JP2002263918A - Throw-away tip and milling tool on which the throw-away tip is installed - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a throw-away tip capable of preventing a cutting edge from being chipped at a corner part and having a long service life, and a milling tool on which the throw-away tip is installed. SOLUTION: A second rake face 10 formed aslant toward a second cutting edge 7 (top part (p)) so as to near a lower surface 3, and the second cutting edge 7 has a negative rake angle γ. Also, a chamfered part 11 is formed at the top part (p) so that the clearance angle θ of the second cutting edge 7 can be reduced. Thus, the included angle δ2 of the second cutting edge 7 at the top part (p) becomes an obtuse angle, and a large tip strength can be given to the top part (p). As a result, the second cutting edge 7 can be prevented from being chipped and worn at the top part (p), and the service life of the throw-away tip 1 can be increased.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a indexable insert and a milling tool to which the indexable insert is mounted.

[0002]

2. Description of the Related Art Conventionally, in a throw-away type insert used for, for example, a ball end mill, a rake face is formed flat, and a height of a cutting edge (a thickness of the insert) is formed to be the same in a side view. Was common.

However, in this indexable insert, the entire cutting edge simultaneously bites into the work material, so that an impactful cutting load acts on the cutting edge, causing chipping of the cutting edge and rapid progress of wear. There was a drawback that it would.

[0004] For this reason, Japanese Utility Model Laid-Open Publication No. 7-31223,
Japanese Unexamined Patent Application Publication No. 11-197934 describes a throw-away type tip in which the cutting edge is curved so that the central portion of the cutting edge is convex in the cutting direction in a side view. According to these indexable inserts, since the cutting edge gradually bites into the work material from the central portion, it is possible to prevent an impact cutting load from acting on the cutting edge.

[0005]

However, in the indexable insert described in Japanese Utility Model Laid-Open Publication No. 7-31223, the rake angle of the cutting edge is set to a negative angle (negative), so that the cutting resistance increases. There is a problem that the sharpness is poor and high-precision cutting cannot be performed. On the other hand, in the throw-away type end mill described in JP-A-11-197934, the rake angle of the cutting edge is a positive angle (positive), so that the cutting edge strength of the cutting edge decreases,
In particular, there is a problem that the cutting edge is apt to be broken or worn at the corner of the throw-away type insert.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and it is possible to prevent a cutting edge from being lost at a corner portion and to provide a throw-away type tip having a long life and a throw-away type tip. It is intended to provide a milling tool to be mounted.

[0007]

In order to achieve this object, a throw-away tip according to claim 1 is formed in a substantially triangular shape or a substantially rectangular shape in a top view, and is provided on each side ridge of the top surface. A cutting edge, wherein the cutting edge includes a first cutting edge having a regular rake angle, and a second cutting edge connected to the first cutting edge and having a negative rake angle. The two cutting edges are formed such that one end on the corner side where the respective side ridges intersects is receded in the direction opposite to the cutting direction with respect to the other end connected to the first cutting edge. The edge angle of the second cutting edge is in a range of approximately 90 ° to approximately 120 ° at a corner portion where each of the edge lines intersects.

According to a second aspect of the present invention, there is provided the indexable insert according to the first aspect,
The rake angle of the second cutting edge is a negative angle in a range of approximately 5 ° to approximately 25 ° at a corner portion where each edge line crosses.

According to a third aspect of the present invention, there is provided the indexable insert according to the first or second aspect, wherein the length of the first cutting edge is substantially equal to the length of each of the side ridges. The length of the second cutting edge is substantially equal to or more than 1/6 of the length of each side ridge portion corresponding to the length of the first cutting edge.

The indexable insert according to a fourth aspect of the present invention is the indexable insert according to any one of the first to third aspects, wherein the side where the flank is formed has a tip mounted on a milling tool body. A flat contact surface that can be in contact with the wall surface of the seat is formed.

