JPH11197933A - Throw-away tip and throw-away ball end mill - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide throw-away ball end mill which costs low and has high strength of a tool main body. SOLUTION: A main cutting edge 17 and an auxiliary cutting edge 18 are asymmetrically provided opposite to each other on the upper surface of a substantially leaf-like plate tip. The main cutting edge 17 and the auxiliary cutting edge 18 respectively include convex curve cutting edges 17a, 18a and linear cutting edges 17c, 18b, wherein the convex curve cutting edges and the linear cutting edges are provided alternately. With respect to a virtual line (m) connecting the intersecting parts of the main cutting edges and the auxiliary cutting edges, the distance to the auxiliary cutting edge 18 is smaller than the distance to the main cutting edge 17. The same tips 10A and 10B are provided on the tool main body of a ball end mill 25. The main cutting edge 17 of the tip 10A is extended from the vicinity of the axis of rotation of the point of the tool main body to the outer periphery side, and the auxiliary cutting edge 18 of the other tip 10B is extended from the position of the outer periphery side retreated to the base end side of the tool main body to the outer periphery side.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a throw-away type ball end mill and a throw-away tip mounted on a throw-away type ball end mill.

[0002]

2. Description of the Related Art Conventionally, in a throw-away type ball end mill, as shown in FIG. 12, for example, a tip part 2 of a tool body 1 is formed in a substantially hemispherical shape. A main throw-away tip (referred to as a main tip) 3 and a sub-throwaway tip (referred to as a sub-tip) 4 are mounted. The main insert 3 is located at the tip 2 of the tool main body 1, and an arc-shaped main cutting edge 5 is disposed on the outer peripheral side starting from the vicinity of the intersection with the rotation axis O. A sub-cutting blade 6 is disposed on the outer peripheral side at a position separated from the distal end portion 2 of the main body 1 on the base end side and at a position radially separated from the rotation axis O. Further, auxiliary tips 7 are arranged on the base end side of the tool body 1 so that the rotation path is continuous from the main tip 3. When the tool body 1 is rotated and cut, the rotation trajectory of the main cutting edge 5 and the sub cutting edge 6 has a substantially hemispherical shape.

[0003]

In this case, since the shapes of the main cutting edge 5 and the sub cutting edge 6 are different, two types of the main tip 3 and the sub tip 4 are prepared in the conventional ball end mill 1. In addition, two types of dies are required for the production, and two types of chips 3 and 4 need to be stored for replacement, which has the disadvantage of increasing the production cost and running cost. In such a ball end mill, since the main tip 3 and the sub-tip 4 can be used twice with a corner change, the main cutting edge 5 and the sub-cutting edge 6 are rotationally symmetrical, and Since the main chip 3 and the sub chip 4 are formed in a leaf shape, the tool body 1
When mounted on the tip 2 of the tool body 1, there is a disadvantage that the thickness of the central portion of the tip 2 of the tool body 1 becomes thin and the strength of the tip 2 becomes small.

The present invention has been made in view of the above circumstances, and has as its object to provide a throw-away chip with reduced cost. It is another object of the present invention to provide a throw-away type ball end mill having a low cost and a high strength of a tool body.

[0005]

The indexable insert according to the present invention is provided with a main cutting edge and a sub cutting edge opposed to each other on a ridge line of an upper surface facing a seating surface, and the main cutting edge and the sub cutting edge are provided. The cutting blade is characterized by being asymmetric. Since one indexable insert is provided with a main cutting edge and a sub cutting edge, for example, when mounting the insert on a tool body of a rolling tool such as a ball end mill, one of the same inserts is mounted on the outer periphery of the main cutting edge. Side, and the other, so that the minor cutting edge is located on the outer peripheral side. One type of chip can be manufactured and stored for replacement, and the cost is low. It will be cheap.

