JP2020127991A - Cutting insert, cutting edge replaceable type ball end mill and end mill main body - Google Patents

Abstract

To provide a cutting insert configured so that defect is prevented from occurring in the insert beginning with an end part of a nick when the nick is formed in a main cutting blade.SOLUTION: The cutting insert comprises rake faces 2 pointed to a rotating direction of an end mill main body, seating surfaces 3 pointed to the opposite side of the direction of the rake faces 2 and flank faces 4 extending to circumferences of the rake faces 2 and the seating surfaces 3. Cutting blades 5 and 6 comprising circular arc-shape cutting blade parts 5a and 6a and linear cutting blade parts 5b and 6b respectively are formed in crossing ridge-line parts between the rake faces 2 and the flank faces 4. Nicks 10 that open to the flank faces 4 are formed on the rake faces 2. A circular arc-shape cutting blade part 5a of the main cutting blade 5 has a basic shape formed in a convex curve shape which approaches the seating surface 3 side after separating from the seating surface 3 side as separating from a linear cutting blade part 5b, excluding the nicks 10. The nick 10 is arranged at a position different from the most protruding point S5 at which the circular arc-shape cutting blade part 5a in the basic shape of the main cutting blade 5 protrudes most with respect to the seating surface 3.SELECTED DRAWING: Figure 14

Description

The present invention is a cutting insert removably attached to an insert mounting seat formed at the tip of an end mill body of a cutting edge replaceable ball end mill that is rotated around an axis, and such a cutting insert is used as an insert mounting seat of the end mill body. The present invention relates to a replaceable blade tip type ball end mill and an end mill body of such a blade tip type ball end mill.

As a cutting insert attached to such a cutting edge exchangeable ball end mill, for example, in Patent Documents 1 and 2, a rake face directed in the rotation direction of the end mill body and an insert mounting seat facing the side opposite to the rake face are disclosed. The seating surface to be seated on the bottom surface and the flanks that extend around the rake face and the seating face are provided, and the ridge line intersecting the rake face and the flank face has a plane viewed from the direction facing the rake face. Two cutting blades each having an arcuate cutting edge portion extending in an arcuate shape and a linear cutting edge portion extending so as to be in contact with the arcuate cutting edge portion are an arcuate cutting edge portion and a linear cutting edge. What is formed by alternately arranging the parts in the circumferential direction of the rake face is described.

Here, in these Patent Documents 1 and 2, in order to reduce cutting resistance and divide chips, a concave groove-shaped nick that reaches the cutting edge and opens to the flank is formed on the rake face. Things are also listed. Further, in Patent Document 3, a main cutting edge and a sub cutting edge are provided so as to face each other on a ridge line of an upper surface facing the seating surface, and the main cutting edge and the sub cutting edge are asymmetrical, and the main cutting edge is The arc-shaped cutting edge part of is longer than the arc-shaped cutting edge part of the sub-cutting edge and is supposed to perform the main cutting, and the main cutting edge and the sub-cutting edge are projected from the seating surface in a side view. A cutting insert for a replaceable cutting edge ball end mill and a replaceable cutting edge ball end mill which are formed in a curved shape are described.

Japanese Patent No. 4771547 U.S. Pat. No. 7,309,193 Japanese Patent Laid-Open No. 11-197933

By the way, like the cutting insert described in Patent Document 3, the cutting edge has an asymmetric main cutting edge and a sub cutting edge, and the arcuate cutting edge portion of the main cutting edge has an arc cutting of the sub cutting edge. A cutting insert that is longer than a blade portion and has a main cutting edge and a sub cutting edge that are formed in a convex curve shape protruding in a direction away from the seating surface in a side view. When a nick is formed on the rake face like this, if this nick overlaps with the most convex point that is most convex from the seating surface of the convex curved cutting edge as described above, the cutting edge will end at the end of the nick. Will be cut into the work material.

Therefore, when a large cutting load is applied to the cutting edge near the nick during cutting, stress is concentrated on the end of the nick, which may cause damage such as chipping of the cutting insert. In particular, like the cutting insert described in Patent Document 3, the circumferential length of the arcuate cutting edge portion of the main cutting edge is longer than the circumferential length of the arcuate cutting edge portion of the sub cutting edge, If the arcuate cutting edge of the main cutting edge is supposed to perform the main cutting, the nick formed on the rake face of the arcuate cutting edge of this main cutting edge is If it overlaps with the most convex point of the main cutting edge that is most convex with respect to the seating surface of the part, a large impact cutting load will act on the edge of this overlapping nick when biting into the work material. The risk of damage to the cutting insert from the end of this nick is even higher.

The present invention has been made under such a background, particularly in a cutting insert for a cutting edge replaceable ball end mill having a basic shape in which a main cutting edge is formed in a convex curved shape that is convex in the end mill rotation direction, When a concave groove-shaped nick that reaches the main cutting edge and opens on the flank is formed on the rake face, even if a large cutting load acts on the main cutting edge near this nick, the cutting insert will start from the end of the nick. We provide a cutting insert that can prevent the occurrence of chipping, etc., and also provide a cutting edge replaceable ball end mill to which such a cutting insert is detachably mounted, and an end mill body of such a cutting edge replacement type ball end mill. It is intended to be provided.

In order to solve the above problems and achieve such an object, the cutting insert of the present invention is attached to and detached from an insert mounting seat formed at a tip end portion of an end mill body of a cutting edge replaceable ball end mill that is rotated around an axis. A cutting insert that can be mounted so that the rake face is oriented in the direction of rotation of the end mill body, a seating face facing away from the rake face and seated on the bottom of the insert mounting seat, and these rake faces. And a flank extending around the seating surface, and an arcuate cutting edge extending in a circular arc in a plan view seen from a direction facing the rake face, at a ridge line intersection of the rake face and the flank face. And two cutting edges each having a linear cutting edge extending so as to contact the arcuate cutting edge, the arcuate cutting edge and the linear cutting edge are provided in the circumferential direction of the rake face. The two cutting edges are formed alternately, and one of the two cutting edges is a main cutting edge and the other is a sub cutting edge, and the arcuate cutting edge portion of the main cutting edge is the sub cutting edge. A circular groove having a radius equal to that of the arcuate cutting edge, and the main cutting edge has a rake face which reaches the main cutting edge and opens on the flank. Nick is formed, at least in the main cutting edge, the arcuate cutting edge portion, apart from the linear cutting edge portion except the nick, away from the seating surface side after the seating surface side Has a basic shape that is formed in a convex curved shape, and the nick is the most convex main cutting edge in which the arcuate cutting edge portion in the basic shape of the main cutting edge is the most convex with respect to the seating surface. It is characterized in that it is arranged at a position different from the point.

Further, in the cutting edge replaceable ball end mill of the present invention, the cutting insert configured in this manner is removably attached to an insert mounting seat formed at the tip of the end mill body rotated about the axis. Characterize. Furthermore, the end mill main body of the present invention is an end mill main body that is rotated about an axis, and the cutting insert configured as described above is detachably attached to an insert mounting seat formed at the tip end portion, The bottom surface of the mounting seat is characterized in that a convex portion with which the wall surface of the groove portion abuts is projected.

In the cutting insert and the tip-replaceable ball end mill configured as described above, in the arcuate cutting edge portion of the main cutting edge whose circumferential length is longer than the arcuate cutting edge portion of the auxiliary cutting edge, However, the arcuate cutting edge part in the basic shape of this main cutting edge is arranged at a position different from the most convex point of the main cutting edge that is most convex with respect to the seating surface, and the main cutting edge is the end of the nick. Does not cut into the work material.

Therefore, even if a large cutting load acts when the main cutting is performed by the main cutting edge, a large impact cutting load does not act on the end of the nick when the main cutting edge bites, and this nick It is possible to prevent damage such as chipping from the end portion of the cutting insert. Therefore, according to the cutting insert and the replaceable blade type ball end mill having the above-described configurations, stable cutting can be performed over a long period of time.

