WO2019082843A1 - Cutting insert and indexable ball end mill - Google Patents

Abstract

A cutting insert (1) to be attached to the insert mounting seat of an indexable ball end mill comprises: a rake face; a seating face (3) facing away from the rake face and seated on the insert mounting seat; and a flank face (4) extending along the periphery of the rake face and the seating face (3). Two cutting edges (5, 6) respectively provided with arcuate cutting edge portions (5a, 6a) and linear cutting edge portions (5b, 6b) are formed at the intersecting ridge between the rake face and the flank face (4). Two grooves (8) respectively having wall surfaces (8a, 8b) which can be brought into contact with the protrusion on the bottom surface of the insert mounting seat are formed on the seating face (3) so as to extend from the linear cutting edge portions (5b, 6b) side of one of the cutting edges (5, 6) to the arcuate cutting edge portions (6a,5a) side of the other of the cutting edges (6, 5) with the two cutting edges (5, 6). The two grooves (8) have a width-narrowing portion (9) that becomes narrower from one side to the other side in the direction in which the grooves (8) extend.

Description

Cutting insert and indexable ball end mill

The present invention relates to a cutting insert removably attached to an insert mounting seat formed at the end of an end mill body of a tip-exchange-type ball end mill, and a tip-exchange-type ball end mill detachably attaching such a cutting insert. It is.
Priority is claimed on Japanese Patent Application No. 2017-207980, filed Oct. 27, 2017, the content of which is incorporated herein by reference.

In a cutting insert used for such a blade-end-exchange-type ball end mill, in the case where two arc-shaped cutting edges are formed on opposite sides in the circumferential direction of the rake face, they are connected to these arc-shaped cutting edges and escaped. Since the side surface of the cutting insert to be the surface is convexly curved, the curvature of the flank surface connected to the arc-shaped cutting edge opposite to the arc-shaped cutting edge used for cutting due to the cutting load at the time of cutting The cutting insert is easy to move along. Therefore, for example, in Patent Literatures 1 and 2, while forming a convex portion projecting on the bottom surface of the insert mounting seat, a groove portion having a wall surface that can abut on the convex portion is formed on the seating surface of the cutting insert. Thus, it is described to prevent such offset movement of the cutting insert.

In Patent Document 1, it is described that only one of two opposing wall surfaces of the groove is brought into contact with one side surface of the protrusion. Further, in Patent Document 2, a main cutting edge and an auxiliary cutting edge respectively provided with an arc-shaped cutting edge portion and a linear cutting edge portion are formed, and the main cutting edge and the auxiliary cutting edge are made asymmetric. It is described that the arc-shaped cutting edges of one type of two cutting inserts of the same shape and size perform cutting from near the axis of the end of the end mill body to the outer circumference and cutting from a position away from this axis to the outer circumference ing.

Unexamined-Japanese-Patent No. 9-174322 gazette Unexamined-Japanese-Patent No. 11-197933 gazette

By the way, in the cutting insert described in the drawings of these Patent Documents 1 and 2, the two opposing wall surfaces of the groove portion are shown to extend in parallel with each other, but in the case where the wall surfaces of the groove portion extend in this way If the width of the projections is increased in order to increase the rigidity of the projections of the end mill body and secure the strength against the displacement movement of the cutting insert, the width of the grooves of the cutting insert also increases and the strength of the cutting insert decreases. There is a risk that the load at the time of cutting may cause damage. On the other hand, if the width of the groove is reduced in order to secure the strength of the cutting insert, the width of the convex part of the end mill main body also has to be reduced, and the mounting rigidity of the cutting insert can not be secured. There is a risk that it will not be possible to reliably prevent the shift movement of the cutting insert due to

The present invention has been made under such a background, and it is possible to reliably remove the cutting insert capable of reliably preventing the shift movement during the cutting without impairing the strength of the cutting insert, and to make the cutting insert removable. It is an object of the present invention to provide an indexable 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 removed from an insert mounting seat formed on the end portion of the end mill main body of an indexable ball end mill rotated about an axis. A cutting insert which can be mounted, the rake face being oriented in the direction of rotation of the end mill body, the seating face being seated against the bottom of the insert seat opposite the rake face, and the rake faces And a flank surface extending around the seating surface, and an arc-shaped cutting edge extending in an arc shape in a plan view seen from the direction opposite to the rake surface at the intersection ridge line portion between the rake surface and the flank surface The two cutting edges respectively provided with the part and the linear cutting edge part extended so as to be in contact with the arc-shaped cutting edge part are the arc-shaped cutting edge part and the linear cutting edge part in the circumferential direction of the rake face The two groove portions formed alternately positioned and having a wall surface that can be abutted to a convex portion protruding from the bottom surface of the insert mounting seat on the seating surface are one cutting edge of the other with the two cutting edges. It is formed to extend from the linear cutting edge side of the blade to the arc-shaped cutting edge side of the other cutting edge, and the two groove portions are directed from one end side to the other end side in the extending direction of the groove portions. Each has a narrow portion where the groove width becomes narrow.

Further, in the indexable ball end mill according to the present invention, such a cutting insert is a convex portion projecting from the bottom surface of the insert mounting seat formed on the tip end portion of the end mill main body rotated about an axis. The wall surface of the above-mentioned groove part is made to abut, and it is removably attached.

The groove portion of the cutting insert according to the cutting insert and the indexable ball end mill having such a configuration has a narrow portion in which the groove width narrows from one end side to the other end side in the extending direction of the groove portion. At 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 the strength can be improved. On the other hand, on the other hand, since the groove width is wide on one end side of the narrow portion, in the indexable ball end mill, in the portion where the narrow portion of the groove abuts the convex portion, the groove extends. By forming the width as it extends from the other end side toward the one end side, it is possible to increase the mounting rigidity with respect to the load at the time of cutting and reliably prevent the shift movement of the cutting insert.

In such cutting inserts and indexable ball end mills, among the cutting edges, the arc-shaped cutting edge portion is used exclusively for cutting. Each of the two groove portions has the linear cutting edge side of the one cutting edge as the one end side, and the arc-shaped cutting edge side of the other cutting edge as the other end side. When the other cutting edge is used for cutting, secure the strength of the cutting insert on the other end side where the narrow portion becomes narrower against the cutting load acting on the arc-shaped cutting edge portion In addition, the shift movement of the cutting insert along the arc-shaped cutting edge of the cutting edge not used for cutting is ensured at one end side of the narrow portion which becomes wide apart from the arc-shaped cutting edge of this cutting edge. It becomes possible to prevent.

In the cutting insert of the present invention, first, one of the two cutting edges is a main cutting edge, and the other is a minor cutting edge. The arc-shaped cutting edge portion of the sub cutting edge is formed so that the circumferential length is short with an equal radius to the arc-shaped cutting edge portion of the main cutting edge, and the cutting insert is described in Patent Document 2 It has an asymmetric shape. With this same shape and size of one type and two types of cutting inserts, it is possible to cut from near the axis of the end of the end mill body to the outer circumference by the arc-shaped cutting edge of the main cutting edge, and at a position away from this axis It is possible to carry out the cutting from the to the outer periphery by the arc-shaped cutting edge portion of the sub cutting edge, which makes the management of the cutting insert easy and economical.

Therefore, in this case, of the two grooves, the groove whose arc-shaped cutting edge side of the sub cutting edge is the other end side is the clearance surface connected to the arc-shaped cutting edge of the sub cutting edge. It may be open.
If the arc-shaped cutting blade portion of the sub cutting blade is formed into a convex curve approaching the seating surface side after being separated from the seating surface side as it is separated from the linear cutting blade portion of the sub cutting blade, Since the arc-shaped cutting edge portion of the sub cutting edge is gradually cut into the work material from the most convex point which is most convex with respect to the seating surface, cutting resistance can be reduced.