[0011] The throwaway tip according to claim 5 is:
The indexable insert according to any one of claims 1 to 4 is mounted.

[0012]

Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a top view of a throw-away tip 1 according to a first embodiment of the present invention, and FIG. 2 is a side sectional view of the throw-away tip 1 taken along line II-II of FIG. Note that the broken line in FIG. 1 indicates the outer shape of the lower surface 3.

The indexable insert 1 mainly comprises an upper surface 2, a lower surface 3 and a side surface 4, is mounted on a milling tool (not shown) such as a ball end mill, and has an intersection ridge line between the upper surface 2 and the side surface 4. This tool is used for cutting a die or the like by using the cutting edges 6 and 7 formed in the portion. In the present embodiment, a throw-away type chip made of a cemented carbide obtained by pressure-sintering tungsten carbide (WC) or the like and used in a ball end mill will be described as an example.

As shown in FIG. 1, the throw-away type chip 1 is formed in a substantially triangular shape when viewed from above.
The lower surface 3 (rear side in FIG. 1) is formed in a flat plate shape facing each other at a predetermined interval. Since the upper surface 2 is formed in a substantially triangular shape having an outer shape larger than the lower surface 3, the side surfaces 4 provided between the upper surface 2 and the lower surface 3 are inclined outward from the lower surface 3 toward the upper surface 2. (See FIG. 2). The side surface 4 is a portion that serves as a flank of a first cutting edge 6 and a second cutting edge 7 described later, and the clearance angle α is a regular angle. In addition,
The clearance angle α is approximately 11 °.

The lower surface 3 is a portion which is a seating surface which comes into contact with the chip mounting seat of the ball end mill, and is formed as a flat flat surface as shown in FIG. A mounting hole 5 is formed substantially at the center of the upper surface 2 and the lower surface 3 of the throw-away type chip 1 in the thickness direction of the throw-away type chip 1 (vertical direction in FIG. 2). The chip 1 is fixed to a milling tool by a clamp screw inserted into the mounting hole 5 with the lower surface 3 in contact with the mounting seat of the ball end mill.

The upper surface 2 is a portion that is exposed in the cutting direction when the throw-away type tip is mounted on a ball end mill, and is mainly formed from the flat portion 8, the first rake face 9, and the second rake face 10. Become. As shown in FIG. 1, each of the three side ridges where the upper surface 2 intersects the side surface 4 is formed in a convex curve shape protruding outward, and the ridge is formed in a substantially arc shape in a top view. A first cutting edge 6 and a second cutting edge 7. The three ridges have the same radius R
The radius R is larger than the radius of a circumscribed circle passing through the three tops P of the upper surface 2.

On the upper surface 2, a flat portion 8 is provided around the opening of the mounting hole 5, and as shown in FIG. 1, the flat portions 8 are connected by three arcs which are convex outward. It is formed in a substantially triangular shape as viewed from above. The flat portion 8 is formed on a flat flat surface, and is substantially parallel to the lower surface 3 (see FIG. 2). A first rake face 9 is formed on the outer periphery of the flat portion 8 in contact with the outer boundary of the flat surface 8.

The first rake face 9 is a portion to be a rake face of the first cutting edge 6, and the outer shape of the first rake face 9 is, as shown in FIG. 9
a and each edge line of the upper surface 2 are connected by a connecting portion S. The three arcs 9 a are formed such that their centers of curvature coincide with the center O of the inner diameter of the mounting hole 5. In addition, the radii r of the three arcs 9 a are formed to be equal to each other, and are smaller than the radius of a circumscribed circle passing through the three tops P of the upper surface 2. Here, the first cutting edge 6 and the second cutting edge 7 are formed on each side ridge line (between the tops P, P) of the upper surface 2 by being divided at the connecting portion S. The radius r of the arc 9a is The length of the cutting edge of one second cutting edge 7 (between the top P and the connecting portion S) is 1/6 or more of the length of each side ridge portion (between the tops P and P) of the upper surface 2. It is set to be the length. Since two second cutting edges 7 are formed on each side ridge of the upper surface 2, the length of each second ridge (between the tops P and P) is set to be equal to or more than ３ of the length of the second cutting edge 7. Will occupy.

