JP2021062477A - Cutting insert - Google Patents

Abstract

To provide a cutting insert, which can prevent slip motion during cutting work, without impairing strength thereof.SOLUTION: A cutting insert 1 comprises a rake face, a seating face 3 and flank faces 4. Two cutting blades 5 and 6 provided with arc-like cutting edges 5a and 6a and linear cutting edges 5b and 6b are formed at cross ridge-line parts between the rake face and the flank faces 4. On the seating face 3 are formed two groove parts 8 having wall surfaces 8a and 8b that can contact a protruding part on a bottom surface of an insert mounting seat so that the groove parts respectively extend from the respective linear cutting edges 5b and 6b sides of one of the cutting blades 5 and 6 toward the respective arc-like cutting edges 6a and 5a sides of the other one of the cutting blades 6 and 5, between the two cutting blades 5 and 6. The two groove parts 8 gradually reduce in groove widths from the linear cutting edges 5b and 6b sides of the cutting blades 5 and 6 toward the arc-like cutting edges 5a and 6a sides of the cutting blades 5 and 6.SELECTED DRAWING: Figure 3

Description

The present invention relates to a cutting insert that can be detachably attached to an insert mounting seat formed at the tip of an end mill body of a ball end mill with a replaceable cutting edge.

In a cutting insert used for such a blade tip exchange type ball end mill, if two arc-shaped cutting edge portions are formed on opposite sides in the circumferential direction of the rake face, they are connected to these arc-shaped cutting edge portions and escape. Since the side surface of the cutting insert, which is the surface, is convexly curved, the flank of the flank that connects to the arc-shaped cutting edge on the opposite side to the arc-shaped cutting edge used for cutting due to the cutting load during cutting. The cutting insert is easily displaced along the line. Therefore, for example, in Patent Documents 1 and 2, a convex portion protruding from the bottom surface of the insert mounting seat is formed, and a groove portion having a wall surface capable of contacting the convex portion is formed on the seating surface of the cutting insert. It is described that this prevents such a misaligned movement of the cutting insert.

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

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

By the way, in the cutting inserts described in the drawings of Patent Documents 1 and 2, it is shown that the two opposing wall surfaces of the groove portion extend in parallel with each other, but in this case, the wall surfaces of the groove portions extend in parallel. In addition, if the width of the convex portion is increased in order to increase the rigidity of the convex portion of the end mill body and secure the strength against the displacement movement of the cutting insert, the width of the groove portion of the cutting insert is also increased, and the strength of the cutting insert is reduced. Invited, there is a risk that damage will easily occur due to the load during cutting. 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 portion of the end mill body must also be reduced, and the mounting rigidity of the cutting insert cannot be secured. There is a risk that it will not be possible to reliably prevent the shifting movement of the cutting insert due to the above.

The present invention has been made under such a background, and an object of the present invention is to provide a cutting insert capable of reliably preventing displacement during cutting without impairing the strength of the cutting insert. There is.

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 the insert mounting seat formed at the tip of the end mill body of the blade tip exchange type ball end mill rotated around the axis. A cutting insert that can be mounted, a rake surface that is oriented in the direction of rotation of the end mill body, a seating surface that faces the opposite side of the rake surface and is seated on the bottom surface of the insert mounting seat, and these rakes. A flank extending around the surface and the seating surface is provided, and an arcuate cutting extending in an arc shape in a plan view from a direction facing the rake plane is provided at the intersection ridge of the rake face and the flank. Two cutting blades each provided with a blade portion and a linear cutting edge portion extending so as to be in contact with the arcuate cutting edge portion are provided with the arcuate cutting edge portion and the linear cutting edge portion in the circumferential direction of the rake face. On the seating surface, two grooves having a wall surface that can come into contact with a convex portion protruding from the bottom surface of the insert mounting seat are formed on the seating surface alternately with the two cutting blades. It is formed so as to extend from the linear cutting edge side of the cutting edge to the arcuate cutting edge portion side of the other cutting edge, and the two grooves are cut from the linear cutting edge portion side of the cutting edge. The groove width becomes narrower along the arcuate cutting edge side of the blade.

Further, in the ball end mill with a replaceable cutting edge of the present invention, such a cutting insert has a convex portion protruding from the bottom surface of the insert mounting seat on an insert mounting seat formed at the tip of the end mill body rotated around the axis. The wall surface of the groove is brought into contact with the surface and is detachably attached.

The groove portion of the cutting insert related to the cutting insert having such a configuration has a narrow portion in which the groove width becomes narrower from one end side to the other end side in the extending direction of the groove portion. On the other end side where the groove width becomes narrow, the wall 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 one end side of the narrow portion, in the blade tip exchange type ball end mill, the convex portion is in contact with the narrow portion of the groove portion, and the groove portion extends in the direction of extension. By forming the width from the other end side toward the one end side, it is possible to increase the mounting rigidity with respect to the load during cutting and reliably prevent the cutting insert from shifting.

In such a cutting insert, the arcuate cutting edge portion of the cutting edge is exclusively used for cutting. For each of the two grooves, the linear cutting edge side of the one cutting edge is the one end side, and the arcuate cutting edge side of the other cutting edge is the other end side. When the other cutting edge is used for cutting, the strength of the cutting insert should be ensured on the other end side where the width of the narrow portion is narrowed against the cutting load acting on the arcuate cutting edge portion. At the same time, the displacement movement of the cutting insert along the arc-shaped cutting edge of the cutting edge that is not used for cutting is surely made on one end side of the wide narrow portion away 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 blades is a main cutting blade and the other is a secondary cutting blade. The arcuate cutting edge portion of the secondary cutting edge is formed with a radius equal to that of the arcuate cutting edge portion of the main cutting edge and a shorter peripheral length, as described in Patent Document 2. It has an asymmetrical shape. With these two cutting inserts of the same shape and size, it is possible to perform cutting from the vicinity of the axis of the tip of the end mill body to the outer circumference 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 outer circumference to the outer periphery by the arcuate cutting edge portion of the secondary cutting edge, which facilitates the management of the cutting insert and is economical.

Therefore, in this case, of the two groove portions, the groove portion whose other end side is the arcuate cutting edge portion side of the secondary cutting edge is the flank that is connected to the arcuate cutting edge portion of the secondary cutting edge. It may be open.
If the arcuate cutting edge portion of the secondary cutting edge is formed in a convex curve shape that approaches the seating surface side after moving away from the seating surface side as it separates from the linear cutting edge portion of the secondary cutting edge. Since the arcuate cutting edge portion of the secondary cutting edge gradually cuts into the work material from the most convex point that is most convex with respect to the seating surface, cutting resistance can be reduced.