That is, in the cutting insert used for the indexable ball end mill, a large cutting load is applied to the tip portion of the arc-shaped cutting edge portion, the flank surface connected to this, and the side surface of the insert main body during cutting. Therefore, it is desirable to reduce the cutting load and the shape of the cutting edge in consideration of the chip dischargeability. In the present invention, attention is also focused on controlling the contact form between the arc-shaped cutting edge portion and the work material.

For example, when contour processing is selected as the cutting method, it is desirable to set the cutting edge tip side where the thickness of the chip becomes thin as the area where the cutting edge bites into the work material. By forming the arc-shaped cutting edge portion in a convex curved shape as described above, the cutting edge becomes 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 main body, the cutting material bites on the work material from the tip end side of the arc-shaped cutting edge portion where the thickness of chips increases. , A large cutting load is applied to the tip. Therefore, the strength of the cutting edge can be improved by thickening the arc-shaped cutting edge portion as a convex curve and providing the most convex point.

When the groove portion opens to the flank surface connected to the arc-shaped cutting edge portion of the sub cutting edge, and the arc-shaped cutting edge portion of the sub cutting edge is formed in a convex curve, the arc cutting shape of the above-mentioned sub cutting edge The opening of the groove to the flank connected to the blade has a linear cut of the minor cutting edge than the most convex point at which the arcuate cutting edge of the minor cutting edge is most convex with respect to the seating surface. Located on the blade side. Thereby, it is possible to prevent the cutting insert from being damaged from the opening of the groove by the impact when the arc-shaped cutting edge portion of the sub cutting edge bites into the work material from the most convex point and cuts it.

Specifically, in a bottom view seen from the direction opposite to the seating surface, a straight line connecting the most convex point and the center of the arc-shaped cutting edge of the sub cutting edge, and the arc cutting of the sub cutting edge The end portion of the groove portion facing the straight cutting edge portion side of the sub cutting edge of the groove portion opened to the flank face continuous with the blade portion and the flank face to the seating surface side of the flank and the sub cutting edge It is desirable that a first crossing angle formed by a straight line connecting the center of the arc-shaped cutting edge portion be in the range of 5 ° to 60 °.

If the first intersection angle is smaller than 5 °, the opening of the groove to the flank connected to the arc-shaped cutting edge of the sub cutting edge too close to the most convex point and the arc cutting edge of the sub cutting edge There is a risk that the cutting insert may be damaged when the part bites. On the other hand, when the first crossing angle is as large as 60 ° or more, when attaching the cutting insert 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 and the projection may interfere with the mounting hole and the screw hole.

Also, as described above, when the groove opens to the flank surface connected to the arc-shaped cutting edge of the sub cutting edge, and the arc-shaped cutting edge of the sub cutting edge is formed in a convex curved shape, the above seating In a bottom view as seen from the direction opposite to the surface, a straight line connecting the most convex point and the center of the arc-shaped cutting edge of the sub cutting edge, and the sub of the sub cutting edge toward the arc-shaped cutting edge It is desirable that the second crossing angle formed by the extension line of the linear cutting edge of the cutting edge be in the range of 10 ° to 50 °.

If this second crossing angle is so small that it is less than 10 °, the most convex point will be too close to the axis of the end mill body when the minor cutting edge is used for cutting, and the minor rotational speed about the minor axis is minor The arc-shaped cutting edge portion of the cutting edge cuts into the work material, and the effect of reducing the cutting resistance may be lost. On the other hand, if the second crossing angle is so large that it exceeds 50 °, the straight line of the minor cutting edge than the most convex point on the flank connecting the opening of the groove to the arcuate cutting edge of the minor cutting edge as described above. When it is intended to be positioned on the side of the cutting edge, there is a possibility that the groove and the projection may interfere with the mounting hole of the cutting insert and the screw hole of the insert mounting seat.

Second, the cutting insert according to the present invention is not an asymmetric shape as described above, but an insert connecting the center of the rake surface and the center of the seating surface in the same manner as the cutting insert described in Patent Document 1, for example. It may be formed in a 180 ° rotational symmetry in the circumferential direction of the rake surface with respect to the center line.

In the second case, for example, a cutting insert having two main cutting edges provided with an arc-shaped cutting edge portion having a circumferential length of 1⁄4 arc, and a radius equal to that of the cutting insert and a circumferential length being short Prepare a cutting insert having two auxiliary cutting edges with arc-shaped cutting edges, and cut from near the axis of the end mill body tip to the outer periphery by the arc-shaped cutting edge of the main cutting edge, and from this axis It is possible to cut from the remote position to the outer periphery by means of the arc-shaped cutting edge of the secondary cutting edge.

Even in the second case, the other end of the groove may be open at the flank surface connected to the arc-shaped cutting edge. Further, the cutting blade 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 arc-shaped cutting blade side to the linear cutting blade side. However, in the second case, the opening of the groove to the flank connected to the arc-shaped cutting edge is more than the most convex point at which the cutting edge is most convex with respect to the seating surface. It is desirable to be located in the said circular-arc-shaped cutting-blade part side of a cutting blade.

Specifically, in a bottom view seen from the direction opposite to 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, and the cutting edge It is preferable that a third crossing angle formed by a contact point between the arc-shaped cutting edge portion and the linear cutting edge portion and a straight line connecting the center of the arc-shaped cutting edge portion be in a range of 40 ° or less. If the third crossing angle becomes larger than this range, the opening of the groove to the flank continuing to the arc-shaped cutting edge becomes too close to the most convex point, and the cutting edge changes from the most convex point to the work material The cutting insert may be damaged when biting.

Further, as in the second case and the first case described above, the radii of the arc-shaped cutting edges 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 arc-shaped cutting edge portion of the cutting blade as viewed from the direction facing the seating surface. It is desirable that the range is from r to 0.18 × r.

If the groove width at the other end where the narrowest part is the narrowest is so narrow that it falls below the above range, the width of the convex part of the insert mounting seat also has to be reduced, and it becomes difficult to ensure rigidity reliably. There is a fear. On the other hand, by ensuring that the groove width at the other end of the narrow portion exceeds the above range and the wall surfaces of the groove become parallel to each other, securing the thickness on the other end side of the narrow portion There is a risk that the stress can not be dispersed to maintain the strength of the cutting insert.

As described above, according to the present invention, by the narrow part of the groove formed in the seating surface of the cutting insert, the thickness of the cutting insert is secured on the other end side where the groove width becomes narrow, and the stress is dispersed. Thus, 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 portion becomes wide at one end side, the convex portion of the indexable ball end mill can be formed wide, and the mounting rigidity of the cutting insert is enhanced to surely prevent the shift movement. It becomes possible.