As shown on the right side of the mounting hole 5 in FIG. 2, the first rake face 9 is bent in a curved manner from the outer boundary line of the flat face 8 and approaches the lower face 3, and then the first cutting edge 9 is cut. Upward away from the lower surface 3 toward 6 (upper side in FIG. 2)
It is formed to be inclined. Therefore, the rake angle β of the first cutting edge 6 is a regular angle, and the cutting edge angle δ1 of the first cutting edge 6 is an acute angle. The rake angle β of the first cutting edge 6 is
The first cutting edge 6 has substantially the same angle over the entire length (between the connecting portions S, S, see FIG. 1), and is approximately 10 °. The first rake face 9 is formed on a straight line in the side sectional view shown in FIG. 2, but may be formed in a convex or concave curve shape if the rake angle β is a regular angle.

The second rake face 10 is a portion to be a rake face of the second cutting edge 7, and as shown in FIG.
a and the two second cutting edges 7, 7 are formed in a substantially triangular shape in a top view. The top P where the second cutting edges 7, 7 intersect
Are formed in an arc shape when viewed from above. Here, the shape near the top P will be described with reference to FIG.

FIG. 3A shows an arrow IIIa in FIG.
FIG. 2 is a side view of the throw-away tip 1 as viewed from a direction. A ridge line below the top P rounded in an arc shape (the lower side in FIG. 3A) and crossing the side surfaces 4 and 4 in a top view has a direction of the lower surface 3 (the lower side in FIG. 3A). A side chamfer 11 is formed, the width of which converges. The chamfered portion 11 chamfers the corner portion of the indexable insert 1, that is, the flank of the top portion P rounded in an arc shape. Therefore, the first cutting edge 6 and the second cutting edge 6
Among the cutting edges 7, the apex P where the chamfered portion 11 serves as a flank has the smallest regular clearance angle.
The details of the clearance angle will be described later.

Returning to FIG. 1 and FIG. As shown in FIG. 1, the second rake face 10 extends from the circular-arc portion 9 a having a radius r corresponding to the boundary with the first rake face 9 to the lower surface 3 (the far side in the drawing of FIG. 1) toward the top P. It is formed so as to descend gradually so as to approach gradually. That is, as shown on the left side of the mounting hole 5 in FIG.
It is formed so as to be inclined downward (downward in FIG. 2) so as to approach the lower surface 3 from the arc portion 9a which is the boundary portion with the first rake face 9 toward the second cutting edge 7 (top P). for that reason,
The second cutting edge 7 has a negative rake angle γ.

The rake angle γ of the second cutting edge 7 is formed such that it continuously becomes a large negative angle from the connecting portion S toward the top P, and is approximately 18 ° at the top P. . Further, as described above, since the chamfered portion 11 is formed on the top P, the clearance angle θ of the second cutting edge 7 at the top P is, as shown in FIG. The angle is a regular angle smaller than α (= approximately 11 °). Note that the clearance angle θ is approximately 8 °. Therefore, the edge angle δ2 of the second cutting edge 7 at the top P is obtuse (edge angle δ2 = approximately 100 °), and a large edge strength can be given to the top P.
The loss and wear of the cutting edge 7 can be prevented, and the tool life of the indexable insert 1 can be improved.

The above-mentioned cutting edge angle δ2 of the second cutting edge 7
Is desirably in the range of approximately 90 ° to approximately 120 °. In that case, the rake angle γ is desirably in the range of approximately 5 ° to approximately 25 ° in order to prevent the cutting force from becoming excessive while improving the edge strength of the second cutting edge 7. . Further, the second rake face 9 is formed on a straight line in the side sectional view shown in FIG. 2, but may be formed in a convex or concave curve shape if the rake angle is a negative angle.