That is, in a cutting insert used in a ball end mill with a replaceable cutting edge, a large cutting load is applied to the tip of the arcuate cutting edge portion, the flank connected to the tip portion, and the side surface of the insert body during cutting. Therefore, it is desired to reduce the cutting load and to have a cutting edge shape in consideration of chip evacuation. 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 processing is selected as the cutting method, it is desirable to set the cutting edge tip side where the chip thickness becomes thin as the area where the cutting edge bites the work material. By forming the arc-shaped cutting edge portion in a convex curved shape as described above, the cutting edge has a twisted shape, and the impact acting on the cutting edge can be reduced, so that the cutting edge shape becomes more preferable.

On the other hand, when scanning line machining is selected as the cutting method, when cutting in the axial direction of the end mill body, the cutting edge becomes thicker and 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 strength of the cutting edge can be improved by forming the arcuate cutting edge portion into a convex curve shape and providing the most convex point to increase the wall thickness.

When the groove portion opens on the flank that is connected to the arcuate cutting edge portion of the secondary cutting edge and the arcuate cutting edge portion of the secondary cutting edge is formed in a convex curved shape, the arcuate cutting of the secondary cutting edge is performed. The opening of the groove portion to the flank that is connected to the blade portion is a linear cutting of the secondary cutting edge rather than the most convex point at which the arcuate cutting edge portion of the secondary cutting edge is most convex with respect to the seating surface. Located on the blade side. As a result, 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 secondary cutting edge bites the work material from the most convex point and cuts.

Specifically, in the bottom view viewed 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 auxiliary cutting edge and the arcuate cutting of the auxiliary cutting edge. The end of the crossing ridge of the groove portion that faces the linear cutting edge side of the secondary cutting edge and the flank that opens to the flank surface connected to the blade portion, and the sub-cutting edge It is desirable that the first intersection angle formed by the straight line connecting the center of the arcuate cutting edge portion is in the range of 5 ° to 60 °.

If the first crossing angle is so small that it is less than 5 °, the opening of the groove to the flank that connects to the arcuate cutting edge of the secondary cutting edge is too close to the most convex point, and the arcuate cutting edge of the secondary cutting edge. The cutting insert may be damaged when the part bites. On the other hand, if the first intersection angle is large enough to exceed 60 °, when the cutting insert is attached by inserting a clamp screw into the mounting hole formed in the cutting insert and screwing it into the screw hole of the insert mounting seat. Grooves and protrusions may interfere with mounting holes and screw holes.

Further, as described above, when the groove portion opens on the flank surface connected to the arcuate cutting edge portion of the secondary cutting edge and the arcuate cutting edge portion of the secondary cutting edge is formed in a convex curved shape, the seating is performed. 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 to the arcuate cutting edge portion side of the sub cutting edge in the bottom view viewed from the direction facing the surface. It is desirable that the second intersection angle formed by the extension line of the linear cutting edge portion of the cutting edge is in the range of 10 ° to 50 °.

If this second crossing angle is small enough to be less than 10 °, the most convex point will be too close to the axis of the end mill body when the secondary cutting edge is used for cutting, and the secondary will start from the part where the rotation speed around the axis is small. The arcuate cutting edge portion of the cutting edge cuts into the work material, which may impair the effect of reducing cutting resistance. On the other hand, when the second intersection angle is large enough to exceed 50 °, the straight line of the secondary cutting edge is more straight than the most convex point on the flank that connects the opening of the groove to the arcuate cutting edge portion of the secondary cutting edge as described above. When trying to position it on the side of the cutting edge, there is a possibility that the groove or convex portion may interfere with the mounting hole of the cutting insert or the screw hole of the insert mounting seat.

Secondly, the cutting insert of the present invention does not have an asymmetrical shape as described above, and is an insert connecting the center of the rake face and the center of the seating surface, as in the case of the cutting insert described in Patent Document 1, for example. It may be formed in a 180 ° rotationally symmetric shape in the circumferential direction of the rake face with respect to the center line.

In this second case, for example, a cutting insert having two main cutting edges having an arcuate cutting edge portion having a circumference of 1/4 arcuate shape and a cutting insert having the same radius and a short circumference. A cutting insert having two secondary cutting blades equipped with an arc-shaped cutting blade is prepared, and cutting is performed from the vicinity of the axis of the tip of the end mill body to the outer periphery by the arc-shaped cutting edge of the main cutting blade, and from this axis. Cutting from a distant position to the outer circumference can be performed by the arcuate cutting edge portion of the secondary cutting edge.

Even in this second case, the other end of the groove portion may be opened to the flank surface connected to the arcuate cutting edge portion. Further, the cutting edge may be formed in a convex curve shape that approaches the seating surface side after moving away from the seating surface side toward the linear cutting edge portion side from the arcuate cutting edge portion side. However, in this second case, the opening of the groove portion to the flank that is connected to the arcuate cutting edge portion is more than the most convex point at which 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 side.

Specifically, in the bottom view viewed 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 of the cutting edge. It is desirable that the third intersection angle formed by the contact point between the arcuate cutting edge portion and the linear cutting edge portion and the straight line connecting the center of the arcuate cutting edge portion is in the range of 40 ° or less. When the third crossing angle becomes larger than this range, the opening of the groove to the flank that is 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 first case described above, the radii of the arcuate cutting edge portions of the two cutting edges formed in one cutting insert are 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 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, which is the narrowest in the narrow portion, is narrow enough to be less 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 wide enough to exceed the above range and the wall surfaces of the grooves are close to parallel to each other, the wall thickness is secured on 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, the narrow portion of the groove formed on the seating surface of the cutting insert ensures the wall thickness of the cutting insert and disperses the stress on the other end side where the groove width becomes narrow. 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 portion is widened on the one end side, the convex portion of the ball end mill with a replaceable cutting edge can be formed wide, and the mounting rigidity of the cutting insert is increased to surely prevent the displacement movement. It becomes possible.