In addition, at least one nick of the main cutting edge is disposed on the end side opposite to the contact point between the arcuate cutting edge section and the linear cutting edge section with respect to the most convex point of the main cutting edge. Is desirable. Thereby, before the chips generated by being cut into the work material from the main cutting edge most convex point of the arc-shaped cutting edge portion of the main cutting edge is extended or can be divided before becoming wide, It is possible to surely reduce the cutting resistance.

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

When this angle is in the range of more than 47° or in the range of less than 43°, the most convex point of the main cutting edge is the contact point side with the linear cutting edge part in the arcuate cutting edge part, or this contact point. It is located too far on the opposite end side, and the arcuate cutting edge part of the main cutting edge is to be cut into the work material from the rear end outer peripheral side and the tip inner peripheral side of the tip-replaceable ball end mill, The cutting resistance may not be reduced sufficiently.

On the other hand, on the rake face of the sub-cutting edge, a concave groove-shaped nick that reaches the sub-cutting edge and opens to the flank is formed, and the arc-shaped cutting edge portion of the sub-cutting edge is the nick. Except when the auxiliary cutting edge has a basic shape formed in a convex curved shape that approaches the seating surface side after being separated from the seating surface side as it moves away from the linear cutting edge portion of the sub cutting edge, The nick of the cutting edge is a sub-position in which the arcuate cutting edge portion in the basic shape of the auxiliary cutting edge is the most convex with respect to the seating surface, at the position most recessed on the seating surface side in the opening to the flank. It is desirable that the cutting edge is arranged at a position different from the most convex point.

In the arcuate cutting edge part of the sub cutting edge, whose circumferential length will be shorter than the arcuate cutting edge part of the main cutting edge, the cutting load acting on the sub cutting edge is smaller than that of the main cutting edge. The position of the nick that is most recessed on the seating surface side does not coincide with the most convex point of the sub cutting edge where the arcuate cutting edge of the sub cutting edge is most convex with respect to the seating surface, and is located at a different position. For example, it is possible to prevent the cutting insert from being damaged such as a defect from the end of the nick of the auxiliary cutting edge. However, in the sub cutting edge as well, it is more preferable that the entire nick is arranged at a position different from the most convex point of the sub cutting edge, like the main cutting edge.

In addition, such a nick of the sub cutting edge has a position in which the most recessed portion on the seating surface side in the opening portion to the flank is opposite to the nick of the arcuate cutting edge portion of the main cutting edge, It is preferable that the auxiliary cutting blade is arranged closer to the contact point between the arcuate cutting edge portion and the linear cutting edge portion than the most convex point of the blade. That is, since the arcuate cutting edge portion of the sub-cutting edge has a shorter circumferential length than the arcuate cutting edge portion of the main cutting edge, the sub-cutting portion of the auxiliary cutting edge that is most recessed on the seating surface side of the nick is thus cut off. By disposing on the contact side of the arcuate cutting edge portion of the blade and the linear cutting edge portion, it becomes possible to divide the chips generated by the arcuate cutting edge portion of the auxiliary cutting edge into substantially equal widths.

Further, also in the sub cutting edge, along the rotation axis of the rotation locus of the sub cutting edge around the rotation axis parallel to the linear cutting edge portion passing through the center of the arcuate cutting edge portion in the plan view. In the cross section, a portion of the rotary shaft extending from the center of the arcuate cutting edge portion to the end side opposite to the contact point with the linear cutting edge portion in the arcuate cutting edge portion, the center and the sub-portion. It is desirable that the straight line connecting the most convex point of the cutting edge intersects at an angle within the range of 43° to 47°.

Like the main cutting edge most convex point of the arcuate cutting edge portion of the main cutting edge, if this angle is in the range of more than 47° or less than 43°, the sub cutting edge most convex point becomes The arc-shaped cutting edge is located too much on the contact side with the linear cutting edge or on the end side opposite to this contact, and the arc-shaped cutting edge of the auxiliary cutting edge is located behind the replaceable ball end mill. There is a risk that the cutting resistance cannot be reduced sufficiently because the work material is cut from the outer peripheral side or the inner peripheral side of the tip.

As described above, according to the present invention, the arcuate cutting edge portion of the main cutting edge can be prevented from being cut into the work piece from the end of the nick, so that the main cutting edge of the main cutting edge is cut. It is possible to prevent damage to the cutting insert such as chipping due to a large impact cutting load acting on the end of the nick when biting into the work material, and ensure stable cutting over a long period of time. It becomes possible to do.

It is a perspective view showing one embodiment of a cutting insert of the present invention. It is the top view seen from the direction which opposes the rake face of the embodiment shown in FIG. It is the bottom view seen from the direction which faces the seating surface of the embodiment shown in FIG. FIG. 3 is a side view as seen from the direction of arrow A in FIG. 2. FIG. 3 is a side view as seen from the direction of arrow B in FIG. 2. It is a side view of the arrow C direction view in FIG. FIG. 3 is a side view taken along the arrow D in FIG. 2. It is a side view of the arrow E direction view in FIG. FIG. 9 is a perspective view of a tip end portion of an end mill body showing an embodiment of a cutting edge replaceable ball end mill and an end mill body of the present invention in which the cutting inserts of the embodiment shown in FIGS. 1 to 8 are respectively attached to two insert mounting seats. FIG. 10 is a front view of the embodiment shown in FIG. 9. FIG. 11 is a bottom view as seen from the direction of arrow A in FIG. 10. It is a side view of the arrow B direction in FIG. It is a perspective view which shows the positional relationship of two cutting inserts in the blade tip exchange type ball end mill of the embodiment shown in FIG. It is the perspective view which looked at the two cutting inserts which showed the positional relationship in FIG. 13 from the direction which the main cutting edge opposes the rake surface of the 1st cutting insert used for cutting.

1 to 8 show an embodiment of the cutting insert of the present invention, and FIGS. 9 to 12 show the cutting edge exchange of the present invention in which two cutting inserts of this embodiment are attached to an insert mounting seat. FIG. 13 shows one embodiment of a ball end mill and an end mill main body, and FIGS. 13 and 14 show the positional relationship between two cutting inserts in the cutting edge replaceable ball end mill of this embodiment.

The cutting insert 1 of the present embodiment is formed of a hard material such as cemented carbide into a leaf-shaped plate shape in plan view as shown in FIG. The upper surface of the cutting insert 1 is the leaf-shaped rake surface 2 as described above. Further, the lower surface facing away from the rake surface 2 is a leaf-shaped tree having a shape similar to that of the rake surface 2 and is a flat seating surface 3 to be seated on the bottom surface of the insert mounting seat. The flank extending between the seat and the seating surface 3 is a flank 4.

At the intersection ridge line portion between the rake face 2 and the flank face 4, arcuate cutting edge portions 5a and 6a extending in an arc shape as shown in FIG. Two cutting blades respectively provided with linear cutting blade portions 5b, 6b extending so as to contact the arc-shaped cutting blade portions 5a, 6a are provided with the arc-shaped cutting blade portions 5a, 6a and the linear cutting blade portions 5b, 6b. It is formed by alternately arranging in the circumferential direction of the rake face 2. One of the two cutting edges is the main cutting edge 5, and the other second cutting edge is the sub cutting edge 6.

Further, the flank surface 4 is inclined toward the inner peripheral side of the cutting insert 1 from the rake surface 2 toward the seating surface 3 side, and the cutting insert 1 of the present embodiment is a positive type cutting insert. There is. Further, a mounting hole 7 having a circular cross section formed so as to penetrate the cutting insert 1 is opened at the center of the rake surface 2 and the seating surface 3, and the rake surface 2 of the inner peripheral surface of the mounting hole 7 is cut. The inner diameter of the side portion is formed so as to decrease toward the seating surface 3 side.

