JPWO2019082843A1 - Cutting insert and replaceable ball end mill - Google Patents

Abstract

A cutting insert (1) to be mounted on an insert mounting seat of a replaceable blade end mill, a rake face, a seating face (3) facing the side opposite to the rake face and seated on the insert mounting seat, and a rake face. And a flank 4 extending around the seating surface (3), and an arcuate cutting edge (5a, 6a) and a straight cutting edge (5b) are provided at the ridge line intersecting the rake surface and the flank (4). , 6b) with two cutting edges (5, 6), and the seating surface (3) has two groove portions having wall surfaces (8a, 8b) capable of abutting against the convex portion of the bottom surface of the insert mounting seat. (8) is an arc shape of two cutting blades (5, 6) from the linear cutting blade portion (5b, 6b) side of one cutting blade (5, 6) to the other cutting blade (6, 5). The two groove portions (8) are formed so as to extend toward the cutting edge portions (6a, 5a), and the width of the groove portions (8) becomes narrower from one end side toward the other end side in the extending direction of the groove portions (8) ( 9).

Description

The present invention relates to a cutting insert removably attached to an insert mounting seat formed at a tip end portion of an end mill body of a replaceable cutting edge ball end mill, and a replaceable cutting edge ball end mill to which such a cutting insert is removably mounted. Is.
The present application claims priority to Japanese Patent Application No. 2017-207980 filed in Japan on October 27, 2017, the contents of which are incorporated herein by reference.

In the cutting insert used for such a cutting edge replaceable ball end mill, in the case where two arcuate cutting edge portions are formed on the opposite sides in the circumferential direction of the rake face, the escape is continuous with these arcuate cutting edge portions. Since the side surface of the cutting insert that becomes the surface becomes convexly curved, the curvature of the flank that is continuous with the arcuate cutting edge part on the side opposite to the arcuate cutting edge part used for cutting due to the cutting load during cutting It is easy for the cutting insert to slip and move along. Therefore, for example, in Patent Documents 1 and 2, a convex portion that protrudes on the bottom surface of the insert mounting seat is formed, and on the seating surface of the cutting insert, a groove portion that has a wall surface that can contact the convex portion is formed. By doing so, it is described that such shifting movement of the cutting insert is prevented.

Patent Document 1 describes that only one of the two wall surfaces of the groove portion facing each other is brought into contact with one side surface of the convex portion. Further, in Patent Document 2, by forming a main cutting edge and a sub cutting edge each having an arcuate cutting edge section and a linear cutting edge section, and making the main cutting edge and the sub cutting edge asymmetrical , It is described that the cutting is performed from the vicinity of the axis of the end mill body to the outer circumference and the cutting from the position away from the axis to the outer circumference by the arcuate cutting edge portions of the two cutting inserts of the same shape and the same size. ing.

JP, 9-174322, A JP-A-11-197933

By the way, in the cutting inserts described in the drawings of these Patent Documents 1 and 2, it is shown that two wall surfaces facing each other of the groove portion extend in parallel to each other. In addition, if the width of this convex part is increased in order to increase the rigidity of the convex part of the end mill body and secure the strength against the displacement movement of the cutting insert, the width of the groove part of the cutting insert also becomes large, which reduces the strength of the cutting insert. There is a risk that the load during cutting may cause damage. On the other hand, if the width of the groove is reduced to secure the strength of the cutting insert, the width of the convex part of the end mill body must be reduced, and the mounting rigidity of the cutting insert cannot be ensured, and the load during cutting is reduced. There is a risk that it will not be possible to reliably prevent the displacement movement of the cutting insert due to.

The present invention has been made under such a background, and the cutting insert capable of surely preventing the displacement movement during the cutting process without deteriorating the strength of the cutting insert, and the cutting insert can be attached and detached. The purpose of the present invention is to provide a replaceable cutting edge type ball end mill attached to the.

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 main body of a cutting edge replaceable ball end mill rotated about 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 as seen from a direction facing the rake face, at an intersecting ridge line portion between 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 seating surface is formed by alternately arranging two groove portions each having a wall surface capable of contacting a convex portion projecting from the bottom surface of the insert mounting seat with the two cutting edges. It is formed so as to extend from the linear cutting edge portion side of the blade to the arcuate cutting edge portion side of the other cutting edge, and the two groove portions extend from one end side to the other end side in the direction in which the groove portions extend. Each has a narrow portion where the groove width becomes narrow.

In addition, the cutting edge replaceable ball end mill of the present invention has such a cutting insert, an insert mounting seat formed at a tip end portion of an end mill body rotated about an axis, and a convex portion protruding from a bottom surface of the insert mounting seat. Is attached detachably by abutting the wall surface of the groove portion.

Since the groove portion of the cutting insert and the cutting insert with the replaceable cutting edge type ball end mill having such a configuration has a narrow portion in which the groove width is narrowed from one end side to the other end side in the extending direction of the groove portion. On the other end side where the groove width of the narrow portion is narrowed, the thickness of the cutting insert 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 portion, in the cutting edge replaceable ball end mill, the convex portion is the portion in contact with the narrow portion of the groove portion, and By forming the width so as to widen from the other end side toward the one end side, it is possible to enhance mounting rigidity against a load during cutting and reliably prevent the cutting insert from shifting.

In such a cutting insert and a replaceable cutting edge type ball end mill, the arcuate cutting edge portion of the above cutting edges is exclusively used for cutting. In each of the two groove portions, the linear cutting edge portion side of the one cutting edge is the one end side, and the arcuate cutting edge portion side of the other cutting edge is the other end side. When the other cutting edge is used for cutting, ensure the strength of the cutting insert on the other end side where the width of the narrow part becomes narrower against the cutting load acting on the arcuate cutting edge part. In addition, the displacement of the cutting insert along the arcuate cutting edge of the cutting edge that is not used for cutting can be ensured at one end side of the narrow part that is wide apart from the arcuate cutting edge of this cutting edge. It becomes possible to prevent it.

In the cutting insert of the present invention, firstly, 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 sub cutting edge is formed to have a short circumference with the same radius as the arcuate cutting edge portion of the main cutting edge, and the cutting insert is disclosed in Patent Document 2. It has an asymmetric shape. With this type and two cutting inserts of the same shape and size, it is possible to perform cutting from the vicinity of the axis of the end mill main body to the outer periphery by the arcuate cutting edge of the main cutting edge, and at a position away from this axis. It is possible to perform cutting from the to the outer circumference by the arcuate cutting edge portion of the sub cutting edge, which facilitates management of the cutting insert and is economical.

Therefore, in this case, among the two groove portions, the groove portion having the arcuate cutting edge portion side of the sub cutting edge as the other end side is formed on the flank that is continuous with the arcuate cutting edge portion of the sub cutting edge. It may be open.
If the arcuate cutting edge portion of the sub-cutting edge is formed in a convex curved shape that approaches the seating surface side after being separated from the seating surface side as the sub-cutting blade is separated from the linear cutting edge part, Since the arcuate cutting edge portion of the auxiliary cutting edge gradually cuts into the work material from the most convex point that is most convex with respect to the seating surface, it is possible to reduce cutting resistance.

That is, in the cutting insert used for the cutting edge replaceable ball end mill, during cutting, a large cutting load is applied to the tip end of the arcuate cutting edge, the flank continuous with this, and the side surface of the insert body. Therefore, there is a demand for a cutting edge shape that reduces this cutting load and considers chip discharge performance. In the present invention, attention has also been paid to controlling the contact form between the arcuate cutting edge portion and the work material.

For example, when contour line machining is selected as the cutting method, it is desirable to set the tip side of the cutting edge where the chip thickness becomes thin as the area where the cutting edge bites into the work material. By forming the arcuate cutting edge portion in the shape of the convex curve as described above, the cutting edge has a twisted shape and the impact acting on the cutting edge can be reduced, so that a more preferable cutting edge shape is obtained.

On the other hand, when scanning line processing is selected as the cutting method, when cutting in the axial direction of the end mill body, the thickness of the chip becomes thicker so that the cutting material bites into the work material from the tip side of the arcuate cutting edge. A large cutting load is applied to the tip. Therefore, the arcuate cutting edge portion is formed into a convex curve shape to provide the most convex point to increase the wall thickness, whereby the strength of the cutting edge can be improved.