It is a perspective view which shows the 1st Embodiment of the cutting insert of this invention. It is a plan view of the embodiment shown in FIG. It is a bottom view of the embodiment shown in FIG. It is a side view of the arrow line A direction view in FIGS. 2 and 3. It is a side view of the arrow line B direction view in FIGS. 2 and 3. It is a side view of the arrow C direction view in FIGS. 2 and 3. It is a side view of the arrow line D direction view in FIGS. 2 and 3. It is a perspective view which shows the 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 detachably attached. It is a front view of the tip end part of the end mill main body shown in FIG. 9 is a plan view of the arrow line A in FIG. 9. It is a side view of the arrow line B direction view in FIG. It is a bottom view of the arrow C direction view in FIG. It is a side view of the arrow line D direction view in FIG. It is a perspective view which shows the tip part of the 1st Embodiment of the cutting edge exchange type ball end mill of this invention. It is a front view of the embodiment shown in FIG. FIG. 15 is a plan view of the arrow line A in FIG. It is a side view of the arrow line B direction view in FIG. It is a bottom view of the arrow C direction view in FIG. It is a side view of the arrow line D direction view in FIG. It is a figure which shows the stress dispersion state by the simulation analysis when the groove width of the other end of the narrow portion in a groove part is changed, and is the case where the groove width is constant. It is a figure which shows the stress dispersion state by the simulation analysis when the groove width of the other end of the narrow part in a groove part is changed, and has a narrow part, and is a narrow part with respect to the radius r of an arcuate cutting edge part. The groove width at the other end of the is 0.133 × r. It is a figure which shows the stress dispersion state by the simulation analysis when the groove width of the other end of the narrow part in a groove part is changed, and has a narrow part, and is a narrow part with respect to the radius r of an arcuate cutting edge part. The groove width at the other end of the is 0.067 × r. It is a perspective view which shows the 2nd Embodiment of the cutting insert of this invention. FIG. 21 is a plan view of the embodiment shown in FIG. It is a bottom view of the embodiment shown in FIG. It is a side view of the arrow line A direction view in FIGS. 22 and 23. It is a side view of the arrow line B direction view in FIGS. 22 and 23. It is a perspective view which shows the 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 detachably attached. It is a front view of the tip end part of the end mill main body shown in FIG. FIG. 27 is a plan view of the arrow line A in FIG. 27. It is a side view of the arrow line B direction view in FIG. 27. It is a bottom view of the arrow C direction view in FIG. 27. It is a side view of the arrow line D direction view in FIG. 27. It is a perspective view which shows the tip part of the 2nd Embodiment of the cutting edge exchange type ball end mill of this invention. It is a front view of the embodiment shown in FIG. 32. It is a plan view of the arrow line A direction view in FIG. 33. It is a side view of the arrow line B direction view in FIG. 33. It is a bottom view of the arrow C direction view in FIG. 33. It is a side view of the arrow line D direction view in FIG. 33.

<< First Embodiment >>
1 to 7 show the cutting insert 1 of the first embodiment of the present invention. 8 to 13 show the tip of the end mill main body 11 in the first embodiment of the ball end mill having a replaceable cutting edge of the present invention to which the cutting insert 1 of the first embodiment is detachably attached. 14 to 19 show the first embodiment of the ball end mill having a replaceable cutting edge 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 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 a plan view as shown in FIG. The upper surface of the cutting insert 1 is the leaf-shaped rake face 2 as described above. The lower surface facing the opposite side of the rake face 2 is a leaf-shaped surface having a shape substantially similar to that of the rake face 2, and is a flat seating surface 3 that sits on the bottom surface of the insert mounting seat. The side surface extending around between the rake surface 2 and the seating surface 3 is the flank surface 4.

At the intersecting ridge line portion between the rake face 2 and the flank face 4, arcuate cutting edge portions 5a and 6a extending in an arc shape as shown in FIG. 2 in a plan view from the direction facing the rake face 2 and this circle. Two cutting blades having linear cutting edge portions 5b and 6b extending so as to be in contact with the arc-shaped cutting edge portions 5a and 6a form the arc-shaped cutting edge portions 5a and 6a and the linear cutting edge portions 5b and 6b, respectively. The rake face 2 is formed so as to be alternately positioned in the circumferential direction. One of these two cutting blades is the main cutting blade 5, and the other cutting blade is the secondary cutting blade 6.

Further, the flank surface 4 is inclined so as to be directed toward the inner peripheral side of the cutting insert 1 from the rake surface 2 toward the seating surface 3, 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 in the central portion of the rake face 2 and the seating surface 3, and the rake face 2 side of the mounting hole 7 is the seating surface. The diameter is reduced toward the 3rd side.

In the plan view, the arcuate cutting edge portion 5a of the main cutting edge 5 has a substantially 1/4 arc shape, whereas the arcuate cutting edge portion 6a of the sub cutting edge 6 has a circular shape of the main cutting edge 5. The radius is equal to that of the arcuate cutting edge portion 5a, but the peripheral length is shorter than that of the arcuate cutting edge portion 5a of the main cutting edge 5. That is, the arc-shaped cutting edge portion 6a is formed in an arc shape shorter than the 1/4 arc. Along with this, the linear cutting edge portion 5b of the main cutting edge 5 is conversely shorter than the linear cutting edge portion 6b of the sub cutting edge 6. That is, as shown in FIGS. 2 and 3, the cutting insert 1 of the present embodiment is not 180 ° rotationally symmetric with respect to the insert center line X, which is the center line of the mounting hole 7, but is asymmetric. ..

In the plan view, the linear cutting edge portions 5b and 6b of the main cutting edge 5 and the sub cutting edge 6 are formed by 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. 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 secondary cutting edge 6 intersect from the first end 2a of the intersecting rake face 2 It extends closer to each other as it goes toward. Further, these first and second end portions 2a and 2b are chamfered so as to 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 at an obtuse angle. 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 and 6a of the main cutting edge 5 and the sub cutting edge 6 move away from the seating surface 3 side and then approach the seating surface 3 side as they move away from the linear cutting edge portions 5b and 6b, respectively. It is formed in a convex curve shape, and the point where the convex curve formed by the arcuate cutting edge portion 6a of the secondary cutting edge 6 is the most distant and convex with respect to the seating surface 3 is the arcuate shape of the secondary 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 secondary cutting edge 6 have an arcuate cutting edge portion 5a as shown in FIGS. 4 and 6 even when viewed from the side facing the flank surface 4. , 6a is in contact with the convex curve, and extends in a substantially straight line approaching the seating surface 3 side as the distance from the arcuate cutting edge portions 5a and 6a increases.

Around the opening of the mounting hole 7 in the central portion of the rake face 2, a protrusion having a substantially elliptical shape in a plan view is projected in a direction away from the seating surface 3 than the main cutting blade 5 and the sub cutting blade 6. 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 surface 3 side toward the inside of the rake face 2 away from the main cutting blade 5 and the secondary cutting blade 6, and then forms a concave curved surface on the outer peripheral surface of the protrusion 2c. It is in a row.