Here, in the plan view facing the rake face 2, the arcuate cutting edge portion 5a of the main cutting edge 5 has a substantially quarter arc shape. On the other hand, the arcuate cutting edge portion 6a of the sub cutting edge 6 has the same radius as the arcuate cutting edge portion 5a of the main cutting edge 5, but the circumferential length is the arcuate cutting edge portion of the main cutting edge 5. It is shorter than 5a, that is, it is formed in an arc shape shorter than a quarter arc. Along with this, the linear cutting edge portion 5b of the main cutting edge 5 is, conversely, made shorter than the linear cutting edge portion 6b of the sub cutting edge 6. That is, the cutting insert 1 of the present embodiment is not symmetrical about 180° about the center line of the mounting hole 7, but is asymmetric.

The linear cutting edge portions 5b and 6b of the main cutting edge 5 and the sub cutting edge 6 are the arcuate cutting edge portion 5a of the main cutting edge 5 and the linear cutting edge portion 6b of the sub cutting edge 6 in the plan view. The second end of the rake surface 2 where the linear cutting edge portion 5b of the main cutting edge 5 and the arcuate cutting edge portion 6a of the sub cutting edge 6 intersect from the first end portion 2a of the rake surface 2 where They extend so as to come closer to each other toward the portion 2b. Further, the first and second end portions 2a and 2b are chamfered so as to obtusely intersect the arcuate cutting edge portions 5a and 6a of the main cutting edge 5 and the sub cutting edge 6 and the linear cutting edge portions 5b and 6b. It is formed into a shape. The first end 2a is located closer to the seating surface 3 than the second end 2b.

Further, the arcuate cutting edge portions 5a, 6a of the main cutting edge 5 and the auxiliary cutting edge 6 are separated from the seating surface 3 side as they are separated from the linear cutting edge portions 5b, 6b except for nicks described later. Is formed so as to have a convex curved basic shape that approaches the seating surface 3 side afterward, and the convex curve formed by these arcuate cutting edge portions 5a and 6a is convex farthest from the seating surface 3. The points (the most protruding points most protruding from the seating surface 3) are the main cutting edge most convex points S5 and the sub cutting edge most convex points S6, respectively. The linear cutting edge portions 5b and 6b of the main cutting edge 5 and the sub cutting edge 6 are arcuate cutting edges as shown in FIGS. 4 and 6 even in a side view seen from a direction facing the flank 4. It is in contact with the convex curve formed by the portions 5a and 6a, and extends in a substantially straight line shape that approaches the seating surface 3 side as it moves away from the arcuate cutting edge portions 5a and 6a.

Here, in the main cutting edge 5, around the rotation axis (axis O of the end mill body 11 described later) that passes through the center P of the arcuate cutting edge 5a and is parallel to the linear cutting edge 5b in the plan view. In the cross section of the rotation locus of the main cutting edge 5 along the rotation axis, as shown on the right side of FIG. 14, a straight line from the center P of the arc-shaped cutting edge section 5a to the arc-shaped cutting edge section 5a of the rotation axis. A portion extending to the end side opposite to the contact point Q5 with the cutting blade portion 5b (the first end portion 2a side. In the cutting edge replaceable ball end mill, the tip side of the end mill body 11 described later), the center P and the main portion The straight line L5 that connects the cutting edge most convex point S5 intersects at an angle θ5 within the range of 43° to 47°. In the present embodiment, this angle θ5 is set to 45°.

As for the auxiliary cutting edge 6, as shown on the left side of FIG. 14 (however, the left side of FIG. 4 is a bottom view as seen from the seating surface 3 side), the main cutting edge 5 is seen in the plan view. Around the rotation axis (also the axis O of the end mill body 11 which will be described later) that passes through the center P of the arcuate cutting edge 6a that coincides with the center P of the arcuate cutting edge 5a and is parallel to the linear cutting edge 6b. In a section along the rotation axis of the rotation locus of the auxiliary cutting blade 6, a contact point Q6 between the center P of the arc-shaped cutting edge portion 6a of the rotation axis and the linear cutting edge portion 6b of the arc-shaped cutting edge portion 6a. Is the opposite end side (the second end 2b side. Similarly, in the cutting edge exchangeable ball end mill, a portion extending to the tip side of the end mill body 11 which will be described later), the center P, and the auxiliary cutting edge most convex point S6. And a straight line L6 connecting with each other intersect at an angle θ6 within the range of 43° to 47°. In the present embodiment, this angle θ6 is also 45°.

Further, the periphery of the opening of the mounting hole 7 in the central portion of the rake face 2 has a substantially elliptical shape in plan view, which protrudes farther from the seating surface 3 than the main cutting edge 5 and the sub cutting edge 6. The protrusion 2c is formed. The upper end surface of the protrusion 2c is a flat surface parallel to the seating surface 3, and the mounting hole 7 is open to the upper end surface of the protrusion 2c. Furthermore, the outer peripheral surface of the protrusion 2c is inclined toward the inside of the rake face 2 as it goes toward the upper end surface side. Further, the rake face 2 extends toward the seating face 3 side away from the main cutting edge 5 and the sub-cutting edge 6 toward the inside of the rake face 2 and then forms a concave curved surface on the outer peripheral surface of the protrusion 2c. It is in a row.

Furthermore, the flanks 4 that are continuous with the linear cutting edge portions 5b and 6b of the main cutting edge 5 and the sub cutting edge 6 are formed in a flat plane that is inclined as described above. On the other hand, the flank 4 which is continuous with the arcuate cutting edge portions 5a, 6a of the main cutting edge 5 and the sub-cutting edge 6 has a circumferential direction of the cutting insert 1 along the arcuate cutting edge portions 5a, 6a on the rake face 2 side. However, on the side of the seating surface 3 of the flank 4 of the arcuate cutting edge portion 5a of the main cutting edge 5, a flat surface portion 4a inclined in a flat shape as shown in FIGS. 3, 5, and 6 is formed. Are formed.

A groove 8 is formed on the seating surface 3. Here, in the present embodiment, as shown in FIG. 3 in a bottom view seen from a direction perpendicular to the seating surface 3, the two first and second groove portions 8A and 8B are provided in the seating surface 3 with mounting holes. No. 7 opening is provided, and the openings are formed on opposite sides of the opening. The first groove 8A is formed closer to the first end 2a side 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 side of the rake face 2. There is.

These groove portions 8 are formed in a substantially rectangular shape whose cross section orthogonal to the extending direction of the groove portions 8 is flat in the extending direction of the mounting hole 7, that is, extending in the direction substantially perpendicular to the seating surface 3 and facing each other. It is provided with two first and second wall surfaces 8a and 8b, and a bottom surface 8c extending between the first and second wall surfaces 8a and 8b and parallel to the seating surface 3. The first wall surface 8a of each groove 8 faces the first end 2a side of the rake surface 2, and the second wall surface 8b faces the second end 2b side of the rake surface 2. It should be noted that the intersection ridge line portion between the first and second wall surfaces 8a and 8b and the seating surface 3 is chamfered by a convex curved surface, and the corner portion where the first and second wall surfaces 8a and 8b and the bottom surface 8c intersect is concave. It is formed into a curved surface.

Further, the first groove portion 8A has an opening on the flank 4 connected to the linear cutting edge portion 6b of the auxiliary cutting edge 6 and an opening on the flank surface 4 continuous with the arcuate cutting edge portion 5a of the main cutting edge 5. Not formed in a blind groove shape. The end of the main cutting edge 5 on the arcuate cutting edge 5a side of the first groove 8A is connected to the seating surface 3 so as to form a concave curved surface from the bottom surface 8c. Further, in the first groove portion 8A, the first and second wall surfaces 8a and 8b extend in parallel to each other in the bottom view, that is, the groove width of the first groove portion 8A is constant, and The end portion of the main cutting edge 5 on the arcuate cutting edge portion 5a side of the groove portion 8A extends so as to be orthogonal to the first and second wall surfaces 8a and 8b, and the first groove portion 8A has the seating surface 3 It is formed in a substantially trapezoidal shape when viewed from the direction opposite to.