The distance to the sub cutting edge may be set to be smaller than the distance to the main cutting edge with respect to an imaginary line connecting two intersections of the main cutting edge and the sub cutting edge. If this tip is mounted on a tool body such as a ball end mill with the main cutting edge positioned on the outer peripheral side, the space of the sub-cutting edge located inside the tool main body by cutting out the tool main body is small, The thickness at the center of the tip of the tool body can be secured, and the strength of the tool body is high. The throw-away insert has a main cutting edge and a sub-cutting edge each formed of a convex curved blade and a straight blade, and the convex cutting blade and the linear blade are alternately arranged in a substantially leaf-shaped plate shape. The straight blade of the blade may be shorter than the straight blade of the sub cutting edge. The area of the convex curved edge of the main cutting edge becomes large, and when mounted on the tip of the ball end mill, a large amount of cutting by the convex curved edge of the main cutting edge can be secured. The main cutting edge and the sub cutting edge may have a convex curve shape protruding in a direction away from the seating surface in a side view. The strength of the bolted portion (insertion hole) for mounting the insert to the tool body is high, and the overall strength of the insert is increased. The main insert and the secondary insert are rotated by being mounted on a ball end mill or the like. The rotation locus becomes substantially hemispherical.

The two intersections of the main cutting edge and the sub cutting edge are
One may have a greater thickness from the seating surface than the other. The strength of the cutting edge in the thick part can be enhanced. Also, the intersection between the straight cutting edge of the main cutting edge and the convex curved cutting edge of the sub cutting edge is
The thickness from the seating surface may be set to be larger than the intersection of the convex curved blade of the main cutting blade and the straight blade of the sub cutting blade. In this case, the shoulder of the work material is cut by a straight blade located on the base end side of the main cutting edge of the tip mounted on the tip end side of the tool body such as a ball end mill, and the impact during cutting is reduced. Although large, the chip thickness at this portion is large, so that the cutting edge can be prevented from being lost. In addition, the tip of the convex curved blade of the sub-cutting edge of the tip, which is disposed relatively on the base end side of the tool body, has a large peripheral speed and a large impact at the time of cutting by being sent toward the distal end. Since the insert thickness is large, the loss of the cutting edge can be suppressed.

A throw-away type ball end mill according to the present invention is a ball end mill in which a plurality of throw-away tips are provided at a tip end of a tool body, and a rotation locus of a cutting edge of the throw-away tip is substantially hemispherical. The throw-away insert is a throw-away insert according to any one of claims 1 to 6, wherein one of the throw-away inserts is arranged such that a main cutting edge extends from the vicinity of the rotation axis at the tip of the tool body to the outer peripheral side. The other indexable insert is characterized in that the sub cutting edge is disposed to extend to the outer peripheral side at a position retracted from the distal end of the tool body to the proximal end side. Since one type of insert can be used as the main cutting edge and the sub cutting edge, the production cost and running cost are low.

The main cutting edge and the sub cutting edge are located in a region facing each other in a direction perpendicular to the rotation axis of the tool body.
The rotation trajectories may be overlapped on a cross section orthogonal to the rotation axis. Good finishing accuracy during cutting and good cutting balance for each cutting edge. Further, the main cutting edge and the sub cutting edge may be arranged at equally dividing positions in a circumferential direction in a cross section orthogonal to the rotation axis of the tool main body. By locating the main cutting edge and the sub-cutting edge at equally divided positions in the circumferential direction, the impact during cutting is not biased, the cutting balance is good, and the finished surface is good without chatter vibration.

The main cutting edge and the sub cutting edge may be arranged at unequally divided positions in the circumferential direction in a cross section orthogonal to the rotation axis of the tool body. Since the main cutting edge and the sub cutting edge do not resonate and do not generate vibration during cutting, the cutting performance is improved. Also, when viewed in the rotating direction of the tool body, the angle from the main cutting edge to the sub cutting edge in the rotational direction rearward direction is set smaller than the angle from the main cutting edge to the rotational direction forward direction sub cutting edge. May be. The cutting volume of the main cutting edge protruding to the tip side of the tool body is larger than the cutting volume of the sub cutting edge at the position retracted in the outer peripheral direction from the main cutting edge to the main cutting edge. By making the rotation stroke to the blade relatively short, the cutting volumes of both cutting blades can be evenly balanced.