The flanks 4 connected to the linear cutting edge portions 5b and 6b of the main cutting edge 5 and the sub cutting edge 6 are formed in an inclined flat shape as described above. On the other hand, the flanks 4 connected to the arcuate cutting edge portions 5a and 6a of the main cutting edge 5 and the sub cutting edge 6 are in the circumferential direction of the cutting insert 1 along the arcuate cutting edge portions 5a and 6a on the rake face 2 side. However, the seating surface 3 side has a flat surface portion 4a which is notched in a plane shape while being inclined 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, the first and second groove portions 8A and 8B are the mounting holes 7 on the seating surface 3 in the bottom view viewed from the direction perpendicularly facing the seating surface 3. It is formed on opposite sides of each other with the opening at a distance from the opening. The first groove 8A is formed on the first end 2a side of the rake face 2 with respect to the opening of the mounting hole 7, and the second groove 8B is formed on the second end 2b side of the rake face 2. Has been done.

These groove portions 8 are formed in a substantially rectangular shape in which the cross section orthogonal to the direction in which the groove portion 8 extends is flattened in the insert center line X direction in which the mounting hole 7 extends. That is, the groove portion 8 extends between the first and second wall surfaces 8a and 8b extending in a direction substantially perpendicular to the seating surface 3 and facing each other and the first and second wall surfaces 8a and 8b. It has a bottom surface 8c parallel to the surface 3. The first wall surface 8a of each groove 8 faces the first end 2a side of the rake face 2, and the second wall surface 8b faces the second end 2b side of the rake face 2. The intersecting ridges of the first and second wall surfaces 8a and 8b and the seating surface 3 are chamfered by a convex curved surface, and the corners where the first and second wall surfaces 8a and 8b and the bottom surface 8c intersect are concave curved surfaces. Is formed in.

The first and second groove portions 8A and 8B have a narrow portion 9 in which the groove width becomes narrower from one end side to the other end side in the direction in which the first and second groove portions 8A and 8B extend, respectively. ing. In the present embodiment, the flank 4 side connected to the linear cutting edge portions 6b and 5b of the secondary cutting edge 6 and the main cutting edge 5 is set as one end side of the first and second groove portions 8A and 8B, and the main cutting edge is formed. The flank 4 side connected to the arcuate cutting edge portions 5a and 6a of the sub cutting edge 5 and 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 have the narrow portion 9 as a whole.

In the narrow portion 9, in the present embodiment, the ratio of narrowing the groove width 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 form a straight line from one end side to the other end side and approach each other in the bottom view. Is formed in. In the present embodiment, the first and second groove portions 8A and 8B have a relief surface 4 connected to the linear cutting edge portions 6b and 5b of the auxiliary cutting edge 6 and the main cutting edge 5, the main cutting edge 5 and the auxiliary cutting edge 6. It is formed in the shape of a through groove that opens on both sides of the flank 4 connected to 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 portion 6a of the auxiliary cutting edge 6 is formed by the arcuate cutting edge portion 6a of the auxiliary cutting edge 6 having a convex curved shape in a side view. It is located on the linear cutting edge portion 6b side of the secondary 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, a straight line L1 connecting the most convex point S and the center P of the arc formed by the arc-shaped cutting edge portion 6a of the secondary cutting edge 6 and the secondary cutting edge 6 The end Q and the center P of the intersecting ridge line portion (excluding the chamfered portion) between the first wall surface 8a and the flank surface 4 of the second groove portion 8B facing the linear cutting edge portion 6b side of the above to the seating surface 3 side. The first intersection angle θ1 formed by the straight line L2 connecting the two 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 sub to the arcuate cutting edge portion 6a side of the sub cutting edge 6 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 portion 8B that opens to the escape surface 4 of the arcuate cutting edge portion 6a of the secondary cutting edge 6 is the narrow portion 9 second. The radius is in the range of 0.05 × r to 0.18 × r with respect to the radius r seen from the seating surface 3 side of the arcuate cutting edge portion 6a of the auxiliary cutting edge 6 located on the other end side of the groove portion 8B of the above. .. 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 deviates from the arc shape, the arc closest to the deviated shape is virtually drawn. Therefore, the radius r is obtained 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 portion (arc-shaped cutting edge portion 6a of the secondary cutting edge 6) located on the other end side of the groove portion (second groove portion 8B) having the narrow portion 9. The 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 or the plan view seen from the rake face 2 side. The length R in 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 linearly in the bottom view when viewed from the direction facing the seating surface 3, the groove widths W1 and W2 are the first and second wall surfaces. It is the width in the direction perpendicular to the bisector of the straight line 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 is the secondary cutting edge 6 toward the arcuate cutting edge portion 6a side of the secondary cutting edge 6. The inclination angle α formed by 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 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 extension 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 made smaller than the inclination angle β. ing. In the present embodiment, in the bottom view, the first groove 8A extends in a direction that intersects the linear cutting edge 6b of the secondary cutting edge 6 at an acute angle on the first end 2a side, and the second groove 8B Extends on the second end 2b side in a direction that intersects the linear cutting edge portion 5b of the main cutting edge 5 at an acute angle. These 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 portion 9.

The cutting insert 1 of 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, and is detachably attached to the insert mounting seat 12 of FIGS. It constitutes the first embodiment of the cutting edge exchange type ball end mill of the present invention shown in 19. The end mill main body 11 is formed of a metal material such as a steel material, and the tip end portion thereof has a columnar shape centered on the axis O on the base end side, and the tip end side is on the base end side having a center on the axis O. It is a convex hemisphere with the same radius as a cylinder. The blade tip exchange type ball end mill of the present embodiment is attached to the insert mounting seat 12 by feeding the end mill main body 11 in a direction intersecting the axis O while being rotated in the end mill rotation direction T around the axis O. The work material is cut by the cutting insert 1.

In the present embodiment, two tip pockets 13 are formed so as to cut out the outer periphery of the tip portion of the end mill main body 11, and insert mounting seats 12 are respectively formed on the bottom surfaces of these tip pockets 13 facing the end mill rotation direction T. They are formed on opposite sides with a space in the circumferential direction. Then, one kind of first and second cutting inserts 1A and 1B of the same shape and the same size based on the first embodiment are attached to these two insert mounting seats 12, respectively.

These insert mounting seats 12 have a flat bottom surface 12a facing the end mill rotation direction T, a wall surface 12b on the inner peripheral side of the tip and an outer peripheral side of the tip extending from the bottom surface 12a in the end mill rotation direction T and facing the outer peripheral side of the end mill main body 11. It is provided with a wall surface 12c on the outer peripheral side of the rear end facing.
The wall surfaces 12b and 12c are formed in a flat shape that inclines outward from the insert mounting seat 12 as the distance from the bottom surface 12a increases, and the main cutting edge 5 and the sub-cutting blade 5 and the sub-cutting are formed with the seating surface 3 of the cutting insert 1 seated on the bottom surface 12a. It is possible to contact the flat flank 4 connected to the linear cutting edge portions 5b and 6b of the blade 6 and the flat surface portion 4a on the seating surface 3 side of the flank surface 4 connected to the arcuate cutting edge portions 5a and 6a. ..

