JP7260748B2 - Cutting inserts, indexable end mills - Google Patents

Description

The present invention provides a cutting insert that is detachably attached to an insert mounting seat formed at the tip of an end mill body of an indexable end mill that rotates about an axis, and such a cutting insert is detachably attached to the insert mounting seat of the end mill body. Removably mounted indexable end mills and end mill bodies for such indexable end mills.

As cutting inserts to be attached to such indexable end mills, for example, Patent Documents 1 and 2 disclose cutting inserts for indexable ball end mills, in which the rake face is oriented in the direction of rotation of the end mill body and the rake face and a flank extending around the rake and seating surfaces. , two cutting edges each provided with an arc-shaped cutting edge portion extending in an arc shape in a plan view viewed from the direction facing the rake face, and a linear cutting edge portion extending so as to contact the arc-shaped cutting edge portion. , which is formed by alternately arranging arcuate cutting edge portions and linear cutting edge portions in the circumferential direction of the rake face.

Further, in these Patent Documents 1 and 2, in order to reduce cutting resistance and to divide chips, the rake face is provided with a groove-like nick that reaches the cutting edge and opens to the flank face. Are listed. Furthermore, the seating surfaces of the cutting inserts disclosed in Patent Documents 1 and 2 are formed with grooves that open to the flanks. Abutment is possible to ensure mounting stability of the cutting insert in the insert mounting seat.

Japanese Patent No. 4771547 U.S. Pat. No. 7,309,193

However, in the case of cutting inserts in which a recessed nick that reaches the cutting edge is formed on the rake face and a groove that opens to the flank face is formed on the seating surface, the nick escapes in the direction in which the cutting edge extends. If the opening to the face overlaps the opening to the flank of the groove, the thickness of the cutting insert on the flank between the nick and the groove is reduced and the strength is reduced. Therefore, when a large cutting load is applied during cutting, the cutting insert may be damaged such as chipping in the portion between the nick and the groove where the strength is reduced.

The present invention has been made under such a background, and the cutting insert has a rake face formed with a nick reaching the cutting edge and a groove formed on the seating surface opening to the flank face. To provide a cutting insert capable of securing the strength of and preventing damage such as chipping even when a large cutting load is applied, and an indexable ball end mill in which such a cutting insert is detachably attached, and An object of the present invention is to provide an end mill main body for such an indexable ball end mill.

In order to solve the above problems and achieve such objects, the cutting insert of the present invention is attachable to and detachable from an insert mounting seat formed at the tip of the end mill body of an indexable end mill that rotates about its axis. comprising a rake face facing in the direction of rotation of the end mill body, a seating face facing the opposite side of the rake face and seated on the bottom surface of the insert mounting seat, and these rake faces and a flank extending around the seating surface, and an arc-shaped cutting edge extending in an arc shape in a plan view viewed from a direction facing the rake surface at an intersection ridge between the rake surface and the flank surface. and a linear cutting edge extending in contact with at least one end of the arc-shaped cutting edge. A plurality of concave groove-shaped nicks are formed on the seating surface, and a groove portion having a wall surface capable of abutting against a projection projecting from the bottom surface of the insert mounting seat is formed on the seating surface so as to open to the flank surface. and the openings of all the nicks to the flank face are arranged at positions that do not overlap the openings of the grooves to the flank face in a perspective view from the rake face side. Characterized by

Also, in the indexable end mill of the present invention, the cutting insert configured as described above protrudes from the bottom surface of the insert mounting seat formed at the tip of the end mill body that rotates around the axis. The wall surface of the groove portion is brought into contact with the convex portion, and is detachably attached. Further, the end mill main body of the present invention is an end mill main body of an indexable end mill that rotates about an axis, in which a cutting insert configured as described above can be detachably attached to an insert mounting seat formed at the tip. It is characterized in that the bottom surface of the insert mounting seat is provided with a protruding portion that is brought into contact with the wall surface of the groove portion.

In the cutting insert and indexable end mill having such a configuration, the nick formed on the rake face of the cutting insert is the opening of the groove formed on the seating surface to the flank face in a perspective view from the rake face side. and the thickness of the cutting insert on the flank face is between the opening to the flank face of this groove and the opening to the flank face of the nick in the direction in which the cutting edge extends. The formation of smaller parts can be avoided.

Therefore, it is possible to secure the thickness of the cutting insert between the nick and the seating surface and between the rake surface and the groove to maintain the strength. Accordingly, even if a large cutting load acts on the cutting insert during cutting, it is possible to prevent damage such as chipping of the cutting insert.

Here, it is preferable that the opening of the groove portion to the flank face is located closer to the arcuate cutting edge portion than the at least one nick, the side of the arcuate cutting edge portion contacting the linear cutting edge portion. As a result, chips separated by the nick located on the side opposite to the point of contact between the arcuate cutting edge and the linear cutting edge are caught in the opening to the flank of the groove, causing clogging or damage. It is possible to prevent a situation in which the machined surface of the cutting material is damaged.

Moreover, it is desirable that the groove has a narrow portion in which the width of the groove becomes narrower from one end to the other end in the direction in which the groove extends. As a result, the thickness of the cutting insert is ensured on the other end side of the groove portion where the groove width of the narrow portion is narrow, stress is dispersed, and strength can be improved.

On the other hand, since the groove width becomes wider at one end of the narrow width portion, in the indexable end mill and the end mill main body, the convex portion is positioned in the direction in which the groove extends at the portion where the narrow width portion of the groove abuts. By increasing the width from the other end side toward the one end side, it is possible to increase the mounting rigidity against the load during cutting and reliably prevent the cutting insert from slipping.

Further, the nick is formed on the rake face of the arc-shaped cutting edge, and the opening of at least one of the grooves to the flank face opens to the flank face of the linear cutting edge. good too. As a result, it is possible to increase the distance in the cutting edge extending direction of the opening to the flank between the nick and the groove, thereby further reliably preventing damage to the cutting insert between the nick and the groove. .

Furthermore, the two cutting edges are formed by alternately locating the arc-shaped cutting edge portion and the linear cutting edge portion in the circumferential direction of the rake face, which are described in Patent Documents 1 and 2. It may be a cutting insert for such an indexable ball end mill. In this case, two grooves are formed in the seating surface, one of the two grooves being a through groove opening to both of the flanks of the two cutting edges, and the other being a through groove opening to both of the flanks of the two cutting edges. It may be a blind groove that opens only on the flank face of one cutting edge, so that in a cutting edge where only one groove opens on the flank face, damage to the cutting insert between the nicks is more assured. It is possible to prevent

In addition, the two cutting edges are formed by alternately locating the arc-shaped cutting edge portion and the linear cutting edge portion in the circumferential direction of the rake face to form a cutting insert for an indexable ball end mill. one of these two cutting edges is a major cutting edge and the other is a minor cutting edge, and the arc-shaped cutting edge portion of the major cutting edge is the arc-shaped cutting edge of the minor cutting edge The length in the circumferential direction may be long with the same radius with respect to the portion.

In this case, two insert mounting seats are formed in the end mill body of the indexable ball end mill, and two cutting inserts of the same shape and size are mounted. The rotational trajectories of the arc-shaped cutting edge portions are on the axis line so that the other minor cutting edge extends toward the rear end outer circumference side from a position away from the axis line of the tip inner circumference of the end mill body. One type of cutting insert can be used for cutting by attaching one hemisphere centered at .

Further, in this case, the arc-shaped cutting edge portion of the main cutting edge, excluding the nick, moves away from the seating surface side as it separates from the linear cutting edge portion of the main cutting edge, and then moves toward the seating surface side. The arc-shaped cutting edge portion of the major cutting edge is formed so as to have a basic shape formed in an approaching convex curve shape, so that the arc-shaped cutting edge portion in the basic shape becomes the most convex with respect to the seating surface. Since the main cutting edge gradually cuts into the work material from the most convex point, the cutting resistance can be reduced.

In this case, by forming the nick of the main cutting edge at a position that does not overlap with the most convex point of the main cutting edge, the arc-shaped cutting edge portion of the main cutting edge extends from the end of the nick to the work material. Therefore, it is possible to prevent the main cutting edge from being damaged such as chipping from the end of such a nick.

Further, when the nick of the major cutting edge is formed at a position different from the most convex point of the major cutting edge, at least one nick of the major cutting edge is located at a position higher than the most convex point of the major cutting edge. It is desirable that the contact point between the arcuate cutting edge and the linear cutting edge is located on the opposite end side. As a result, the chips generated by cutting into the work material from the most convex point of the main cutting edge can be divided before they extend or become wide, and cutting resistance can be reliably reduced. .

Further, in the main cutting edge, the rotational trajectory of the main cutting edge around the rotational axis that passes through the center of the arc-shaped cutting edge portion in plan view and is parallel to the linear cutting edge portion is along the rotational axis. In a cross section, a portion of the rotating shaft extending from the center of the arc-shaped cutting edge toward the end opposite to the point of contact with the linear cutting edge of the arc-shaped cutting edge, It is desirable that the straight line connecting the point of maximum convexity of the cutting edge intersects at an angle within the range of 43° to 47°.

If this angle is in the range of more than 47° or less than 43°, the most convex point of the major cutting edge is on the contact side of the arc-shaped cutting edge with the linear cutting edge, or on the contact point with this contact. If it is positioned too far on the opposite end side, the arc-shaped cutting edge of the main cutting edge will cut into the work material from the outer circumference of the rear end or the inner circumference of the tip of the indexable ball nose end mill. There is a possibility that the cutting resistance cannot be sufficiently reduced.

On the other hand, similarly to the above, one of the two cutting edges is a major cutting edge and the other is a minor cutting edge, and the arc-shaped cutting edge portion of the major cutting edge is the arc-shaped portion of the minor cutting edge. When the circumferential length is long with the same radius with respect to the cutting edge portion, the arcuate cutting edge portion of the minor cutting edge is also a linear cutting edge portion of the minor cutting edge except for the nick. The arc-shaped cutting edge portion of the minor cutting edge also has a basic shape formed in a convex curve that moves away from the seating surface side and then approaches the seating surface side as it separates from the seating surface. The work material is cut from the most convex point of the sub-cutting edge, which makes it possible to reduce the cutting resistance.