It is a perspective view which shows 1st Embodiment of the cutting insert of this invention. It is a top view of embodiment shown in FIG. FIG. 2 is a bottom view of the embodiment shown in FIG. 1; FIG. 5 is a side view in the direction of arrow A in FIGS. 2 and 3. FIG. 5 is a side view in the direction of arrow B in FIGS. 2 and 3. FIG. 5 is a side view in the direction of arrow C in FIGS. 2 and 3. FIG. 5 is a side view in the direction of arrow D in FIGS. 2 and 3. It is a perspective view showing the tip part of the end mill main part in a 1st embodiment of the indexable ball end mill of the present invention to which the cutting insert of a 1st embodiment is attached removably. 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 arrow A direction in FIG. It is a side view seen from the arrow B direction in FIG. FIG. 10 is a bottom view as viewed in the direction of arrow C in FIG. 9; FIG. 10 is a side view in the direction of arrow D in FIG. 9; It is a perspective view which shows the front-end | tip part of 1st Embodiment of the blade-tip-exchange-type ball end mill of this invention. FIG. 15 is a front view of the embodiment shown in FIG. It is a top view of arrow A direction in FIG. FIG. 16 is a side view in the direction of arrow B in FIG. 15; It is a bottom view of arrow C direction in FIG. It is a side view in the arrow D direction in FIG. It is a figure which shows the dispersion | distribution state of the stress by simulation analysis at the time of changing the groove width of the other end of the narrow part in a groove part, Comprising: It is a case where groove width is constant. It is a figure which shows the dispersion | distribution state of the stress by simulation analysis at the time of changing the groove width of the other end of the narrow part in a groove part, Comprising: It has a narrow part and the narrow part to radius r of an arc-like 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 at the time of changing the groove width of the other end of the narrow part in a groove part, Comprising: It has a narrow part and the narrow part to radius r of an arc-like cutting edge part. Is the case where the groove width at the other end is 0.067 × r. It is a perspective view which shows 2nd Embodiment of the cutting insert of this invention. Figure 22 is a plan view of the embodiment shown in Figure 21; Figure 22 is a bottom view of the embodiment shown in Figure 21; FIG. 24 is a side view in the direction of arrow A in FIGS. 22 and 23; FIG. 24 is a side view as 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 blade-tip-exchange-type ball end mill of this invention with 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. It is a top view of arrow A direction in FIG. FIG. 28 is a side view in the direction of the arrow B in FIG. 27. FIG. 28 is a bottom view as seen in the direction of arrow C in FIG. 27. FIG. 28 is a side view in the direction of arrow D in FIG. 27. It is a perspective view which shows the front-end | tip part of 2nd Embodiment of the blade-tip-exchange-type ball end mill of this invention. It is a front view of embodiment shown in FIG. It is a top view of arrow A direction in FIG. 33 view. FIG. 34 is a side view in the direction of the arrow B in FIG. 33. It is a bottom view of arrow C direction in FIG. 33 view. FIG. 34 is a side view in the direction of arrow D in FIG. 33.

First Embodiment
1 to 7 show a cutting insert 1 according to a first embodiment of the present invention. FIGS. 8 to 13 show the tip of the end mill body 11 in the first embodiment of the indexable ball end mill according to the present invention to which the cutting insert 1 of the first embodiment is detachably mounted. FIGS. 14 to 19 show the first embodiment of the indexable ball end mill according to the present invention in which the cutting insert 1 of the first embodiment is detachably mounted to the insert mounting seat 12 of the end mill main body 11. It shows the tip.

The cutting insert 1 of the present embodiment is formed 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 a leaf-shaped rake face 2 as described above. The lower surface facing the rake surface 2 is a flat seating surface 3 which is in the form of a leaf similar to the rake surface 2 and which rests on the bottom surface of the insert mounting seat. A side surface extending circumferentially between the rake face 2 and the seating face 3 is a flank 4.

At a crossing ridge line portion between the rake face 2 and the flank face 4, as shown in FIG. 2 in a plan view seen from the direction opposite to the rake face 2, arc-shaped cutting edges 5a, 6a extending in an arc shape, and this circle The two cutting edges respectively provided with the linear cutting edges 5b, 6b extending so as to contact the arc-shaped cutting edges 5a, 6a are the arc-shaped cutting edges 5a, 6a and the linear cutting edges 5b, 6b. It is formed to be alternately positioned in the circumferential direction of the rake face 2. One of the two cutting edges is a main cutting edge 5, and the other cutting edge is a minor cutting edge 6.

Moreover, the flank 4 inclines so that it may go to the inner peripheral side of the cutting insert 1 as it goes to the seating surface 3 side from the scoop surface 2, and the cutting insert 1 of this embodiment is made into a positive type. Further, at the central portion of the rake face 2 and the seating face 3, a mounting hole 7 having a circular cross section formed to penetrate the cutting insert 1 is opened, and the rake face 2 side of the mounting hole 7 is a seating face The diameter is reduced toward the three sides.

In the plan view, the arc-shaped cutting edge portion 5 a of the main cutting edge 5 has a substantially 1⁄4 arc shape, whereas the arc-shaped cutting edge portion 6 a of the minor cutting edge 6 is a circle of the main cutting edge 5. The radius is equal to that of the arc-shaped cutting edge 5 a, but the circumferential length is shorter than the arc-shaped cutting edge 5 a of the main cutting edge 5. That is, the arc-shaped cutting edge portion 6a is formed in an arc shape shorter than a 1⁄4 arc. Along with this, the linear cutting edge portion 5 b of the main cutting edge 5 is shorter than the linear cutting edge portion 6 b of the minor cutting edge 6. That is, as shown in FIG. 2 and FIG. 3, the cutting insert 1 of the present embodiment is not 180 ° rotational symmetric about the insert center line X which is the center line of the mounting hole 7 but is asymmetric. .

The linear cutting edges 5b and 6b of the main cutting edge 5 and the auxiliary cutting edge 6 are, as viewed from above, the arc-shaped cutting edge 5a of the main cutting edge 5 and the linear cutting edge 6b of the auxiliary cutting edge 6. Second end 2b of the rake face 2 where the linear cutting edge 5b of the main cutting edge 5 intersects with the arc-shaped cutting edge 6a of the minor cutting edge 6 from the first end 2a of the intersecting rake face 2 It extends close to each other as it Further, these first and second end portions 2a and 2b are chamfered such that they intersect at an obtuse angle with the arc-shaped 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 the shape of a circle. The first end 2a is located closer to the seating surface 3 than the second end 2b.

The arc-shaped cutting edges 5a and 6a of the main cutting edge 5 and the sub cutting edge 6 approach the seating surface 3 after being separated from the seating surface 3 as they are separated from the respective linear cutting edges 5b and 6b. The point which is formed in the shape of a convex curve, and the convex curve formed by the arc-shaped cutting edge portion 6a of the minor cutting edge 6 is the most distant and convex with respect to the seating surface 3 is the arc shape of the minor cutting edge 6 This is the most convex point S of the cutting edge 6a.
The linear cutting edges 5b and 6b of the main cutting edge 5 and the auxiliary cutting edge 6 are also arc-shaped cutting edge 5a as shown in FIGS. 4 and 6 in a side view seen from the direction opposite to the flank 4 , 6a, and extends in a substantially straight line approaching the seating surface 3 as it is separated from the arc-shaped cutting edges 5a, 6a.

Around the opening of the mounting hole 7 in the central part of the rake face 2, a protrusion having a substantially elliptical shape in a plan view projecting in a direction away from the seating surface 3 than the main cutting edge 5 and the sub cutting edge 6 2c is formed. The upper end surface of the projection 2 c is a flat surface parallel to the seating surface 3, and the mounting hole 7 is opened at the upper end surface of the projection 2 c. The outer peripheral surface of the projection 2c is inclined toward the inside of the rake surface 2 as it goes to the upper end face side. Further, the rake face 2 extends toward the seating face 3 as it goes away from the main cutting edge 5 and the sub cutting edge 6 toward the inner side of the rake face 2 and then forms a concave curved surface on the outer peripheral face of the projection 2 c. It is connected.

The flanks 4 connected to the linear cutting edges 5b and 6b of the main cutting edge 5 and the auxiliary cutting edge 6 are formed in a planar shape inclined as described above. On the other hand, the flanks 4 connected to the arc-shaped cutting edges 5a and 6a of the main cutting edge 5 and the sub cutting edge 6 along the arc-shaped cutting edges 5a and 6a on the rake surface 2 side are circumferential directions of the cutting insert 1 The seat portion 3 has a flat portion 4a which is notched in the plane while being inclined as described above.

On the other hand, as shown in FIG. 3, a groove 8 is formed in the seating surface 3. In the present embodiment, the first and second two groove portions 8A and 8B, as shown in FIG. The openings are spaced apart from each other and are formed on opposite sides of the openings. 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. It is done.