When the groove is opened in the flank that is continuous with the arcuate cutting edge of the sub-cutting edge, and the arcuate cutting edge of this sub-cutting edge is formed in a convex curved shape, the arc-shaped cutting of the sub-cutting edge The opening of the groove portion to the flank that is continuous with the blade portion is a linear cutting of the sub cutting edge rather than the most convex point where the arc-shaped cutting edge portion of the sub cutting edge is most convex with respect to the seating surface. Located on the blade side. Accordingly, it is possible to prevent the cutting insert from being damaged from the opening of the groove due to the impact when the arcuate cutting edge portion of the sub cutting edge bites into the work material from the most convex point and cuts.

Specifically, in a bottom view seen from a direction facing the seating surface, a straight line connecting the most convex point and the center of the arcuate cutting edge portion of the sub cutting edge, and the arcuate cutting of the sub cutting edge. Of the sub-cutting edge and the end portion of the ridge line intersecting the wall surface of the groove portion facing the linear cutting edge portion side of the sub-cutting edge that opens to the flank continuous with the blade portion and the flank surface It is desirable that the first intersection angle formed by the straight line connecting the center of the arcuate cutting edge portion be in the range of 5° to 60°.

If the first intersecting angle is smaller than 5°, the opening of the groove portion to the flank that is continuous with the arcuate cutting edge portion of the auxiliary cutting edge is too close to the most convex point, and the arcuate cutting edge of the auxiliary cutting edge is formed. The cutting insert may be damaged when the part bites. On the other hand, if the first crossing angle is large enough to exceed 60°, when the cutting insert is mounted by inserting the clamp screw into the mounting hole formed in the cutting insert and screwing it into the screw hole of the insert mounting seat, There is a possibility that the groove or the protrusion may interfere with the mounting hole or the screw hole.

Also, as described above, when the groove portion opens in the flank that is continuous with the arcuate cutting edge portion of the sub cutting edge, and the arcuate cutting edge portion of this sub cutting edge is formed in a convex curve shape, the seating In a bottom view seen from the direction facing the surface, a straight line connecting the most convex point and the center of the arcuate cutting edge portion of the sub-cutting edge, and the sub-cutting edge to the arc-shaped cutting edge portion side of the sub-cutting edge. The second intersecting angle formed by the extension line of the linear cutting edge portion of the cutting edge is preferably in the range of 10° to 50°.

If the second crossing angle is smaller than 10°, the most convex point will be too close to the axis of the end mill body when the auxiliary cutting edge is used for cutting, and the sub-rotation speed around the axis will be small. The arcuate cutting edge portion of the cutting edge cuts into the work material, which may impair the effect of reducing the cutting resistance. On the other hand, when the second crossing angle is larger than 50°, the straight line of the sub-cutting edge is larger than the most convex point in the flank that connects the opening of the groove to the arc-shaped cutting edge of the sub-cutting edge as described above. When attempting to position it on the side of the shaped cutting edge, there is still a risk that the groove and the protrusion will interfere with the mounting hole of the cutting insert and the screw hole of the insert mounting seat.

Secondly, the cutting insert of the present invention is not an asymmetrical shape as described above, but an insert that connects the center of the rake face and the center of the seating face, like the cutting insert described in Patent Document 1, for example. It may be formed in a 180° rotationally symmetrical shape with respect to the center line in the circumferential direction of the rake face.

In the second case, for example, a cutting insert having two main cutting edges having an arcuate cutting edge portion having a circumferential length of 1/4 arc shape, and a radius equal to the cutting insert and having a short circumferential length. A cutting insert having two auxiliary cutting edges with arcuate cutting edges is prepared, and the arc cutting edge portion of the main cutting edge performs cutting from near the axis of the end mill body tip to the outer periphery, and from this axis It is possible to perform the cutting from the distant position to the outer circumference by the arcuate cutting edge portion of the auxiliary cutting edge.

Also in this second case, the other end of the groove may be opened to the flank that is continuous with the arcuate cutting edge. In addition, the cutting edge may be formed in a convex curve shape that approaches the seating surface side after being separated from the seating surface side as it goes from the arcuate cutting edge part side to the linear cutting edge part side. However, in the second case, the opening of the groove portion to the flank that is continuous with the arcuate cutting edge portion is more than the most convex point where the cutting edge is most convex with respect to the seating surface. It is desirable that the cutting edge is located on the arcuate cutting edge portion side.

Specifically, in a bottom view seen from the direction facing the seating surface, a straight line connecting the most convex point of the cutting edge and the center of the arcuate cutting edge portion of the cutting edge, and the cutting edge It is desirable that the third intersection angle between the contact point between the arcuate cutting edge portion and the straight-lined cutting edge portion and the straight line connecting the center of the arcuate cutting edge portion be within the range of 40° or less. If the third crossing angle becomes larger than this range, the opening of the groove to the flank, which is also connected to the arcuate cutting edge, is too close to the most convex point, and the cutting edge moves from the most convex point to the work material. The cutting insert may be damaged when it bites.

Further, as in the second case and the above-described first case, the radii of the arcuate cutting edge portions of the two cutting edges formed in one cutting insert become equal to each other. In this case, the groove width at the other end of the narrow portion in the groove portion is 0.05× with respect to the radius r of the arcuate cutting edge portion of the cutting edge when viewed from the direction facing the seating surface. It is desirable that the range is r to 0.18×r.

If the groove width at the other end, which is the narrowest in the narrow portion, is narrower than the above range, the width of the convex portion of the insert mounting seat must be reduced, and it becomes difficult to reliably secure the rigidity. There is a risk. On the other hand, when the groove width at the other end of the narrow portion is wider than the above range and the wall surfaces of the groove portions are close to parallel to each other, the wall thickness is secured at the other end side of the narrow portion. It may not be possible to disperse the stress and maintain the strength of the cutting insert.

As described above, according to the present invention, due to the narrow portion of the groove portion formed on the seating surface of the cutting insert, the thickness of the cutting insert is secured and the stress is dispersed on the other end side where the groove width is narrowed. However, the strength can be improved, and damage to the cutting insert due to the load during cutting can be prevented. On the other hand, since the groove width of the narrow part is widened on the one end side, the convex part of the cutting edge replaceable ball end mill can be formed wide, and the mounting rigidity of the cutting insert is increased to reliably prevent the displacement movement. It becomes possible.

It is a perspective view showing a 1st embodiment of a cutting insert of the present invention. 2 is a plan view of the embodiment shown in FIG. 1. FIG. 2 is a bottom view of the embodiment shown in FIG. 1. FIG. FIG. 4 is a side view as seen from the direction of arrow A in FIGS. 2 and 3. FIG. 4 is a side view as seen from the direction of arrow B in FIGS. 2 and 3. FIG. 4 is a side view when viewed in the direction of arrow C in FIGS. 2 and 3. It is a side view of the arrow D direction in FIG. 2 and FIG. It is a perspective view which shows the front-end|tip part of the end mill main body in 1st Embodiment of the cutting-edge exchange type ball end mill of this invention to which the cutting insert of 1st Embodiment is removably attached. It is a front view of the front-end|tip part of the end mill main body shown in FIG. It is a top view of the arrow A direction in FIG. It is a side view of the arrow B direction in FIG. It is a bottom view of the arrow C direction in FIG. FIG. 10 is a side view taken along the arrow D in FIG. 9. It is a perspective view showing a tip part of a 1st embodiment of a cutting edge exchange type ball end mill of the present invention. FIG. 15 is a front view of the embodiment shown in FIG. 14. FIG. 16 is a plan view seen from the direction of arrow A in FIG. 15. FIG. 16 is a side view as seen from the direction of arrow B in FIG. 15. FIG. 16 is a bottom view when viewed in the direction of arrow C in FIG. 15. FIG. 16 is a side view taken along the arrow D in FIG. 15. It is a figure which shows the dispersion|distribution state of the stress by simulation analysis when changing the groove width of the other end of the narrow part in a groove part, and is a case where a groove width is constant. It is a figure which shows the dispersion|distribution state of the stress by simulation analysis when changing the groove width of the other end of the narrow part in a groove part, and has a narrow part and the narrow part with respect to the radius r of an arcuate cutting edge part. Is the case where the groove width at the other end is 0.133×r. It is a figure which shows the dispersion|distribution state of the stress by simulation analysis when changing the groove width of the other end of the narrow part in a groove part, and has a narrow part and the narrow part with respect to the radius r of an arcuate cutting edge part. Is the case where the groove width at the other end is 0.067×r. It is a perspective view showing a 2nd embodiment of the cutting insert of the present invention. FIG. 22 is a plan view of the embodiment shown in FIG. 21. FIG. 22 is a bottom view of the embodiment shown in FIG. 21. FIG. 24 is a side view as seen from the direction of arrow A in FIGS. 22 and 23. FIG. 24 is a side view when viewed in the direction of arrow B in FIGS. 22 and 23. It is a perspective view which shows the front-end|tip part of the end mill main body in 2nd Embodiment of the cutting-edge exchange type ball end mill of this invention to which the cutting insert of 2nd Embodiment is attached detachably. It is a front view of the front-end|tip part of the end mill main body shown in FIG. FIG. 28 is a plan view seen from the direction of arrow A in FIG. 27. FIG. 28 is a side view taken along arrow B in FIG. 27. FIG. 28 is a bottom view when viewed in the direction of arrow C in FIG. 27. FIG. 28 is a side view taken along the arrow D in FIG. 27. It is a perspective view showing a tip part of a 2nd embodiment of a cutting edge exchange type ball end mill of the present invention. FIG. 33 is a front view of the embodiment shown in FIG. 32. FIG. 34 is a plan view as seen from the direction of arrow A in FIG. 33. FIG. 34 is a side view seen from the direction of arrow B in FIG. 33. It is a bottom view of the arrow C direction view in FIG. FIG. 34 is a side view taken along the arrow D in FIG. 33.