Also in this case, the nick of the minor cutting edge is positioned at the most recessed position toward the seating surface in the opening to the flank face, and the arcuate cutting edge portion of the basic shape of the minor cutting edge is aligned with the seating surface. By arranging it in a position that does not overlap with the most convex point of the minor cutting edge that is the most convex with respect to the surface, it prevents the arc-shaped cutting edge of the minor cutting edge from cutting into the work material from the end of the nick. Therefore, it becomes easy to prevent the chipping of the minor cutting edge from the end of such a nick.

Contrary to the nick of the arc-shaped cutting edge portion of the major cutting edge, such a nick of the minor cutting edge is located closer to the arc-shaped cutting edge portion of the minor cutting edge than the convex point of the minor cutting edge. It is desirable that it be arranged on the contact side with the linear cutting edge. That is, since the arc-shaped cutting edge portion of the minor cutting edge is shorter in the circumferential direction than the arc-shaped cutting edge portion of the major cutting edge, the position of the minor cutting edge that is most recessed toward the seating surface side of the nick is the minor cutting edge. By arranging it on the contact side of the arc-shaped cutting edge portion and the linear cutting edge portion of the blade, it is possible to divide the chips generated by the arc-shaped cutting edge portion of the minor cutting edge into approximately equal widths and lengths. It becomes possible to divide into short chips.

Further, the groove portion opening on the flank face of the minor cutting edge opens on the contact side of the arcuate cutting edge portion and the linear cutting edge portion of the minor cutting edge rather than the convexity point of the minor cutting edge. It is desirable that As a result, when the minor cutting edge cuts into the work material from the minor cutting edge's most convex point, the seating surface on the opposite side of the minor cutting edge's most convex portion is the groove portion that opens to the flank of the minor cutting edge. can be prevented from being unsupported by the insert mounting seat, and the supporting rigidity of the minor cutting edge most convex point in the arc-shaped cutting edge portion of the minor cutting edge can be improved.

Further, it is desirable that at least one nick of the minor cutting edge is arranged between the most convex point of the minor cutting edge and the groove portion opening to the flank of the minor cutting edge. As a result, chips generated by cutting into the work material from the most convex point of the minor cutting edge can be separated by the nicks between the grooves and the grooves, and are supported by the insert mounting seat due to the opening of the grooves. It is possible to reduce the cutting load acting on the minor cutting edge of the portion that is not cut.

Furthermore, in the minor cutting edge, the rotational locus of the minor cutting edge around the rotational axis that passes through the center of the arcuate cutting edge portion in plan view and is parallel to the linear cutting edge portion is along the rotational axis. In the cross section, a portion of the rotating shaft extending from the center of the arc-shaped cutting edge toward the end opposite to the point of contact with the linear cutting edge of the arc-shaped cutting edge, the center and the It is desirable that the straight line connecting the minor cutting edge convex point intersects at an angle within the range of 43° to 47°.

If this angle exceeds 47° or falls below 43°, the most convex point of the minor cutting edge is on the contact side of the arc-shaped cutting edge with the linear cutting edge, or on the contact point with this contact. If it is positioned too far on the opposite end side, the arc-shaped cutting edge of the minor cutting edge will cut into the work material from the outer circumference of the rear end or the inner circumference of the tip of the indexable ball nose end mill. There is a possibility that the cutting resistance cannot be sufficiently reduced.

Further, the cutting insert of the present invention is not the cutting insert of the indexable ball end mill as described above, but the cutting edge has another linear cutting edge portion extending in contact with the other end of the arcuate cutting edge portion. The cutting insert of an indexable radius end mill may be provided with another linear cutting edge portion serving as the bottom cutting edge of the indexable end mill.

In this case, the two cutting edges are formed by sequentially arranging the other linear cutting edge portion, the arcuate cutting edge portion, and the linear cutting edge portion in the circumferential direction of the rake face. This makes it possible to use the cutting edge twice with one cutting insert. Further, when two cutting edges are formed in this manner, two grooves are formed in the seating surface, and one of the two grooves is a through hole opening to both of the flanks of the two cutting edges. It may be a groove and the other may be a blind groove that opens only on the flank face of one cutting edge.

As described above, according to the present invention, the thickness of the cutting insert is reduced between the opening to the flank face of the groove and the opening to the flank face of the nick in the direction in which the cutting edge extends. The thickness of the cutting insert between the nick and the seating surface and between the rake face and the groove can be secured to maintain strength, so that cutting Even if a large cutting load acts on the insert, it is possible to prevent damage such as chipping.

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 viewed from a direction facing the rake face; FIG. 2 is a bottom view of the embodiment shown in FIG. 1 viewed from a direction facing the seating surface; FIG. 3 is a side view seen in the direction of an arrow A in FIG. 2; FIG. 3 is a side view seen in the direction of an arrow B in FIG. 2; FIG. 3 is a side view seen in the direction of an arrow C in FIG. 2; FIG. 3 is a side view seen in the direction of an arrow D in FIG. 2; FIG. 3 is a side view seen in the direction of an arrow E in FIG. 2; An end mill main body showing a first embodiment of an indexable end mill (index indexable ball end mill) and an end mill main body of the present invention in which the cutting inserts of the embodiment shown in FIGS. 1 to 8 are attached to two insert mounting seats, respectively. Fig. 2 is a perspective view of the tip; Figure 10 is a front view of the embodiment shown in Figure 9; FIG. 11 is a bottom view of FIG. 10 viewed in the direction of arrow A; FIG. 11 is a side view seen in the direction of an arrow B in FIG. 10; FIG. 13 is a perspective view showing the positional relationship between two cutting inserts in the indexable end mill of the embodiment shown in FIGS. 9 to 12; Fig. 13 is a perspective view of the two cutting inserts whose positional relationship is shown in a direction facing the rake face of the first cutting insert (right cutting insert in Fig. 13) whose main cutting edge is used for cutting. be. FIG. 5 is a plan view of a second embodiment of the cutting insert of the present invention, viewed from the direction facing the rake face; FIG. 16 is a bottom view of the embodiment shown in FIG. 15 viewed from a direction facing the seating surface; FIG. 16 is a side view seen in the direction of an arrow A in FIG. 15; 15. It is a side view of the arrow B direction view in FIG. FIG. 16 is a side view seen in the direction of an arrow C in FIG. 15; FIG. 16 is a side view seen in the direction of arrow D in FIG. 15; A perspective view showing a second embodiment of an indexable end mill (index indexable radius end mill) and an end mill main body of the present invention in which the cutting inserts of the embodiment shown in FIGS. 15 to 20 are respectively mounted on two insert mounting seats. is. Figure 22 is a front view of the embodiment shown in Figure 21; FIG. 23 is a plan view seen in the direction of an arrow A in FIG. 22; FIG. 23 is a side view seen in the direction of an arrow B in FIG. 22; FIG. 23 is a side view seen in the direction of an arrow C in FIG. 22; FIG. 26 is a perspective view showing the positional relationship between two cutting inserts in the indexable end mill of the embodiment shown in FIGS. 21 to 25; 27 is a perspective view of the two cutting inserts whose positional relationship is shown in FIG. 26, viewed from the direction facing the rake face of the right cutting insert in FIG. 26; FIG. FIG. 21 is a bottom view of a modification of the second embodiment shown in FIGS. 15 to 20, viewed from the direction facing the seating surface; FIG. 29 is a perspective view showing the positional relationship between two cutting inserts when the modified cutting insert shown in FIG. 28 is attached to an end mill body of an indexable end mill (index indexable radius end mill).

1 to 8 show a first embodiment of the cutting insert of the present invention, and FIGS. 9 to 11 show two cutting inserts of this first embodiment attached to an insert mounting seat. FIG. 12 and FIG. 13 show the first embodiment of the indexable ball end mill and the end mill main body, which are the first embodiment of the indexable end mill of the present invention, and FIGS. It shows the positional relationship of two cutting inserts in the replaceable end mill.

The cutting insert 1 of the present embodiment is made of a hard material such as cemented carbide, and is shaped like a leaf-shaped plate in plan view as shown in FIG. The upper surface of this cutting insert 1 is the leaf-shaped rake face 2 as described above. The lower surface facing away from the rake surface 2 is a leaf-shaped flat seating surface 3 that is substantially similar to the rake surface 2 and is seated on the bottom surface of the insert mounting seat. A flank 4 is a side surface extending circumferentially between and the seating surface 3 .

At the intersection ridgeline between the rake face 2 and the flank face 4, arcuate cutting edge portions 5a and 6a extending arcuately as shown in FIG. Two cutting edges each having linear cutting edge portions 5b and 6b extending in contact with the arcuate cutting edge portions 5a and 6a are connected to the arcuate cutting edge portions 5a and 6a and the linear cutting edge portions 5b and 6b. They are formed alternately in the circumferential direction of the rake face 2 . One of these two cutting edges, a first cutting edge, is a major cutting edge 5 and the other second cutting edge is a minor cutting edge 6 .

Further, the flank 4 is inclined toward the inner peripheral side of the cutting insert 1 as it goes from the rake face 2 to the seating surface 3 side, and the cutting insert 1 of this embodiment is a positive type cutting insert. there is Further, a mounting hole 7 having a circular cross section is formed through the cutting insert 1 at the center of the rake surface 2 and the seating surface 3. The mounting hole 7 on the rake surface 2 side is the seating surface It is formed so as to decrease in diameter toward the three sides.