The grooves 8 each have a cross section perpendicular to the direction in which the grooves 8 extend, and are formed in a substantially rectangular shape flat in the direction of the insert center line X in which the attachment holes 7 extend. That is, the groove portion 8 extends in a direction substantially perpendicular to the seating surface 3 and extends between the first and second wall surfaces 8a and 8b facing each other, and between the first and second wall surfaces 8a and 8b. And a bottom surface 8c parallel to the surface 3. The first wall surface 8 a of each groove 8 faces the first end 2 a side of the rake face 2, and the second wall surface 8 b faces the second end 2 b side of the rake face 2. The crossing 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 intersect the bottom surface 8c is concavely curved Is formed.

The first and second groove portions 8A and 8B have narrow portions 9 in which the groove width is narrowed from one end side to the other end side in the direction in which the first and second groove portions 8A and 8B extend. ing. In this embodiment, the flanks 4 connected to the linear cutting edges 6b and 5b of the sub cutting edge 6 and the main cutting edge 5 are one end sides of the first and second groove portions 8A and 8B, and the main cutting edge A flank 4 side connected to the arc-shaped cutting edge portions 5a and 6a of the secondary cutting edge 6 and the secondary cutting edge 6 is the other end side. Furthermore, as shown in FIG. 3, the first and second groove portions 8A and 8B are entirely formed as the narrow portion 9 as a whole.

In this embodiment, the narrowing width of the narrow portion 9 is constant from one end side to the other end side of the first and second groove portions 8A and 8B in this embodiment. 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 in a straight line form and approach each other from the one end side to the other end side in the bottom view Is formed. The first and second groove portions 8A and 8B are, in the present embodiment, a flank 4 connected to the minor cutting edge 6 and the linear cutting edges 6b and 5b of the major cutting edge 5, the major cutting edge 5 and the minor cutting edge 6 It is formed in the shape of a through groove which is open to both of the flanks 4 connected to the arc-shaped cutting edges 5a and 6a.

The opening of the second groove 8B to the flank 4 connected to the arc-shaped cutting edge 6a of the auxiliary cutting edge 6 has an arc-shaped cutting edge 6a of the auxiliary cutting edge 6 having a convex curved shape in a side view. It is located on the side of the linear cutting edge 6 b of the minor cutting edge 6 with respect to the most convex point S which is the most convex with respect to the seating surface 3. Specifically, as shown in FIG. 3 in the bottom view, the minor cutting edge 6 is a straight line L1 connecting the most convex point S and the center P of the arc formed by the arcuate cutting edge portion 6a of the minor cutting edge 6; End Q of the second ridge 8B of the second groove 8B facing the straight cutting edge 6b and the flank Q on the side of the seating surface 3 (except for the chamfered portion) of the flank 4 and the center P And a straight line L2 connecting the first straight angle L1 and the straight line L2.

Similarly, in the bottom view, the straight line L1 connecting the most convex point S and the center P of the arc-shaped cutting edge 6a of the minor cutting edge 6 and the minor sub-portion 6 toward the arc-shaped cutting edge 6a. 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 portion 9 at the other end of the second groove 8B opened at the flank 4 of the arc-shaped cutting edge 6a of the sub cutting edge 6 is the second narrow portion 9 The radius r as viewed from the seating surface 3 side of the arc-shaped cutting edge portion 6a of the sub cutting edge 6 located on the other end side of the groove portion 8B is in the range of 0.05 × r to 0.18 × r. . For example, the groove width W1 is in the range of 1 mm to 7 mm. However, in FIG. 3, when the shape seen from the seating surface 3 side of the arc-shaped cutting edge portion 6a is a shape shifted from the arc, the arc closest to the shifted 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 from the seating surface 3 side of the arc-shaped cutting edge (arc-shaped cutting edge 6a of the sub cutting edge 6) located on the other end side of the groove (second groove 8B) having the narrow portion 9 The above flat surface 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 viewed from the bottom or the plan view viewed from the rake face 2 side The length R in the visual or bottom view is in the range of 0.10 × R to 0.32 × R. When the first and second wall surfaces 8a and 8b extend in a straight line in a bottom view as viewed from the direction opposite to the seating surface 3, the groove widths W1 and W2 are the first and second wall surfaces. The width in the direction perpendicular to the bisector of the straight line formed by 8a and 8b.

In the bottom view, a straight line L4 formed by an extension surface of the second groove 8B to the other end side of the second wall 8b corresponds to the auxiliary cutting edge 6 to the arc-shaped cutting edge 6a side of the auxiliary cutting edge 6. The inclination angle α formed with respect to the extension line L3 of the linear cutting edge portion 6b is in the range of 45 ° to 90 °. Similarly, in the bottom view, the inclination angle β between the straight line L5 formed by the extension surface of the first wall surface 8a of the second groove 8B and the linear cutting edge 5b of the main cutting edge 5 is 45 ° to 90 °. The inclination angle γ made by the straight line L4 formed by the extension surface of the second wall 8b of the second groove 8B with respect to the linear cutting edge 5b of the main cutting edge 5 is made smaller than the above-mentioned inclination angle β. ing. In the present embodiment, in the bottom view, the first groove 8A extends in a direction intersecting the straight cutting edge 6b of the minor cutting edge 6 at the first end 2a side, and the second groove 8B Extends in a direction crossing the straight cutting edge 5b of the main cutting edge 5 at an acute angle on the second end 2b side. The groove widths W1 and W2, the first and second crossing angles θ1 and θ2, and the inclination angles α to γ may be applied to the first groove 8A having the same narrow portion 9.

The cutting insert 1 according to the first embodiment is detachably attached to the insert mounting seat 12 formed at the tip of the end mill main body 11 shown in FIGS. 8 to 13 as described above. The first embodiment of the indexable ball end mill of the present invention shown in 19 is configured. The end mill main body 11 is formed of a metal material such as steel material, and the tip end portion thereof is cylindrical with the base end side centered on the axis O, and the tip end side is a base end side having a center on the axis O It has a convex hemispherical shape with a radius equal to that of a cylinder. The indexable ball end mill according to the present embodiment is attached to the insert mounting seat 12 by the end mill body 11 being fed in a direction crossing the axis O while being rotated in the end mill rotation direction T around the axis O. The cutting material is cut by the cutting insert 1.

In the present embodiment, two chip pockets 13 are formed by cutting out the outer periphery of the end portion of the end mill main body 11, and the insert mounting seats 12 are respectively provided on the bottom surfaces of these chip pockets 13 facing the end mill rotational direction T. It is formed in the mutually opposite side at intervals in the circumferential direction. Then, the first and second cutting inserts 1A and 1B of the same shape and size based on the first embodiment are attached to the two insert mounting seats 12, respectively.

These insert mounting seats 12 have a flat bottom surface 12a facing in 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 main body 11, and the tip outer circumference side And a wall surface 12c facing the rear end on the outer peripheral side.
The wall surfaces 12b and 12c are formed in a flat shape that inclines to the outside of the insert mounting seat 12 as they are separated from the bottom surface 12a, and the main cutting edge 5 and the minor cutting edge are in a state where the seating surface 3 of the cutting insert 1 is seated on the bottom surface 12a. It is possible to abut on the flat surface 4a on the side of the seating surface 3 of the flank 4 connected to the linear cutting edge 5b, 6b of the blade 6 and the flank 4 connected to the arc-shaped cutting edge 5a, 6a. .

Between the wall surfaces 12 b and 12 c, a recessed recess 12 d is formed to avoid contact with the curved flank 4 of the cutting insert 1. In the bottom surface 12a, a screw hole 12e is formed in 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 planar shape in which the seating surface 3 of the cutting insert 1 is seated on the bottom surface 12a as described above, and the straight cutting edges 5b and 6b of the main cutting edge 5 and the sub cutting edge 6 are continuous. The center line of the mounting hole 7 of the cutting insert 1 with the flat surface 4a on the seating surface 3 side of the flank 4 being continuous with the flank 4 and the arc-shaped cutting edges 5a and 6a in contact with the wall surfaces 12b and 12c. It is made to be slightly eccentric to the recessed part 12d side rather than.