Next, the side surface 4 and the cutting edge shape of the indexable insert 1 will be described with reference to FIG. FIG. 3B is a side view of the indexable tip 1 as viewed from the direction of arrow IIIb in FIG.

The first cutting edge 6 is formed substantially parallel to the lower surface 3 in a side view, and one end of the second cutting edge 7 is provided at both ends (connecting portion S) of the first cutting edge 6. Departments are connected. The second cutting edge 7 is at the other end (top P).
Is inclined so as to approach the lower surface 3 side (the lower side in FIG. 3B) from one end connected to the first cutting edge 6, that is, the side opposite to the cutting direction (FIG. 3B). To the lower side). For this reason, the top P has the first cutting edge 6 and the second cutting edge 6.
The cutting edge 7 is arranged at the position closest to the lower surface, that is, at a position retracted from the cutting direction.

Therefore, such a throw-away tip 1
When cutting the work material by the first cutting edge 6, the first cutting edge 6 projects in the cutting direction and the second cutting edge 7 is retracted in the anti-cutting direction. Then, the second cutting edge 7 cuts the work material while sequentially moving the cutting point toward the top P. Therefore, it is possible to prevent a shocking cutting load at the time of biting from acting on the cutting edge, and it is possible to reduce vibration at the time of cutting, so that high-precision cutting characteristics can be obtained. It is.

The side surface 4 is formed in a curved shape that protrudes outward when viewed from above (see FIG. 1). On the side surface 4, a contact surface 4 a having a flat surface expands toward the lower surface 3. Two are formed so that it may become. Therefore, when the throw-away tip 1 is mounted on a ball end mill, the contact surface 4a can be brought into close contact with the wall surface of the mounting seat of the ball end mill. It can be firmly fixed without losing it.

Next, cutting tests performed using a ball end mill equipped with the indexable insert 1 configured as described above will be described below. FIGS. 4A and 4B are schematic cross-sectional views of the work material 21 used in the cutting test. In FIG. 4A, a ball end mill 40 to which the throw-away type tip 1 is mounted is illustrated using a two-dot chain line.

The cutting test includes a side cutting test (hereinafter referred to as test A) shown in FIG. 4A and a groove cutting test (hereinafter referred to as test B) shown in FIG. 4B. Two different
Various cutting tests were performed. These tests A and B are:
The ball end mill 40 (see a two-dot chain line in FIG. 4A) that is vertically upright with the surface to be cut 22 is
Along the following conditions (see FIG. 4)
This is a test in which the surface to be cut 22 is cut by moving (a) and (b) in the direction perpendicular to the paper surface) and the cutting time until the cutting edge is damaged is measured.

The detailed specifications of the cutting test (common to tests A and B) are as follows: work material: Inconel 718 (HRC45), machine used: horizontal machining center, spindle rotation speed: 250 revolutions / min, axial depth of cut Z: 12.5 mm, cutting oil material: oily. In addition, the details of the test A
Table feed: 18 mm / min, depth of cut X in the radial direction: 4 mm, cutting method: down cut, and detailed specifications regarding test B are shown in Table feed: 7 mm / mi.
n.

In the cutting test, the indexable insert 1 described in the present embodiment (hereinafter referred to as the present invention).
And the present invention product does not form the second rake face 10 on the upper surface 2, that is, the second cutting edge 7 is not formed, and the cutting edge is constituted only by the first cutting edge 6. (Hereinafter, referred to as a conventional product). The product of the present invention and the conventional product are both made of the same tool material (hard metal). The rotation radius R of the ball end mill, that is, the cutting edge radius R of the first cutting edge 6 and the second cutting edge 7 (see FIG. 1) is R = 25 mm.

FIG. 4C is a diagram showing the test results in the tests A and B for the product of the present invention and the conventional product. In FIG. 4C, the time shown in parentheses is the total cutting time that has elapsed from the start of each test A and B to the termination of the test.