<<First Embodiment>>
1 to 7 show a cutting insert 1 according to a first embodiment of the present invention. 8 to 13 show the tip end portion of the end mill body 11 in the first embodiment of the cutting edge replaceable ball end mill of the present invention to which the cutting insert 1 of the first embodiment is detachably attached. FIG. 14 to FIG. 19 show the cutting edge replaceable ball end mill of the first embodiment of the present invention in which the cutting insert 1 of the first embodiment is detachably attached to the insert mounting seat 12 of the end mill body 11. It shows a tip portion.

The cutting insert 1 of the present embodiment is made of a hard material such as cemented carbide and has 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. The lower surface facing away from the rake surface 2 is a leaf shape of a tree that is substantially similar to the rake surface 2, and is a flat seating surface 3 that is seated on the bottom surface of the insert mounting seat. A side surface extending between the rake surface 2 and the seating surface 3 is a flank surface 4.

At the ridge line portion where the rake face 2 and the flank face 4 intersect, arc-shaped 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 with 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 these two cutting edges is the main cutting edge 5, and the other 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. 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 face 2 and the seating face 3, and the rake face 2 side of the mounting hole 7 is the seating face. The diameter is reduced toward the 3rd side.

In the plan view, the arcuate cutting edge 5a of the main cutting edge 5 has a substantially quarter arc shape, while the arcuate cutting edge 6a of the sub cutting edge 6 has a circular shape of the main cutting edge 5. It has the same radius as the arcuate cutting edge 5a, but the circumference is shorter than the arcuate cutting edge 5a of the main cutting edge 5. That is, the arcuate cutting edge portion 6a is formed in an arcuate shape shorter than a quarter arc. Accordingly, 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 asymmetrical by 180° around the insert center line X which is the center line of the mounting hole 7 as shown in FIGS. 2 and 3, but is asymmetrical. ..

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 2b of the rake face 2 where the linear cutting edge 5b of the main cutting edge 5 and the arcuate cutting edge 6a of the auxiliary cutting edge 6 intersect from the first end 2a of the rake surface 2 that intersects They extend so as to approach each other. 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 in a shape. The first end 2a is located closer to the seating surface 3 than the second end 2b.

The arcuate cutting edge portions 5a, 6a of the main cutting edge 5 and the auxiliary cutting edge 6 move away from the seating surface 3 side as they move away from the linear cutting edge portions 5b, 6b, and then approach the seating surface 3 side. It is formed in a convex curved shape, and the point where the convex curve formed by the arcuate cutting edge portion 6a of the sub cutting edge 6 is most distant from the seating surface 3 and becomes convex is the arc shape of the sub cutting edge 6. It is the most convex point S of the cutting edge portion 6a.
The linear cutting edge portions 5b and 6b of the main cutting edge 5 and the sub cutting edge 6 are arcuate cutting edge portions 5a as shown in FIGS. 4 and 6 even in a side view seen from the direction facing the flank 4. , 6a in contact with the convex curve formed by the curved surfaces, and extend in a substantially straight line shape that approaches the seating surface 3 side as the distance from the arcuate cutting edge 5a, 6a increases.

Around the opening of the mounting hole 7 in the central part of the rake face 2, a protrusion that protrudes farther from the seating surface 3 than the main cutting edge 5 and the auxiliary cutting edge 6 and has a substantially elliptical shape in plan view. 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. The outer peripheral surface of the protrusion 2c is inclined toward the inside of the rake face 2 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.

The flank 4 which is continuous with the linear cutting edge portions 5b and 6b of the main cutting edge 5 and the sub cutting edge 6 is formed in a flat plane shape as described above. On the other hand, the flank 4 which is continuous with the arcuate cutting edges 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 edges 5a, 6a on the rake face 2 side. Although it is curved, the seating surface 3 side has the flat surface portion 4a which is notched in a flat shape while inclining as described above.

On the other hand, as shown in FIG. 3, a groove 8 is formed on the seating surface 3. In the present embodiment, as shown in FIG. 3, when viewed from the direction perpendicular to the seating surface 3, the first and second two groove portions 8A and 8B are formed in the mounting hole 7 of the seating surface 3. It is formed on the opposite side to each other with a space between the opening and 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. Has been done.

Each of the groove portions 8 is formed in a substantially rectangular shape whose cross section orthogonal to the extending direction of the groove portion 8 is flat in the insert center line X direction in which the mounting hole 7 extends. That is, the groove portion 8 extends in a direction substantially perpendicular to the seating surface 3 and faces two mutually opposing first and second wall surfaces 8a and 8b, and a seating portion extending between the first and second wall surfaces 8a and 8b. And a bottom surface 8c parallel to the surface 3. The first wall surface 8a of each groove portion 8 faces the first end 2a side of the rake surface 2, and the second wall surface 8b faces the second end portion 2b side of the rake surface 2. The ridge portion of the intersection 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 a concave curved surface. Is formed in.

Each of the first and second groove portions 8A and 8B has a 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 first and second groove portions 8A and 8B. ing. In the present embodiment, the flank 4 side of the sub cutting edge 6 and the linear cutting edge portions 6b, 5b of the main cutting edge 5 is defined as one end side of the first and second groove portions 8A, 8B, and the main cutting edge 5 and the flank 4 side which is connected to the arcuate cutting edge portions 5a, 6a of the sub cutting edge 6 is the other end side. Further, as shown in FIG. 3, the first and second groove portions 8A and 8B are entirely the narrow portion 9.

In this narrow portion 9, the narrowing ratio of the groove width in this embodiment is constant from one end side to the other end side of the first and second groove portions 8A and 8B. That is, in the narrow portion 9, the first and second wall surfaces 8a and 8b of the first and second groove portions 8B are linearly approaching each other from the one end side toward the other end side in the bottom view. Is formed in. In the present embodiment, these first and second groove portions 8A and 8B are flanks 4 and main cutting edges 5 and sub cutting edges 6 which are continuous with the linear cutting edge portions 6b and 5b of the sub cutting edge 6 and the main cutting edge 5. Is formed in the shape of a through groove that is open to both of the flanks 4 that are continuous with the arcuate cutting edge portions 5a and 6a.

The opening of the second groove 8B to the flank 4 connected to the arcuate cutting edge 6a of the sub-cutting edge 6 has an arcuate cutting edge 6a of the sub-cutting edge 6 having a convex curved shape in a side view. It is located closer to the linear cutting edge portion 6b of the sub cutting edge 6 than the most convex point S that is most convex with respect to the seating surface 3. Specifically, as shown in FIG. 3 in the bottom view, the sub-cutting edge 6 and the straight line L1 connecting the most convex point S and the center P of the arc formed by the arc-shaped cutting edge 6a of the sub-cutting edge 6 are formed. End Q to the seating surface 3 side of the ridge line portion (excluding the chamfered portion) of the first wall surface 8a of the second groove portion 8B facing the linear cutting edge portion 6b and the flank surface 4 and the center P The first intersecting angle θ1 formed by the straight line L2 that connects with is in the range of 5° to 60°.