Of the two insert mounting seats 12, the first insert mounting seat 12A is formed by cutting out the tip end portion of the end mill body 11 to the range including the axis O at the tip end as shown in FIGS. 9 and 10 ing. In the first insert mounting seat 12A, the first cutting insert 1A extends from the vicinity of the axis O of the arc-shaped cutting edge 5a of the main cutting edge 5 and is positioned on a convex hemisphere having a center on the axis O In addition, the linear cutting edge portion 5b of the main cutting edge 5 is mounted on a cylindrical surface centered on the axis O in contact with the convex hemisphere. Therefore, the flat flank 4 connected to the linear cutting edge 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 The flat surface portion 4a of the flank 4 of the arc-shaped cutting edge portion 6a of the sub cutting edge 6 in the first cutting insert 1A is brought into contact.

The first convex portion 14A, to which the first groove 8A formed on the seating surface 3 of the first cutting insert 1A can abut, is formed on the bottom surface 12a of the first insert mounting seat 12A. It projects from the outer peripheral surface of the tip end portion of the end mill main body 11 toward the wall surface 12 c so as to project to the tip side more than 12 e. Furthermore, on the bottom surface 12a of the first insert mounting seat 12A, a second convex portion 14B which can be in contact with the second groove portion 8B protrudes between the screw hole 12e and the wall surface 12c. It is formed 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 reaching the wall surface 12c, while the second convex portion 14B is formed in an isolated island shape spaced apart from the concave portion 12d and not reaching the concave portion 12d. It is 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 rotational direction T. Among these, the first convex portion 14A is one end side from the other end side in a direction in which the first groove portion 8 extends with respect to the first groove portion 8A which is the entire narrow portion 9 (the end mill main body 11 As it goes from the outer peripheral side to the inner peripheral side), the connecting portion with the wall surface 12c is formed to be wider except for being constricted. The second convex portion 14B is the same as the second groove portion 8B which is also the narrow portion 9 as a whole, from the other end side in the direction in which the second groove portion 8B extends. It is formed to be wider as it goes from the peripheral side to the outer peripheral side).

The first and second grooves 8A and 8B extend the width of the first and second protrusions 14A and 14B (the width in the direction orthogonal to the direction in which the first and second protrusions 14A and 14B extend). The width is slightly smaller than the width (the width in the direction orthogonal to the direction in which the first and second groove portions 8A and 8B extend) at the position in contact with the first and second protrusions 14A and 14B in the direction. The protrusion height from the bottom surface 12a of the first and second convex portions 14A and 14B 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.

The second insert mounting seat 12B of the two insert mounting seats 12 is formed at a position slightly away from the axis O at the tip end side of the end mill body 11, as shown in FIGS. 9 and 12. The second cutting insert 1B is inserted into the second insert mounting seat 12B from the position where the arc-shaped cutting edge portion 6a of the sub cutting edge 6 is away from the axis O, of the main cutting edge 5 of the first cutting insert 1A. The linear cutting edge 6b of the auxiliary cutting edge 6 is positioned on the convex hemisphere where the arc-shaped cutting edge 5a is located, and the linear cutting edge 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 located. Therefore, the flat flank 4 connected to the linear cutting edge 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 The flat portion 4a of the flank 4 of the arcuate cutting edge 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 protrusion is formed between the screw hole 12e and the wall surface 12c. The convex portion 14D is formed. The third and fourth convex portions 14C and 14D also extend from the outer peripheral surface of the tip end portion of the end mill body 11 toward the inner peripheral side, and the third convex portion 14C is a wall surface 12b of the second insert mounting seat 12B. The fourth convex portion 14D is formed in front of the concave portion 12d of the second insert mounting seat 12B, and the fourth convex portion 14D is spaced apart from the concave portion 12d. Therefore, the second groove 8B of the second cutting insert 1B abuts on the third convex portion 14C, and the first groove 8A of the second cutting insert 1B abuts on the fourth convex portion 14D.

The third and fourth convex portions 14C and 14D also have a substantially rectangular shape in which the cross section orthogonal to the extending direction of the third and fourth convex portions 14C and 14D is flat in the end mill rotational direction T, Among the third convex portions 14C, the entire second groove 8B of the abutting second cutting insert 1B is the narrow portion 9, while the second groove 8B extends in the direction in which the second groove 8B extends. The fourth groove 14A is formed to be wider as it goes from the other end side to the one end side (from the outer peripheral side of the end mill body 11 to the inner peripheral side) from the other end side. As it goes from the other end side in the extending direction to the one end side (from the inner peripheral side of the end mill main body 11 to the outer peripheral side), it is formed to be wider as a whole.

Furthermore, the widths of these third and fourth convex portions 14C and 14D (the width in the direction orthogonal to the direction in which the third and fourth convex portions 14C and 14D extend) are also the second and first groove portions 8B and 8A. Slightly smaller than the width (the width in the direction orthogonal to the direction in which the second and first groove portions 8B and 8A extend) in the position in which the third and fourth protrusions 14C and 14D abut ing. Further, the protruding 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.

The first and second cutting inserts 1A and 1B are seated on such first and second insert mounting seats 12A and 12B as described above, and a clamp screw having an inverted truncated conical head is provided. When 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 than the center line of the mounting hole 7 of the cutting insert 1, so the cutting insert 1 is pressed to the recess 12 d side.

At this time, in the first insert mounting seat 12A, the plane of the flank 4 connected to the linear cutting edge 6b of the minor cutting edge 6 of the first cutting insert 1A and the plane of the flank 4 connected to the arc-shaped cutting edge 6a. The portion 4a is pressed against the wall surfaces 12b and 12c, respectively. Further, in the second insert mounting seat 12B, the flank 4 continuous with the linear cutting edge 5b of the main cutting edge 5 of the second cutting insert 1B is pressed by the wall surface 12b, and the arc cutting of the main cutting edge 5 is performed. The flat portion 4a of the flank 4 connected to the blade 5a is pressed against the wall surface 12c.

And, along with this, in the first insert mounting seat 12A, the first and second grooves 8A, 8B of the first cutting insert 1A in the first and second convex portions 14A, 14B are the tips of the end mill body 11 Abut from the side. Therefore, the first and second convex portions 14A and 14B are provided with the second and third grooves 8A and 8B of the first cutting insert 1A in the side surface 14a facing the tip end side of the end mill main body 11. The wall surface 8b abuts, and a slight gap is opened 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 similarly provided to the third and fourth convex portions 14C and 14D from the tip end side of the end mill main body 11 Abut. Accordingly, in the third and fourth convex portions 14C and 14D, the first wall surface 8a of the second and first groove portions 8B and 8A abuts on the side surface 14a facing the tip end side of the end mill main body 11, A slight gap 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, when the first and second groove portions 8A and 8B abut on the first to fourth convex portions 14A to 14D, the shift movement of the cutting insert 1 due to the load at the time of cutting can be prevented. .

In the cutting insert 1 and the indexable ball end mill having the above-described structure, the first and second groove portions 8A and 8B of the cutting insert 1 are one end side in the direction in which the first and second groove portions 8A and 8B extend. The narrowing portion 9 having a narrowing of the groove width from the side toward the other end side is provided, and the cutting width of the narrowing portion 9 is reduced. On the other end side of the first and second groove portions 8A and 8B, cutting inserts A large thickness of 1 can be secured to improve the strength. For this reason, even if an excessive load acts on the cutting insert 1 at the time of cutting, it is possible to prevent the cutting insert 1 from being damaged from the first and second groove portions 8A and 8B.