A recessed recess 12d is formed between the wall surfaces 12b and 12c in order 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 flat surface in which the seating surface 3 of the cutting insert 1 is seated on the bottom surface 12a as described above and is connected to the linear cutting edge portions 5b and 6b of the main cutting edge 5 and the sub cutting edge 6. The center line of the mounting hole 7 of the cutting insert 1 in a state where the flat surface portion 4a on the seating surface 3 side of the flank surface 4 connected to the flank surface 4 and the arcuate cutting edge portions 5a and 6a is in contact with the wall surfaces 12b and 12c. It is designed to be slightly eccentric to the recess 12d side.

The first insert mounting seat 12A of these two insert mounting seats 12 is formed so as to cut out the tip end portion of the end mill main body 11 on the tip end side to a range including the axis O as shown in FIGS. 9 and 10. ing. In the first insert mounting seat 12A, the first cutting insert 1A is located on a convex hemisphere having an arcuate cutting edge portion 5a of the main cutting edge 5 extending from the vicinity of the axis O and having a center 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 in contact with the convex hemisphere. Therefore, the wall surface 12b of the first insert mounting seat 12A is brought into contact with the flat relief surface 4 connected to the linear cutting edge portion 6b of the auxiliary cutting edge 6 in the first cutting insert 1A, and the wall surface 12c is brought into contact with the flat relief surface 4. The flat surface portion 4a of the flank 4 of the arcuate cutting edge portion 6a of the secondary cutting edge 6 in the first cutting insert 1A is brought into contact with the first cutting insert 1A.

Then, on the bottom surface 12a of the first insert mounting seat 12A, a first convex portion 14A to which the first groove portion 8A formed on the seating surface 3 of the first cutting insert 1A can come into contact is a screw hole. It is formed so as to project toward the tip end side from 12e and extend from the outer peripheral surface of the tip end portion of the end mill main 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 to 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 formed. 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 peninsula shape reaching the wall surface 12c, while the second convex portion 14B is formed in a remote island shape not reaching the concave portion 12d at intervals from the concave portion 12d. Has been done.

The first and second convex portions 14A and 14B have a substantially rectangular shape in which the cross section orthogonal to the extending direction of the first and second convex portions 14A and 14B is flattened 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 direction in which the first groove portion 8 extends with respect to the first groove portion 8A having the narrow portion 9 as a whole. It is formed so as to become wider 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 having a narrow portion 9 as a whole, from the other end side in the direction in which the second groove portion 8B extends to the one end side (inside the end mill main body 11). It is formed so as to become wider as a whole from the peripheral side to the outer peripheral side).

The widths of the first and second convex portions 14A and 14B (widths in the direction orthogonal to the extending direction of the first and second convex portions 14A and 14B) are such that the first and second groove portions 8A and 8B extend. It is slightly smaller than the width at the position where it abuts the first and second convex portions 14A and 14B in the direction (the width in the direction orthogonal to the extending direction of the first and second groove portions 8A and 8B). The height of protrusion 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.

The second insert mounting seat 12B of the two insert mounting seats 12 is formed from a position slightly distant from the axis O on the distal end side of the end mill main body 11 as shown in FIGS. 9 and 12. The second cutting insert 1B is attached to the second insert mounting seat 12B, and the arcuate cutting edge portion 6a of the secondary cutting edge 6 is placed on the main cutting edge 5 of the first cutting insert 1A from a position away from the axis O. The arcuate cutting edge portion 5a is positioned on the convex hemisphere where the arcuate cutting edge portion 5a is located, and the linear cutting edge portion 6b of the sub cutting edge 6 is formed 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 cylindrical surface in which it is located. Therefore, the wall surface 12b of the second insert mounting seat 12B is brought into contact with the flat flank surface 4 connected to the linear cutting edge portion 5b of the main cutting edge 5 of the second cutting insert 1B, and the wall surface 12c is brought into contact with the flat flank surface 4. 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 with the cutting insert 1B.

A third convex portion 14C is formed on the bottom surface 12a of the second insert mounting seat 12B on the tip side of the screw hole 12e, and a fourth convex portion 14C 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 end portion of the end mill main 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. The fourth convex portion 14D is formed in front of the concave portion 12d of the second insert mounting seat 12B at a distance 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.

Further, these 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 flattened in the end mill rotation direction T. Of these, the third convex portion 14C has a narrow portion 9 as a whole of the second groove portion 8B of the second cutting insert 1B that comes into contact with the third convex portion 14C, whereas the second groove portion 8B extends in the direction of extension. It is formed so as to become wider as a whole from the other end side toward 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 such that the first groove portion 8A It is formed so as to become wider as a whole from the other end side in the extending direction toward 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 widths of the second and first groove portions 8B and 8A. Is slightly smaller than the width at the position where the third and fourth convex portions 14C and 14D abut in the extending direction (the width in the direction orthogonal to the extending direction of the second and first groove portions 8B and 8A). 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 the first and second insert mounting seats 12A and 12B as described above, and a clamp screw having an inverted truncated cone-shaped head is provided. When the screw hole 12e is inserted through 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 of the center line of the mounting hole 7 of the cutting insert 1. 1 is pressed against the recess 12d side.

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

At the same time, in the first insert mounting seat 12A, the first and second groove portions 8A and 8B of the first cutting insert 1A are attached to the first and second convex portions 14A and 14B at the tip of the end mill main body 11. Contact from the side. Therefore, the first and second convex portions 14A and 14B have the second groove portions 8A and 8B of the first cutting insert 1A on the side surface 14a facing the tip end side of the end mill main body 11. The wall surfaces 8b come into contact with each other, and a slight gap is provided between the first wall surface 8a and the bottom surface 8c in 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 connected to the third and fourth convex portions 14C and 14D from the tip end side of the end mill main body 11. Contact. Therefore, the second and first groove portions 8B and 8A come into contact with the third and fourth convex portions 14C and 14D, respectively, with the side surfaces 14a facing the tip end side of the end mill main body 11 and the first wall surface 8a. 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. In this way, by bringing the first and second groove portions 8A and 8B into contact with the first to fourth convex portions 14A to 14D, it is possible to prevent the cutting insert 1 from shifting due to a load during cutting. ..

In the cutting insert 1 and the cutting edge replaceable ball end mill having the above configuration, the first and second groove portions 8A and 8B of the cutting insert 1 are on one end side in the direction in which the first and second groove portions 8A and 8B extend. A cutting insert is provided on the other end side of the first and second groove portions 8A and 8B, which have a narrow portion 9 in which the groove width narrows toward the other end side and the groove width of the narrow portion 9 becomes smaller. It is possible to secure a large wall thickness of 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 from 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 becomes wider on the contrary. The first to fourth convex portions 14A to 14D at the portion where one end side of the groove portions 8A and 8B abut can be formed wide. Therefore, it is possible to increase the mounting rigidity of the cutting insert 1 with respect to the load during the cutting process, and it is possible to more reliably prevent the displacement movement of the cutting insert 1 and perform the cutting process with high accuracy.