Similarly, in the bottom view, the straight line L1 connecting the most convex point S and the center P of the arcuate cutting edge portion 6a of the sub cutting edge 6 and the subordinate of the sub cutting edge 6 to the arcuate cutting edge portion 6a side. The second intersection angle θ2 formed by the extension line L3 of the linear cutting edge portion 6b of the cutting edge 6 is in the range of 10° to 50°.
In the present embodiment, the groove width W1 of the narrow width portion 9 at the other end of the second groove portion 8B that is open to the flank 4 of the arcuate cutting edge portion 6a of the sub cutting edge 6 is the second narrow width portion 9 The radius r of the arcuate cutting edge 6a of the auxiliary cutting edge 6 located on the other end side of the groove 8B is 0.05×r to 0.18×r with respect to the radius r viewed from the seating surface 3 side. .. For example, the groove width W1 is in the range of 1 mm to 7 mm. However, in FIG. 3, when the shape of the arcuate cutting edge portion 6a viewed from the seating surface 3 side is a shape deviating from the arc, the arc closest to the deviating shape is virtually drawn. Then, the radius r is determined from this virtual arc.

On the other hand, the groove width W2 at one end of the narrow portion 9 is W2>W1. The groove width W2 is measured from the seating surface 3 side of the arcuate cutting edge portion (the arcuate cutting edge portion 6a of the sub cutting edge 6) located on the other end side of the groove portion (second groove portion 8B) having the narrow width portion 9. The above plane of the linear cutting edge portion 5b of the main cutting edge 5 in the range of 0.10×r to 0.30×r with respect to the radius r of the bottom view as seen or the plane view as seen from the rake face 2 side. The length R in view or bottom view is in the range of 0.10×R to 0.32×R. These groove widths W1 and W2 are the first and second wall surfaces when the first and second wall surfaces 8a and 8b extend linearly in a bottom view as seen from the direction facing the seating surface 3. It is the width in the direction perpendicular to the straight bisector formed by 8a and 8b.

In the bottom view, the straight line L4 formed by the extension surface of the second groove portion 8B to the other end side of the second wall surface 8b indicates that the sub cutting edge 6 extends toward the arcuate cutting edge portion 6a of the sub cutting edge 6. The inclination angle α formed by the linear cutting edge portion 6b with respect to the extension line L3 is in the range of 45° to 90°. Similarly, in the bottom view, the inclination angle β formed by the straight line L5 formed by the extension surface of the first wall surface 8a of the second groove portion 8B with respect to the linear cutting edge portion 5b of the main cutting edge 5 is 45° to 90°. The inclination angle γ formed by the straight line L4 formed by the extended surface of the second wall surface 8b of the second groove portion 8B with respect to the linear cutting edge portion 5b of the main cutting edge 5 is smaller than the above inclination angle β. ing. In the present embodiment, in the bottom view, the first groove portion 8A extends in a direction intersecting with the linear cutting edge portion 6b of the auxiliary cutting edge 6 at an acute angle on the first end 2a side, and at the same time, the second groove portion 8B. On the second end 2b side extends in a direction intersecting with the linear cutting edge portion 5b of the main cutting edge 5 at an acute angle. The groove widths W1 and W2, the first and second intersection angles θ1 and θ2, and the inclination angles α to γ may be similarly applied to the first groove portion 8A having the same narrow width portion 9.

Such a cutting insert 1 of the first embodiment is detachably attached to the insert mounting seat 12 formed at the tip of the end mill body 11 shown in FIGS. A first embodiment of the replaceable cutting edge type ball end mill of the present invention shown in FIG. 19 is constituted. The end mill body 11 is formed of a metal material such as steel, and the tip end portion thereof has a columnar shape with the base end side being the center of the axis O, and the tip end side of the base end side having the center on the axis O. It is a convex hemisphere with the same radius as a cylinder. The replaceable cutting edge ball end mill of the present embodiment is attached to the insert mounting seat 12 by the end mill body 11 being rotated in the end mill rotation direction T about the axis O and being fed in a direction intersecting the axis O. The work piece is cut by the cutting insert 1.

In the present embodiment, two tip pockets 13 are formed by cutting out the outer periphery of the tip portion of the end mill body 11, and the insert mounting seats 12 are provided on the bottom surfaces of these tip pockets 13 that face the end mill rotation direction T, respectively. It is formed on the opposite side with an interval in the circumferential direction. Then, one type of first and second cutting inserts 1A and 1B of the same shape and size according to the first embodiment are attached to these two insert mounting 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 outward of the insert mounting seat 12 as the distance from the bottom surface 12a increases, and the seating surface 3 of the cutting insert 1 is seated on the bottom surface 12a. The flat flank 4 of the blade 6 which is continuous with the linear cutting blades 5b and 6b and the flat flank 4a of the flank 4 which is continuous with the arcuate cutting blades 5a and 6a on the seating surface 3 side can be brought into contact with each other. ..

A recess 12d is formed between the wall surfaces 12b and 12c to avoid contact with the curved flank 4 of the cutting insert 1. The bottom surface 12a is formed with a screw hole 12e into which a clamp screw (not shown) inserted into the mounting hole 7 of the cutting insert 1 is screwed. The center line of the screw hole 12e is a plane shape that 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. With the flat surface 4a of the flank 4 continuous with the flank 4 and the arcuate cutting edge 5a, 6a on the seating surface 3 side being in contact with the wall surfaces 12b, 12c, the center line of the mounting hole 7 of the cutting insert 1 Is slightly eccentric to the recess 12d side.

Of these two insert mounting seats 12, the first insert mounting seat 12A is formed so as to cut out the tip portion of the end mill body 11 to the range including the axis O on the tip 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 sub 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 brought into 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, the first convex portion 14A with which the first groove portion 8A formed on the seating surface 3 of the first cutting insert 1A can come into contact is formed. It is formed so as to project from the tip end side of 12e and extend from the outer peripheral surface of the tip end portion of the end mill body 11 toward the wall surface 12c. Further, on the bottom surface 12a of the first insert mounting seat 12A, a second convex portion 14B with which the second groove portion 8B can abut is projected between the screw hole 12e and the wall surface 12c, and the tip of the end mill main body 11 is protruded. It is formed so as to extend from the outer peripheral surface of the portion toward the recess 12d. In the present embodiment, the first convex portion 14A is formed in a peninsular shape that reaches the wall surface 12c, while the second convex portion 14B is formed in an isolated island shape that is spaced from the concave portion 12d and does not reach the concave portion 12d. Has been done.

The first and second convex portions 14A and 14B have a substantially rectangular shape in which a cross section orthogonal to the extending direction of the first and second convex portions 14A and 14B is flat in the end mill rotation direction T. Of these, the first convex portion 14A is one end side (of the end mill main body 11) from the other end side in the extending direction of the first groove portion 8A with respect to the first groove portion 8A which is the narrow portion 9 as a whole. It is formed so as to become wider as it goes from the outer peripheral side to the inner peripheral side, except that the connecting portion with the wall surface 12c is constricted. The second convex portion 14B is the same as the second groove portion 8B, which is the narrow portion 9 as a whole, from the other end side in the extending direction of the second groove portion 8B to the one end side (inside the end mill body 11). It is formed so as to become wider as it goes from the peripheral side to the outer peripheral side.

The width of each of the first and second convex portions 14A and 14B (the width in the direction orthogonal to the direction in which the first and second convex portions 14A and 14B extend) is extended by the first and second groove portions 8A and 8B. It is slightly smaller than the width (the width in the direction orthogonal to the extending direction of the first and second groove portions 8A and 8B) at the position where the first and second convex portions 14A and 14B come into contact with each other in the direction. The protruding height of the first and second convex portions 14A and 14B from the bottom surface 12a is also slightly smaller than the depth of the first and second groove portions 8A and 8B from the seating surface 3 of the first cutting insert 1A.

Of the two insert mounting seats 12, the second insert mounting seat 12B is formed at a position slightly away from the axis O on the tip end side of the end mill body 11 to the outer peripheral side, as shown in FIGS. The second cutting insert 1B has the arcuate cutting edge portion 6a of the auxiliary cutting edge 6 on the second insert mounting seat 12B from the position away from the axis O of the main cutting edge 5 of the first cutting insert 1A. The arcuate cutting edge portion 5a is located on the convex hemisphere, and the linear cutting edge portion 6b of the sub cutting edge 6 is replaced by the linear cutting edge portion 5b of the main cutting edge 5 of the first cutting insert 1A. It is attached so as to be positioned on the above-mentioned cylindrical surface. Accordingly, the flat 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 brought into contact with 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 third convex portion 14C is formed on the tip side of the screw hole 12e, and a fourth convex portion is formed between the screw hole 12e and the wall surface 12c. The convex portion 14D is formed. These third and fourth convex portions 14C and 14D also extend from the outer peripheral surface of the tip portion of the end mill body 11 toward the inner peripheral side, and the third convex portion 14C is the wall surface 12b of the second insert mounting seat 12B. Is spaced apart from the wall surface 12b, and the fourth protrusion 14D 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 abuts on the third convex portion 14C, and the first groove portion 8A of the second cutting insert 1B abuts on the fourth convex portion 14D.