On the other hand, in the present embodiment, the second groove portion 8B is provided on both the flank surface 4 connected to the linear cutting edge portion 5b of the main cutting edge 5 and the flank surface 4 connected to the arcuate cutting edge portion 6a of the sub cutting edge 6. It is formed in the shape of a through groove that opens. In the present embodiment, the second groove portion 8B has the narrow portion 9 in which the groove width becomes narrower from one end side to the other end side in the extending direction of the second groove portion 8B. Here, in the present embodiment, the flank 4 side that is continuous with the linear cutting edge portion 5b of the main cutting edge 5 is defined as the one end side of the second groove portion 8B, and the arc-shaped cutting edge portion 6a of the sub cutting edge 6 is formed. The flank 4 side which continues is made into the other end side.

Further, as shown in FIG. 3, in the present embodiment, the entire second groove portion 8B is the narrow portion 9. In this embodiment, the narrow width portion 9 has a constant narrowing width from the 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 in a linear shape from the one end side toward the other end side in the bottom view.

Further, the opening of the second groove portion 8B to the flank 4 which is continuous with the arcuate cutting edge portion 6a of the sub cutting edge 6 has a linear cutting edge of the sub cutting edge 6 more than the most convex point S6 of the sub cutting edge. It is located on the side of the portion 6b. Specifically, in the bottom view, the straight line L6 connecting the most convex point S6 of the sub cutting edge and the center P of the arc formed by the arc-shaped cutting edge portion 6a of the sub cutting edge 6 and the straight line of the sub cutting edge 6 The end of the ridge line portion (excluding the chamfered portion) intersecting the first wall surface 8a of the second groove portion 8B facing the curved cutting edge portion 6b and the flank 4 to the seating surface 3 side is connected to the center P. A first intersection angle formed by 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 the present embodiment) is equal to that 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 arcuate cutting edge located on the other end side (the arcuate cutting edge 6a of the sub cutting edge 6) viewed from the seating surface 3 side. The range is xr, for example, the range is 1 mm to 7 mm. However, when the shape of the arcuate cutting edge portion 6a viewed from the seating surface 3 side is deviated from the arc, the arc closest to the deviated shape is virtually drawn, and The radius r is determined from the arc of.

On the other hand, the groove width W2 (not shown) at one end of the narrow portion 9 is W2>W1, and the arc-shaped cut is located on the other end side of the groove portion (second groove portion 8B) having the narrow portion 9. 0.10×r to 0. 0 with respect to the radius r of the blade portion (the arcuate cutting edge portion 6a of the sub cutting edge 6) viewed from the seating surface 3 side or the plan view viewed from the rake surface 2 side. Within a range of 30×r, a range of 0.10×R to 0.32×R with respect to the length R (not shown) in the plan view or bottom view of the linear cutting edge portion 5b of the main cutting edge 5. It is said that.

When the groove widths W1 and W2 extend linearly when viewed from the direction in which the first and second wall surfaces 8a and 8b face the seating surface 3, the groove widths W1 and W2 extend linearly. Is a width in a direction perpendicular to a straight bisector of the straight wall surfaces 8a and 8b, and one groove wall surface (for example, the first wall surface 8a) is curved and the other groove wall surface (for example, the first wall surface 8a) is curved. When the second wall surface 8b) is linear, the width is in the direction perpendicular to the linear groove wall surface.

In such a cutting insert 1, a nick 10 in the form of a groove is formed on the rake face 2 of the main cutting edge 5 so as to reach the main cutting edge 5 and open to the flank 4. The nick 10 of No. 5 is arranged at a position different from the most convex point S5 of the main cutting edge. Further, in the present embodiment, the rake face 2 of the auxiliary cutting edge 6 is also provided with a concave groove-shaped nick 10 that reaches the auxiliary cutting edge 6 and opens to the flank 4, and this nick of the auxiliary cutting edge 6 is formed. 10 is also arranged at a position different from the most convex point S6 of the sub cutting edge.

In the present embodiment, the nick 10 is formed in a concave groove shape by notching the rake face 2 in a concave curve shape such as a concave arc when viewed from the direction facing the flank surface 4, and the seating surface 3 The distance between and is gradually increased toward the inner side of the rake face 2, and is formed so as to cut off from the rake face 2 before reaching the upper end face of the protrusion 2c. The valley bottom line that connects the portion having a small gap with the seating surface 3 toward the inner side of the rake surface 2 through the above-mentioned position M that is most recessed on the seating surface 3 side of the opening to the flank 4 of the nick 10, It extends so as to be substantially orthogonal to the cutting edge in a plan view facing the rake face 2. The boundary between the nick 10 and the rake face 2 is rounded in a convex curved shape over the opening to the flank 4.

In addition, in the present embodiment, a plurality (two) of nicks 10 are formed at intervals with respect to one cutting edge (main cutting edge 5 and sub cutting edge 6). Of these, the two nicks 10 of the main cutting edge 5 are both formed so as to reach the arcuate cutting edge portion 5a, and one of the nicks 10 of the sub cutting edge 6 reaches the arcuate cutting edge portion 6a. At the same time, the remaining one is formed so as to reach the linear cutting edge portion 6b.

These nicks 10 make the two cutting inserts 1 match the center P of the arcuate cutting edge portions 5a, 6a of the main cutting edge 5 and the sub cutting edge 6 of each other, and these arcuate cutting edge portions 5a, 6a and the linear cutting edge portions 5b, 6b are overlapped and viewed, the nick 10 reaching the main cutting edge 5 of the one cutting insert 1 and the nick reaching the auxiliary cutting edge 6 of the other cutting insert 1 when overlapped with each other. 10 and 10 are formed so as not to overlap each other but to overlap with the cutting edge extending between the nicks 10.

Further, in the nicks 10 of the main cutting edge 5 and the sub cutting edge 6, the position M most recessed on the seating surface 3 side in the opening to the flank 4 is shown in FIG. 14 in a perspective view from the rake surface 2 side. As described above, the groove 8 is arranged at a position different from the opening to the flank 4. In the present embodiment, not only the position M most recessed on the seating surface 3 side, but also the entire opening to the flank 4 is shown in FIG. 14 in a perspective view from the rake face 2 side. It is formed so as not to overlap the opening to the flank 4. However, in the nick 10 that reaches the sub cutting edge 6, the edge portion farther from the position M most recessed on the seating surface 3 side is slightly different from the opening of the groove 8 to the flank 4 in the perspective view from the rake face 2 side. They may overlap.

Furthermore, in the present embodiment, in the main cutting edge 5, in the perspective view from the rake face 2 side, the nick 10 has a groove M at a position M most recessed on the seating face 3 side in the opening to the flank 4. It is arranged on the side of the first end 2a opposite to the contact point Q5 of the arcuate cutting edge 5a with the linear cutting edge 5b than the opening of No. Particularly, in the present embodiment, as described above, in the main cutting edge 5, the groove portion 8 (second groove portion 8B) is opened only in the flank 4 of the linear cutting edge portion 5b as described above. The nicks 10 are both formed on the rake face 2 of the arcuate cutting edge 5a.

Further, in the present embodiment, at least one nick 10 of the main cutting edge 5 is opposite to the contact point Q5 between the arcuate cutting edge 5a and the straight cutting edge 5b than the main cutting edge most convex point S5. It is arranged on the first end 2a side. Specifically, the two nicks 10 formed to reach the main cutting edge 5 in the present embodiment are located on the contact Q5 side and the first end 2a side with the main cutting edge most convex point S5 in between. It is arranged.

Further, in the present embodiment, the two nicks 10 of the auxiliary cutting edge 6 have a position where the position M most recessed toward the seating surface 3 side in the opening to the flank 4 is smaller than the auxiliary cutting edge most convex point S6. The blade 6 is arranged on the contact point Q6 side between the arcuate cutting edge 6a and the linear cutting edge 6b. Further, the groove portion 8 (first and second groove portions 8A, 8B) which is open to the flank 4 of the sub cutting edge 6 has an arcuate cutting edge portion 6a of the sub cutting edge 6 more than the most convex point S6 of the sub cutting edge. To the contact point Q6 with the linear cutting edge portion 6b, and the first groove portion 8A is opened beyond the contact point Q6 to the second end 2b side of the rake face 2.