First, in Test A, at 3 and 46 minutes after the start of the side surface cutting test, a defect occurred in the corner portion (the position corresponding to the top P in FIG. 1) of the conventional product. On the other hand, the product of the present invention does not have any chipping edge even after 3 hours and 46 minutes have passed,
The wear was advancing due to normal wear, and was able to withstand cutting sufficiently thereafter.

Next, in Test B, a defect occurred in the conventional product when 38 minutes had passed since the start of the groove cutting test. In addition, the defect site | part was the corner part (position corresponding to the top part P in FIG. 1) similarly to the test A. On the other hand, the product of the present invention showed normal wear and abrasion was progressing without breakage of the cutting edge even after the elapse of 38 minutes, and was able to withstand cutting sufficiently thereafter.

As described above, the indexable insert 1 is provided with the second rake face 10 forming the negative rake angle γ and the chamfered portion 11 forming the positive relief angle θ at the top P. I have. Therefore, the second at the top P
By improving the cutting edge strength of the cutting edge 7, it is possible to prevent the cutting edge from being chipped or worn at the top P, and as a result, it is possible to improve the life of the indexable insert 1.

Next, a second embodiment will be described with reference to FIG. The indexable tip 1 of the first embodiment is
In contrast to the triangular flat plate, the indexable tip 30 of the second embodiment is formed in a substantially rectangular flat plate. The same parts as those in the first embodiment are denoted by the same reference numerals, and description thereof will be omitted.

FIG. 5A shows a throw-away type tip 3.
FIG. 5B is a top view of FIG. 5A, and FIG.
It is a sectional side view in the Vb line. Note that the broken line in FIG. 5A indicates the outer shape of the lower surface 3.

The throw-away tip 30 is shown in FIG.
As shown in (a), it is formed in a rectangular shape in a top view,
A first cutting edge 6 and a second cutting edge 7 which are formed in a straight line are provided at each of four side ridges where the upper surface 2 intersects the side surface 4.

As in the first embodiment, the upper surface 2 has a flat surface 8, a first rake surface 9 for providing a first rake angle β to the first cutting edge 6, and a negative angle for the second cutting edge 7. And a second rake face 10 for providing a rake angle. Also, the arc portion 9a
Of the second cutting edge 7 is the same as in the first embodiment.
The cutting edge length (between the top P and the connecting portion S) is set to be 1/6 or more of the length of each side ridge of the upper surface 2. The top part P where the second cutting edges 7, 7 intersect is formed by being rounded in an arc shape when viewed from above, and is chamfered by the chamfered part 11 on the side surface 4 side as in the first embodiment. The chamfering forms a regular relief angle θ at the second cutting edge 7 at the top P.

With this configuration, even if the throw-away tip 30 has a substantially rectangular flat plate shape, the top P
In this case, the cutting edge angle δ2 of the second cutting edge 7 can be made obtuse, and the cutting edge strength can be improved.

The present invention has been described based on the embodiments. However, the present invention is not limited to the above embodiments.
It can be easily inferred that various improvements and modifications can be made without departing from the spirit of the present invention.

For example, the throw-away tips 1 and 30
Is a high-hardness material such as titanium carbide, titanium nitride, titanium carbonitride, aluminum titanium oxide,
Alternatively, these may be combined and multi-layer coated. Further, in the second embodiment, the case where the throw-away tip 30 is formed in a substantially square shape as an example of the throw-away type tip 30 formed in a rectangular shape when viewed from the top is described. However, the tip is formed in a rectangular shape or a parallelogram shape. It may be. In the case of forming a parallelogram, the second rake face 1 is formed only at corners where the edge strength is particularly reduced, that is, at two tops P where the crossing angles of the cutting edges are acute when viewed from above.
0 may be provided.