On the other hand, the narrow portion 9 widens conversely at one end side in the direction in which the first and second groove portions 8A and 8B extend, so in the end mill main body 11 of the indexable ball end mill, the first and second The first to fourth convex portions 14A to 14D in the portions where the one end sides of the groove portions 8A and 8B abut can be formed wide. For this reason, the attachment rigidity of the cutting insert 1 with respect to the load at the time of cutting can be improved, the shift movement of the cutting insert 1 can be prevented more reliably, and highly precise cutting can be performed.

Further, 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 arc-shaped cutting edge portions 5a and 6a of the main cutting edge 5 and the sub cutting edge 6, respectively. The groove width W1 at the other narrowest end of the narrow portion 9 is 0. 0 with respect to the radius r of the arcuate cutting edges 5a and 6a as viewed from the seating surface 3 side. Since the range is from 05 × r to 0.18 × r, this also makes it possible to increase the mounting rigidity while surely improving the strength of the cutting insert 1. That is, when the groove width W1 at the other end of the narrow portion 9 is so narrow that it falls below the above range, the width of the first to fourth convex portions 14A to 14D in the insert mounting seat 12 also has to be narrowed While there is a possibility that the mounting rigidity of the insert 1 can not be increased, 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 grooves 8A and 8B When the second wall surfaces 8a and 8b are close to parallel, the other end side of the first and second grooves 8A and 8B secures a large thickness of the cutting insert 1 to ensure the strength of the cutting insert 1 It may not be possible and damage may occur when an excessive load is applied.

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

In FIG. 20, the region on the groove side of the portion drawn white on the seating surface 3 is a range in which stress is concentrated. Then, compared to the result of FIG. 20A in which the groove width is constant and does not have the narrow portion 9, the portions drawn white in FIGS. 20B and 20C 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 concentrated is small. From this result, the stress can be dispersed by providing the narrow portion 9 to ensure the strength of the cutting insert 1, and the groove width W1 is set in 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, and more 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, 0.30 × W2 to 0.85 × It is more preferable that the range be W2, and it is more preferable that the range be 0.32 × W2 to 0.80 × W2. 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, 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 more desirable.

In the cutting insert 1 of the present embodiment, the arc-shaped cutting edge portion 6a of the minor cutting edge 6 has a radius equal to that of the arc-shaped cutting edge portion 5a of the major cutting edge 5, but the circumferential length is shortened. It is done. And in connection with this, also in the blade-tip-exchange-type ball end mill of the present embodiment, the first insert mounting seat 12A is formed so as to cut out the tip end portion of the end mill main body 11 to the range including the axis O at the tip end side. On the other hand, the second insert mounting seat 12B is formed at a position slightly away from the axis O toward the outer periphery. These first and second insert mounting seats 12A and 12B have the same shape and size as the one type two cutting inserts 1, and the first cutting insert 1A uses the arc-shaped cutting edge portion 5a of the main cutting edge 5 as the end mill body 11 The second cutting insert 1B is positioned in the same convex hemisphere so that the second cutting insert 1B extends from a position away from the axis O of the second cutting insert 1B so as to extend from near the axis O of the tip. I am doing it.

For this reason, cutting from the vicinity of the axis O of the tip of the end mill main body 11 to the outer periphery and cutting from a position away from the axis O to the outer periphery can be performed by one kind of cutting insert 1 and management of the cutting insert 1 is easy. And the mold for manufacturing the cutting insert 1 is only one type. Further, in the case where wear or the like occurs in the main cutting edge 5 of the first cutting insert 1A and the sub cutting edge 6 of the second cutting insert 1B due to cutting, these cutting inserts 1 are inserted into the insert mounting seat 12 on the opposite side. 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 to the second one.

Furthermore, in the present embodiment, the second groove 8B having a narrow portion 9 having a wide end at one end and a narrow end at the other end is cut from the side of the arc-shaped cutting edge 6a of the sub cutting edge 6 It extends toward the linear cutting edge 5 b of the blade 5. Among these, the linear cutting blade 5b of the main cutting blade 5 is the one end side, and the arc-shaped cutting blade 6a side of the sub cutting blade 6 is the other end side. It is supposed to be. For this reason, when the sub cutting edge 6 is used for cutting as the second cutting insert 1 B, a flank surface in which the second groove 8 B is continuous with the arc-shaped cutting edge 6 a of the sub cutting edge 6 as in this embodiment. Even if it is opened at 4, the load acting on the sub cutting edge 6 can be received at the other end side of the narrow portion 9 of the second groove portion 8B which has become narrower, and the strength can be secured. It is. The offset movement of the second cutting insert 1B along the arc-shaped cutting edge 5a of the main cutting edge 5 not used for cutting is determined by the narrow portion 9 of the second groove 8B separated from the arc-shaped cutting edge 5a. The wide end can be reliably prevented. The same applies to the case where the cutting insert 1 is used as the first cutting insert 1A.

In this embodiment, after the arc-shaped cutting edge portion 5a of the main cutting edge 5 and the arc-shaped cutting edge portion 6a of the sub cutting edge 6 are separated from the seating surface 3 side as they are separated from the linear cutting edge portions 5b and 6b It is formed in convex curve shape which approaches the seating surface 3 side. Therefore, since the arc-shaped cutting blade portions 5a and 6a bite and cut into the work material from the most convex point S which is most distant and convex with respect to the seating surface 3 at the time of cutting, cutting Resistance can be reduced. At 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 is narrowed, the thickness at the most convex point S can be secured to improve the strength Damage to the cutting insert 1 due to a load during processing can be prevented. The 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 a 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 thickness of the cutting insert 1 is secured by the most convex point S is a region indicated by a symbol U in FIG. 4 and FIG. The value of the insert 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 the range of 0.70 × t to 1.00 × t is More preferably, the range of 0.75 × t to 1.00 × t is more desirable.

In this embodiment, the arc-shaped cutting edges 5a, 6a are thus formed in a convex curve. Although the second groove 8B is opened to the flank 4 continuous with the arc-shaped cutting edge 6a of the sub cutting edge 6 as described above, the opening to the flank 4 of the second groove 8B is It is located closer to the linear cutting edge portion 6 b of the auxiliary cutting edge 6 than the most convex point S of the arc-shaped cutting edge portion 6 a of the auxiliary cutting edge 6. Therefore, it is possible to avoid that the impact when the arc-shaped cutting edge portion 6a of the sub cutting edge 6 bites into the work material from the most convex point S and directly propagates to the opening 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 by such an impact.

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

When the first intersection angle θ1 is smaller than 5 °, the opening of the second groove 8B to the flank 4 is the largest portion of the arcuate cutting edge 6a of the minor cutting edge 6 with which the flank 4 is continuous. There is a possibility that the cutting insert 1 may be damaged due to an impact when the arc-shaped cutting edge portion 6a gets too close to the convex point S and bites into the work material from the most convex point S. Conversely, when the first intersection angle θ1 is larger than 60 °, the clamp screw inserted in the mounting hole 7 of the cutting insert 1 is screwed into the screw hole 12e of the insert mounting seat 12 as in the present embodiment. When 1 is attached, there is a possibility that the second groove 8B and the first and second projections 14A and 14B may interfere with the mounting hole 7 and the screw hole 12e. The first crossing angle θ1 is more preferably in the range of 5 ° to 30 °, and still more preferably in the range of 5 ° to 15 °.