Furthermore, at least one nick 10 of the sub cutting edge 6 has a position M most recessed on the seating surface 3 side in the opening to the flank 4 where the sub cutting edge most convex point S6 and the sub cutting edge 6 escape. It is arranged between the groove portion 8 that opens to the surface 4. Here, in the present embodiment, one nick 10 out of the two nicks 10 of the sub cutting edge 6 has an opening to the flank 4 of the sub cutting edge 6 of the sub cutting edge most convex point S6 and the second groove portion 8B. And the other one nick 10 is located in the linear cutting edge portion 6b beyond the contact point Q6, and the auxiliary cutting edge most convex point S6 and the auxiliary cutting edge 6 of the first groove portion 8A It is arranged between the flank 4 and the opening.

Here, the cutting insert 1 formed of such a hard material as a cemented carbide is manufactured according to the basic process of powder metallurgy. That is, when the cutting insert 1 is made of cemented carbide, a mold is made by using a granular granulated powder containing tungsten carbide powder and cobalt powder as main components and, if necessary, chromium, tantalum, etc. as auxiliary components. The powder press molding using is performed.

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

The cutting insert 1 configured as described above is detachably attached to the insert mounting seat 12 formed at the tip of the end mill body 11 as shown in FIGS. It constitutes an embodiment. The end mill main body 11 is formed of a metal material such as steel, and the tip end portion thereof has a columnar shape whose base end side is centered on the axis O, and the tip end side is a base end side cylinder whose center is on the axis O. It is a convex hemisphere with the same radius as. The replaceable cutting edge ball end mill according to the present embodiment is attached to the insert mounting seat 12 by feeding the end mill body 11 in a direction intersecting with the axis O while rotating the end mill body 11 around the axis O in the end mill rotation direction T. The work piece is cut by the cutting insert 1.

Here, in the present embodiment, two tip pockets 13 are formed by cutting out the outer periphery of the tip end portion of the end mill main body 11, and insert mounting is performed on the bottom surfaces of these tip pockets 13 facing the end mill rotation direction T, respectively. Seats 12 are formed on the opposite sides of the seat 12 at intervals in the circumferential direction. Then, one type of first and second cutting inserts 1A and 1B of the same shape and size based on the above-described embodiment are attached to these two insert attachment seats 12, respectively.

These insert mounting seats 12 include a flat bottom surface 12a facing the end mill rotation direction T, a wall surface 12b on the tip inner circumference side extending from the bottom surface 12a in the end mill rotation direction T and facing the outer circumference side of the end mill body 11, and a tip outer circumference side. And a wall surface 12c on the outer peripheral side of the rear end. The wall surfaces 12b and 12c are formed in a flat shape that is inclined to the outside of the insert mounting seat 12 as the distance from the bottom surface 12a increases, and when the seating surface 3 of the cutting insert 1 is seated on the bottom surface 12a, It is possible to contact the flat flank 4 of the auxiliary cutting edge 6 which is continuous with the linear cutting edges 5b and 6b and the flat surface 4a of the flank 4 which is continuous with the arcuate cutting edges 5a and 6a on the seating surface 3 side. ing.

Further, a concave portion 12d is formed between the wall surfaces 12b and 12c so as to avoid contact with the curved flank 4 of the cutting insert 1. Further, a screw hole (not shown) into which the clamp screw 15 inserted into the mounting hole 7 of the cutting insert 1 is screwed is formed on the bottom surface 12a. The center line of the screw hole is a plane which connects the seating surface 3 of the cutting insert 1 to the bottom surface 12a and connects to the linear cutting edge portions 5b and 6b of the main cutting edge 5 and the sub cutting edge 6 as described above. Center of the mounting hole 7 of the cutting insert 1 in a state in which the flat surface 4a of the flank 4 that is continuous with the flank 4 and the arcuate cutting edges 5a and 6a on the seating surface 3 side is brought into contact with the wall surfaces 12b and 12c. It is designed to be slightly eccentric to the recess 12d side with respect to the line.

Of these two insert mounting seats 12, the first insert mounting seat 12A is formed so as to cut out the tip end portion of the end mill body 11 to the range including the axis O on the tip end side as shown in FIGS. 9 and 10. ing. In this first insert mounting seat 12A, the first cutting insert 1A extends on the arcuate cutting edge portion 5a of the main cutting edge 5 from the vicinity of the axis O and is located on a convex hemisphere centered on the axis O. At the same time, 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 that is in contact with the convex hemisphere.

Therefore, the flat flank 4 continuous with the linear cutting edge portion 6b of the auxiliary cutting edge 6 in 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 surface portion 4a of the flank 4 of the arcuate cutting edge portion 6a of the sub cutting edge 6 in the first cutting insert 1A is brought into contact.

Then, on the bottom surface 12a of the first insert mounting seat 12A, there is provided a first convex portion 14A with which the wall surface of the groove portion 8 formed on the seating surface 3 of the first cutting insert 1A can abut, And the wall surface 12c, and is formed so as to extend from the outer peripheral surface of the tip end portion of the end mill main body 11 toward the recess 12d and in front of the recess 12d at a distance from the recess 12d. Therefore, the second groove portion 8B of the groove portions 8 formed on the seating surface 3 of the first cutting insert 1A comes into contact with the first convex portion 14A, so that the first insert mounting seat 12A is attached. The convex portion with which the first groove portion 8A abuts is not formed.

Here, the first convex portion 14A has a substantially rectangular shape in which a cross section orthogonal to the direction in which the first convex portion 14A extends is flat in the end mill rotation direction T, and the whole is the narrow portion 9. With respect to the second groove portion 8B, the width becomes wider as it goes from the other end side in the extending direction of the second groove portion 8B to the one end side (from the inner peripheral side to the outer peripheral side of the end mill body 11). Is formed in.

However, the width of the first convex portion 14A (the width in the direction orthogonal to the extending direction of the first convex portion 14A) is at a position where it abuts on the first convex portion 14A in the extending direction of the second groove portion 8B. Is slightly smaller than the width (width in the direction orthogonal to the direction in which the second groove portion 8B extends), and the protruding height from the bottom surface 12a of the first convex portion 14A is also seated in 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 tip end portion of the second insert attachment seat 12B of the two insert attachment seats 12 is slightly separated from the axis O on the tip end side of the end mill body 11 to the outer peripheral side as shown in FIGS. 10 and 11. Formed from the position. The second cutting insert 1B has a second cutting insert 1B on which the arcuate cutting edge portion 6a of the auxiliary cutting edge 6 of the main cutting edge 5 of the first cutting insert 1A is separated from the axis O. The linear cutting edge portion 6b of the auxiliary cutting edge 6 is located on the convex hemisphere where the arcuate cutting edge portion 5a is located, and the linear cutting edge portion 5b of the main cutting edge 5 of the first cutting insert 1A is It is attached so as to be located on the above-mentioned cylindrical surface.

Therefore, the flat surface 4 which is 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. The flat surface 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.

Then, on the bottom surface 12a of the second insert mounting seat 12B, a second convex portion 14B is formed on the tip side of the screw hole, and a third convex portion is formed between the screw hole and the wall surface 12c. The portion 14C is formed. These second and third convex portions 14B and 14C also extend from the outer peripheral surface of the tip portion of the end mill body 11 toward the inner peripheral side, and the second convex portion 14B is the wall surface 12b of the second insert mounting seat 12B. Is spaced apart from the wall surface 12b, and the third protrusion 14C is formed spaced apart from the recess 12d before the recess 12d of the second insert mounting seat 12B. Therefore, the second groove portion 8B of the second cutting insert 1B comes into contact with the second convex portion 14B, and the first groove portion 8A of the second cutting insert 1B comes into contact with the third convex portion 14C.

Further, these second and third convex portions 14B and 14C also have a substantially rectangular shape in which a cross section orthogonal to the extending direction of the second and third convex portions 14B and 14C is flat in the end mill rotation direction T, In the second convex portion 14B, the entire second groove portion 8B of the second cutting insert 1B with which the second convex portion 14B abuts is the narrow portion 9, while in the direction in which the second groove portion 8B extends. It is formed so as to be wide as a whole from the other end side to the one end side (from the outer peripheral side to the inner peripheral side of the end mill body 11). The width of the third convex portion 14C is constant over the extending direction of the third convex portion 14C.