[0011]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a throw-away tip and a throw-away type ball end mill according to an embodiment of the present invention. 1 to 5 show a throw-away tip according to an embodiment.
7 shows a ball end mill to which a throw-away tip according to the embodiment is mounted. 1 is a plan view of the throw-away tip, FIG. 2 is a side view of the throw-away tip shown in FIG. 1 in the direction A, FIG. 3 is a side view of the throw-away tip shown in FIG. 1 in the direction B, and FIG. FIG. 5 is a side view in the C direction of the away tip, FIG. 5 is a side view in the D direction of the throw away tip shown in FIG. 1, and FIG. 6 is a tip side view of the ball end mill according to the embodiment equipped with the throw away tip shown in FIG. 7 is a front end view of the ball end mill shown in FIG. A throw-away tip (hereinafter sometimes referred to as a tip) 10 according to the embodiment shown in FIGS. 1 to 5 has a substantially leaf-shaped plate shape, and is provided with an upper surface 12 opposed to a lower surface 11 forming a seating surface. Side 1
Reference numeral 3 denotes a positive chip which is provided so as to be gradually inclined outward from the lower surface 11 toward the upper surface 12.

The chip 10 has an insertion hole 14 for bolting which penetrates from the center of the upper surface 12 to the lower surface 11. On the lower surface 11 of the chip 10, for example, two key grooves 1 are provided before and after the insertion hole 14 so as to intersect the longitudinal direction of the lower surface 11.
5a and 15b are formed. On the upper surface 12 of the chip 10 shown in FIG. 1, two roughly convex ridges are formed to face each other, one of which is a main cutting edge 17 and the other is a sub cutting edge 18, Cutting blade 17 and sub cutting blade 18
Both ends are connected at intersections 20 and 21 forming acute corners, and are non-rotationally symmetric and non-linearly symmetric two-bladed blades. The main cutting edge 17 extends from one intersection 20 to the other intersection 2
1, the convex curved blade 17a and the straight blade 17b are smoothly connected to each other to form a convex curved shape, and the sub cutting blade 18 is connected to the linear blade 17b of the main cutting blade 17 via the intersection 21. The convex curved blade 18a and the straight blade 18b are smoothly connected to each other and have a convex curved shape reaching the intersection 20.

Further, the two convex curved blades 17a and 18a have the same or equivalent radius R and have a convex curved shape which draws a ridge on a spherical surface, and the straight blade 17b of the main cutting blade 17 is the sub cutting edge 1b.
8 is shorter than the straight blade 18b. Therefore, the convex curved blade 17a of the main cutting blade 17 is longer than the convex curved blade 18a of the sub cutting blade 18, so that the main cutting is performed. In addition, it is preferable that the intersection angle α between the extension lines of the two straight blades 17b and 18b is set in a range of 5 ° to 30 °. Since the curve forming a hemispherical surface by the convex curve blades 17a and 18a is determined, if the intersection angle α is smaller than 5 °, the tip center portion of the tool main body is formed in order to form a chip mounting seat of a concave groove for mounting the chip 10. The wall thickness is reduced 2
As a ball end mill equipped with a single blade tip, the strength becomes insufficient. If the intersection angle α is larger than 30 °, the width of the chip 10 becomes smaller, the chip strength becomes weaker, and the insertion hole 14 cannot be provided. In addition, in a plan view of the chip 10 shown in FIG.
The (maximum) distance to the main cutting edge 17 is larger than the (maximum) distance to the sub cutting edge 18 with respect to the imaginary line m connecting 0 and 21. In other words, the area Sa of the region surrounded by the virtual line m and the main cutting edge 17 is larger than the area Sb of the region surrounded by the virtual line m and the sub cutting edge 18.

As shown in FIGS. 2 to 5, the thickness of the chip 10 at the intersection 21 is set to be larger at the upper and lower surfaces than at the intersection 20. Then, in a side view of the chip 10, the main cutting edge 17 of the upper surface 12 has a convex curved shape protruding in a direction away from the lower surface 11, as shown in FIGS. Draw a ridgeline. As shown in FIG. 5, the secondary cutting edge 18 also has a convex curved shape protruding in a direction away from the lower surface 11, and the convex curved blade 18 a forms a ridge line on the spherical surface of the same or equivalent R as the main cutting edge 17. Draw. The upper surface 12 has a half surface 12a from the main cutting edge 17 to the imaginary line m and a half surface 12a from the sub cutting edge 18 to the imaginary line m.
center line 23 where b overlaps the virtual line m from the cutting edge side
, And are connected by a center line 23. The thickness of the chip 10 in the upper and lower surface directions is maximum around the insertion hole 14 and minimum at the intersection 20.