In the present embodiment, similarly in the bottom view, the minor cutting edge 6 is a straight line L1 connecting the most convex point S of the arcuate cutting edge portion 6a of the minor cutting edge 6 and the center P of the arcuate cutting edge portion 6a. The second crossing angle θ2 formed by the extension line L3 of the linear cutting edge 6b of the auxiliary cutting edge 6 toward the arc-shaped cutting edge 6a side is in the range of 10 ° to 50 °. The convex curved arc-shaped cutting edge portion 6a of the minor cutting edge 6 reliably prevents interference between the second groove portion 8B and the first and second convex portions 14A and 14B and the mounting hole 7 and the screw hole 12e. Cutting resistance can be reduced. Also in this case, although illustration is abbreviate | omitted, the same may be said of the circular-arc-shaped cutting blade part 5a of the main cutting blade 5. FIG.

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 faces the seating surface 3 of the second cutting insert 1B or the bottom view or It is substantially parallel to the axis O of the end mill body 11 in a plan view seen from the direction opposite to the rake face 2 along the center line of the mounting hole 7. Therefore, the second intersection angle θ2 is approximately equal to the intersection angle between the axis O and the straight line L1 connecting the center P of the arc-shaped cutting edge 6a located on the axis O and the most convex point S. Become. However, the linear cutting blade portions 5b, 6b may have a slight back taper angle when the cutting insert 1 is attached to the end mill main body 11, and therefore the crossing angle θ2 is exactly the crossing between 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 8B or the first and second convex portions 14A, There is a possibility that the 14 B may interfere with the mounting hole 7 or the screw hole 12 e. If the second intersection angle θ2 is smaller than 10 °, the most convex point S at the arc-shaped cutting edge 6a of the second cutting insert 1B is too close to the axis O, and the rotational speed around the axis O is The arc-shaped cutting edge portion 6a of the sub cutting edge 6 cuts into the work material from a small portion, and the effect of reducing the cutting resistance may be lost. The second crossing angle θ2 is more preferably in the range of 20 ° to 50 °, and still more preferably in the range of 35 ° to 50 °.

Second and Third Embodiments
Next, FIGS. 21 to 25 show a second embodiment of the cutting insert according to the present invention, and FIGS. 26 to 31 show a cutting insert 21 according to the second embodiment and a third embodiment. 32 to 37 show a tip end portion of an end mill main body 41 in a second embodiment of the indexable ball end mill according to the present invention, in which the cutting insert 31 of the present invention is detachably mounted. 3. The tip portion of the second embodiment of the indexable ball end mill according to 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 an indicator of In the embodiment shown in FIGS. 21 to 37, the same reference numerals are assigned to the elements common to the embodiments shown in FIGS. 1 to 19, and the description will be omitted, and the groove widths W1, W2, the first, the The second crossing angles θ1 and θ2, the inclination angles α to γ, and the like are also common, and therefore the illustration is omitted.

The cutting insert 1 according to the first embodiment includes the arc-shaped cutting edges 5a and 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 rotationally symmetrical shape 180 ° 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 is the same as the main cutting edge 5 of the cutting insert 1 of the first embodiment, and an arc-shaped cutting edge portion 5a having a substantially 1⁄4 arc shape and a linear cutting edge in contact therewith. The portions 5 b are alternately provided in the circumferential direction of the rake face 2. The cutting insert 31 according to the third embodiment is the same as the minor cutting edge 6 of the cutting insert 1 according to the first embodiment, and an arc-shaped cutting edge portion 6a having a circumferential length shorter than 1⁄4 arc shape and a linear shape contacting this. Two cutting edges 6 b are alternately provided in the circumferential direction of the rake face 2. The radii of the arc-shaped cutting edge portion 5a in the main cutting edge 5 of the second embodiment and the arc-shaped cutting edge portion 6a in the sub cutting edge 6 of the third embodiment are equal to each other.

Therefore, the linear cutting edges 5b of the two main cutting edges 5 of the cutting insert 21 of the second embodiment and the linear cutting edges of the two minor cutting edges 6 of the cutting insert 31 of the third embodiment. 6b are parallel to each other. Further, the distance between the linear cutting edges 5b of the two main cutting edges 5 of the cutting insert 21 of the second embodiment is the linear cutting of the two minor cutting edges 6 of the cutting insert 31 of the third embodiment. It is larger than the interval of blade parts 6b.

Also in the cutting inserts 21 and 31 according to the second and third embodiments, the seating surface 3 is provided with projections projecting from the bottom surface 12a of the third and fourth insert mounting seats 12C and 12D of the end mill body 41. Two groove parts 8 having a wall surface which can be abutted are the other cutting blades from the linear cutting blade parts 5b and 6b side of one cutting blade with each other by the above-mentioned two cutting blades (main cutting blade 5 and sub cutting blade 6) It is formed to extend to the side of the arc-shaped cutting edge 5a, 6a. Each of the two groove portions 8 has a narrow portion 9 in which the groove width is narrowed from one end side to the other end side in the direction in which the groove portion 8 extends. Also in the second and third embodiments, the narrow-width portion 9 has one end side with the linear cutting edge portions 5b and 6b, and the other end side with the arc-shaped cutting edge portions 5a and 6a.

Also in the second and third embodiments, the groove 8 is opened to the flank 4 where the other end is connected to the arc-shaped cutting edges 5a and 6a as in the first embodiment, and one end is also cut straight It is open to the flank 4 connected to the blade portions 5b and 6b. In these second and third embodiments, as shown in FIG. 21 and FIG. 25, the two cutting edges (main cutting edge 5 and sub cutting edge 6) are generally on the arc-shaped cutting edge portions 5a and 6a side. From this, as it goes to the linear cutting blade parts 5b and 6b side, after separating from the seating surface 3 side, it is formed in convex curve shape which approaches the seating surface 3 side. The opening of the groove 8 to the flank 4 connected to the arc-shaped cutting edges 5a and 6a is arc-shaped 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 cutting blade 5a, 6a side.

Specifically, as shown in FIG. 23 in a bottom view seen from the direction opposite to 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 Third line formed by straight line L6 connecting center P1 of cutting edge 5a and straight line L7 connecting contact point V of arc-shaped cutting edge 5a of main cutting edge 5 and straight cutting edge 5b and center P1 It is desirable that the intersection angle θ3 of the angle .theta.3 be in the range of 40.degree. 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 arc-shaped cutting edge portion 5a of the main cutting edge 5 is extended from the vicinity of the axis O at the end portion of the end mill main body 41 and positioned on a convex hemisphere centered on the axis O At the same time, the linear cutting blade portion 5b of the main cutting blade 5 is mounted on the third insert mounting seat 12C so as to be positioned on a cylindrical surface centered on the axis O contacting the convex hemisphere. The cutting insert 31 of the third embodiment is an arc-shaped cutting edge of the main cutting edge 5 of the cutting insert 21 of the second embodiment from a position at which the arc-shaped cutting edge portion 6a of the sub 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 attached to the fourth insert mounting seat 12D so as to be located on the cylindrical surface.

First to fourth convex portions 14A to 14D are formed on the bottom surface 12a of the third and fourth insert mounting seats 12C and 12D. The groove portion 8 having the narrow 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 the first to fourth convex portions 14A to 14D. It is attached. The first convex portion 14A on the tip end side of the third insert mounting seat 12C of the end mill main body 41 in the indexable ball end mill of the second embodiment is different from the first embodiment in the peninsular shape, The second to fourth convex portions 14B to 14D are formed in the same manner as the second to fourth convex portions 14B to 14D.

Also in such cutting inserts 21 and 31 of the second and third embodiments and the indexable ball end mill of the second embodiment, the groove 8 having the narrow portion 9 on the seating surface 3 of the cutting inserts 21 and 31. Is formed. The groove 8 is capable of coming into contact with the protrusions 14A to 14D formed on the insert mounting seats 12C and 12D, and therefore, cutting is performed in the same manner as the cutting insert 1 and the indexable ball end mill of the first embodiment. The strength of the inserts 21 and 31 can be improved to prevent damage, and the shift movement of the cutting inserts 21 and 31 at the time of cutting can be prevented to perform 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 from the arc-shaped cutting edge portions 5a and 6a side toward the linear cutting edge portions 5b and 6b side Since it is formed in the shape of a convex curve approaching the seating surface 3 side after leaving the surface 3 side, the main cutting edge 5 and the sub cutting edge 6 can be made to bite from the most convex point S to the work material gradually As a result, cutting resistance can be reduced, and improvement in cutting edge strength due to thickening can be promoted.