Here, in the plan view facing the rake face 2, the arc-shaped cutting edge portion 5a of the main cutting edge 5 has a substantially 1/4 arc shape. On the other hand, the arcuate cutting edge portion 6a of the minor cutting edge 6 has the same radius as the arcuate cutting edge portion 5a of the major cutting edge 5, but the length in the circumferential direction is equal to that of the major cutting edge 5. It is shorter than the portion 5a, that is, formed in an arc shape shorter than a quarter arc. Along with this, the linear cutting edge portion 5b of the major cutting edge 5 is made shorter than the linear cutting edge portion 6b of the minor cutting edge 6. As shown in FIG. That is, the cutting insert 1 of this embodiment is not symmetrical about the center line of the mounting hole 7 by 180 degrees, but asymmetrical.

The linear cutting edge portions 5b and 6b of the major cutting edge 5 and the minor cutting edge 6 are the same as the arcuate cutting edge portion 5a of the major cutting edge 5 and the linear cutting edge portion 6b of the minor cutting edge 6 in the above-described plan view. from the first end 2a of the rake face 2 where the two intersect to the second end of the rake face 2 where the linear cutting edge 5b of the major cutting edge 5 and the arcuate cutting edge 6a of the minor cutting edge 6 intersect They extend closer to each other toward the portion 2b. These first and second end portions 2a and 2b are chamfered so as to intersect the arcuate cutting edge portions 5a and 6a and the linear cutting edge portions 5b and 6b of the major cutting edge 5 and the minor cutting edge 6 at an obtuse angle. formed in the shape of The first end 2a is positioned closer to the seating surface 3 than the second end 2b.

Further, the arcuate cutting edge portions 5a and 6a of the major cutting edge 5 and the minor cutting edge 6 are separated from the seating surface 3 as they are separated from the respective linear cutting edge portions 5b and 6b, except for nicks which will be described later. It is formed to have a basic shape of a convex curve that approaches the seating surface 3 side after cutting, and the convex curve formed by these arc-shaped cutting edge portions 5a and 6a becomes convex farthest from the seating surface 3. The point (the most protruding point from the seating surface 3) is the major cutting edge most convex point S5 and the minor cutting edge most convex point S6. The linear cutting edge portions 5b and 6b of the major cutting edge 5 and the minor cutting edge 6 also have arcuate cutting edge portions as shown in FIGS. It is in contact with the convex curve formed by the portions 5a and 6a and extends in a substantially straight line approaching the seating surface 3 side as the distance from the arcuate cutting edge portions 5a and 6a increases.

Here, in the main cutting edge 5, a rotation axis passing through the center P of the arcuate cutting edge portion 5a in plan view and parallel to the linear cutting edge portion 5b (an axis O of the end mill main body 11 to be described later) is rotated. In the cross section along the rotation axis of the rotation locus of the main cutting edge 5, as shown on the right side of FIG. A portion extending toward the end portion opposite to the contact point Q5 with the cutting edge portion 5b (the first end portion 2a side; in the case of an indexable end mill, the tip end side of the end mill body 11, which will be described later); A straight line L5 connecting the blade maximum convex point S5 intersects at an angle θ5 within the range of 43° to 47°. In this embodiment, this angle θ5 is set to 45°.

14 (however, the left side of FIG. 4 is a bottom view of the minor cutting edge 6 as seen from the seating surface 3 side). Passing through the center P of the arcuate cutting edge portion 6a that coincides with the center P of the arcuate cutting edge portion 5a, and parallel to the linear cutting edge portion 6b (similarly, the axis O of the end mill body 11 described later) around In a cross-section along the rotation axis of the rotation locus of the minor cutting edge 6, a point of contact Q6 between the center P of the arcuate cutting edge portion 6a and the linear cutting edge portion 6b of the arcuate cutting edge portion 6a of the rotation axis. extends to the opposite end side (the second end 2b side; similarly, in the case of an indexable end mill, the tip end side of the end mill body 11, which will be described later); The connecting straight line L6 intersects at an angle θ6 within the range of 43° to 47°. In this embodiment, this angle θ6 is also set to 45°.

Around the opening of the mounting hole 7 in the central portion of the rake face 2, there is a substantially elliptical shape in plan view that protrudes in a direction away from the seating surface 3 more than the major cutting edge 5 and the minor cutting edge 6. A protrusion 2c is formed. The upper end surface of this protrusion 2c is a flat surface parallel to the seating surface 3, and the mounting hole 7 opens to the upper end surface of this protrusion 2c. Further, the outer peripheral surface of the protrusion 2c is inclined toward the inner side of the rake face 2 toward the upper end surface. Further, the rake face 2 extends toward the seating surface 3 as it moves away from the major cutting edge 5 and the minor cutting edge 6 and extends toward the inner side of the rake face 2, and then forms a concave curved surface on the outer peripheral surface of the protrusion 2c. are connected.

Furthermore, the flanks 4 connected to the linear cutting edge portions 5b and 6b of the major cutting edge 5 and the minor cutting edge 6 are formed in an inclined flat shape as described above. On the rake face 2 side, the flank 4 connected to the arcuate cutting edge portions 5a and 6a of the major cutting edge 5 and the minor cutting edge 6 extends in the circumferential direction of the cutting insert 1 along these arcuate cutting edge portions 5a and 6a. However, on the seating surface 3 side of the flank 4 of the arcuate cutting edge portion 5a of the main cutting edge 5, there is a flat portion 4a inclined flat as shown in FIGS. is formed.

As shown in FIG. 3, a groove portion 8 is formed in the seating surface 3. As shown in FIG. Here, in the present embodiment, as shown in FIG. They are spaced apart from the opening of the hole 7 and formed on opposite sides of the opening. The first groove 8A is formed closer to the first end 2a of the rake face 2 than the opening of the mounting hole 7, and the second groove 8B is formed closer to the second end 2b of the rake face 2. there is

These grooves 8 are formed in a substantially rectangular cross-section perpendicular to the direction in which the grooves 8 extend and are flattened in the direction in which the mounting holes 7 extend. and a bottom surface 8c parallel to the seating surface 3 extending between the first and second wall surfaces 8a and 8b. The first wall surface 8a of each groove 8 faces the first end 2a of the rake face 2, and the second wall surface 8b faces the second end 2b of the rake face 2. As shown in FIG. The intersection ridges between the first and second wall surfaces 8a and 8b and the seating surface 3 are chamfered with convex curved surfaces, and the corners where the first and second wall surfaces 8a and 8b and the bottom surface 8c intersect are concave. It is formed in a curved shape.

The first groove portion 8A opens on the flank surface 4 that continues to the linear cutting edge portion 6b of the minor cutting edge 6, and opens on the flank surface 4 that continues to the arcuate cutting edge portion 5a of the major cutting edge 5. It is formed in the shape of a blind groove that does not The end portion of the first groove portion 8A on the side of the arc-shaped cutting edge portion 5a of the main cutting edge 5 continues from the bottom surface 8c to the seating surface 3 so as to form a concave surface. Furthermore, in the first groove portion 8A, the first and second wall surfaces 8a and 8b extend parallel to each other in the bottom view. The end portion of the groove portion 8A on the side of the arcuate cutting edge portion 5a of the main cutting edge 5 extends perpendicular to the first and second wall surfaces 8a and 8b. is formed in a substantially trapezoidal shape when viewed from the direction facing the .

On the other hand, in this embodiment, the second groove portion 8B is formed on both the flank 4 that continues to the linear cutting edge portion 5b of the major cutting edge 5 and the flank surface 4 that continues to the arcuate cutting edge portion 6a of the minor cutting edge 6. It is formed in the shape of an open through groove. In this embodiment, the second groove portion 8B has a narrow portion 9 in which the groove width narrows from one end side to the other end side in the direction in which the second groove portion 8B extends. Here, in the present embodiment, the side of the flank 4 connected to the linear cutting edge portion 5b of the major cutting edge 5 is one end side of the second groove portion 8B, and the arcuate cutting edge portion 6a of the minor cutting edge 6 The continuous flank 4 side is the other end side.

Further, as shown in FIG. 3, the entire second groove portion 8B is the narrow portion 9 in this embodiment. In the present embodiment, the width of the narrow portion 9 is made constant from one end side to the other end side of the second groove portion 8B. That is, the first and second wall surfaces 8a and 8b of the second groove portion 8B are formed so as to approach each other linearly from one end side to the other end side in the bottom view.

Furthermore, the opening of the second groove portion 8B to the flank 4 connected to the arcuate cutting edge portion 6a of the minor cutting edge 6 is located at a higher angle than the minor cutting edge peak point S6. It is located on the part 6b side. Specifically, in the bottom view, the straight line L6 connecting the minor cutting edge most convex point S6 and the center P of the arc formed by the arcuate cutting edge portion 6a of the minor cutting edge 6 and the straight line of the minor cutting edge 6 The end of the intersection ridge (excluding the chamfered portion) between the first wall surface 8a of the second groove portion 8B and the flank surface 4 facing the side of the cutting edge portion 6b and the center P is connected to the seating surface 3 side. A first crossing angle with a straight line (not shown) is in the range of 5° to 60°.

The groove width W1 (not shown) at the other end of the narrow portion 9 (the other end of the second groove portion 8B in this embodiment) is the width of the groove portion (second groove portion 8B) having the narrow portion 9. 0.05×r to 0.18 with respect to the radius r (not shown) of the arc-shaped cutting edge portion (arc-shaped cutting edge portion 6a of the minor cutting edge 6) located on the other end side as viewed from the seating surface 3 side xr, for example, 1 mm to 7 mm. However, if the shape of the circular arc-shaped cutting edge 6a viewed from the seating surface 3 side is deviated from the circular arc, a virtual arc that is closest to the deviated shape is drawn, and this virtual , the radius r will be obtained from the arc of .