The indexable insert 10 according to the present embodiment has the above-described configuration. Next, a two-blade ball end mill in which a plurality of, for example, two indexable inserts 10 are mounted is shown in FIGS. 7 will be described. The ball end mill 25 includes a substantially cylindrical tool body 2.
6 has a substantially hemispherical shape, and has two concave grooves 24a and 24b which are circumferentially opposed to the rotation center O of the tool body 26 and are displaced in the direction of the rotation axis O. The chip mounting seats 28 and 29 having different shapes are formed in the respective grooves 24a and 24b. One of the tip mounting seats 28 is formed closer to the tip of the tip mounting seat 29 and closer to the rotation axis O.
A bottom surface 28a on which 0a and 30b are formed, and a side wall 28b formed by a linear flat surface portion 31a and a concave curved surface portion 31b which receive the side surface 13 of the sub-cutting edge 18 of the chip 10 and serve as a chip mounting reference. ing. Similarly, the other chip mounting seat 29 has a bottom surface 29 a on which two keys 32 a and 32 b are formed and a side surface 1 of the main cutting blade 17 of the chip 10.
Receiving 3 and a linear flat part 3 which serves as a chip attachment reference
3a and a side wall 29b formed by the concave curved surface portion 33b are provided.

The indexable insert 10 is mounted on one of the chip mounting seats 28 with the main cutting edge 17 positioned on the outer peripheral side, and the key grooves 15a, 15b on the lower surface 11 are provided.
Keys 30a and 30b are fitted to the bottom surface 28a, respectively.
And the side surface 13 of the sub-cutting edge 18 is
8b, and is fixed by bolts 35. In the tip mounted state, the crossing portion 20 located on the distal end side of the throw-away tip 10 projects from the distal end portion 27 of the tool body 26 to the distal end side and is located substantially on the rotation axis O. The main cutting blade 17 protrudes from the distal end portion 27 to the outer peripheral side, and forms the convex curved blade 1.
7a, the straight blade 17b is arranged along the outer periphery of the tool body 26 along the curve of the tip 27, and further behind it. In this case, the flat portion 3 of the side wall 28b of the chip mounting seat 28
The side surface 13 of the straight blade 18b of the sub cutting edge 18 abutting on 1a forms an angle of, for example, 15 ° with respect to the rotation axis O (see FIG. 6). This throw-away chip 10 is the main chip 10A.

The same tip 10 is also located on the other tip mounting seat 29 at the distal end side with the intersection 21 spaced radially outward from the rotation axis O, and the sub cutting edge 18 is located at the outer peripheral side. Is similarly positioned and fixed.
The sub cutting edge 18 is an outer peripheral blade, and the convex curved blade 18a is displaced from the main cutting edge 17 of the main chip 10A to the base end side and the outer peripheral side at a position from the intersection 21 at the tip to the tip 27. The straight blade 18b extends further behind the tool body 2
6 are arranged along the outer circumference. This throw-away chip 10 is used as a sub chip 10B. And the tool body 26
The straight blade 18 located on the base end side of the sub cutting edge 18
An auxiliary tip may be further attached so that b and the rotation locus of the cutting blade overlap.

Such a two-flute ball end mill 25
In the above, since the main cutting edge 17 and the sub cutting edge 18 can be provided by using two identical chips 10, only one type of mold is required when manufacturing the chip 10, and the chip 10 to be stored for replacement is also one. Since only one type is required, the production cost and the running cost can be reduced. Moreover, in the main tip 10A located on the tip side of the tool main body 26, the main cutting edge 17 is arranged on the outer peripheral side, so that the center line 2 of the tip 10A is
The width (area) of the part on the side of the sub-cutting edge 18 located on the inner side with respect to 3 is small, the space occupied by the chip 10A mounted by cutting out the tip part 27 of the tool main body 26 is small, and the space of the sub-tip 10B is small. Since the tip mounting seat 29 is displaced toward the base end side, a large thickness of the central portion 27a of the tip end portion 27 can be ensured, and the strength of the tool main body 26 is high.