Further, the widths of the second and third convex portions 14B and 14C (widths in the direction orthogonal to the extending direction of the second and third convex portions 14B and 14C) are also the second and first groove portions 8B and 8A. Is made slightly smaller than the width (width in the direction orthogonal to the extending direction of the second and first groove portions 8B and 8A) at the position where it abuts the second and third convex portions 14B and 14C in the extending direction. ing. Further, the protruding height of the second and third convex portions 14B, 14C from the bottom surface 12a of the second insert mounting seat 12B is also the second, first groove portion 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 the clamp screw 15 has the inverted truncated cone head. When the cutting insert is inserted into the mounting hole 7 and screwed into the screw hole, the center line of the screw hole is slightly eccentric to the recess 12d side from the center line of the mounting hole 7 of the cutting insert 1. 1 is pressed against the recess 12d side.

At this time, in the first insert mounting seat 12A, the plane of the flank 4 continuous with the linear cutting edge 6b of the auxiliary cutting edge 6 of the first cutting insert 1A and the flank 4 continuous with the arcuate cutting edge 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 that is 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, and the arc cutting of the main cutting edge 5 is performed. The flat surface portion 4a of the flank 4 that is continuous with the blade portion 5a is pressed against the wall surface 12c.

At the same time, in the first insert mounting seat 12A, the second groove 8B of the first cutting insert 1A abuts the first protrusion 14A 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 on the side surface 14a of the end mill body 11 facing the tip side of the first convex portion 14A, and the second groove portion A slight gap is provided between the first wall surface 8a and the first convex portion 14A in 8B.

Further, in the second insert mounting seat 12B, the second and first groove portions 8B and 8A of the second cutting insert 1B are provided on the second and third convex portions 14B and 14C from the tip side of the end mill body 11 as well. Abut. Therefore, the second and third convex portions 14B and 14C are in contact with the first wall surface 8a of the second and first groove portions 8B and 8A, respectively, on the side surface 14a of the end mill body 11 facing the tip side. 2. A slight gap is provided between the second wall surface 8b of the first groove portions 8B and 8A and the second and third convex portions 14B and 14C. In this way, the first and second convex portions 14A to 14C are brought into contact with the first and second groove portions 8A and 8B, whereby the displacement of the cutting insert 1 due to the load during cutting can be prevented. ..

In the replaceable cutting edge type ball end mill configured as described above, the second cutting insert 1B has the arcuate cutting edge portion 6a of the sub cutting edge 6 as described above, and the main cutting edge 5 of the first cutting insert 1A. Is located on the convex hemisphere on which the arcuate cutting edge 5a is located, and the linear cutting edge 6b is on the cylindrical surface on which the linear cutting edge 5b of the main cutting edge 5 of the first cutting insert 1A is located. It is attached so that it is located.

And these 1st, 2nd cutting inserts 1A and 1B make the center P of the arcuate cutting edge parts 5a and 6a of the main cutting edge 5 and the sub cutting edge 6 mutually match, and also these arcuate cutting edges When the portions 5a, 6a and the linear cutting edge portions 5b, 6b are viewed in an overlapping manner, the nick 10 reaching the main cutting edge 5 of the one cutting insert 1 and the auxiliary cutting edge 6 of the other cutting insert 1 are overlapped. The nicks 10 reaching to the nicks 10 do not overlap each other but overlap the cutting edges extending between the nicks 10.

Therefore, by making the feed amount per blade of the end mill body 11 smaller than the retreat amount of the nick 10 from the cutting edge in a plan view facing the rake surface 2, the nick 10 is most recessed on the seating surface 3 side. The dead position M is not cut into the work material, the chips can be divided and generated, and the cutting resistance can be reduced. A ridge is left on the portion left uncut by the nick 10 on the machined surface of the work material. This ridge has the cutting edge of the cutting insert 1 on the opposite side rotated by 1/2 turn of the end mill body. By cutting, it is cut and removed.

In the cutting insert 1 and the blade tip exchange type ball end mill having the above-described configuration, the arcuate cutting edge portion 5a of the main cutting edge 5 having a circumferential length longer than that of the arcuate cutting edge portion 6a of the auxiliary cutting edge 6 is provided. The reaching nick 10 is arranged at a position different from the main cutting edge most convex point S5 at which the arcuate cutting edge portion 5a in the basic shape of the main cutting edge 5 is most convex with respect to the seating surface 3. Therefore, the main cutting edge is cut into the work material from the most convex point S5 of the main cutting edge, and is not cut into the work material from the end of the nick 10.

Therefore, even when a large cutting load is applied to the main cutting edge 5 when the main cutting edge 5 having a long circumferential length of the arcuate cutting edge portion 5a performs the main cutting, the main cutting edge 5 is not covered by the main cutting edge 5a. A large impact cutting load does not act on the end portion of the nick 10 when it bites into the work material, and damage such as chipping to the cutting insert 1 from the end portion of the nick 10 can be prevented. Therefore, according to the cutting insert 1 and the replaceable cutting edge ball end mill having the above-described configurations, stable cutting can be performed over a long period of time.

Further, in this way, although the nick 10 of the main cutting edge 5 is formed at a position different from the most convex point S5 of the main cutting edge, in the present embodiment, at least one nick 10 of the main cutting edge 5 is It is arranged closer to the first end 2a side than the contact point Q5 between the arcuate cutting edge 5a and the straight cutting edge 5b with respect to the blade most convex point S5. Therefore, the main cutting edge 5a of the arc cutting edge portion 5a of the main cutting edge 5 should be divided so that chips generated by being cut into the work material from the most convex point S5 of the main cutting edge do not extend or become wider. The cutting resistance can be reliably reduced.

Further, in the present embodiment, in the main cutting edge 5, along the rotation axis of the rotation locus about the rotation axis that passes through the center P of the arc-shaped cutting edge portion 5a and is parallel to the linear cutting edge portion 5b in the plan view. In the cross section, that is, the cross section along the axis O of the rotation locus of the main cutting edge 5 around the axis O of the end mill body 11, a straight line from the center P of the arc cutting edge 5a to the arc cutting edge 5a of the rotation axis. A portion extending toward the first end 2a side opposite to the contact point Q5 with the shaped cutting edge portion 5b, that is, a portion extending from the center P of the axis O to the tip side of the end mill body 11, the center P and the main cutting edge portion A straight line L5 connecting the convex point S5 intersects at an angle θ5 within the range of 43° to 47°. Therefore, the main cutting edge 5 can be cut into the work material from substantially the center of the arcuate 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 in the range of less than 43°, the main cutting edge most convex point S5 is the contact point Q5 with the linear cutting edge portion 5b in the arcuate cutting edge portion 5a. Side, or on the side of the first end 2a opposite to the contact Q5. Therefore, the arcuate cutting edge portion 5a of the main cutting edge 5 is cut into the work material from the outer peripheral side of the rear end of the ball end mill and the inner peripheral side of the tip, and the cutting resistance can be sufficiently reduced. May not be possible.

On the other hand, in the present embodiment, the arcuate cutting edge portion 6a of the sub cutting edge 6 also moves away from the seating surface 3 side as it moves away from the linear cutting edge portion 6b of the sub cutting edge 6 except for the nick 10, and then the seating surface 3 It has a basic shape formed in a convex curve shape that approaches the side. Therefore, like the arcuate cutting edge portion 5a of the main cutting edge 5, the arcuate cutting edge portion 6a of the sub cutting edge 6 has the most convex shape with respect to the seating surface 3 in this basic shape. Since the material is cut from the point S6, the cutting resistance can be reduced.