On the other hand, the groove width W2 (not shown) at one end of the narrow portion 9 satisfies W2>W1, and the groove portion (second groove portion 8B) having the narrow width portion 9 has an arc-shaped cutting portion located on the other end side. 0.10×r to 0.10×r to 0.10×r to 0.10×r to 0.10×r to 0.10×r to a radius r of the blade portion (arc-shaped cutting edge portion 6a of the minor cutting edge 6) in a bottom view viewed from the seating surface 3 side or a plan view viewed from the rake face 2 side. In the range of 30×r, the length R (not shown) of the linear cutting edge portion 5b of the main cutting edge 5 in the above plan view or bottom view is in the range of 0.10×R to 0.32×R. It is said that

Note that when the first and second wall surfaces 8a and 8b extend linearly in a bottom view viewed from the direction facing the seating surface 3, the groove widths W1 and W2 are equal to those of the first and second wall surfaces 8a and 8b. is the width in the direction perpendicular to the bisector of the straight line formed by the wall surfaces 8a and 8b, one groove wall surface (for example, the first wall surface 8a) is curved, When the wall surface 8b) of 2 is linear, it is the width in the direction perpendicular to the linear groove wall surface.

In the cutting insert 1 as described above, a groove-shaped nick 10 is formed on the rake face 2 to reach the cutting edge and open to the flank face 4 . 14 in a perspective view from the side of the rake face 2, the opening of the groove 8 is arranged at a position that does not overlap the opening of the groove 8 to the flank face 4. As shown in FIG.

In this embodiment, the nick 10 is formed in the shape of a concave groove by notching the rake face 2 in the shape of a concave curve such as a concave arc when viewed from the direction facing the flank face 4 . The distance between and is gradually increased toward the inner side of the rake face 2, and is formed so as to rise from the rake face 2 before reaching the upper end surface of the protrusion 2c. A valley bottom line that passes through the most recessed position M on the seating surface 3 side of the nick 10 and connects a portion with a small distance from the seating surface 3 toward the inside of the rake surface 2 is a plan view facing the rake surface 2. , extending substantially perpendicular to the cutting edge. The boundary between the nick 10 and the rake face 2 is rounded to form a convex surface along the opening to the flank face 4 .

Further, in this embodiment, a plurality of (two) nicks 10 are formed at intervals on each cutting edge (major cutting edge 5 and minor cutting edge 6). Of these, the two nicks 10 of the major cutting edge 5 are both formed to reach the arcuate cutting edge portion 5a, and one of the nicks 10 of the minor cutting edge 6 reaches the arcuate cutting edge portion 6a. In addition, the remaining one is formed so as to reach the linear cutting edge portion 6b. Furthermore, these nicks 10 are arranged so that the entire opening to the flank 4 does not overlap the opening of the groove 8 to the flank 4 as shown in FIG. is formed in

These nicks 10 align the two cutting inserts 1 so that the centers P of the arcuate cutting edge portions 5a and 6a of the major cutting edge 5 and the minor cutting edge 6 are aligned with each other, and these arcuate cutting edge portions 5a and 6a are aligned. When 6a and linear cutting edge portions 5b, 6b are superimposed and viewed, a nick 10 reaching the main cutting edge 5 of one of the overlapping cutting inserts 1 and a nick reaching the minor cutting edge 6 of the other cutting insert 1 10 are formed so as to overlap the cutting edge extending between the nicks 10 without overlapping each other.

Further, in the present embodiment, in the perspective view from the rake face 2 side of the main cutting edge 5 , the nick 10 has an arc-shaped cutting edge portion where the opening to the flank face 4 is closer than the opening to the groove portion 8 . It is arranged on the side of the first end portion 2a opposite to the contact point Q5 with the linear cutting edge portion 5b in 5a. In particular, in the present embodiment, as described above, in the main cutting edge 5, the groove 8 (second groove 8B) opens only in the flank 4 of the linear cutting edge 5b, whereas the nick 10 Both are formed on the rake face 2 of the arcuate cutting edge portion 5a.

Further, the arc-shaped cutting edge portion 5a of the main cutting edge 5, except for the nick 10, moves away from the seating surface 3 side as it separates from the linear cutting edge portion 5b of the main cutting edge 5, and then moves away from the seating surface 3 side. , and the nick 10 of the main cutting edge 5 is such that the arcuate cutting edge portion 5a in the basic shape of the main cutting edge 5 is closest to the seating surface 3. It is formed at a position that does not overlap with the convex main cutting edge point S5.

In particular, in the present embodiment, at least one nick 10 of the major cutting edge 5 is located in a direction opposite to the point of contact Q5 between the arcuate cutting edge portion 5a and the linear cutting edge portion 5b rather than the major cutting edge convexity point S5. It is arranged on the first end 2a side. Specifically, the two nicks 10 in this embodiment are arranged on the side of the contact Q5 and the side of the first end portion 2a with the main cutting edge most convex point S5 therebetween.

In this embodiment, the arc-shaped cutting edge portion 6a of the minor cutting edge 6, except for the nick 10, also moves away from the seating surface 3 as it separates from the linear cutting edge portion 6b of the minor cutting edge 6, as described above. The basic shape of the minor cutting edge 6 is formed in a convex curved shape that approaches the seating surface 3 side later. The cutting edge portion 6a is arranged at a position that does not overlap with the minor cutting edge maximum convex point S6 where the cutting edge portion 6a is most convex with respect to the seating surface 3. As shown in FIG.

In particular, in this embodiment, the two nicks 10 of the minor cutting edge 6 are closer to the point of contact Q6 between the arcuate cutting edge portion 6a and the linear cutting edge portion 6b of the minor cutting edge 6 than the minor cutting edge peak point S6. placed on the side. In addition, the grooves 8 (first and second grooves 8A and 8B) that open to the flank 4 of the minor cutting edge 6 are located closer to the arcuate cutting edge 6a of the minor cutting edge 6 than the minor cutting edge peak point S6. and the linear cutting edge portion 6b.

Furthermore, at least one nick 10 of the minor cutting edge 6 is arranged at the opening to the flank face 4 between the minor cutting edge maximum convex point S6 and the groove 8 opening to the flank face 4 of the minor cutting edge 6. It is Here, in the present embodiment, one nick 10 of the two nicks 10 of the minor cutting edge 6 is the minor cutting edge most convex point S6 and the opening to the flank surface 4 of the minor cutting edge 6 of the second groove portion 8B. Another nick 10 is located on the linear cutting edge portion 6b beyond the contact point Q6, and is located between the minor cutting edge peak point S6 and the minor cutting edge 6 of the first groove portion 8A. and the opening to the flank 4.

Here, the cutting insert 1 made of hard material such as cemented carbide is manufactured according to the basic steps of powder metallurgy. That is, when the cutting insert 1 is made of a cemented carbide, granulated granulated powder containing tungsten carbide powder and cobalt powder as main components and, if necessary, chromium, tantalum, etc. as subcomponents is used to mold the mold. Perform powder press molding using

The press-formed body thus obtained is sintered for a predetermined time in a sintering furnace controlled to an appropriate atmosphere and temperature, whereby a sintered body that becomes the cutting insert 1 can be manufactured. The basic shape of the cutting insert 1 is reflected by the design of the die, and the detailed shape of the cutting insert 1 is obtained by die molding. Furthermore, in order to improve the precision of the cutting edge shape of the cutting insert 1, grinding processing using a grinding wheel may be performed as necessary.

The cutting insert 1 configured in this way is detachably attached to the insert mounting seat 12 formed at the tip of the end mill body 11 of the first embodiment as shown in FIGS. constitutes a first embodiment of an indexable end mill. The indexable end mill of this first embodiment is an indexable ball end mill.

The end mill main body 11 is formed of a metal material such as steel, and the tip portion thereof has a cylindrical shape centered on the axis O on the base end side, and a base end side cylinder centered on the axis O on the tip end side. It has a convex hemispherical shape with a radius equal to . In the indexable end mill of the present embodiment, the end mill main body 11 is rotated around the axis O in the end mill rotation direction T and sent out in a direction intersecting the axis O, whereby the cutting edge is attached to the insert mounting seat 12. A work material is cut by the insert 1 .

Here, in this embodiment, two tip pockets 13 are formed by notching the outer circumference of the end mill main body 11, and inserts are attached to the bottom faces of these tip pockets 13 facing the end mill rotation direction T, respectively. Seats 12 are circumferentially spaced and formed opposite each other. Then, to these two insert mounting seats 12 are mounted first and second cutting inserts 1A and 1B of the same shape and size based on the first embodiment, respectively.

These insert mounting seats 12 have a flat bottom surface 12a facing in the end mill rotation direction T, a tip inner peripheral wall surface 12b extending from the bottom surface 12a in the end mill rotation direction T and facing the outer peripheral side of the end mill main body 11, and a tip outer peripheral wall surface. and a wall surface 12c on the outer peripheral side of the rear end facing the . The wall surfaces 12b and 12c are formed in a planar shape that inclines outwardly of the insert mounting seat 12 as the distance from the bottom surface 12a increases. The planar flank 4 connected to the linear cutting edge portions 5b and 6b of the blade 6 and the flat portion 4a of the flank 4 connected to the arcuate cutting edge portions 5a and 6a on the side of the seating surface 3 can be brought into contact. .

A concave portion 12d is formed between the wall surfaces 12b and 12c to avoid contact with the curved flank surface 4 of the cutting insert 1. As shown in FIG. Further, the bottom surface 12a is formed with a screw hole (not shown) into which a clamp screw 15 inserted through the mounting hole 7 of the cutting insert 1 is screwed. The center line of this threaded hole is a plane connected to the linear cutting edge portions 5b and 6b of the major cutting edge 5 and the minor cutting edge 6 with the seating surface 3 of the cutting insert 1 seated on the bottom surface 12a as described above. The center of the mounting hole 7 of the cutting insert 1 is in contact with the wall surfaces 12b and 12c with the planar portion 4a of the flank 4 on the side of the seating surface 3 connected to the curved flank 4 and the arcuate cutting edge portions 5a and 6a. It is slightly eccentric to the concave portion 12d side of the line.