Moreover, in the cutting inserts 21 and 31 according to the second and third embodiments, the other end of the groove 8 is opened to the flank 4 connected to the arc-shaped cutting edges 5a and 6a. Because the main cutting edge 5 and the sub cutting edge 6 are positioned closer to the arc-shaped cutting edge portions 5a and 6a 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, In the same manner as in the above embodiment, it is possible to avoid that the impact when the most convex point S bites is propagated directly to the opening of the groove 8 in the direction of the insert center line X, and such an impact from the opening of the groove 8 Damage to the cutting inserts 21 and 31 can also be prevented.

As described above, when the other end of the groove 8 is opened to the arc-shaped cutting edge 5a, 6a or one end of the groove 8 is also linear as in the cutting inserts 21 and 31 of the second and third embodiments. In the case of opening on the flank 4 connected to the cutting edges 5b and 6b, the above-mentioned most convex point S of the main cutting edge 5 and the sub cutting edge 6 in a bottom view seen from the direction facing the seating surface 3 A straight line L6 connecting the center P1 of the arc-shaped cutting edges 5a and 6a, and a contact point V of the arc-shaped cutting edges 5a and 6a of the main cutting edge 5 and the sub cutting edge 6 and the straight cutting edges 5b and 6b If the third intersection angle θ3 formed by the straight line L7 connecting the arc-shaped 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, this results in the inability to reliably prevent damage to the cutting inserts 21, 31. 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 still more preferably in the range of 35 ° or less.

In addition, the cutting inserts 21 and 31 of the second and third embodiments are formed to have a rotational symmetry of 180 ° 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. It is done. For this reason, wear and the like occur on the main cutting edge 5 and the sub cutting edge 6 of the cutting inserts 21 and 31 used for cutting in the state of being attached to the third and fourth insert mounting seats 12C and 12D, respectively. Once the life is reached, the cutting inserts 21 and 31 are once removed, rotated 180 ° around the insert center line X, and re-attached to the third and fourth insert mounting seats 12C and 12D, thereby achieving the first embodiment and the first embodiment. Similarly, two use is possible with one cutting insert 21, 31 respectively.

According to the present invention, by the narrow part of the groove formed on the seating surface of the cutting insert, the thickness of the cutting insert is secured on the other end side where the groove width becomes narrow, stress is dispersed, and strength is improved. It is possible to prevent damage to the cutting insert due to the load during cutting. Since the groove width of the narrow portion becomes wide on one end side of the groove portion, the convex portion of the indexable ball end mill can be formed wide, and the mounting rigidity of the cutting insert can be enhanced to surely prevent the shift movement. It becomes possible.

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

Claims (12)

1. A cutting insert detachably mounted on an insert mounting seat formed on a tip of an end mill body of an indexable ball end mill rotated about an axis, comprising:
   A rake face directed in the rotational direction of the end mill body, a seating face opposite to 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 Equipped with
   An arc-shaped cutting edge extending in an arc shape and a arc-shaped cutting edge extending in contact with the arc-shaped cutting edge in a plan view seen from the direction opposite to the rake surface The two cutting edges respectively provided with the linear cutting edge portion are formed by alternately positioning the arc-shaped cutting edge portion and the linear cutting edge portion in the circumferential direction of the rake face,
   In the seating surface, two groove portions having wall surfaces capable of coming into contact with the convex portions protruding from the bottom surface of the insert mounting seat are the other from the linear cutting edge side of one cutting edge with the other two cutting edges. It is formed to extend to the arc-shaped cutting edge side of the cutting edge of the
   A cutting insert characterized in that each of the two groove portions 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.
2. Each of the two groove portions is characterized in that the linear cutting edge side of the one cutting edge is the one end side, and the arc-shaped cutting edge side of the other cutting edge is the other end side. The cutting insert according to claim 1.
3. Of the two cutting edges, one is the main cutting edge and the other is the secondary cutting edge,
   The circumferential length of the arc-shaped cutting edge portion of the sub cutting edge is equal to the radius of the arc-shaped cutting edge portion of the main cutting edge, and the circumferential length is formed short. Cutting inserts.
4. Among the two groove portions, the groove portion having the arc cutting edge side of the sub cutting edge as the other end side is opened to the flank surface connected to the arc cutting edge portion of the sub cutting edge,
   The arc-shaped cutting edge portion of the sub cutting edge is formed in a convex curve shape which approaches the seating surface side after being separated from the seating surface side as being away from the linear cutting edge portion of the sub cutting edge,
   The opening of the groove to the flank surface connected to the arc-shaped cutting edge of the sub cutting edge is greater than the most convex point at which the arc-shaped cutting edge 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 linear cutting edge side of the sub cutting edge.
5. In a bottom view seen from the direction opposite to the seating surface,
   A straight line connecting the most convex point and the center of the arc-shaped cutting edge of the sub cutting edge;
   The groove which opens in the flank surface connected to the arc-shaped cutting edge part of the sub cutting edge toward the seating surface side of the crossing ridge line part of the wall surface facing the linear cutting edge side of the sub cutting edge and the flank surface The first crossing angle formed by the end and a straight line connecting the center of the arc-shaped cutting edge of the sub cutting edge is in the range of 5 ° to 60 °. Cutting insert as described.
6. In a bottom view seen from the direction opposite to the seating surface,
   A straight line connecting the most convex point and the center of the arc-shaped cutting edge of the sub cutting edge;
   The second crossing angle formed by the extension line of the linear cutting edge of the auxiliary cutting edge toward the arc-shaped cutting edge of the auxiliary cutting edge is in the range of 10 ° to 50 °. The cutting insert according to claim 4 or claim 5.
7. It is formed in a 180 ° rotational symmetry shape in the circumferential direction of the rake surface with respect to an insert center line connecting the center of the rake surface and the center of the seating surface. Cutting insert.
8. The other end of the groove portion is open to the flank surface connected to the arcuate cutting edge portion, and
   The cutting blade is formed in a convex curve shape which approaches the seating surface side after being separated from the seating surface side as it goes from the arc-shaped cutting blade side to the linear cutting blade side.
   The opening of the groove to the flank connected to the arc-shaped cutting edge part is the arc-shaped cutting edge side of the cutting edge than the most convex point where the cutting edge is most convex with respect to the seating surface A cutting insert according to claim 7, characterized in that it is located at.
9. In a bottom view seen from the direction opposite to the seating surface,
   A straight line connecting the most convex point of the cutting edge and the center of the arc-shaped cutting edge of the cutting edge;
   The third intersection angle formed by the contact point between the arc-shaped cutting edge portion of the cutting edge and the linear cutting edge portion and the straight line connecting the center of the arc-shaped cutting edge portion is in the range of 40 ° or less The cutting insert according to claim 8, characterized in that:
10. 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 arc-shaped cutting edge portion of the cutting blade as viewed from the direction facing the seating surface. The cutting insert according to any one of claims 3 to 9, wherein x is in the range of r.
11. The cutting insert according to any one of claims 1 to 10 protrudes from a bottom surface of the insert mounting seat to an insert mounting seat formed at a tip end portion of an end mill main body rotated about an axis. A blade-tip-replaceable ball end mill characterized in that the wall surface of the groove is brought into contact with a convex portion to be detachably attached.
12. The convex portion is formed in a portion where the narrow portion of the groove abuts, and the convex portion is formed to be wider from the other end side in the extending direction of the groove toward the one end side An indexable ball end mill according to Item 11.

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