In addition, in the present embodiment, the nick 10 of the auxiliary cutting edge 6 is formed on the rake face 2 of the auxiliary cutting edge 6 as well as the concave groove-shaped nick 10 reaching the auxiliary cutting edge 6 and opening to the flank 4 is formed. 10 is also formed at a position different from the most convex point S6 of the sub cutting edge. Therefore, like the arcuate cutting edge portion 5a of the main cutting edge 5, the arcuate cutting edge portion 6a of the sub cutting edge 6 is also cut into the work material from the auxiliary cutting edge most convex point S6. The impact cutting load does not act on the end portion of the nick 10 of the sub cutting edge 6 when attached, and the damage of the cutting insert 1 from the end portion of the nick 10 of the sub cutting edge 6 can be prevented. it can.

However, since the arcuate cutting edge 6a of the sub cutting edge 6 has a circumferential length shorter than that of the arcuate cutting edge 5a of the main cutting edge 5, and the cutting load acting on the main cutting edge 5 is smaller, Even if the entire nick 10 is not at a position different from the most convex point S6 of the auxiliary cutting edge as in the embodiment, the position M of the auxiliary cutting edge 6 that is most recessed on the seating surface 3 side of the nick 10 is the auxiliary cutting edge. When the cutting insert 1 is arranged at a different position without being coincident with the most convex point S6, it is possible to prevent the cutting insert 1 from being damaged by the end of the nick 10 of the auxiliary cutting edge 6.

Further, in the present embodiment, in the nick 10 of the sub cutting edge 6, the position M most recessed on the seating surface 3 side in the opening portion to the flank 4 is more than the sub cutting edge most convex point S6. Is arranged on the contact point Q6 side between the arcuate cutting edge 6a and the linear cutting edge 6b. As described above, since the arcuate cutting edge portion 6a of the sub cutting edge 6 has a shorter length in the circumferential direction than the arcuate cutting edge portion 5a of the main cutting edge 5, the sub cutting edge 6 is thus seated on the nick 10. The position M most recessed on the side of the surface 3 is opposite to the arcuate cutting edge 5a of the main cutting edge, on the side of the contact point Q6 between the arcuate cutting edge 6a of the auxiliary cutting edge 6 and the straight cutting edge 6b. By arranging them, it becomes possible to divide the chips generated by the arcuate cutting edge portion 6a of the sub cutting edge 6 into substantially equal widths.

Furthermore, in the present embodiment, also in the sub cutting edge 6, the sub cutting around the rotation axis that passes through the center P of the arcuate cutting edge portion 6a of the sub cutting edge 6 in plan view and is parallel to the linear cutting edge portion 6b. In the cross section of the rotation locus of the blade 6 along the rotation axis, that is, the cross section of the sub cutting edge 6 around the axis O of the end mill body 11 along the axis O of the rotation locus, the circle of the sub cutting edge 6 of the rotation axis is shown. A portion extending from the center P of the arcuate cutting edge portion 6a to the end side opposite to the contact point Q6 with the linear cutting edge portion 6b in the arcuate cutting edge portion 6a, that is, a portion extending to the tip side of the end mill main body 11; A straight line L6 connecting the center P and the sub-cutting edge most convex point S6 intersects at an angle θ6 within the range of 43° to 47°. Therefore, like the main cutting edge 5, the arcuate cutting edge 6a of the sub cutting edge 6 can be cut into the work material from approximately the center thereof, so that the cutting resistance can be reliably reduced.

That is, as in the case of the main cutting edge 5, when the angle θ6 is in the range of more than 47° or in the range of less than 43°, the auxiliary cutting edge most convex point S6 is in the arc-shaped cutting edge portion 6a. It is located too much on the side of the contact point Q6 with the linear cutting edge portion 6b or on the side of the second end portion 2b opposite to this contact point Q6, so that the arcuate cutting edge portion 6a of the auxiliary cutting edge 6 is replaced with a cutting edge replaceable ball. There is a possibility that cutting resistance cannot be sufficiently reduced because the end mill is cut into the work piece from the outer peripheral side of the rear end or the inner peripheral side of the tip.

On the other hand, in the present embodiment, the position M most recessed on the seating surface 3 side in the opening portion of the nick 10 formed on the rake surface 2 to the flank surface 4 is as shown in FIG. As shown in FIG. 5, the groove portion 8 formed on the seating surface 3 is arranged at a position different from the opening portion to the flank surface 4. That is, in the direction in which the cutting blade extends, the most recessed position M of the nick 10 on the seating surface 3 side does not overlap the opening of the groove 8 to the flank 4.

Therefore, the thickness of the cutting insert 1 can be ensured and the strength can be maintained between the most recessed position M of the nick 10 and the seating surface 3, whereby the cutting edge in the vicinity of the nick 10 can be maintained. Even if a large cutting load acts on the cutting insert 1 and the cutting load propagates from the most recessed position M of the nick 10 to the seating surface 3 side, damage such as a defect occurs in the cutting insert 1 with the groove 8. Can be prevented. Therefore, according to the cutting insert 1 and the replaceable cutting edge type ball end mill having the above-described configurations, stable cutting can be performed over a long period of time even under cutting conditions under which such a large cutting load acts.

In particular, in the present embodiment, these nicks 10 are not limited to the above-mentioned position M that is most recessed on the seating surface 3 side, but the entire opening portion to the flank surface 4 is the groove portion 8 in the perspective view from the rake face 2 side. It is formed so as not to overlap with the opening to the flank 4. Therefore, it is possible to prevent the thin portion of the cutting insert 1 from being formed due to the nick 10 and the groove portion 8 partially overlapping with each other, and it is possible to more reliably prevent damage such as chipping. be able to.

However, similarly to the above, particularly in the auxiliary cutting edge 6 in which the cutting load acting due to the circumferential length of the arcuate cutting edge portion 6a being shorter than that of the main cutting edge 5, the seating surface 3 of the nick 10 is reduced. If the position M most recessed to the side does not overlap with the groove portion 8, as described above, a perspective view from the side of the rake face 2 where the edge and the end apart from the position M most recessed to the seating surface 3 side of the nick 10 is provided. In, the groove 8 may slightly overlap the opening to the flank 4.

Further, in the cutting insert of the present embodiment, the second groove portion 8B of the groove portion 8 has a narrow width portion 9 in which the groove width becomes narrower from one end side to the other end side in the extending direction of the second groove portion 8B. have. As a result, at the other end side where the groove width of the narrow portion 9 becomes narrower, the wall thickness of the cutting insert 1 can be secured to disperse the stress and improve the strength.

On the other hand, on the contrary, since the groove width becomes wider on the one end side of the narrow width portion 9, the first convex portion 14A corresponds to the narrow width portion 9 of the second groove portion 8B in the end mill body 11 of the cutting edge replaceable ball end mill. By forming the contact groove so that the width thereof becomes wider from the other end side in the extending direction of the second groove portion 8B toward the one end side, the mounting rigidity with respect to the load at the time of cutting is increased and the cutting insert 1 is displaced. It is possible to reliably prevent movement.

Further, in the present embodiment, in the main cutting edge 5, in the perspective view from the rake face 2 side, the nick 10 has a position M most recessed on the seating face 3 side in the opening to the flank face 2 It is arranged on the side of the first end 2a opposite to the contact Q5 of the arcuate cutting edge 5a with the linear cutting edge 5b than the opening of the groove 8B.

Therefore, the most recessed position M of the main cutting edge 5 on the seating surface side of the nick 10 is the second groove portion on the arc-shaped cutting edge portion 5a side of the main cutting edge 5 with respect to the opening of the second groove portion 8B. It will be arranged at a position different from the opening of the flank 8B to the flank 4. Therefore, even if the nick 10 is formed on the arcuate cutting edge portion 5a of the main cutting edge 5 whose circumferential length is longer than that of the auxiliary cutting edge 6, the main cutting edge having such a long circumferential length is formed. It is possible to reliably prevent damage to the cutting insert 1 due to a large cutting load acting on the arcuate cutting edge portion 5a of No. 5.