In addition, these third and fourth convex portions 14C and 14D also have a substantially rectangular shape in which a cross section orthogonal to the extending direction of the third and fourth convex portions 14C and 14D is flat in the end mill rotation direction T, In the third convex portion 14C, the entire second groove portion 8B of the second cutting insert 1B with which the third convex portion 14C abuts is the narrow portion 9, while the second groove portion 8B extends in the direction in which the second groove portion 8B extends. It is formed so as to become wider 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), and the width of the fourth convex portion 14D is equal to that of the first groove portion 8A. It is formed so as to widen as a whole from the other end side in the extending direction to the one end side (from the inner peripheral side to the outer peripheral side of the end mill main body 11).

Further, the widths of the third and fourth convex portions 14C and 14D (widths in the direction orthogonal to the extending direction of the third and fourth convex portions 14C and 14D) 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 against the third and fourth convex portions 14C and 14D in the extending direction. ing. Further, the protrusion heights of the third and fourth convex portions 14C and 14D from the bottom surface 12a of the second insert mounting seat 12B are also 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.

When 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, a clamp screw having an inverted truncated cone head is attached. When it is inserted into the mounting hole 7 and screwed into the screw hole 12e, the center line of the screw hole 12e 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, a 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.

Along with this, in the first insert mounting seat 12A, the first and second convex portions 14A and 14B are provided with the first and second groove portions 8A and 8B of the first cutting insert 1A at the tip of the end mill body 11. Abut from the side. Therefore, in these first and second convex portions 14A and 14B, on the side surface 14a facing the tip side of the end mill body 11, the first and second groove portions 8A and 8B of the first cutting insert 1A The wall surface 8b comes into contact with each other, and a slight gap is provided between the first wall surface 8a and the bottom surface 8c of the first and second groove portions 8A and 8B and the first convex portion 14A.

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 third and fourth convex portions 14C and 14D from the tip end side of the end mill body 11 as well. Abut. Therefore, in these third and fourth convex portions 14C and 14D, the first wall surface 8a of the second and first groove portions 8B and 8A is in contact with the side surface 14a of the end mill body 11 which faces the tip side, A slight space is provided between the second wall surface 8b of the second and first groove portions 8B and 8A and the third and fourth convex portions 14C and 14D. As described above, the first and second convex portions 14A to 14D are brought into contact with the first and second groove portions 8A and 8B, so that the displacement of the cutting insert 1 due to the load during cutting can be prevented. ..

Then, in the cutting insert 1 and the blade tip exchange type ball end mill configured as described above, the first and second groove portions 8A and 8B of the cutting insert 1 are located at one end side in the extending direction of the first and second groove portions 8A and 8B. Has a narrow portion 9 in which the groove width narrows toward the other end side, and the cutting insert is provided on the other end side of the first and second groove portions 8A, 8B in which the groove width of the narrow portion 9 decreases. It is possible to secure a large wall thickness of No. 1 and improve the strength. Therefore, even if an excessive load acts on the cutting insert 1 during cutting, it is possible to prevent the cutting insert 1 from being damaged by the first and second groove portions 8A and 8B.

On the other hand, on the one end side in the direction in which the first and second groove portions 8A and 8B extend, the narrow portion 9 is widened conversely, so in the end mill main body 11 of the cutting edge replaceable ball end mill, the first and second The first to fourth convex portions 14A to 14D can be formed wide at the portions where one ends of the groove portions 8A and 8B abut. Therefore, the mounting rigidity of the cutting insert 1 with respect to the load during the cutting process can be enhanced, and the displacement movement of the cutting insert 1 can be more reliably prevented, and the highly accurate cutting process can be performed.

In addition, in the cutting insert 1 of the present embodiment, the first and second cutting inserts 1A and 1B have the same shape and the same size, and the arcuate cutting edge portions 5a and 6a of the main cutting edge 5 and the sub cutting edge 6 are formed. Are also equal to each other, and the groove width W1 at the narrowest other end of the narrow portion 9 is 0. 0 with respect to the radius r of the arcuate cutting edge portions 5a and 6a when viewed from the seating surface 3 side. It is set in the range of 05×r to 0.18×r, which also makes it possible to more reliably improve the strength of the cutting insert 1 and increase the mounting rigidity. That is, if the groove width W1 at the other end of the narrow portion 9 is narrower than the above range, the widths of the first to fourth convex portions 14A to 14D of the insert mounting seat 12 must be narrowed and the cutting is performed. While it may not be possible to increase the mounting rigidity of the insert 1, the groove width W1 at the other end of the narrow portion 9 is so wide that it exceeds the above range, and the first and second groove portions 8A, 8B When the second wall surfaces 8a and 8b are close to parallel, it is possible to secure a large thickness of the cutting insert 1 on the other end side of the first and second groove portions 8A and 8B to secure the strength of the cutting insert 1. It becomes impossible to do so, and damage may occur when an excessive load is applied.

20A to 20C are diagrams showing a stress distribution state by simulation analysis when the groove width W1 at the other end of the groove portion 8 is changed, and the arcuate cutting edge portion located on the other end side of the groove portion 8. (For example, when the radius r of the arcuate cutting edge portion 6a of the sub cutting edge 6) is 15.0 mm, FIG. 20A shows that the groove width W1 is constant at 3.0 mm over the entire length of the groove (narrow portion). FIG. 20B has a narrow portion 9 and the groove width W1 at the other end with respect to the radius r of the arcuate cutting edge portion 6a is 2.0 mm (0.133×r). 20C also has the narrow width portion 9 and the groove width W1 at the other end with respect to the radius r of the arcuate cutting edge portion 6a is 1.0 mm (0.067×r). The analysis shows that the rotation speed of the end mill main body 11 is 2500 min ⁻¹ , the rotation speed is 230 m/min, the feed speed is 1500 mm/min (the feed amount per blade is 0.3 mm/1 blade), and the cutting depth and the cutting width are both 15 mm, the work material was assumed to be S45C (hardness 220 HB), and the material of the end mill body was assumed to be SKD61 (hardness 45 HRC, tensile strength 1600 MPa, fatigue strength 500 MPa), and evaluated by von Mises stress.

In FIG. 20, the region on the groove portion side of the white portion of the seating surface 3 is the area where the stress is concentrated. Then, compared with the result of FIG. 20A in which the groove width is constant and there is no narrow portion 9, the portions depicted in white in FIG. 20B and C having the narrow portion 9 are smaller and the stress is dispersed. In particular, in FIG. 20C in which the groove width W1 is small, the range in which the stress is most concentrated is small. From this result, it is possible to disperse the stress and secure the strength of the cutting insert 1 by providing the narrow portion 9, and the groove width W1 is set to the range of 0.05×r to 0.18×r. It turns out that is desirable.

The groove width W1 is more preferably in the range of 0.06×r to 0.17×r, further preferably in the range of 0.065×r to 0.16×r. The groove width W1 is preferably in the range of 0.25×W2 to 0.90×W2 with respect to the groove width W2 at one end of the narrow portion 9, and is 0.30×W2 to 0.85×. The range of W2 is more preferable, and the range of 0.32×W2 to 0.80×W2 is further preferable. On the other hand, the groove width W2 at one end of the narrow portion 9 is preferably in the range of 0.10×r to 0.30×r with respect to the radius r, and is in the range of 0.12×r to 0.28×r. Is more desirable, and the range of 0.15×r to 0.26×r is even more desirable.

In the cutting insert 1 of the present embodiment, 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 circumference is shortened, that is, formed asymmetrically. Has been done. Along with this, also in the blade edge exchange type ball end mill of the present embodiment, the first insert mounting seat 12A is formed so as to cut out the tip portion of the end mill body 11 to the range including the axis O on the tip side. On the other hand, the second insert mounting seat 12B is formed at a position slightly separated from the axis O toward the outer peripheral side. The first and second insert mounting seats 12A and 12B have two cutting inserts 1 of the same shape and size, and the first cutting insert 1A has the arcuate cutting edge portion 5a of the main cutting edge 5 and the end mill body 11a. The second cutting insert 1B is positioned in the same convex hemispherical shape so as to extend from the vicinity of the axis O of the tip and the second cutting insert 1B extends the arcuate cutting edge portion 6a of the auxiliary cutting edge 6 from a position away from the axis O. I am making it.