In this ball end mill 25, when the rotary cutting is performed about the rotation axis O, the convex cutting edges 17a, 18a of the main cutting edge 17 of the main chip 10A and the sub cutting edge 18 of the sub chip 10B are cut. The rotation trajectory has a substantially hemispherical shape with a radius R. Moreover, the main cutting edge 17 and the sub-cutting edge 18 have the same rotation locus at a portion facing each other in a cross section orthogonal to the rotation axis O. Therefore, the cutting balance is good, the impact at the time of cutting is not biased, and chatter vibration does not occur. Moreover, the finished surface of the work material becomes good. Further, the main cutting edge 17 and the sub cutting edge 18 are substantially 180 ° rotationally symmetric with respect to the rotation axis O, that is, are at equally divided positions. For example, in a cross section orthogonal to the rotation axis O at the intersection 21 at the tip of the sub cutting edge 18 shown in FIG. 8, the rotation locus of the intersection 21 is T1, and the intersection 21 of the sub cutting edge 18 (reference numeral 18a1). )
The point 17a1 of the main cutting edge 17 overlaps a position 180 ° away from the main cutting edge 17. As a result, the cutting balance is further stabilized, and the finishing by high-precision cutting can be performed.

In addition, in the main cutting edge 17 of the main chip 10A, a straight blade 17b for cutting the shoulder portion of the processing surface.
Although the impact at the time of cutting is large, the intersection 21 forming the base end of the straight blade 17b is thicker than the intersection 20 on the distal end, so that there is no loss of this part.
At the tip of the tool body 26, the tip intersection 20 of the main tip 10A is on the rotation axis O and is hardly used for cutting, but the intersection 2 located at the tip of the sub tip 10B.
1 is separated from the rotation axis O toward the base end and the outer periphery,
Although the peripheral speed is large and the impact when sending in the direction of the rotation axis O is large, also in this case, since the thickness of the intersection portion 21 is large, it is possible to prevent the loss of this portion.

As described above, according to the indexable insert 10 according to the present embodiment, the main cutting edge 17 and the sub cutting edge 18 are provided on one tip 10. There is no need to prepare two types of chips, and two types of chips are used to form the main cutting edge 17.
And the sub-cutting edge 18 can be provided, respectively, so that the manufacturing cost and running cost of the chip 10 can be reduced. Moreover, the main cutting edge 1 with respect to the center line 23 of the tip 10
Since the distance from the cutting edge 7 to the sub-cutting edge 18 is made smaller, the thickness of the tip central portion 27a of the tool body 26 at the tip portion 27 of the tool body 26 can be set large when the ball is mounted on the ball end mill 25. Strength can be secured.

Further, according to the ball end mill 25 equipped with the throw-away tip 10, in the region where the main cutting edge 17 and the sub cutting edge 18 are opposed to the rotation axis O, the rotation locus of the two cutting edges 17, 18 Since they are the same, the cutting balance is good, the impact at the time of cutting is not biased, and the finished processed surface is good without causing chatter vibration. In addition, in the mounted state, the main cutting edge 17 and the sub cutting edge 18 are provided at equally divided positions in a cross section orthogonal to the rotation axis O of the tool body 26, so that the cutting balance is further improved.

In the above-described embodiment, on the upper surface 12 of the indexable insert 10, the intersections 20 and 21 at both ends are sharp corners where the main cutting edge 17 and the sub cutting edge 18 intersect at a point (pin angle). Instead of this, as a modified example, a throwaway tip having a small cutting edge formed by cutting corners of the intersections 20 and 21 may be provided. That is, as shown in FIG. 8, at the intersections 20 and 21 at both ends of the throw-away tip 40 (only one intersection 20 is shown in the figure), the upper and lower surfaces 12, It may be cut in 11 directions, and the intersection ridgeline between the cut side surface and the upper surface 12 may be used as the small cutting blade 41. By doing so, it is possible to suppress the loss of the corner portion at the intersection 20 (21). Then, the main cutting blade 17 is positioned on the outer peripheral side of the ball end mill 25 so that
When the is attached as the main tip, the small cutting blade 41 may be disposed outside near the rotation axis O at the tip of the tip 40.