Particularly, in the present embodiment, in the case of such a configuration, in the main cutting edge 5, the second groove portion 8B is opened only in the flank 4 of the linear cutting edge portion 5b, and the arcuate cutting edge is formed. The nick 10 is formed only on the rake face 2 of the blade portion 5a. For this reason, it becomes possible to reliably divide the extended chips and the wide chips generated by the arcuate cutting edge portion 5a of the main cutting edge 5 having a longer circumferential length than the sub cutting edge 6. Since the groove 8 is not opened in the flank 4 of the arcuate cutting edge 5a of the main cutting edge 5, damage to the cutting insert 1 can be prevented more reliably.

Further, in the present embodiment, the groove portion 8 (first and second groove portions 8A, 8B) that is opened to the flank 4 of the sub cutting edge 6 has a circle of the sub cutting edge 6 that is larger than the most convex point S6 of the sub cutting edge. The arcuate cutting edge portion 6a and the linear cutting edge portion 6b are opened at the contact point Q6 side. Therefore, when the auxiliary cutting edge 6 is cut into the workpiece from the auxiliary cutting edge most convex point S6 as described above, the seating surface 3 on the side opposite to the auxiliary cutting edge most convex portion S6 is It is possible to prevent the groove portion 8 opening to the flank 4 of the blade 6 from not being supported by the bottom surface 12a of the second insert mounting seat 12B, and the sub-cutting blade most convex in the arc-shaped cutting blade portion 6a of the sub-cutting blade 6. The support rigidity of the point S6 can be improved.

Furthermore, in the present embodiment, at least one nick 10 of the auxiliary cutting edge 6 has a position M most recessed toward the seating surface 3 side in the opening portion to the flank 4 and the auxiliary cutting edge most convex point S6, It is arranged between the cutting edge 6 and the groove 8 (second groove 8</b>B) that opens in the flank 4. As a result, the chips generated by being cut into the work material from the most convex point S6 of the auxiliary cutting edge can be immediately divided by the nick 10 between the groove portion 8 (second groove portion 8B), and the groove portion 8 Since the opening is provided, it is possible to reduce the cutting load that acts on the sub cutting edge 6 in the portion not supported by the bottom surface 12a of the second insert mounting seat 12B.

1 (1A, 1B) Cutting Insert 2 Rake Surface 3 Seating Surface 4 Relief Surface 5 Main Cutting Edge 5a Circular Cutting Edge of Main Cutting Edge 5b Linear Cutting Edge of Main Cutting Edge 6 Sub Cutting Edge 6a Sub Cutting Arc-shaped cutting edge portion 6b of blade 6 Linear cutting edge portion of secondary cutting edge 7 Mounting hole 8, 8A, 8B Groove portion 9 Narrow portion 10 Nick 11 End mill body 12 (12A, 12B) Insert mounting seat 14A, 14B, 14C Convex part M Position most recessed on the seating surface 3 side of the nick 10 P Center of arc formed by the arcuate cutting edges 5a and 6a of the main cutting edge 5 and the sub cutting edge 6 Q5 Arc cutting edge of the main cutting edge 5 Contact between the portion 5a and the straight cutting edge 5b Q6 Contact between the arcuate cutting edge 6a of the auxiliary cutting edge 6 and the straight cutting edge 6b S5 Main convex point of the main cutting edge S6 Maximum convex point of the secondary cutting edge L5 Center A straight line connecting P to the most convex point S5 of the main cutting edge L6 A straight line connecting the center P to the most convex point S6 of the secondary cutting edge θ5 A straight cutting edge that passes through the center P of the arcuate cutting edge portion 5a of the main cutting edge 5 Angle θ6 sub-cutting, at which a straight line L5 intersects with a portion extending from the center P in the section along the rotation axis of the rotation path of the main cutting edge 5 around the rotation axis parallel to the portion 5b to the end side opposite to the contact point Q5 What is the contact point Q6 from the center P in the cross section along the rotation axis of the rotation locus of the auxiliary cutting edge 6 around the rotation axis parallel to the linear cutting edge portion 6b and passing through the center P of the arcuate cutting edge portion 6a of the blade 6? Angle at which a portion extending to the opposite end side and the straight line L6 intersect O axis of the end mill body 11 T end mill rotation direction

Claims (8)

A cutting insert removably attached to an insert mounting seat formed at the tip of the end mill body of a cutting edge replaceable ball end mill that is rotated around an axis,
A rake face oriented in the rotation direction of the end mill body, a seating face facing 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. With and
An arcuate cutting edge portion that extends in an arcuate shape in a plan view seen from a direction facing the rake surface, and an arcuate cutting edge portion that extends in contact with the arcuate cutting edge portion, at the ridge line portion intersecting the rake surface and the flank surface. Two cutting edges each provided with a linear cutting edge are formed by alternately positioning the arcuate cutting edge and the linear cutting edge in the circumferential direction of the rake face,
One of the two cutting edges is a main cutting edge and the other is a sub cutting edge,
The arcuate cutting edge portion of the main cutting edge is formed with a long circumferential length with an equal radius with respect to the arcuate cutting edge portion of the auxiliary cutting edge,
On the rake face of the main cutting edge, a groove-shaped nick that reaches the main cutting edge and opens to the flank is formed,
In at least the main cutting edge, the arcuate cutting edge portion is formed in a convex curved shape that approaches the seating surface side after being separated from the seating surface side as it is separated from the linear cutting edge part except for the nick. Has a basic shape
The nick is a cutting characterized in that the arcuate cutting edge portion in the basic shape of the main cutting edge is arranged at a position different from the most convex point of the main cutting edge that is most convex with respect to the seating surface. insert. At least one nick of the main cutting edge is arranged on the end side opposite to the contact point between the arcuate cutting edge section and the linear cutting edge section with respect to the most convex point of the main cutting edge. The cutting insert according to claim 1, 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 parallel to the linear cutting edge portion passing through the center of the arc-shaped cutting edge portion in the plan view. ,
A portion of the rotary shaft extending from the center of the arcuate cutting edge portion to the end side opposite to the contact point with the linear cutting edge portion in the arcuate cutting edge portion, the center and the main cutting edge portion. The cutting insert according to claim 1 or 2, wherein a straight line connecting the convex point intersects at an angle within a range of 43° to 47°. On the rake face of the sub cutting edge, a groove-shaped nick that reaches the sub cutting edge and opens to the flank is formed,
The arcuate cutting edge portion of the sub-cutting edge is formed in a convex curve shape that is closer to the seating surface side after being separated from the seating surface side as being separated from the linear cutting edge portion of the sub-cutting edge except for the nick. Has a basic shape
The nick of the sub-cutting edge is the most recessed position on the seating surface side in the opening to the flank, and the arcuate cutting edge part in the basic shape of the sub-cutting edge is the most convex with respect to the seating surface. The cutting insert according to any one of claims 1 to 3, wherein the cutting insert is arranged at a position different from the highest convex point of the secondary cutting edge. The nick of the sub-cutting edge is that the position most recessed to the seating surface side in the opening to the flank is more than the most convex point of the sub-cutting edge, the arcuate cutting edge section and the linear cutting edge section. The cutting insert according to claim 4, wherein the cutting insert is arranged on a contact point side with. In the sub-cutting edge, in a cross section along the rotation axis of the rotation locus of the main cutting edge around the rotation axis parallel to the linear cutting edge portion passing through the center of the arc-shaped cutting edge portion in the plan view. ,
A portion of the rotary shaft extending from the center of the arcuate cutting edge portion to the end side opposite to the contact point with the linear cutting edge portion in the arcuate cutting edge portion, the center and the sub cutting edge portion. The cutting insert according to claim 4 or 5, wherein a straight line connecting the convex point intersects at an angle within a range of 43° to 47°. The cutting insert according to any one of claims 1 to 6 is detachably attached to an insert attachment seat formed at a tip end portion of an end mill body rotated about an axis. Replaceable cutting edge ball end mill. An end mill body rotated about an axis,
A cutting insert according to any one of claims 1 to 6 is removably attached to an insert mounting seat formed at the tip end portion,
An end mill main body, wherein a convex portion with which a wall surface of the groove portion abuts is projected from a bottom surface of the insert mounting seat.

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