Therefore, it is possible to perform cutting from the vicinity of the axis O of the tip of the end mill body 11 to the outer circumference and cutting from a position away from the axis O to the outer circumference by one kind of cutting insert 1, and the management of the cutting insert 1 is easy. In addition to the above, it is possible to use only one mold for manufacturing the cutting insert 1. In addition, when the main cutting edge 5 of the first cutting insert 1A and the sub cutting edge 6 of the second cutting insert 1B are abraded by cutting, these cutting inserts 1 are mounted on the opposite side of the insert mounting seat 12 It is economical because the first cutting insert 1A can be reused as the second cutting insert 1B and the second cutting insert 1B can be reused as the first cutting insert 1A by reattaching the first cutting insert 1A to the first cutting insert 1A.

Further, in the present embodiment, the second groove portion 8B having the narrow width portion 9 whose one end side is wide and the other end side is narrow is provided with the main cutting from the arc-shaped cutting edge portion 6a side of the sub cutting edge 6. The blade 5 extends toward the straight cutting edge portion 5b side. Of the narrow width portion 9, the linear cutting edge portion 5b side of the main cutting edge 5 is the one end side, and the arcuate cutting edge portion 6a side of the sub cutting edge 6 is the other end side, and the narrow width portion 9 is narrow. It is supposed to be. Therefore, when the sub cutting edge 6 is used for cutting as the second cutting insert 1B, the flank face where the second groove portion 8B is continuous with the arcuate cutting edge portion 6a of the sub cutting edge 6 as in the present embodiment. Even if it is opened to 4, the load acting on the auxiliary cutting edge 6 can be received by the other end side of the narrowed portion 9 of the narrowed second groove portion 8B, and the strength can be secured. Is. The displacement movement of the second cutting insert 1B along the arcuate cutting edge 5a of the main cutting edge 5 that is not used for cutting is caused by the narrow portion 9 of the second groove 8B that is distant from the arcuate cutting edge 5a. It can be surely prevented at the one end of the wide width. This is the same when the cutting insert 1 is used as the first cutting insert 1A.

In the present embodiment, the arcuate cutting edge part 5a of the main cutting edge 5 and the arcuate cutting edge part 6a of the sub cutting edge 6 are separated from the seating surface 3 side again as they are separated from the linear cutting edge parts 5b and 6b. It is formed in a convex curve shape that approaches the seating surface 3 side. Therefore, the arcuate cutting edge portions 5a and 6a gradually bite into the work material from the most convex point S, which becomes the most convex with respect to the seating surface 3 during cutting, and cuts. The resistance can be reduced. On the other end side where the groove width W1 of the second groove portion 8B formed on the seating surface 3 of the cutting insert 1 becomes narrower, the wall thickness at the most convex point S can be secured to improve the strength. It is possible to prevent the cutting insert 1 from being damaged by the load during processing. The wall thickness at the most convex point S is the distance from the seating surface 3 to the most convex point S in the direction perpendicular to the seating surface 3 as indicated by the symbol t in FIG. In the narrow portion 9 on the other end side of the second groove portion 8B, the range in which the wall thickness of the cutting insert 1 is ensured by the most convex point S is the region indicated by the symbol U in FIGS. 4 and 7. The value of the insert wall thickness in the region indicated by the symbol U is preferably in the range of 0.65×t to 1.00×t with respect to the above t value, and in the range of 0.70×t to 1.00×t. It is more desirable, and the range of 0.75×t to 1.00×t is even more desirable.

In this embodiment, the arcuate cutting edge portions 5a and 6a are thus formed in a convex curved shape. Although the second groove portion 8B is open to the flank surface 4 that is continuous with the arcuate cutting edge portion 6a of the sub cutting edge 6 as described above, the opening portion of the second groove portion 8B to the flank surface 4 is It is located closer to the linear cutting edge 6b of the sub cutting edge 6 than the most convex point S of the arcuate cutting edge 6a of the sub cutting edge 6. Therefore, it is possible to prevent the impact when the arcuate cutting edge portion 6a of the sub cutting edge 6 bites into the work material from the most convex point S and cuts into the work material, and directly propagates to the opening portion of the second groove portion 8B. It is also possible to prevent the cutting insert 1 from being damaged from the opening of the second groove 8B due to such an impact.

In order to reliably prevent the damage of the cutting insert 1 due to such an impact, the most convex point S and the center P of the arcuate cutting edge portion 6a of the sub cutting edge 6 in the bottom view are set as in the present embodiment. A connecting straight line L1 and an end portion Q of the intersecting ridge line portion of the second groove portion 8B facing the linear cutting edge portion 6b side of the sub cutting edge 6 and the flank surface 4 toward the seating surface 3 side. It is desirable that the first intersecting angle θ1 formed by the straight line L2 that connects the center P of the arcuate cutting edge portion 6a of the sub cutting edge 6 be in the range of 5° to 60°. This is the same for the arcuate cutting edge portion 5a of the main cutting edge 5 and the opening portion on the other end side of the first groove portion 8A, although not shown.

When the first intersection angle θ1 is smaller than 5°, the opening of the second groove portion 8B to the flank 4 will cause the opening of the arcuate cutting edge 6a of the secondary cutting edge 6 where the flank 4 is continuous. There is a possibility that the cutting insert 1 may be damaged due to the impact when the arcuate cutting edge portion 6a bites the work material from the most convex point S too close to the convex point S. On the contrary, when the first intersecting angle θ1 is larger than 60°, the clamp screw inserted into the mounting hole 7 of the cutting insert 1 as in the present embodiment is screwed into the screw hole 12e of the insert mounting seat 12 to cut the cutting insert. When attaching 1, the second groove 8B and the first and second protrusions 14A and 14B may interfere with the attachment hole 7 and the screw hole 12e. The first intersection angle θ1 is more preferably in the range of 5° to 30°, and even more preferably in the range of 5° to 15°.

In this embodiment, similarly, in the bottom view, a straight line L1 connecting the most convex point S of the arcuate cutting edge 6a of the sub cutting edge 6 and the center P of this arcuate cutting edge 6a, and the sub cutting edge 6 The second intersecting angle θ2 formed by the extension line L3 of the linear cutting edge portion 6b of the sub cutting edge 6 toward the arc-shaped cutting edge portion 6a is in the range of 10° to 50°. Also, while preventing interference between the second groove portion 8B and the first and second convex portions 14A, 14B and the mounting hole 7 and the screw hole 12e, it is ensured by the convex curved arc-shaped cutting edge portion 6a of the sub cutting edge 6. It is possible to reduce the cutting resistance. Although not shown in the drawing, the same applies to the arcuate cutting edge portion 5a of the main cutting edge 5.

That is, when the cutting insert 1 is attached to the second insert mounting seat 12B as the second cutting insert 1B, the extension line L3 is viewed from the bottom surface facing the seating surface 3 of the second cutting insert 1B, or It is substantially parallel to the axis O of the end mill body 11 when seen in a plan view from the direction facing the rake face 2 along the center line of the mounting hole 7. Therefore, the second intersection angle θ2 is substantially equal to the intersection angle formed by the axis O and the straight line L1 connecting the center P of the arcuate cutting edge 6a located on the axis O and the most convex point S. Become. However, the linear cutting edge portions 5b and 6b may have a slight back taper angle when the cutting insert 1 is attached to the end mill body 11, and therefore, the intersection angle θ2 is exactly the intersection of the straight line L1 and the axis O. It does not have to be equal to the corner.

Therefore, when the second intersection angle θ2 is larger than 50°, the second groove portion 8B and the first and second convex portions 14A, 14A, when the first intersection angle θ1 is within the above range. 14B may interfere with the mounting hole 7 and the screw hole 12e. If the second intersection angle θ2 is smaller than 10°, the most convex point S is too close to the axis O in the arcuate cutting edge portion 6a of the second cutting insert 1B, and the rotation speed around the axis O is small. The arcuate cutting edge portion 6a of the sub cutting edge 6 cuts into the work material from the small portion, and the effect of reducing the cutting resistance may be impaired. The second intersection angle θ2 is more preferably in the range of 20° to 50°, and even more preferably in the range of 35° to 50°.

<<Second Embodiment and Third Embodiment>>
Next, FIGS. 21 to 25 show a second embodiment of the cutting insert of the present invention, and FIGS. 26 to 31 show the cutting insert 21 of the second embodiment and the third embodiment. FIG. 32 to FIG. 37 show the tip end portion of the end mill body 41 in the second embodiment of the replaceable cutting edge type ball end mill of the present invention to which the cutting insert 31 of FIG. Tip part of the second embodiment of the cutting edge replaceable ball end mill of the present invention in which the cutting inserts 21 and 31 of the second and third embodiments are detachably attached to the third and fourth insert mounting seats 12C and 12D. Is shown. In the embodiments shown in FIGS. 21 to 37, elements common to those of the embodiments shown in FIGS. 1 to 19 are designated by the same reference numerals and description thereof will be omitted, and the groove widths W1, W2 and the first, The second intersection angles θ1 and θ2, the inclination angles α to γ, and the like are also common, and are not shown.