Of these two insert mounting seats 12, the first insert mounting seat 12A is formed by notching the tip of the end mill body 11 to a range including the axis O, as shown in FIGS. ing. In the first insert mounting seat 12A, the first cutting insert 1A is positioned on a convex hemisphere having the arc-shaped cutting edge portion 5a of the main cutting edge 5 extending from the vicinity of the axis O and having the center on the axis O. In addition, the linear cutting edge portion 5b of the main cutting edge 5 is attached so as to be positioned on a cylindrical surface centered on the axis O in contact with the convex hemisphere.

Therefore, the planar flank 4 continuous with the linear cutting edge portion 6b of the minor cutting edge 6 of the first cutting insert 1A is brought into contact with the wall surface 12b of the first insert mounting seat 12A, and the wall surface 12c is in contact with the wall surface 12c. The flat portion 4a of the flank 4 of the arc-shaped cutting edge portion 6a of the minor cutting edge 6 of the first cutting insert 1A is brought into contact.

On the bottom surface 12a of the first insert mounting seat 12A, a first convex portion 14A that can abut against the wall surface of the groove portion 8 formed in the seating surface 3 of the first cutting insert 1A is formed. and the wall surface 12c, and extends from the outer peripheral surface of the tip of the end mill body 11 toward the recess 12d to the front of the recess 12d with a space therebetween. Therefore, the second groove portion 8B of the groove portions 8 formed in the seating surface 3 of the first cutting insert 1A abuts against the first convex portion 14A, and the first insert mounting seat 12A contacts the first convex portion 14A. A convex portion with which the first groove portion 8A abuts is not formed.

Here, the first convex portion 14A has a substantially rectangular cross-section perpendicular to the direction in which the first convex portion 14A extends and is flattened in the end mill rotation direction T, and the entirety is a narrow portion 9. With respect to the second groove portion 8B, the overall width is increased from the other end side to the one end side (from the inner peripheral side to the outer peripheral side of the end mill body 11) in the direction in which the second groove portion 8B extends. is formed in

However, the width of the first protrusion 14A (the width in the direction perpendicular to the direction in which the first protrusion 14A extends) is (the width in the direction orthogonal to the extending direction of the second groove portion 8B), and the protrusion height from the bottom surface 12a of the first protrusion 14A is also the seating of the first cutting insert 1A. It is made slightly smaller than the depth of the second groove portion 8B from the surface 3.

On the other hand, the second insert mounting seat 12B of the two insert mounting seats 12 is formed at a position slightly away from the axis O to the outer peripheral side on the tip side of the end mill main body 11 as shown in FIGS. there is The second cutting insert 1B is mounted on the second insert mounting seat 12B so that the arcuate cutting edge portion 6a of the minor cutting edge 6 of the second cutting insert 1B is mounted on the main cutting edge 5 of the first cutting insert 1A from a position away from the axis O. The linear cutting edge portion 6b of the minor cutting edge 6 is aligned with the linear cutting edge portion 5b of the major cutting edge 5 of the first cutting insert 1A. It is attached so as to be positioned on the above-mentioned cylindrical surface.

Therefore, the planar flank 4 continuous with the linear cutting edge portion 5b of the main cutting edge 5 of the second cutting insert 1B is brought into contact with the wall surface 12b of the second insert mounting seat 12B, and the wall surface 12c is in contact with the wall surface 12c. The flat portion 4a of the flank 4 of the arcuate cutting edge portion 5a of the main cutting edge 5 of the second cutting insert 1B is brought into contact.

A second convex portion 14B is formed on the bottom surface 12a of the second insert mounting seat 12B on the tip side of the screw hole, and a third convex portion 14B is formed between the screw hole and the wall surface 12c. A portion 14C is formed. These second and third protrusions 14B and 14C also extend from the outer peripheral surface of the tip of the end mill body 11 toward the inner peripheral side, and the second protrusion 14B extends toward the wall surface 12b of the second insert mounting seat 12B. The third protrusion 14C is formed to the front of the recess 12d of the second insert mounting seat 12B with a space to the wall 12b. Therefore, the second groove 8B of the second cutting insert 1B contacts the second projection 14B, and the first groove 8A of the second cutting insert 1B contacts the third projection 14C.

Further, the second and third protrusions 14B and 14C also have a substantially rectangular cross-section perpendicular to the direction in which the second and third protrusions 14B and 14C extend, which is flattened in the end mill rotation direction T, Of these, the second convex portion 14B is formed in the direction in which the second groove portion 8B extends, whereas the entire second groove portion 8B of the second cutting insert 1B that abuts thereon is the narrow portion 9. It is formed so that it becomes wider as a whole as it goes from the other end side to the one end side (from the outer peripheral side to the inner peripheral side of the end mill main body 11). The width of the third protrusion 14C is constant along the direction in which the third protrusion 14C extends.

Furthermore, the widths of the second and third protrusions 14B and 14C (the widths in the direction orthogonal to the direction in which the second and third protrusions 14B and 14C extend) are also the same as the second and first grooves 8B and 8A. is slightly smaller than the width at the position contacting the second and third protrusions 14B and 14C in the extending direction (the width in the direction perpendicular to the extending direction of the second and first grooves 8B and 8A). ing. Also, the protrusion heights of the second and third projections 14B and 14C from the bottom surface 12a of the second insert mounting seat 12B are also the same as the second and first groove portions 8B from the seating surface 3 of the second cutting insert 1B. It is slightly smaller than the depth of 8A.

The first and second cutting inserts 1A and 1B are seated on the first and second insert mounting seats 12A and 12B as described above, and a clamp screw 15 having an inverted truncated conical head is provided. is inserted into the mounting hole 7 and screwed into the screw hole. 1 is pressed against the side of the recess 12d.

At this time, in the first insert mounting seat 12A, the plane of the flank 4 connecting to the linear cutting edge portion 6b of the minor cutting edge 6 of the first cutting insert 1A and the flank surface 4 connecting to the arcuate cutting edge portion 6a The portion 4a is pressed against the wall surfaces 12b and 12c, respectively. In addition, in the second insert mounting seat 12B, the flank 4 continuous with the linear cutting edge portion 5b of the main cutting edge 5 of the second cutting insert 1B is pressed against the wall surface 12b, thereby The flat portion 4a of the flank 4 that continues to the blade portion 5a is pressed against the wall surface 12c.

Along with this, the second groove portion 8B of the first cutting insert 1A abuts against the first convex portion 14A of the first insert mounting seat 12A from the tip end side of the end mill body 11 . Therefore, the second wall surface 8b of the second groove portion 8B of the first cutting insert 1A abuts against the side surface 14a of the end mill body 11 facing the distal end side of the first protrusion 14A, and the second groove portion A small gap is provided between the first wall surface 8a and the first protrusion 14A at 8B.

Also, in the second insert mounting seat 12B, the second and first grooves 8B and 8A of the second cutting insert 1B are formed in the second and third projections 14B and 14C from the tip end side of the end mill body 11. abut. Therefore, the first wall surfaces 8a of the second and first grooves 8B and 8A abut on the side surfaces 14a of the end mill body 11 facing the tip side of the second and third protrusions 14B and 14C, respectively. 2. A slight gap is provided between the second wall surface 8b of the first grooves 8B and 8A and the second and third projections 14B and 14C. In this manner, the first and second grooves 8A and 8B abut against the first to third projections 14A to 14C, thereby preventing the cutting insert 1 from slipping due to load during cutting. .

In the indexable end mill (ball end mill) configured in this way, as described above, the second cutting insert 1B has the arcuate cutting edge portion 6a of the minor cutting edge 6 of the first cutting insert 1A. The cutting edge 5 is positioned on the convex hemisphere where the arcuate cutting edge 5a is located, and the linear cutting edge 6b is positioned on the cylinder where the linear cutting edge 5b of the main cutting edge 5 of the first cutting insert 1A is located. It is installed so that it is positioned on the surface.

These first and second cutting inserts 1A and 1B are arranged such that the centers P of the arcuate cutting edge portions 5a and 6a of the major cutting edge 5 and the minor cutting edge 6 are aligned with each other, and these arcuate cutting edges are When the portions 5a, 6a and the linear cutting edge portions 5b, 6b are superimposed and viewed, a nick 10 reaching the main cutting edge 5 of one of the overlapping cutting inserts 1 and the minor cutting edge 6 of the other cutting insert 1 are shown. The nicks 10 reaching the cutting edges 10 do not overlap each other, but overlap the cutting edge extending between the nicks 10 .

Therefore, by setting the feed amount per blade of the end mill body 11 to be smaller than the retraction amount of the nick 10 from the cutting edge in plan view facing the rake surface 2, the nick 10 is most recessed toward the seating surface 3 side. The position M is not cut into the work material, so that the chips can be divided and generated, and the cutting resistance can be reduced. On the machined surface of the work material, a ridge is left in the part left uncut by the nick 10, but this ridge is removed by the cutting edge of the cutting insert 1 on the opposite side when the end mill main body rotates 1/2. It is cut and removed by being cut.

In the cutting insert 1 and the indexable ball end mill configured as described above, in the cutting insert 1, the opening of the nick 10 formed on the rake face 2 to the flank face 4 is, in a perspective view from the rake face 2 side, As shown in FIG. 14, it is arranged at a position that does not overlap the opening of the groove 8 formed in the seating surface 3 to the flank 4 . That is, the opening of the nick 10 to the flank 4 does not overlap the opening of the groove 8 to the flank 4 in the direction in which the cutting edge extends.

For this reason, between the most recessed position M of the nick 10 and the seating surface 3, and between the opening of the groove 8 to the flank surface 4 and the rake surface 2, the thickness of the cutting insert 1 is secured to provide strength. Therefore, even if a large cutting load acts on the cutting edge during cutting, it is possible to prevent the cutting insert 1 from being damaged such as chipping between the nick 10 and the groove portion 8. can. Therefore, according to the cutting insert 1 and the indexable end mill configured as described above, stable cutting can be performed over a long period of time even under cutting conditions where such a large cutting load acts.