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 have the same shape and the same size. The groove width W1 at the other end of the narrowed portion 9 which is the narrowest is 0. The range is set to 05 × r to 0.18 × r, and this also makes it possible to increase the mounting rigidity while further reliably improving the strength of the cutting insert 1. That is, if the groove width W1 at the other end of the narrow portion 9 is narrow enough to be smaller than the above range, the widths of the first to fourth convex portions 14A to 14D in the insert mounting seat 12 must also be narrowed for cutting. While there is a risk that the mounting rigidity of the insert 1 cannot be increased, the groove width W1 at the other end of the narrow portion 9 is wide enough to exceed the above range, and the first and second groove portions 8A and 8B have the first and second grooves. When the second wall surfaces 8a and 8b are close to parallel, it is possible to secure a large wall 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 and may cause damage when an excessive load is applied.

20A to 20C are views showing a stress dispersion state by simulation analysis when the groove width W1 at the other end of the groove 8 is changed, and is an arcuate cutting edge portion located on the other end side of the groove 8. (For example, when the radius r of the arcuate cutting edge portion 6a of the secondary cutting edge 6) is 15.0 mm, FIG. 20A shows the case where the groove width W1 is constant at 3.0 mm over the entire length of the groove portion (narrow portion). 9), FIG. 20B shows a case where the narrow portion 9 is provided and the groove width W1 at the other end of the arcuate cutting edge portion 6a with respect to the radius r is 2.0 mm (0.133 × r). 20C also has a narrow portion 9, and the groove width W1 at the other end of the arcuate cutting edge portion 6a with respect to the radius r is 1.0 mm (0.067 × r). The analysis shows 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 (the feed amount per blade is 0.3 mm / blade), and the depth of cut and the cutting width are both. Assuming 15 mm, the work material was S45C (hardness 220HB), and the material of the end mill body was SKD61 (hardness 45HRC, tensile strength 1600MPa, fatigue strength 500MPa), evaluation was performed by Mieses stress.

In FIG. 20, the region on the groove side of the portion drawn in white on the seating surface 3 is the range in which the stress is concentrated. Then, the stress is dispersed in FIGS. 20B and 20C having the narrow portion 9 because the white portion is smaller than the result in FIG. 20A in which the groove width is constant and the narrow portion 9 is not provided. In particular, in FIG. 20C where the groove width W1 is small, the range where 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 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 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 desirable, and the range of 0.32 × W2 to 0.80 × W2 is even more desirable. 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 a 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 peripheral length is shortened, that is, the cutting insert 1 is formed asymmetrically. Has been done. Along 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 on the tip end side to a range including the axis O. On the other hand, the second insert mounting seat 12B is formed from a position slightly distant from the axis O on 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 an arcuate cutting edge portion 5a of the main cutting edge 5 and an end mill body 11 The second cutting insert 1B is positioned in the same convex hemispherical shape so as to extend from the vicinity of the axis O at the tip and to extend the arcuate cutting edge portion 6a of the secondary cutting edge 6 from a position away from the axis O. I'm letting you.

Therefore, one type of cutting insert 1 can perform cutting from the vicinity of the axis O at the tip of the end mill main body 11 to the outer circumference and cutting from a position away from the axis O to the outer circumference, and the cutting insert 1 can be easily managed. At the same time, only one type of mold is required to manufacture the cutting insert 1. Further, when the main cutting edge 5 of the first cutting insert 1A and the auxiliary cutting edge 6 of the second cutting insert 1B are worn due to cutting, these cutting inserts 1 are placed on the insert mounting seat 12 on the opposite side. 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 above, which is economical.

Further, in the present embodiment, the second groove portion 8B having the narrow portion 9 having the width at one end side and the width at the other end side is the main cutting from the arcuate cutting edge portion 6a side of the secondary cutting edge 6. The blade 5 extends toward the linear cutting edge portion 5b side. The narrow portion 9 is narrow because 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. It is designed to be. Therefore, when the secondary cutting edge 6 is used for cutting as the second cutting insert 1B, a flank surface in which the second groove portion 8B is connected to the arcuate cutting edge portion 6a of the secondary cutting edge 6 as in the present embodiment. Even if the opening is open to 4, the load acting on the auxiliary cutting edge 6 can be received by the other end side of the narrow portion 9 of the narrowed second groove portion 8B, and the strength can be secured. Is. The displacement of the second cutting insert 1B along the arcuate cutting edge portion 5a of the main cutting edge 5 that is not used for cutting is the narrow portion 9 of the second groove portion 8B away from the arcuate cutting edge portion 5a. It can be reliably prevented on one end side of the wide width. This is the same even when the cutting insert 1 is used as the first cutting insert 1A.

In the present embodiment, the arcuate cutting edge portion 5a of the main cutting edge 5 and the arcuate 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, and then again. 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 and cut from the most convex point S, which is the most distant and convex with respect to the seating surface 3 during cutting. 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 is narrowed, the wall thickness at the most convex point S can be secured to improve the strength, and cutting can be achieved. It is possible to prevent damage to the cutting insert 1 due to a 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 shown by the reference numeral 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 secured by the most convex point S is the region indicated by the reference numeral U in FIGS. 4 and 7. The value of the insert wall thickness in the region indicated by reference numeral U is preferably in the range of 0.65 × t to 1.00 × t with respect to the t value, and is preferably in the range of 0.70 × t to 1.00 × t. More preferably, the range of 0.75 × t to 1.00 × t is even more desirable.

In the present embodiment, the arcuate cutting edge portions 5a and 6a are thus formed in a convex curved shape. Although the second groove 8B is open to the flank 4 connected to the arcuate cutting edge 6a of the secondary cutting edge 6 as described above, the opening of the second groove 8B to the flank 4 is open. It is located closer to the linear cutting edge portion 6b of the secondary cutting edge 6 than the most convex point S of the arcuate cutting edge portion 6a of the secondary cutting edge 6. Therefore, it is possible to prevent the impact when the arcuate cutting edge portion 6a of the secondary cutting edge 6 bites into the work material and cuts from the most convex point S 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 due to 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 arcuate cutting edge portion 6a of the secondary cutting edge 6 are formed in the bottom view. The straight line L1 to be connected and the end Q to the seating surface 3 side of the intersecting ridge line portion between the first wall surface 8a and the flank surface 4 of the second groove portion 8B facing the linear cutting edge portion 6b side of the secondary cutting edge 6. It is desirable that the first intersection angle θ1 formed by the straight line L2 connecting the arcuate cutting edge portion 6a of the secondary cutting edge 6 with the center P is in the range of 5 ° to 60 °. Although not shown, the same applies to the arcuate cutting edge portion 5a of the main cutting edge 5 and the opening on the other end side of the first groove portion 8A.