The cutting insert 1 of the first embodiment is provided with the arcuate cutting edge portions 5a, 6a having different circumferential lengths on the main cutting edge 5 and the sub cutting edge 6 and is asymmetric with respect to the insert center line X passing through the center of the mounting hole 7. On the other hand, the cutting inserts 21 and 31 of the second and third embodiments are characterized in that they are formed in a 180° rotationally symmetrical shape in the circumferential direction of the rake face 2 with respect to the insert center line X.

Further, the cutting insert 21 of the second embodiment has an arc-shaped cutting edge portion 5a having a substantially 1/4 arc shape and a linear cutting edge that is in contact with the main cutting edge 5 of the cutting insert 1 of the first embodiment. Two portions 5b are alternately provided in the circumferential direction of the rake face 2. The cutting insert 31 of the third embodiment has an arcuate cutting edge portion 6a having a peripheral length shorter than a 1/4 arcuate shape and a linear shape in contact with the auxiliary cutting edge 6 of the cutting insert 1 of the first embodiment. Two cutting blades 6b are provided alternately in the circumferential direction of the rake face 2. The radii of the arcuate cutting edge 5a in the main cutting edge 5 of the second embodiment and the arcuate cutting edge 6a of the sub cutting edge 6 in the third embodiment are made equal to each other.

Therefore, the linear cutting edge portions 5b of the two main cutting edges 5 of the cutting insert 21 of the second embodiment and the linear cutting edge portions of the two auxiliary cutting edges 6 of the cutting insert 31 of the third embodiment. 6b is parallel to each other. Further, the distance between the linear cutting edge portions 5b of the two main cutting edges 5 of the cutting insert 21 of the second embodiment is determined by the linear cutting of the two sub cutting edges 6 of the cutting insert 31 of the third embodiment. It is larger than the interval between the blade portions 6b.

Also in the cutting inserts 21 and 31 of the second and third embodiments, the seating surface 3 has a convex portion protruding from the bottom surface 12a of the third and fourth insert mounting seats 12C and 12D of the end mill body 41. Two groove portions 8 having wall surfaces that can come into contact with each other are formed by the above-mentioned two cutting blades (main cutting blade 5 and sub-cutting blade 6) from the straight cutting blade portions 5b, 6b of one cutting blade to the other cutting blade. Are formed so as to extend toward the arcuate cutting edge portions 5a, 6a. Each of these two groove portions 8 has a narrow portion 9 whose groove width becomes narrower from one end side toward the other end side in the extending direction of the groove portion 8. Also in these second and third embodiments, the narrow portion 9 has one end side on the linear cutting edge portions 5b and 6b side and the other end side on the arcuate cutting edge portions 5a and 6a side.

Also in these second and third embodiments, as in the first embodiment, the groove portion 8 has the other end opened to the flank 4 connected to the arcuate cutting edge portions 5a and 6a, and one end thereof is also linearly cut. It is opened to the flank 4 which is continuous with the blade portions 5b and 6b. In these second and third embodiments, as shown in FIGS. 21 and 25, the two cutting edges (the main cutting edge 5 and the sub cutting edge 6) are entirely on the side of the arcuate cutting edge 5a, 6a. From the seating surface 3 side toward the straight cutting edge portions 5b, 6b side, and is then formed in a convex curve shape that approaches the seating surface 3 side. The opening of the groove 8 to the flank 4 that is continuous with the arcuate cutting edges 5a and 6a is more arcuate than the most convex point S where the main cutting edge 5 and the sub cutting edge 6 are most convex with respect to the seating surface 3. It is located on the side of the cutting edges 5a and 6a.

Specifically, as shown in FIG. 23 in a bottom view seen from the direction facing the seating surface 3, the most convex point S of the cutting edge (the main cutting edge 5 in FIG. 3) and the arc shape of the main cutting edge 5 are shown. A third straight line L6 connecting the center P1 of the cutting edge 5a and a straight line L7 connecting the center V of the arcuate cutting edge 5a of the main cutting edge 5 and the straight cutting edge 5b. It is desirable that the intersection angle θ3 of is within a range of 40° or less. Of course, the third intersection angle θ3 may be 0°, that is, the straight line L6 and the straight line L7 may overlap.

In the cutting insert 21 of the second embodiment, the arcuate cutting edge portion 5a of the main cutting edge 5 extends from the vicinity of the axis O at the tip of the end mill body 41 and is positioned 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 mounted on the third insert mounting seat 12C so as to be positioned on a cylindrical surface centered on the axis O that is in contact with the convex hemisphere. The cutting insert 31 of the third embodiment has an arcuate cutting edge of the main cutting edge 5 of the cutting insert 21 of the second embodiment from the position where the arcuate cutting edge portion 6a of the auxiliary cutting edge 6 is separated from the axis O. The linear cutting edge portion 6b of the auxiliary cutting edge 6 is positioned on the convex hemisphere where the portion 5a is positioned, and the linear cutting edge portion 5b of the main cutting edge 5 of the cutting insert 21 of the second embodiment is positioned. It is mounted on the fourth insert mounting seat 12D so as to be positioned on the cylindrical surface.

First to fourth convex portions 14A to 14D are also formed on the bottom surface 12a of the third and fourth insert mounting seats 12C and 12D. The groove portion 8 having the narrow width portion 9 formed on the seating surface 3 of the cutting inserts 21 and 31 of the second and third embodiments is brought into contact with these first to fourth convex portions 14A to 14D. It is attached. The first convex portion 14A on the tip side of the third insert mounting seat 12C of the end mill main body 41 in the blade tip exchangeable ball end mill of the second embodiment is different from the first embodiment in which the peninsular shape is different from the first embodiment. The second to fourth convex portions 14B to 14D are formed in the shape of isolated islands.

Also in the cutting inserts 21, 31 of the second and third embodiments and the cutting edge exchangeable ball end mill of the second embodiment, the groove portion 8 having the narrow portion 9 on the seating surface 3 of the cutting inserts 21, 31. Are formed. Since the groove portion 8 is capable of abutting on the convex portions 14A to 14D formed on the insert mounting seats 12C and 12D, like the cutting insert 1 and the tip-replaceable ball end mill of the first embodiment, the cutting is performed. It is possible to improve the strength of the inserts 21 and 31 and prevent damage, and prevent misalignment of the cutting inserts 21 and 31 at the time of cutting, thereby performing high-precision processing.

In the cutting inserts 21 and 31 of the second and third embodiments, the main cutting edge 5 and the sub cutting edge 6 are seated as they move from the arcuate cutting edge 5a, 6a side toward the linear cutting edge 5b, 6b side. Since it is formed in a convex curve shape that approaches the seating surface 3 side after being separated from the surface 3 side, it is possible to gradually cause the main cutting edge 5 and the sub cutting edge 6 to bite into the work material from the most convex point S thereof. Therefore, it is possible to reduce the cutting resistance and promote the improvement of the cutting edge strength by increasing the wall thickness.

Moreover, in the cutting inserts 21 and 31 of the second and third embodiments, the other end of the groove portion 8 is open to the flank 4 that is continuous with the arcuate cutting edge portions 5a and 6a, whereas the groove portion 8 is Of the first cutting edge 5 and the sub cutting edge 6 are located closer to the arcuate cutting edge portions 5a, 6a than the most convex point S at which the main cutting edge 5 and the sub cutting edge 6 are most convex with respect to the seating surface 3, and therefore the first It is possible to prevent the impact when the most convex point S bites from directly propagating to the opening portion of the groove portion 8 in the insert center line X direction, as in the embodiment of FIG. It is also possible to prevent the cutting inserts 21 and 31 from being damaged.

In this way, when the other end of the groove portion 8 is opened to the arcuate cutting edge portions 5a and 6a, and one end of the groove portion 8 is also linear like the cutting inserts 21 and 31 of the second and third embodiments. In the case of opening in the flank 4 which is continuous with the cutting edge portions 5b and 6b, in the bottom view seen from the direction facing the seating surface 3, the maximum convex point S of the main cutting edge 5 and the sub cutting edge 6 is formed. A straight line L6 connecting the centers P1 of the arcuate cutting edge parts 5a and 6a, and a contact point V between the arcuate cutting edge parts 5a and 6a of the main cutting edge 5 and the sub cutting edge 6 and the straight cutting edge parts 5b and 6b. If the third intersection angle θ3 formed by the straight line L7 connecting the arcuate cutting edges 5a and 6a with the center p1 is too large, the most convex point S approaches the opening of the groove 8 to the flank 4 too much, As described above, the damage to the cutting inserts 21 and 31 cannot be reliably prevented, which occurs. Therefore, the third intersection angle θ3 is preferably in the range of 40° or less, more preferably in the range of 37° or less, and further preferably in the range of 35° or less.