Further, in the present embodiment, the opening of the groove 8 to the flank 4 is closer to the points of contact Q5, Q6 with the straight cutting edge portions 5b, 6b of the arcuate cutting edge portions 5a, 6a than at least one nick 10. are placed in For this reason, chips generated by being cut by nicks 10 arranged on the side opposite to the contact points Q5 and Q6 between the arcuate cutting edge portions 5a and 6a and the linear cutting edge portions 5b and 6b can escape from the groove portion 8. It is possible to prevent situations such as clogging caused by being caught in the opening of the surface 4 and damage to the machined surface of the work material by caught chips, and stable high-quality cutting of the machined surface. can be done by

Furthermore, in the cutting insert of this embodiment, the second groove portion 8B of the groove portion 8 has a narrow portion 9 in which the groove width becomes narrower from one end side to the other end side in the direction in which the second groove portion 8B extends. have. As a result, the thickness of the cutting insert 1 can be ensured on the other end side where the groove width of the narrow portion 9 is narrowed, stress can be dispersed, and strength can be improved.

On the other hand, since the groove width becomes wider at one end side of the narrow width portion 9, the narrow width portion 9 of the second groove portion 8B abuts against the first convex portion 14A in the end mill body 11 of the indexable end mill. By forming the contact portion so that the width increases from the other end side in the direction in which the second groove portion 8B extends toward the one end side, the mounting rigidity against the load during cutting is increased, and the cutting insert 1 shifts. can be reliably prevented.

In addition, in this embodiment, in the main cutting edge 5, the nick 10 is formed on the rake face 2 of the arc-shaped cutting edge portion 5a, and at least one groove portion 8 (second groove portion 8B) is formed on the flank surface 4. The opening opens to the flank 4 of the linear cutting edge 5b. Therefore, in the main cutting edge 5, the interval in the cutting edge extending direction of the opening between the nick 10 and the groove portion 8 to the flank surface 4 can be increased, and the wall thickness between the nick 10 and the groove portion 8 can be increased. It is possible to more reliably prevent the cutting insert 1 from being damaged due to the formation of a thin portion.

Furthermore, in the present embodiment, the two cutting edges, the major cutting edge 5 and the minor cutting edge 6, extend in the circumferential direction of the rake face 2 along the arcuate cutting edge portions 5a and 6a and the linear cutting edge portions 5b and 6b. The cutting inserts are formed alternately, and are used as cutting inserts for indexable ball end mills as described in Patent Documents 1 and 2.

Two groove portions 8, a first groove portion 8A and a second groove portion 8B, are also formed on the seating surface 3. Of these, the second groove portion 8B has two groove portions, a major cutting edge 5 and a minor cutting edge 6. The first groove portion 8A is a blind groove that opens only to the flank 4 of the minor cutting edge 6, while the first groove 8A is a through groove that opens to both the flank 4 of the cutting edge. Therefore, the groove 8 that opens to the flank 4 of the major cutting edge 5 is only the second groove 8B, and damage to the cutting insert 1 between the nicks 10 can be prevented more reliably.

Further, in this embodiment, when the cutting insert 1 of the indexable ball end mill is used as described above, one of the two cutting edges is the major cutting edge 5 and the other is the minor cutting edge 6. The arcuate cutting edge portion 5a of the major cutting edge 5 is formed to have the same radius as the arcuate cutting edge portion 6a of the minor cutting edge 6, and is longer in the circumferential direction.

For this reason, as in the indexable ball end mill and the end mill body 11 of the present embodiment, two insert mounting seats 12A and 12B of the same shape and size are formed, and the first and second two insert mounting seats of the same shape and size are formed. The cutting inserts 1A and 1B are arranged so that the main cutting edge 5 of the first cutting insert 1A extends from the vicinity of the axis O on the inner circumference of the tip of the end mill body 11 to the outer circumference of the rear end, and the second cutting insert 1B is arranged so as to extend to the outer circumference of the rear end. One type of cutting insert 1 can be manufactured by mounting the arc-shaped cutting edge portions 5a and 6a so that the rotational trajectories of the arcuate cutting edge portions 5a and 6a form one hemisphere so that the blade 6 extends from a position away from the axis O to the outer peripheral side of the rear end. It is possible to perform cutting with

Further, in the present embodiment, the arc-shaped cutting edge portion 5a of the main cutting edge 5, except for the nick 10, moves away from the seating surface 3 as it separates from the linear cutting edge portion 5b of the main cutting edge 5, and then moves to the seating surface 3. In this basic shape, the arcuate cutting edge portion 5a gradually covers the seating surface 3 from the most convex point S5 of the main cutting edge. Since the cutting material is cut, the cutting resistance can be reduced.

Furthermore, when the arc-shaped cutting edge portion 5a of the main cutting edge 5 cuts into the work material from the main cutting edge most convex point S5, in the present embodiment, the nick 10 of the main cutting edge 5 It is formed at a position that does not overlap with the blade maximum convex point S5. Therefore, it is possible to prevent the arc-shaped cutting edge portion 5a of the main cutting edge 5 from cutting into the work material from the end of the nick 10. It is also possible to prevent the blade 5 from being chipped or the like.

Furthermore, in order to form the nick 10 of the main cutting edge 5 at a position that does not overlap the main cutting edge most convex point S5, in the present embodiment, at least one nick 10 of the main cutting edge 5 is It is arranged on the first end 2a side opposite to the point of contact Q5 between the arc-shaped cutting edge portion 5a and the linear cutting edge portion 5b from the cutting edge maximum convexity point S5. For this reason, the chips generated by cutting into the work material from the main cutting edge maximum convex point S5 of the arcuate cutting edge portion 5a of the main cutting edge 5 should be divided so as not to extend or widen. It is possible to achieve a reliable reduction in cutting resistance.

In the present embodiment, in the main cutting edge 5, along the rotation axis of the rotation locus around the rotation axis passing through the center P of the arcuate cutting edge portion 5a and parallel to the linear cutting edge portion 5b in the above plan view. , that is, a cross section along the axis O of the rotation trajectory of the main cutting edge 5 around the axis O of the end mill body 11, from the center P of the arc-shaped cutting edge 5a of the rotation shaft to the arc-shaped cutting edge 5a A portion extending toward the first end portion 2a opposite to the contact point Q5 with the linear cutting edge portion 5b, that is, a portion extending toward the tip end side of the end mill body 11, the center P and the main cutting edge maximum convexity point S5. The connecting straight line L5 intersects at an angle θ5 within the range of 43° to 47°. Therefore, the main cutting edge 5 can cut into the work material from substantially the center of the arc-shaped cutting edge portion 5a, and the cutting resistance can be reliably reduced.

That is, when the angle θ5 is in the range of more than 47° or less than 43°, the point S5 of the main cutting edge is the point of contact Q5 between the arcuate cutting edge 5a and the linear cutting edge 5b. side, or the first end 2a side opposite to this contact Q5. Therefore, the arc-shaped cutting edge portion 5a of the main cutting edge 5 cuts into the work material from the outer circumference of the rear end or the inner circumference of the tip of the indexable ball end mill, thereby sufficiently reducing the cutting resistance. may not be possible.

On the other hand, in the present embodiment, the arc-shaped cutting edge portion 6a of the minor cutting edge 6, excluding the nick 10, also separates from the seating surface 3 side as it separates from the linear cutting edge portion 6b of the minor cutting edge 6, and then The arc-shaped cutting edge portion 6a of the minor cutting edge 6, like the major cutting edge 5, is the most convex with respect to the seating surface 3 in this basic shape. Since the work material is cut from the sub-cutting edge most convex point S6, the cutting resistance can be reduced.

Further, the nick 10 of the minor cutting edge 6 is also arranged at a position where the opening to the flank 4 does not overlap the minor cutting edge peak point S6 in the basic shape of the minor cutting edge 6 . Therefore, even at the nick 10 of the minor cutting edge 6, it is possible to prevent the arc-shaped cutting edge portion 6a of the minor cutting edge 6 from cutting into the work material from the end thereof. It is also possible to easily prevent the minor cutting edge 6 from being chipped from the part.

Further, in the present embodiment, the nick 10 of the minor cutting edge 6 has an opening to the flank face 4 that is more linearly cut than the arcuate cutting edge portion 6a of the minor cutting edge 6 rather than the minor cutting edge peak point S6. It is arranged on the contact Q6 side with the blade portion 6b. That is, since the arcuate cutting edge portion 6a of the minor cutting edge 6 is shorter in the circumferential direction than the arcuate cutting edge portion 5a of the major cutting edge 5, the nick 10 of the minor cutting edge 6 is thus formed on the main cutting edge. Conversely to the arcuate cutting edge portion 5a of the minor cutting edge 6, the arcuate cutting edge portion 6a of the minor cutting edge 6 is arranged on the side of the point of contact Q6 between the arcuate cutting edge portion 6a and the linear cutting edge portion 6b. It is possible to divide the chips generated by the blade portion 6a into pieces having substantially the same width.

Furthermore, in the present embodiment, the grooves 8 (the first and second grooves 8A and 8B) opening in the flank 4 of the minor cutting edge 6 are located further along the minor cutting edge 6 than the minor cutting edge peak point S6. It is open on the contact point Q6 side between the arcuate cutting edge portion 6a and the linear cutting edge portion 6b. Therefore, when the minor cutting edge 6 cuts into the work material from the minor cutting edge most convex point S6 as described above, the seating surface 3 on the side opposite to the minor cutting edge most convex portion S6 is The groove 8 that opens to the flank 4 of the blade 6 can prevent the bottom surface 12a of the second insert mounting seat 12B from becoming unsupported, and the arcuate cutting edge portion 6a of the minor cutting edge 6 can be prevented from being unsupported. It is possible to improve the support rigidity of the point S6.