As shown in FIG. 9, the small cutting blade 41 may be disposed so as to intersect with the rotation axis O, or the small cutting blade 41 straddles the rotation axis O on the opposite side (not shown). May be located in its entirety. Further, as shown in FIG. 10, a connecting portion between the small cutting edge 41 and the convex curved blade 17 a of the main cutting edge 17 may be chamfered to form a chamfered portion 42, whereby the intersection 20 of the tip 40 is formed. Of the cutting edge can be further suppressed.

Next, a second embodiment of the ball end mill will be described with reference to FIG. FIG. 11 is a front end view of the ball end mill corresponding to FIG. 7, and the same portions as those in the first embodiment are denoted by the same reference numerals and description thereof is omitted.
In the ball end mill 44 shown in FIG.
A and the sub chip 10B are arranged at unequal division positions in the circumferential direction of the tool main body 26. For example, when viewed in the rotation direction P of the tool main body 26, the sub cutting edge 18 of the sub chip 10B is located at a position away from the main cutting edge 17 of the main chip 10A by an angle β smaller than 180 ° on the rear side in the rotation direction. ing. Moreover,
In a section orthogonal to the rotation axis O in a region where the rotational trajectories of the main cutting edge 17 and the sub-cutting edge 18 face each other in the radial direction, the main cutting edge 17 and the sub-cutting edge 18 have the same rotational trajectory. For example, in a cross section orthogonal to the rotation axis O at the intersection 21 at the tip of the sub cutting edge 18 shown in FIG. 11, the rotation locus of the intersection 21 is T1 and the angle β is separated from the intersection 21 of the sub cutting edge 18. The point 17a1 of the main cutting edge 17 overlaps the position.

Here, the reason that the angle β is set to an angle smaller than 180 ° rearward in the rotation direction from the main cutting edge 17 is that the main cutting edge 17 is located on the tip side of the sub cutting edge 18 and the cutting amount (cutting amount) is set. Is small, while the sub cutting edge 18 has a small amount of cutting, so by setting the angle β to an appropriate size of less than 180 °, the rotation stroke of the main cutting edge 17 during cutting is reduced. By increasing the rotation stroke of the sub cutting edge 18 (angle (360 ° −β)) together with (angle β), the cutting amount can be balanced. And the main chip 1
Since the main cutting edge 17 and the sub cutting edge 18 at the unequally divided positions do not resonate by arranging the 0A and the sub-tip 10B unequally in the circumferential direction of the tool main body 26, vibration does not occur and cutting performance is improved. Can be improved.

The ball end mill 25 may have a four-blade configuration or the like, and a large number of main chips 10A and sub chips 10B may be arranged. Even in such a case, the unequally divided configuration according to the second embodiment can be adopted. In this case, the angle between the main cutting edge 17 and the sub cutting edge 18 in the rotational direction front is set to the sub cutting edge 18 in the rotational direction rear side. It may be set to be larger than the angle up to.
Further, in the embodiment, the main cutting edge 17 and the sub cutting edge 18 are provided only on the upper surface 12 with the throw-away tip 10 as a positive tip. However, the cutting edge may be formed on both upper and lower surfaces as a negative tip. It is sufficient that the flank does not rub during cutting according to the mounting posture. In the ball end mill 25, the rotation trajectories of the main cutting edge 17 and the fork cutting edge 18 do not have to be the same in a cross section orthogonal to the rotation axis.

[0028]

As described above, the indexable insert according to the present invention has the main cutting edge and the sub cutting edge provided on the ridge of the upper surface facing the seating surface, and the main cutting edge and the sub cutting edge are provided opposite to each other. Since the secondary cutting edge is asymmetric, for example, when mounting a chip on a rolling tool such as a ball end mill, one of the same chips is arranged so that the main cutting edge is located on the outer peripheral side, and the other. Can be arranged such that the sub-cutting edge is located on the outer peripheral side, and it is sufficient to manufacture one kind of chip, mount a plurality of chips, and store it for replacement, and the cost is reduced.