When the first crossing angle θ1 is small enough to be less than 5 °, the opening of the second groove 8B to the flank 4 is the maximum of the arcuate cutting edge 6a of the secondary cutting edge 6 in which the flanks 4 are connected. The cutting insert 1 may be damaged by the impact when the arcuate cutting edge portion 6a is too close to the convex point S and bites the work material from the most convex point S. On the contrary, when the first intersection angle θ1 is larger than 60 °, the clamp screw inserted into 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 to screw the cutting insert. When 1 is attached, the second groove 8B and the first and second convex portions 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 the present embodiment, similarly, in the bottom view, a straight line L1 connecting the most convex point S of the arcuate cutting edge portion 6a of the auxiliary cutting edge 6 and the center P of the arcuate cutting edge portion 6a, and the auxiliary cutting edge 6 The second crossing angle θ2 formed by the extension line L3 of the linear cutting edge portion 6b of the secondary cutting edge 6 to the arcuate cutting edge portion 6a side is in the range of 10 ° to 50 °. Also, while preventing interference between the second groove 8B and the first and second convex portions 14A and 14B and the mounting hole 7 and the screw hole 12e, the convex curved arcuate cutting edge portion 6a of the secondary cutting edge 6 ensures It is possible to reduce the cutting resistance. Although not shown, 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. It is substantially parallel to the axis O of the end mill main body 11 in a plan view seen from a 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 straight line L1 connecting the center P and the most convex point S of the arcuate cutting edge portion 6a located on the axis O and the axis O. 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 main body 11, and therefore the intersection angle θ2 is exactly the intersection between the straight line L1 and the axis O. It does not have to be equal to the angle.

Therefore, when the second intersection angle θ2 is larger than 50 °, the second groove portion 8B and the first and second convex portions 14A, when the first intersection angle θ1 is set to the above range, There is a possibility that 14B interferes with the mounting hole 7 and the screw hole 12e. If the second intersection angle θ2 is so small that it is less than 10 °, the most convex point S of the arcuate cutting edge portion 6a of the second cutting insert 1B gets too close to the axis O, and the rotation speed around the axis O increases. The arcuate cutting edge portion 6a of the secondary cutting edge 6 cuts into the work material from a small portion, which may impair the effect of reducing the cutting resistance. 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 and the third embodiment of the second embodiment. The tip of the end mill main body 41 according to the second embodiment of the blade tip exchange type ball end mill of the present invention to which the cutting insert 31 of the above is detachably attached is shown, and FIGS. 32 to 37 show the end mill main body 41. The tip of the second embodiment of the blade tip exchange type 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, the same reference numerals are given to the elements common to the embodiments shown in FIGS. 1 to 19, and the description thereof will be omitted. Since the second intersection angles θ1 and θ2, inclination angles α to γ, and the like are also common, the illustration is omitted.

The cutting insert 1 of the first embodiment is asymmetric with respect to the insert center line X passing through the center of the mounting hole 7 with arcuate cutting edge portions 5a and 6a having different peripheral lengths for the main cutting edge 5 and the sub cutting edge 6. 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 symmetric 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 a substantially 1/4 arcuate arcuate cutting edge portion 5a and a linear cutting edge in contact with the main cutting edge 5 of the cutting insert 1 of the first embodiment. It has two portions 5b alternately 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 the 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. It has two cutting edge portions 6b alternately in the circumferential direction of the rake face 2. The radii of the arcuate cutting edge portion 5a of the main cutting edge 5 of the second embodiment and the arcuate cutting edge portion 6a of the sub cutting edge 6 of the third embodiment are 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 6 of the two auxiliary cutting edges 6 of the cutting insert 31 of the third embodiment The 6bs are 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 the linear cutting of the two sub cutting edges 6 of the cutting insert 31 of the third embodiment. It is larger than the distance between the blades 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 main body 41. Two groove portions 8 having a contactable wall surface are the two cutting blades (main cutting blade 5 and secondary cutting blade 6), and one cutting edge is linear cutting edge portions 5b, 6b side to the other cutting edge. It is formed so as to extend toward the arcuate cutting edge portions 5a and 6a. Each of these two groove portions 8 has a narrow portion 9 in which the groove width becomes narrower from one end side to the other end side in the direction in which the groove portion 8 extends. Also in these second and third embodiments, the narrow portion 9 has the linear cutting edge portions 5b and 6b on one end side and the arcuate cutting edge portions 5a and 6a on the other end side, respectively.

Also in these second and third embodiments, as in the first embodiment, the groove portion 8 has other ends open to the flank 4 connected to the arcuate cutting edge portions 5a and 6a, and one end is also linearly cut. It is open to the flank 4 connected to the blades 5b and 6b. In these second and third embodiments, as shown in FIGS. 21 and 25, the two cutting blades (main cutting blade 5 and secondary cutting blade 6) are generally on the arcuate cutting edge portions 5a and 6a side. The straight cutting edge portions 5b and 6b are formed in a convex curved shape that moves away from the seating surface 3 side and then approaches the seating surface 3 side. The opening of the groove 8 to the flank 4 connected to the arcuate cutting edges 5a and 6a is arcuate rather 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 edge portions 5a and 6a.

Specifically, as shown in FIG. 23 when viewed from the bottom surface in a direction facing the seating surface 3, the most convex point S of the cutting edge (main cutting edge 5 in FIG. 3) and the arcuate shape of the main cutting edge 5. A third straight line L6 connecting the center P1 of the cutting edge portion 5a and a straight line L7 connecting the contact point V between the arcuate cutting edge portion 5a of the main cutting edge 5 and the linear cutting edge portion 5b and the center P1. It is desirable that the intersection angle θ3 of is in the 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.

The cutting insert 21 of the second embodiment extends the arcuate cutting edge portion 5a of the main cutting edge 5 from the vicinity of the axis O at the tip of the end mill main body 41 and positions it on a convex hemisphere having a center on the axis O. At the same time, the linear cutting edge portion 5b of the main cutting edge 5 is attached to the third insert mounting seat 12C so as to be positioned on the cylindrical surface centered on the axis O 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 a position where the arcuate cutting edge portion 6a of the secondary cutting edge 6 is separated from the axis O. The linear cutting edge portion 6b of the secondary cutting edge 6 is positioned on the convex hemisphere where the portion 5a is located, 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.