Furthermore, at least one nick 10 of the minor cutting edge 6 has an opening to the flank face 4 at the minor cutting edge most convex point S6 and a groove portion 8 opening to the flank face 4 of the minor cutting edge 6 in this embodiment. (second groove portion 8B). As a result, chips generated by cutting into the work material from the minor cutting edge convex point S6 of the minor cutting edge 6 are immediately divided by the nick 10 between the minor cutting edge 6 and the groove 8 (second groove 8B). Since the groove 8 is open, the cutting load acting on the minor cutting edge 6 that is not supported by the bottom surface 12a of the second insert mounting seat 12B can be reduced.

In the present embodiment, the minor cutting edge 6 also rotates along the axis of rotation passing through the center P of the arcuate cutting edge portion 6a of the minor cutting edge 6 in plan view and parallel to the linear cutting edge portion 6b. 6 along the rotation axis, i.e., the cross section along the axis O of the rotation path of the minor cutting edge 6 around the axis O of the end mill body 11, the arc shape of the minor cutting edge 6 of the rotation axis A portion extending from the center P of the cutting edge portion 6a to the end portion side opposite to the point of contact Q6 with the linear cutting edge portion 6b in the arcuate cutting edge portion 6a, that is, the portion extending toward the tip end side of the end mill body 11, and the center A straight line L6 connecting P and the minor cutting edge convexity point S6 intersects at an angle θ6 within the range of 43° to 47°. Therefore, the arc-shaped cutting edge portion 6a of the minor cutting edge 6 can be caused to cut into the work material from substantially the center thereof in the same manner as the major cutting edge 5, so that the cutting resistance can be reliably reduced.

That is, as in the case of the major cutting edge 5, when the angle θ6 exceeds 47° or falls below 43°, the minor cutting edge maximum convex point S6 is The arc-shaped cutting edge 6a of the minor cutting edge 6 is positioned too much on the side of the contact Q6 with the straight cutting edge 6b or on the side of the second end 2b opposite to this contact Q6, and the arc-shaped cutting edge 6a of the minor cutting edge 6 becomes an indexable ball. There is a possibility that cutting force cannot be sufficiently reduced because the workpiece is cut from the rear end outer circumference side or the tip inner circumference side of the end mill.

Next, FIGS. 15 to 20 show a second embodiment in which the present invention is applied to a cutting insert of an indexable radius end mill, and FIGS. 21 to 25 show this second embodiment. 26 shows a second embodiment of an indexable radius end mill and an end mill main body, which is a second embodiment of the indexable end mill of the present invention, in which two cutting inserts are attached to the insert mounting seat. and FIG. 27 show the positional relationship between two cutting inserts in the indexable end mill of the second embodiment. The parts common to those of the cutting insert 1 and the indexable end mill of the first embodiment shown in FIGS.

The cutting insert 21 of the second embodiment is provided with two cutting edges 22, and these cutting edges 22 are provided with an arc-shaped cutting edge portion 22a and a linear cutting edge portion 22b. Although common to the embodiment, the circumferential lengths of the arc-shaped cutting edge portions 22a of the two cutting blades 22 are equal to each other and are substantially 1/4 arc-shaped, and these arc-shaped cutting edge portions 22a The lengths of the linear cutting edge portions 22b extending in contact with one end (the end portion on the counterclockwise side of the mounting hole 7 in FIG. 15) are also equal to each other.

In addition, in the cutting insert 21 of the second embodiment, the arcuate cutting edge portion 22a is also provided at the other end of the arcuate cutting edge portion 22a (the end portion on the clockwise side with respect to the mounting hole 7 in FIG. 15). Another linear cutting edge portion 22c is formed to extend in contact with. The lengths of these other linear cutting edge portions 22c are also equal to each other and shorter than the linear cutting edge portion 22b. Further, the other linear cutting edge portion 22c extends in a direction perpendicular to the linear cutting edge portion 22b or in a direction that intersects the linear cutting edge portion 22b at an angle slightly smaller than 90° when viewed from the direction facing the rake face 2. .

In addition, in the cutting insert 21 of the second embodiment, the two cutting edges 22 extend in the counterclockwise direction around the mounting hole 7 when viewed from the direction facing the rake face 2. A cutting edge portion 22c, an arc-shaped cutting edge portion 22a, and a linear cutting edge portion 22b are positioned in order in the circumferential direction of the rake face 2 and formed. Therefore, the cutting insert 21 has a 180° rotationally symmetrical shape with respect to the mounting hole 7 in plan view facing the rake face 2 except for the nick 10 . Moreover, the two cutting edges 22 are formed on a plane parallel to the seating surface 3 except for the nick 10 in this embodiment, and do not have the most convex point as in the first embodiment.

Furthermore, a plurality of (two) nicks 10 are formed on each of the two cutting edges 22 at positions that do not overlap when the cutting insert 21 is rotated 180° about the mounting hole 7 . Of these two cutting edges 22, the first cutting edge 22A (the cutting edge 22 facing the lower right side in FIG. 15) has a plurality of nicks 10 formed only on the rake face 2 of the arcuate cutting edge portion 22a. It is open on the flank 4 at the bottom, and is not formed on the linear cutting edge 22b or the other linear cutting edge 22c.

In the second cutting edge 22B (the cutting edge 22 facing the upper left in FIG. 15), one of the plurality of (two) nicks 10 is formed on the rake face 2 of the arcuate cutting edge portion 22a, and the other One is formed at the contact point between the arc-shaped cutting edge portion 22a and the linear cutting edge portion 22b. In the first and second cutting edges 22A and 22B, the intervals between the nicks 10 in the circumferential direction of the arcuate cutting edge portion 22a are substantially equal to each other.

Also in the second embodiment, the seating surface 3 of the cutting insert 21 can abut on the projection 33 protruding from the bottom surface of the insert mounting seat 32 formed on the end mill main body 31 of the indexable radius end mill. A groove portion 8 having a wide wall surface is formed so as to open to the flank surface 4 of the cutting insert 21, and the opening portion of the nick 10 to the flank surface 4 is shown in FIG. As shown, it is positioned so as not to overlap the opening of the groove 8 to the flank 4 .

Also in the second embodiment, two grooves 8 are formed in the seating surface 3, and one of the two grooves 8 opens to both of the flanks 4 of the two cutting edges 22A and 22B. While being a through groove, the other is a blind groove that opens only to the flank 4 of one cutting edge 22B. In this embodiment, the first groove portion 8A on the lower side in FIG. , the upper second groove portion 8B is a through groove that opens to the flank surface 4 of the linear cutting edge portion 22b of the first cutting edge 22A and the arcuate cutting edge portion 22a of the second cutting edge 22B. This second groove portion 8B is a narrow portion in which the groove width becomes narrower as it goes from one end side of the flank surface 4 side of the first cutting edge 22A toward the other end side of the flank surface 4 side of the second cutting edge 22B. 9.

Also in the indexable end mill (indexable radius end mill) of the second embodiment, the two cutting inserts 21A and 21B of the second embodiment having the same shape and size as described above are , are detachably attached to the two insert mounting seats 32 formed on the distal end portion of the end mill body 31 on opposite sides in the circumferential direction. However, the two insert mounting seats 32 in the indexable end mill and the end mill main body 31 of this second embodiment are 180° rotationally symmetrical with respect to the axis O of the end mill main body 31, except for the convex portion 33 projecting from the bottom surface 32a. is formed in

Of the two insert mounting seats 32, the bottom surface 32a of the first insert mounting seat 32A shown in FIG. Only the first protrusion 33A is formed. In the first insert mounting seat 32A, the first cutting insert 21A extends the arc-shaped cutting edge portion 22a of the first cutting edge 22A from the inner peripheral side of the front end of the end mill main body 31 to the outer peripheral side of the rear end. Thus, it is detachably attached by the clamp screw 15 .

At this time, the linear cutting edge portion 22b of the first cutting edge 22A is positioned on a cylindrical surface centered on the axis O, and the other linear cutting edge portion 22c is arranged on a plane perpendicular to the axis O. or arranged so as to extend slightly toward the rear end side toward the inner peripheral side of the end mill main body 31 . As shown in FIGS. 24 and 25, in the indexable end mill and the end mill body 31 of the second embodiment, the bottom surface 32a of the insert mounting seat 32 moves toward the rear end of the end mill body 31 in the end mill rotation direction T. , so that the first cutting edge 22A of the first cutting insert 21A mounted as described above and the second cutting edge 22A of the second cutting insert 21B, which will be described below, The cutting edge 22B of is provided with a positive axial rake angle.

Of the two insert mounting seats 32, the bottom surface 32a of the second insert mounting seat 32B shown in FIG. A second convex portion 33B is formed to contact, and a third convex portion 33C is formed on the rear end side of the end mill body 31 to contact the first groove portion 8A of the second cutting insert 21B. . In this second insert mounting seat 32B, the second cutting insert 21B is positioned such that the second cutting edge 22B, except for the nick 10, is the same as the first cutting edge of the first cutting insert 21A in the rotational trajectory about the axis O. 22A and is detachably attached.

In the cutting insert 21 and the indexable end mill (indexable radius end mill) of the second embodiment, the opening of the nick 10 to the flank 4 is the same as in the first embodiment. As shown in FIG. 27 in a perspective view from the side, since it is arranged at a position not overlapping the opening of the groove 8 to the flank 4, there is no gap between the nick 10 and the seating surface 3 and between the groove 8 and the rake. By ensuring the thickness between the surface 2 and the cutting insert 21, even if a large cutting load acts on the cutting insert 21, damage can be prevented.

Further, the cutting insert 21 of the second embodiment is formed with another linear cutting edge portion 22c that contacts the other end of the arcuate cutting edge portion 22a. , the other linear cutting edge portion 22c is arranged on a plane perpendicular to the axis O, or is arranged so as to extend slightly toward the rear end side toward the inner peripheral side of the end mill main body 31. As shown in FIG. Therefore, even if the feed of the end mill main body 31 is increased, the bottom surface of the machined surface of the work can be smoothly finished by allowing the other linear cutting edge portion 22c to act as a polishing edge.