Further, the distance to the sub cutting edge is set smaller than the distance to the main cutting edge with respect to an imaginary line connecting the two intersections of the main cutting edge and the sub cutting edge. To
If the main cutting edge is positioned on the outer peripheral side and mounted on the tip of the tool body such as a ball end mill, the space of the sub cutting edge located inside the tool body by cutting out the tool body is small, The thickness at the center of the tip of the body can be secured,
The strength of the tool body is high. The throw-away insert has a main cutting edge and a sub-cutting edge each formed of a convex curved blade and a straight blade, and the convex cutting blade and the linear blade are alternately arranged in a substantially leaf-shaped plate shape. Since the straight blade of the blade is shorter than the straight blade of the secondary cutting blade, the area of the convex curved blade of the main cutting edge becomes larger, and when mounted on the tip of the ball end mill, cutting by the convex curved blade of the main cutting blade A large amount can be secured. In addition, since the main cutting edge and the sub cutting edge have a convex curve shape protruding in a direction away from the seating surface in a side view, the strength of a bolted portion (insertion hole) for mounting the tip to the tool body is high. Therefore, the strength of the entire chip is increased.

The two intersections of the main cutting edge and the sub cutting edge are
Since one has a greater thickness from the seating surface than the other, the strength of the cutting edge in the thicker portion can be enhanced. Also, the intersection between the straight cutting edge of the main cutting edge and the convex curved cutting edge of the sub cutting edge is
Since the thickness from the seating surface is set larger than the intersection of the convex curve blade of the main cutting edge and the straight blade of the sub cutting edge, the main cutting edge of the tip mounted on the tip side of the tool body such as a ball end mill The shoulder portion of the work material is cut by a straight blade located on the base end side of the workpiece, and the impact at the time of cutting is large. However, the chip thickness of this portion is large, so that the cutting edge can be prevented from being chipped.
In addition, the tip of the convex curve blade of the sub-cutting edge of the tip disposed closer to the base end side of the tool body than the main cutting edge has a large peripheral speed and a large impact at the time of cutting by being sent in the direction of the tip, Since the tip thickness at this portion is large, the loss of the cutting edge can be suppressed.

In a throw-away type ball end mill according to the present invention, the throw-away tip is the throw-away tip according to any one of claims 1 to 6, and the main cutting edge of the throw-away tip is the tip of the tool body. The other indexable insert is disposed so as to extend from the vicinity of the rotation axis to the outer peripheral side, and extend to the outer peripheral side at a position where the sub cutting edge is retracted from the distal end of the tool body to the proximal end side. Since there,
One kind of insert can be used as main cutting edge and sub cutting edge,
Production and running costs are low.

The main cutting edge and the sub cutting edge are located in a region facing each other in a direction perpendicular to the rotation axis of the tool body.
Since the rotation trajectory is the same in a cross section orthogonal to the rotation axis,
Good finishing accuracy during cutting and good cutting balance for each cutting edge. In addition, since the main cutting edge and the sub cutting edge are arranged at equally divided positions in the circumferential direction in a cross section orthogonal to the rotation axis of the tool body, the impact during cutting is not biased, and the cutting balance is good, Finished surface is good without chatter vibration. In addition, the main cutting edge and the sub cutting edge are arranged at unequal division positions in the circumferential direction in a cross section orthogonal to the rotation axis of the tool body, so that the main cutting edge and the sub cutting edge resonate during cutting. Since no vibration occurs, the cutting performance is improved. Also, when viewed in the rotating direction of the tool body, the angle from the main cutting edge to the sub cutting edge in the rotational direction rearward direction is set smaller than the angle from the main cutting edge to the rotational direction forward direction sub cutting edge. Therefore, the cutting volume of the main cutting edge protruding toward the distal end side of the tool body is larger than the cutting volume of the sub cutting edge at the position retracted to the base end side from the main cutting edge, but the rotation stroke of the main cutting edge is By shortening the rotation stroke of the cutting blade, the cutting volumes of both cutting blades can be evenly balanced.

[Brief description of the drawings]

FIG. 1 is a plan view of a throw-away tip according to a first embodiment of the present invention.

FIG. 2 is a side view of the throw-away tip shown in FIG. 1 as viewed from a direction A.

FIG. 3 is a side view of the throw-away tip shown in FIG. 1 as viewed from a direction B.

FIG. 4 is a side view of the throw away tip shown in FIG. 1 as viewed from a direction C.