The first to fourth convex portions 14A to 14D are also formed on the bottom surfaces 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. In the ball end mill with replaceable cutting edge of the second embodiment, the first convex portion 14A on the tip end side of the third insert mounting seat 12C of the end mill main body 41 is different from the first embodiment having a peninsula shape, and other It is formed in a remote island shape like the second to fourth convex portions 14B to 14D of the above.

Also in the cutting inserts 21 and 31 of the second and third embodiments and the cutting edge replaceable 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 and 31. Is formed. Since the groove portion 8 can be brought into contact with the convex portions 14A to 14D formed on the insert mounting seats 12C and 12D, the cutting insert 1 and the cutting edge replaceable ball end mill of the first embodiment are used for cutting. The strength of the inserts 21 and 31 can be improved to prevent damage, and the cutting inserts 21 and 31 can be prevented from shifting during cutting to perform high-precision machining.

In the cutting inserts 21 and 31 of the second and third embodiments, the main cutting edge 5 and the auxiliary cutting edge 6 are seated as they move 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 a convex curve shape that approaches the seating surface 3 side after being separated from the surface 3 side, the main cutting edge 5 and the sub cutting edge 6 can be gradually bitten into the work material from the most convex point S. This makes it possible to reduce cutting resistance and promote improvement in cutting edge strength due to thickening.

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 connected to the arcuate cutting edge portions 5a and 6a, whereas the groove portion 8 is formed. Since the opening of is located on the arcuate cutting edge portions 5a and 6a side of 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, the first It is possible to avoid the impact when the most convex point S bites directly to the opening of the groove 8 in the direction of the insert center line X, as in the embodiment of the above, and such an impact causes the impact from the opening of the groove 8. It is also possible to prevent the cutting inserts 21 and 31 from being damaged.

When the other end of the groove 8 is open to the arcuate cutting edges 5a and 6a in this way, or as in the cutting inserts 21 and 31 of the second and third embodiments, one end of the groove 8 is also linear. When the flank 4 connected to the cutting edges 5b and 6b is open, the most convex points S of the main cutting edge 5 and the auxiliary cutting edge 6 are viewed from the bottom surface when viewed from the direction facing the seating surface 3. The straight line L6 connecting the arcuate cutting edge portions 5a and 6a with the center P1 and the contact points V between 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. If the third intersection angle θ3 formed by the straight line L7 connecting the arcuate cutting edge portions 5a and 6a with the center p1 is too large, the most convex point S is too close to the opening of the groove portion 8 to the flank surface 4. As described above, it becomes impossible to reliably prevent damage to the cutting inserts 21 and 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 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 symmetric 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. Therefore, the main cutting edge 5 and the auxiliary cutting edge 6 of each of the cutting inserts 21 and 31 used for cutting while being attached to the third and fourth insert mounting seats 12C and 12D are worn. When the life is reached, the cutting inserts 21 and 31 are once removed, rotated 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 and 31 can be used twice, respectively.

According to the present invention, the narrow portion of the groove formed on the seating surface of the cutting insert secures 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. This can be achieved, and damage to the cutting insert due to a load during cutting can be prevented. Since the groove width of the narrow portion is widened on one end side of the groove portion, the convex portion of the ball end mill with a replaceable cutting edge can be formed wide, and the mounting rigidity of the cutting insert can be increased to reliably prevent the displacement movement. It will be possible.

1 (1A, 1B), 21, 31 Cutting insert 2 Scooping surface 3 Seating surface 4 Escape surface 5 Main cutting edge 5a Arc-shaped cutting edge part of main cutting edge 5 5b Linear cutting edge part of main cutting edge 5 6 Secondary cutting Blade 6a Arc-shaped cutting edge of the secondary cutting edge 6 6b Linear cutting edge of the secondary cutting edge 6 7 Mounting holes 8, 8A, 8B Grooves 9 Narrow sections 11, 41 End mill body 12 (12A to 12D) Insert mounting seat 14A to 14D Convex part r The radius of the arc-shaped cutting edge portion (6a) located on the other end side of the narrow portion 9 in the groove portion (second groove portion 8B) P The arc-shaped cutting edge portion of the secondary cutting edge 6 in the bottom view. Center of arc formed by 6a P1 Center of arc formed by arc-shaped cutting edge 5a of main cutting edge 5 in bottom view Q First of second groove 8B facing the linear cutting edge 6b side of secondary cutting edge 6 The end of the crossing ridge of the wall surface 8a and the flank 4 toward the seating surface S S most convex point t The wall thickness of the cutting insert 1 at the most convex point S U The wall thickness of the cutting insert 1 is secured by the most convex point S Range V Contact point between arcuate cutting edge 5a and linear cutting edge 5b of the main cutting edge 5 in bottom view L1 Straight line connecting center P and most convex point S in bottom view L2 Center P in bottom view Straight line connecting the end Q L3 Extension line of the linear cutting edge 6b of the secondary cutting edge 6 to the arcuate cutting edge 6a side of the secondary 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 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 X Insert center line O End mill body Axis 11 and 41 T End mill rotation direction θ1 First intersection angle θ2 Second intersection angle θ3 Third intersection angle

Claims (2)

A cutting insert that can be detachably attached to the insert mounting seat formed at the tip of the end mill body of a ball end mill with a replaceable cutting edge that rotates around the axis.
A rake face directed in the rotational direction of the end mill body, a seating surface seated on the bottom surface of the insert mounting seat facing the opposite side of the rake face, and a relief extending around the rake face and the seating surface. With a face,
At the intersecting ridge line portion between the rake face and the flank surface, an arcuate cutting edge portion extending in an arc shape in a plan view from a direction facing the rake face and an arcuate cutting edge portion extending so as to be in contact with the arcuate cutting edge portion. Two cutting edges each having a linear cutting edge portion are formed by alternately locating the arc-shaped cutting edge portion and the linear cutting edge portion in the circumferential direction of the rake face.
On the seating surface, two grooves having a wall surface capable of contacting a convex portion protruding from the bottom surface of the insert mounting seat are formed on the seating surface from the linear cutting edge side of one cutting edge to the other by the two cutting edges. It is formed so as to extend toward the arcuate cutting edge side of the cutting edge of
The two groove portions are cutting inserts in which the groove width becomes narrower from the linear cutting edge portion side of the cutting edge to the arcuate cutting edge portion side of the cutting edge. The rate at which the groove width becomes narrow is constant,
The groove portion includes a first wall surface and a second wall surface facing each other, and a bottom surface parallel to the seating surface is provided between the first wall surface and the second wall surface, and the first wall surface is provided. The cutting insert according to claim 1, wherein the second wall surface extends linearly in a bottom view viewed from a direction facing the seating surface.

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