the inclination angle θ2 of the rake face portion 8 at a position of 40° around the corner blade center line C from the corner blade first end 3a to the corner blade second end 3b shown in Figure 31 is 16.9°, the distance H2 is 1.1 mm, and the distance H3 is 0.8 mm, and the inclination angle θ1 of the land portion 7 at the corner blade second end 3b of the corner blade 3 shown in Figure 30 is 20°, the inclination angle θ2 of the rake face portion 8 is 11.5°, the distance H2 is 1.0 mm, and the distance H3 is 0.5 mm. The other specifications are the same as those of the first embodiment.

In the cutting inserts of the second to fourth embodiments, the inclination angle θ1 of the land portion 7 is equal to or greater than the inclination angle θ2 of the rake face portion 8, so that the same effect as in the first embodiment can be obtained. However, in the third and fourth embodiments, the width W1 of the inclined region B of the second minor cutting edge 5B in the direction perpendicular to the insert center line L is not larger than the width W2 of the parallel region A of the second minor cutting edge 5B in the direction perpendicular to the insert center line L, but is approximately equal to or smaller than the width W2 of the parallel region A of the second minor cutting edge 5B in the direction perpendicular to the insert center line L.

When using indexable cutting tools, stable cutting can be performed over a long period of time, even when cutting high-hardness workpieces or when intermittent cutting is required on workpieces with many holes.

1 Insert body 1A Mounting hole 2 Polygonal surface 2A Boss surface 2a Intersection of boss surface 2A and extension line M from apex 9a of apex 9 to the inside of polygonal surface 2 of rake surface portion 8 in cross section along corner blade center line C 3 Corner blade 3a Corner blade first end 3b Corner blade second end 4 Main cutting edge 4a Main cutting edge first end 5 Minor cutting edge 5A First minor cutting edge 5B Second minor cutting edge 5a Minor cutting edge first end 5b Minor cutting edge second end 6 Relief surface 7 Land portion 8 Rake surface portion 8a Contact point with rear wall surface portion 10 of rake surface portion 8 9 Apex 9a Apex of apex 9 10 Rear wall surface portion 10a Contact point with rear wall surface portion 10 and boss surface 2A in cross section along corner blade center line C
11 Tool body 12 Insert mounting seat 13 Chip pocket 14 Clamp screw L Insert center line C Corner blade center line M Extension line from vertex 9a of apex 9 to the inside of polygonal surface 2 of rake face portion 8 in a cross section along corner blade center line C N Straight line connecting corner blade 3 and vertex 9a of apex 9 in a cross section along corner blade center line C P Reference plane Q Tangent to boss surface 2A and rear wall surface portion 10 θ1 Inclined angle of land portion 7 θ2 Inclined angle of rake face portion 8 H1 Distance in a direction perpendicular to corner blade center line C from corner blade 3 to vertex 9a of apex 9 in a cross section along corner blade center line C H2 Distance in a direction perpendicular to corner blade center line C from vertex 9a of apex 9 to intersection point 2a in a cross section along corner blade center line C H3 Distance in a direction perpendicular to the corner edge center line C from the apex 9a of the apex 9 to the contact point 10a in a cross section along the corner edge center line C A Parallel region B Inclined region G1 Radius of the arc formed by the corner edge 3 G2 Radius of the arc formed by the tangent line Q W1 Width of the inclined region B of the second minor cutting edge 5B in a direction perpendicular to the insert center line L W2 Width of the parallel region A of the second minor cutting edge 5B in a direction perpendicular to the insert center line L O Axis of the tool body 11 T Tool rotation direction

Claims (7)