FIG. 5 is a side view of the throw-away tip shown in FIG. 1 as viewed from a direction D.

6 is a side view of a central portion of the ball end mill according to the embodiment equipped with the throw-away tip shown in FIG.

FIG. 7 is a front end view of the ball end mill shown in FIG. 6;

FIG. 8 is an enlarged view of a top end portion of a first modification of the throw-away tip according to the embodiment mounted on the ball end mill shown in FIG. 6;

FIG. 9 is an enlarged view of an upper end portion similar to FIG. 8, showing a second modification of the throw-away tip according to the embodiment.

FIG. 10 is an enlarged view of a top end similar to FIG. 8, showing a third modification of the throw-away tip according to the embodiment.

FIG. 11 is a front view similar to FIG. 7 of a ball end mill according to a second embodiment of the present invention.

FIG. 12 is a side view of a conventional ball end mill.

[Explanation of symbols]

 10, 40 Indexable insert 10A Main insert 10B Secondary insert 17 Main cutting edge 17a, 18a Convex curved edge 17b, 18b Straight blade 18 Secondary cutting edge 25, 44 Ball end mill 26 Tool body m Virtual line

Claims (11)

[Claims] 1. A throw-away insert in which a main cutting edge and a sub cutting edge are provided opposite to a ridgeline of an upper surface facing a seating surface, and the main cutting edge and the sub cutting edge are asymmetric. 2. A distance between the main cutting edge and the sub cutting edge is set to be smaller than a distance to the main cutting edge with respect to an imaginary line connecting two intersections of the main cutting edge and the sub cutting edge. The indexable insert according to claim 1, characterized in that: 3. The leaf-away insert according to claim 1, wherein the main cutting edge and the sub cutting edge each include a convex curve blade and a straight blade, and the convex curve blade and the straight blade are alternately arranged. The indexable insert according to claim 1, wherein a straight edge of the main cutting edge is shorter than a straight edge of the sub cutting edge. 4. The throwaway according to claim 1, wherein the main cutting edge and the sub cutting edge have a convex curve shape protruding in a direction away from the seating surface in a side view. Chips. 5. The two intersections of the main cutting edge and the sub cutting edge,
The throw-away tip according to any one of claims 1 to 4, wherein one has a greater thickness from the seating surface than the other. 6. The intersection between the straight cutting edge of the main cutting edge and the convex curved cutting edge of the sub cutting edge is closer to the seating surface than the intersection of the convex cutting edge of the main cutting edge and the straight cutting edge of the sub cutting edge. 6. The throw-away tip according to claim 5, wherein the thickness is set large. 7. A throw-away type ball end mill in which a plurality of throw-away tips are provided at a tip portion of a tool main body, and a rotation locus of a cutting edge of the throw-away tip is substantially hemispherical. The indexable insert according to any one of claims 1 to 6, wherein the indexable insert is arranged such that the main cutting edge extends from the vicinity of the rotation axis at the tip of the tool body to the outer peripheral side. The throw-away insert according to claim 1, wherein the auxiliary cutting edge is disposed so as to extend to the outer peripheral side at a position where the sub-cutting edge is retracted from the distal end of the tool main body to the proximal end side. 8. The main cutting edge and the sub-cutting edge have the same rotation trajectory in a section orthogonal to the rotation axis in a region opposed to each other in a direction orthogonal to the rotation axis of the tool body. The throw-away type ball end mill according to claim 7, characterized in that: 9. The cutting tool according to claim 7, wherein the main cutting edge and the sub cutting edge are arranged at equally dividing positions in a circumferential direction in a cross section orthogonal to a rotation axis of the tool main body. The throw-away ball end mill as described. 10. The tool according to claim 7, wherein the main cutting edge and the sub cutting edge are arranged at unequally divided positions in a circumferential direction in a cross section orthogonal to a rotation axis of the tool body. 8. The throw-away ball end mill according to item 8. 11. An angle from the main cutting edge to the sub cutting edge in the rotational direction forward direction from the main cutting edge to the sub cutting edge in the rotational direction rear direction as viewed in the rotational direction of the tool body. 11. The throw-away type ball end mill according to claim 10, wherein the angle is set smaller.