Further, the cutting inserts 21 and 31 of the second and third embodiments are formed in a 180° rotationally symmetrical shape in the circumferential direction of the rake face 2 with respect to the insert center line X which is the center line of the mounting hole 7 as described above. Has been done. For this reason, wear or the like occurs in the main cutting edge 5 and the sub cutting edge 6 of one of the cutting inserts 21 and 31 used for cutting while being attached to the third and fourth insert mounting seats 12C and 12D. When it reaches the end of its life, the cutting inserts 21 and 31 are once removed, rotated by 180° around the insert center line X, and reattached to the third and fourth insert mounting seats 12C and 12D. Similarly, one cutting insert 21, 31 can be used twice each.

According to the present invention, the narrow width portion of the groove portion formed on the seating surface of the cutting insert ensures the wall thickness of the cutting insert on the other end side where the groove width is narrowed to disperse the stress and improve the strength. It is possible to prevent damage to the cutting insert due to the load during cutting. Since the groove width of the narrow part becomes wider on the one end side of the groove part, it is possible to form the convex part of the cutting edge replaceable ball end mill to be wider and increase the mounting rigidity of the cutting insert to reliably prevent the displacement movement. It will be possible.

1 (1A, 1B), 21, 31 Cutting insert 2 Rake surface 3 Seating surface 4 Relief surface 5 Main cutting edge 5a Main cutting edge 5 arcuate cutting edge portion 5b Main cutting edge 5 linear cutting edge portion 6 Sub cutting edge Blade 6a Arc-shaped cutting edge portion 6b of the secondary cutting edge 6b Straight cutting edge portion 7 of the secondary cutting edge 7 Mounting holes 8, 8A, 8B Groove portion 9 Narrow portion 11, 41 End mill body 12 (12A-12D) Insert mounting seat 14A to 14D Convex part r Radius of arcuate cutting edge part (6a) located on the other end side of narrow part 9 in groove part (second groove part 8B) P Arcuate cutting edge part of sub cutting edge 6 in bottom view Center of arc formed by 6a P1 Center of arc formed by arcuate cutting edge portion 5a of main cutting edge 5 in bottom view Q First of second groove portion 8B of secondary cutting edge 6 that faces straight cutting edge portion 6b The edge of the ridge line intersecting the wall surface 8a and the flank 4 toward the seating surface 3 side S The most convex point t The wall thickness of the cutting insert 1 at the most convex point U The wall thickness of the cutting insert 1 is secured by the most convex point S Range V The contact point between the arcuate cutting edge 5a and the linear cutting edge 5b of the main cutting edge 5 in bottom view L1 The straight line connecting the center P and the most convex point S in bottom view L2 The center P in bottom view A straight line L3 connecting the end Q. An extension line of the linear cutting edge 6b of the sub cutting edge 6 toward the arcuate cutting edge 6a side of the sub cutting edge 6 in the bottom view L6 The most convex of the main cutting edge 5 in the bottom view Straight line connecting point S and center P1 L7 Straight line connecting center P1 and contact point V in bottom view W1 Groove width at the other end of narrow portion 9 W2 Groove width at one end of narrow portion 9 Insert center line O End mill body 11 and 41 axis T End mill rotation direction θ1 First crossing angle θ2 Second crossing angle θ3 Third crossing angle

Claims (12)

A cutting insert that is detachably 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 direction of rotation of the end mill body, a seating face facing the side opposite to the rake face and seated on the bottom surface of the insert mounting seat, and a flank face extending around the rake face and the seating face. With and
An arcuate cutting edge portion extending in an arcuate shape in a plan view seen from a direction facing the rake surface, and an arcuate cutting edge portion that intersects with the arcuate cutting edge portion at an intersection ridge portion of the rake surface and the flank surface. Two cutting edges each provided with a linear cutting edge portion are formed by alternately positioning the arcuate cutting edge portion and the linear cutting edge portion in the circumferential direction of the rake face,
On the seating surface, two groove portions having a wall surface capable of contacting a convex portion projecting from the bottom surface of the insert mounting seat are provided from the linear cutting edge portion side of one of the two cutting edges to the other side. Is formed so as to extend toward the arcuate cutting edge of the cutting edge of
The cutting insert characterized in that each of the two groove portions 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 portions. In each of the two groove portions, the linear cutting edge portion side of the one cutting edge is the one end side, and the arcuate cutting edge portion side of the other cutting edge is the other end side. The cutting insert according to claim 1. 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 sub cutting edge is formed to have a short circumference with the same radius as that of the arcuate cutting edge portion of the main cutting edge. Cutting inserts. Of the two groove portions, the groove portion having the arcuate cutting edge portion side of the sub cutting edge as the other end side is open to the flank that is continuous with the arcuate cutting edge portion of the sub cutting edge,
The arc-shaped cutting edge portion of the sub-cutting edge is formed in a convex curved shape that approaches the seating surface side after being separated from the seating surface side as the sub-cutting blade is separated from the linear cutting edge part,
The opening of the groove portion to the flank that is continuous with the arc-shaped cutting edge portion of the sub-cutting edge is more than the most convex point where the arc-shaped cutting edge portion of the sub-cutting edge is most convex with respect to the seating surface. The cutting insert according to claim 3, wherein the cutting insert is located on the side of the linear cutting edge of the sub cutting edge. In a bottom view seen from the direction facing the seating surface,
A straight line connecting the most convex point and the center of the arcuate cutting edge portion of the sub cutting edge,
To the seating surface side of the ridge line intersection of the wall surface facing the linear cutting edge portion side of the sub cutting edge of the groove opening to the flank that is continuous with the arcuate cutting edge portion of the sub cutting edge and the flank surface The first intersection angle formed by the straight line connecting the end portion and the center of the arcuate cutting edge portion of the sub cutting edge is in the range of 5° to 60°. Cutting insert described. In a bottom view seen from the direction facing the seating surface,
A straight line connecting the most convex point and the center of the arcuate cutting edge portion of the sub cutting edge,
A second intersecting angle formed by the extension line of the linear cutting edge portion of the sub cutting edge toward the arcuate cutting edge portion side of the sub cutting edge is in the range of 10° to 50°. The cutting insert according to claim 4 or claim 5. The insert center line connecting the center of the rake face and the center of the seating face is formed in a rotationally symmetrical shape of 180° in the circumferential direction of the rake face. Cutting inserts. The other end of the groove is opened to the flank that is continuous with the arcuate cutting edge,
The cutting edge is formed in a convex curved shape that approaches the seating surface side after being separated from the seating surface side as it goes from the arcuate cutting edge part side to the linear cutting edge part side,
The opening of the groove portion to the flank that is continuous with the arcuate cutting edge portion is closer to the arcuate cutting edge portion of the cutting edge than the most convex point where the cutting edge is most convex with respect to the seating surface. 8. The cutting insert according to claim 7, wherein the cutting insert is located at. In a bottom view seen from the direction facing the seating surface,
A straight line connecting the most convex point of the cutting edge and the center of the arc-shaped cutting edge portion of the cutting edge,
The third intersection angle formed by the straight line connecting the contact point between the arcuate cutting edge portion of the cutting edge and the linear cutting edge portion and the center of the arcuate cutting edge portion is within the range of 40° or less. The cutting insert according to claim 8, characterized in that The groove width at the other end of the narrow portion in the groove portion is 0.05×r to 0.18 with respect to the radius r of the arcuate cutting edge portion of the cutting edge when viewed from the direction facing the seating surface. The cutting insert according to any one of claims 3 to 9, wherein the cutting insert has a range of xr. The cutting insert according to any one of claims 1 to 10 projects from a bottom surface of the insert mounting seat to an insert mounting seat formed at a tip portion of an end mill body rotated about an axis. A replaceable cutting edge type ball end mill, wherein a wall surface of the groove is brought into contact with a convex portion and is detachably attached. In the portion where the narrow portion of the groove portion abuts, the convex portion is formed so as to become wider from the other end side in the extending direction of the groove portion toward the one end side. Item 11. A replaceable cutting edge ball end mill according to Item 11.