28 and 29 show modifications of the cutting insert 21 and the indexable end mill of the second embodiment, which are different from the second embodiment shown in FIGS. The same reference numerals are assigned to common parts. In this modification, in the second groove portion 8B of the two groove portions 8, the second wall surface 8b facing the second end portion 2b side of the rake surface 2 is provided with the second wall surface 8b of the rake surface 2. The difference from the second embodiment is that a concave portion 8d is formed on the side of the end portion 2a of the first embodiment.

The concave portion 8d is formed in a rectangular or trapezoidal shape extending in the direction in which the second groove portion 8B extends when viewed from the direction facing the seating surface 3. In this modification, the concave portion 8d extends in the direction in which the second groove portion 8B extends. A plurality of (two) are formed at intervals. In addition, in the cutting insert 21 of this modified example, the rake face 2, the cutting edge 22, and the nick 10 are formed in the same manner as in the second embodiment.

In the cutting insert 21 of such a modified example, the second wall surface 8b of the second groove portion 8B that abuts on the first convex portion 33A of the first insert mounting seat 32A in the first cutting insert 21A has such a shape. Since the concave portion 8d is formed, when the wall surface (second wall surface 8b) of the groove portion 8 (second groove portion 8B) is formed by a grinding tool, the grinding tool can escape to the concave portion 8d. Molding becomes easier. Although there are two concave portions 8d in this modified example, the number may be one or three or more. Further, the shape of the recess 8d when viewed from the direction facing the seating surface 3 may be circular, semi-circular, semi-elliptic, etc., in addition to the rectangular or trapezoidal shape as described above.

1 (1A, 1B), 21 (21A, 21B) Cutting insert 2 Rake face 3 Seating face 4 Flank face 5 Main cutting edge 5a Circular cutting edge portion of main cutting edge 5 5b Linear cutting edge portion of main cutting edge 5 6 Minor cutting edge 6a Circular cutting edge portion of minor cutting edge 6 6b Linear cutting edge portion of minor cutting edge 6 7 Mounting hole 8 (8A, 8B) Groove portion 9 Narrow portion 10 Nick 11, 31 End mill body 12 (12A , 12B), 32 (32A, 32B) Insert mounting seat 14A, 14B, 14C, 33A, 33B, 33C Convex portion 22 (22A, 22B) Cutting edge 22a Circular cutting edge 22b Linear cutting edge 22c Other straight line Cutting edge portion M Position of nick 10 that is most recessed toward seating surface 3 P Center of arc formed by arc-shaped cutting edge portions 5 a and 6 a of major cutting edge 5 and minor cutting edge 6 Q5 Arc-shaped cutting edge of major cutting edge 5 Contact point Q6 between cutting edge portion 5a and linear cutting edge portion 5b Contact point between arcuate cutting edge portion 6a of minor cutting edge 6 and linear cutting edge portion 6b S5 Most convex point of major cutting edge S6 Most convex point of minor cutting edge L5 Straight line L6 connecting the center P and the most convex point S5 of the major cutting edge Straight line connecting the center P and the most convex point S6 of the minor cutting edge Angle θ6 at which straight line L5 intersects a portion extending from center P to the end opposite to contact point Q5 in a cross section along the rotation axis of the rotation trajectory of main cutting edge 5 about the rotation axis parallel to blade portion 5b From the center P of the cross section along the rotation axis of the rotation trajectory of the minor cutting edge 6 around the rotation axis passing through the center P of the arcuate cutting edge portion 6a of the cutting edge 6 and parallel to the linear cutting edge portion 6b to the point of contact Q6. is the angle at which the portion extending to the opposite end side intersects the straight line L6 O is the axis of the end mill body 11 T is the rotation direction of the end mill

Claims (19)

A cutting insert detachably attached to an insert mounting seat formed at the tip of an end mill body of an indexable end mill that rotates about an axis,
A rake face directed in the direction of rotation of the end mill body, a seating surface facing the opposite side of the rake face and seated on the bottom surface of the insert mounting seat, and a flank extending around the rake face and the seating face. and
An arcuate cutting edge portion extending in an arcuate shape in a plan view viewed from the direction facing the rake surface and at least one end of the arcuate cutting edge portion are in contact with the intersection ridgeline between the rake face and the flank face. A cutting edge is formed with a linear cutting edge portion extending to
The rake face is formed with a plurality of groove-shaped nicks that reach the cutting edge and open to the flank face,
The seating surface is formed with a groove portion having a wall surface capable of abutting against a protrusion protruding from the bottom surface of the insert mounting seat so as to open to the flank surface,
A cutting characterized in that the openings of all the nicks to the flank face are arranged at positions that do not overlap the openings of the grooves to the flank face in a perspective view from the rake face side. insert. 2. The method according to claim 1, wherein the opening of the groove to the flank is located closer to the arcuate cutting edge than at least one of the nicks. Cutting insert as described. 3. The cutting insert according to claim 1, wherein the groove portion has a narrow portion in which the groove width becomes narrower from one end side to the other end side in the extending direction of the groove portion. The nick is formed on the rake face of the arc-shaped cutting edge, and the opening of at least one of the grooves to the flank face is open to the flank face of the linear cutting edge. Cutting insert according to any one of claims 1 to 3. 4. The two cutting edges are formed by alternately locating the arc-shaped cutting edge portion and the linear cutting edge portion in the circumferential direction of the rake face. The cutting insert according to any one of Two grooves are formed in the seating surface,
One of the two grooves is a through groove that opens to both the flanks of the two cutting edges, and the other is a blind groove that opens to the flank of one cutting edge. Item 6. The cutting insert according to item 5. One of the two cutting edges is a major cutting edge and the other is a minor cutting edge,
5. The arc-shaped cutting edge portion of the major cutting edge is formed to have a longer circumferential length with a radius equal to that of the arc-shaped cutting edge portion of the minor cutting edge. 7. The cutting insert according to 6. The arc-shaped cutting edge portion of the main cutting edge is formed in a convex curved shape, excluding the nick, as it separates from the linear cutting edge portion of the main cutting edge and then moves away from the seating surface side and then approaches the seating surface side. has a basic shape,
The nick of the main cutting edge is arranged at a position where the arcuate cutting edge portion in the basic shape of the main cutting edge does not overlap the most convex point of the main cutting edge where it is most convex with respect to the seating surface. The cutting insert according to claim 7, characterized by: The nick of the main cutting edge is arranged on the end side opposite to the point of contact between the arc-shaped cutting edge portion and the linear cutting edge portion from the main cutting edge's most convex point. The cutting insert according to claim 8, wherein In the main cutting edge, in the cross section along the rotation axis of the rotation locus of the main cutting edge around the rotation axis that passes through the center of the arc-shaped cutting edge portion in plan view and is parallel to the linear cutting edge portion ,
A portion of the rotating shaft extending from the center of the arc-shaped cutting edge portion to the end portion side opposite to the contact point of the arc-shaped cutting edge portion with the linear cutting edge portion; 10. The cutting insert according to claim 8 or 9, wherein the straight line connecting the convex points intersects at an angle within the range of 43° to 47°. Except for the nick, the arc-shaped cutting edge portion of the minor cutting edge is formed in a convex curved shape that moves away from the seating surface side and then approaches the seating surface side as it separates from the linear cutting edge portion of the minor cutting edge. has a basic shape,
The nick of the minor cutting edge is arranged at a position where the arcuate cutting edge portion in the basic shape of the minor cutting edge does not overlap with the most convex point of the minor cutting edge where it is most convex with respect to the seating surface. The cutting insert according to any one of claims 7 to 10, characterized in that: The nick of the minor cutting edge is arranged closer to the point of contact between the arc-shaped cutting edge portion and the linear cutting edge portion of the minor cutting edge than the convexity point of the minor cutting edge. The cutting insert according to claim 11. The groove portion opening on the flank of the minor cutting edge opens on the contact side of the arcuate cutting edge portion and the linear cutting edge portion of the minor cutting edge from the minor cutting edge's most convex point. 13. The cutting insert according to claim 11 or 12, characterized in that there is a 11 to 13, wherein at least one nick of the minor cutting edge is arranged between the most convex point of the minor cutting edge and the groove portion opening to the flank of the minor cutting edge. Item 14. The cutting insert according to any one of Item 13. In the above-mentioned minor cutting edge, in the cross section along the above-mentioned rotation axis of the rotation trajectory of the above-mentioned minor cutting edge around the rotation axis that passes through the center of the arc-shaped cutting edge portion in plan view and is parallel to the above-mentioned linear cutting edge portion ,
A portion of the rotating shaft extending from the center of the arc-shaped cutting edge portion to the end portion side of the arc-shaped cutting edge portion opposite to the contact point with the linear cutting edge portion; 15. The cutting insert according to any one of claims 11 to 14, wherein the straight line connecting the convex points intersects at an angle within the range of 43° to 47°. 5. The cutting edge according to any one of claims 1 to 4, characterized in that the cutting edge has another linear cutting edge portion extending in contact with the other end of the arcuate cutting edge portion. cutting insert. The two cutting edges are formed by sequentially arranging the other linear cutting edge portion, the arcuate cutting edge portion, and the linear cutting edge portion in the circumferential direction of the rake face. The cutting insert according to claim 16. Two grooves are formed in the seating surface,
One of the two grooves is a through groove that opens to both the flanks of the two cutting edges, and the other is a blind groove that opens to the flank of one cutting edge. Item 18. The cutting insert according to Item 17. The cutting insert according to any one of claims 1 to 18 protrudes from the bottom surface of the insert mounting seat formed at the tip of the end mill body that rotates around the axis. An indexable end mill, characterized in that it is detachably attached with the wall surface of the groove portion being in contact with the convex portion.

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