An insert body formed in a polygonal plate shape has a mounting hole on each of the polygonal surfaces on the front and back sides thereof, the mounting hole penetrating the insert body and centered on the insert center line;
a corner edge having a convex arc shape centered on a corner edge center line parallel to the insert center line at a corner portion of the polygonal surface in a plan view seen from the insert center line direction, a main cutting edge extending linearly from a corner edge first end of the corner edge in a tangential direction of the corner edge, and a minor cutting edge receding from a main cutting edge first end on a side opposite to the corner edge first end of the main cutting edge with respect to an extension line of the main cutting edge toward the main cutting edge first end side,
The minor cutting edge includes, in the plan view, a first minor cutting edge that is convexly arcuate and has a radius larger than the radius of the corner edge that contacts the main cutting edge at a first end of the main cutting edge, and a second minor cutting edge that extends linearly in a tangential direction of the first minor cutting edge from a first end of the minor cutting edge that is opposite to the first end of the main cutting edge,
The main cutting edge and the first minor cutting edge are located on a parallel region extending along a direction parallel to a reference plane that passes through the corner edge first end and is perpendicular to the insert center line, and the second minor cutting edge has an inclined region that is inclined so as to gradually retreat toward the insert center line toward a minor cutting edge second end opposite to the minor cutting edge first end,
The polygonal surface has the corner edge, the main cutting edge, and the minor cutting edge over their entire lengths.
a land portion is formed which gradually protrudes in the direction of the insert center line from the corner edge, the main cutting edge, and the minor cutting edge toward the inside of the polygonal surface, and a cutting surface portion is formed on the inside of the polygonal surface more than the land portion, which gradually recedes in the direction of the insert center line toward the inside of the polygonal surface,
The land portion has an inclination angle with respect to the reference plane in a cross section perpendicular to the first minor cutting edge on the parallel region ,
Between the land portion and the rake face portion, a convex curved apex portion is formed which is in contact with the land portion and the rake face portion in a cross section along the corner edge center line and in a cross section perpendicular to the major cutting edge and the minor cutting edge,
the land portion of the corner edge has a convex curved shape that is convex in the insert center line direction in a cross section along the corner edge center line, and the inclination angle of a straight line connecting the corner edge and the apex of the top of the land portion at the corner edge first end portion, which protrudes most in the insert center line direction, is 15° to 25° with respect to the reference plane, and the width of the corner edge in a direction parallel to the reference plane between the apex of the top that protrudes most in the insert center line direction and the corner edge is 0.35 mm to 0.45 mm,
The land portion of the first minor cutting edge has a convex curved shape that is convex in the insert center line direction in a cross section perpendicular to the first minor cutting edge on the parallel region, and the inclination angle of the straight line connecting the apex of the top that protrudes most in the insert center line direction and the first minor cutting edge with respect to the reference plane is 15° to 35°, and the width of the apex of the top that protrudes most in the insert center line direction and the first minor cutting edge in a direction parallel to the reference plane is 0.15 mm to 0.45 mm.
Cutting insert. The cutting insert according to claim 1, characterized in that the portion of the second minor cutting edge on the minor cutting edge first end side is located on the parallel region, and the portion of the second minor cutting edge on the minor cutting edge second end side is an inclined region that gradually retreats toward the insert center line direction as it moves from the parallel region toward the minor cutting edge second end. The cutting insert according to claim 1 or 2, characterized in that, when viewed from a direction facing the flank of the minor cutting edge, the width of the inclined region of the second minor cutting edge in a direction perpendicular to the insert center line is greater than the width of the parallel region of the second minor cutting edge in a direction perpendicular to the insert center line. The cutting insert according to any one of claims 1 to 3, characterized in that the polygonal surface is a rectangular surface formed with 180° rotational symmetry around the insert center line, the corner edge is formed at the corner portion where two corner portions located on one diagonal line of the rectangular surface are arranged, and the main cutting edge and the minor cutting edge are formed on the short side portion of the rectangular surface connected to this corner edge. The cutting insert according to claim 4 , wherein the insert body has a shape that is inverted symmetrical. 6. An indexable cutting tool, comprising: an insert mounting seat formed on an outer periphery of a tip portion of a tool body that is rotated in a tool rotation direction about an axis; a cutting insert according to any one of claims 1 to 5 , wherein one of the polygonal faces is oriented in the tool rotation direction, the corner blade formed at the corner portion of the one polygonal face is oriented toward the outer periphery of the tip portion of the tool body, and the main cutting edge extending from the corner blade first end of the corner blade is oriented toward the inner periphery of the tool body, and a clamp screw inserted into the mounting hole is screwed into a bottom surface of the insert mounting seat that faces the tool rotation direction. A tool body for an indexable cutting tool, comprising:
The cutting insert according to any one of claims 1 to 5 is configured to be removably attached to an insert mounting seat formed on the outer periphery of a tip portion of a tool body that is rotated in a tool rotation direction around an axis, with one of the polygonal faces facing the tool rotation direction, the corner blade formed at the corner portion of the one polygonal face facing the outer periphery of the tip portion of the tool body, and the main cutting edge extending from the first end of the corner blade facing the inner periphery of the tool body, by screwing a clamp screw inserted into the mounting hole into a bottom surface of the insert mounting seat facing the tool rotation direction.

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