[0044]

According to the present invention, the cutting edge of the indexable insert has a first cutting edge having a regular rake angle and a second cutting edge connected to the first cutting edge and having a negative rake angle. A second cutting edge, and the second cutting edge cuts one end on the corner side where the respective side ridges intersect with the other end connected to the first cutting edge. It is formed to recede in the direction opposite to the direction. Therefore, when cutting a work material with such a throw-away type insert, the first cutting edge first bites into the work material, and then the second cutting edge gradually bites toward the cutting edge. Will be. Therefore, there is an effect that it is possible to prevent a shocking cutting load at the time of biting from acting on the cutting edge. Also,
Since the rake angle of the first cutting edge is a regular angle, the cutting resistance is reduced, and the sharpness at the time of cutting can be improved. On the other hand, the rake angle of the second cutting edge is a negative angle, and the angle of the cutting edge of the second cutting edge is in a range of approximately 90 ° to approximately 120 ° at a corner portion where each of the side ridges intersects. Therefore, since the edge strength of the cutting edge can be improved, it is possible to prevent chipping and wear of the cutting edge at a corner portion, and as a result, it is possible to improve the life of the indexable insert. .

The rake angle of the second cutting edge is a negative angle in the range of approximately 5 ° to approximately 25 ° at the corner where each side ridge crosses. Therefore, there is an effect that it is possible to prevent the cutting resistance from becoming excessive while having the effect of improving the edge strength of the cutting edge.

The length of the first cutting edge is set to be approximately 5/6 or less with respect to the length of each side ridge, and the length of the second cutting edge is set to the length of the first cutting edge. Correspondingly, the length is approximately 1/6 or more of the length of each side ridge. Therefore, there is an effect that the edge strength of the cutting edge can be secured while maintaining good cutting performance.

On the side surface where the flank is formed, there is formed a flat contact surface which can contact the wall surface of the tip mounting seat formed on the milling tool main body. Therefore, the indexable insert can be brought into contact with the wall surface of the tip mounting seat of the milling tool main body by such a contact surface, so that the indexable insert can be firmly attached to the milling tool without rattling. This has the effect.

[Brief description of the drawings]

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

FIG. 2 is a side sectional view of the indexable tip taken along line II-II in FIG.

3 (a) is a side view of the throw-away type chip as viewed from the direction of arrow IIIa in FIG. 1, and FIG. 3 (b) is a throw-away type chip as viewed from the direction of arrow IIIb in FIG. FIG.

FIGS. 4 (a) and 4 (b) are schematic cross-sectional views of a work material used in a cutting test, and FIG. 4 (c) shows each test A, It is the figure which showed the test result in B.

5A and 5B are views showing a throw-away tip in the second embodiment, FIG. 5A is a top view of the throw-away tip, and FIG. 5B is a view of FIG. Vb
It is a sectional side view in the -Vb line.

[Explanation of symbols]

1, 30 indexable insert 4 side surface (part of flank) 4a contact surface 6 first cutting edge (part of cutting edge) 7 second cutting edge (part of cutting edge) 11 chamfer (flank) Α, θ Escape angle β Rake angle (Regular rake angle) γ Rake angle (Negative rake angle) δ1, δ2 Edge angle P Top (corner) S Top (Corner) (Two cutting edges connected)

Claims (5)

[Claims] 1. A throw-away type chip having a substantially triangular or substantially rectangular shape in a top view and having a cutting edge at each side ridge of the upper surface, wherein the cutting edge has a regular rake angle. One cutting edge,
The second cutting edge is connected to the first cutting edge and has a negative rake angle.
A cutting edge, wherein the second cutting edge has a cutting direction with respect to the other end where one end on the corner side where the respective side ridges intersect is connected to the first cutting edge. And the cutting edge angle of the second cutting edge is in a range of approximately 90 ° to approximately 120 ° at a corner portion where each of the side ridges intersects. A throw-away tip. 2. The rake angle of the second cutting edge is approximately 5 ° to approximately 25 ° at a corner portion where each side ridge line intersects.
2. The indexable insert according to claim 1, wherein the negative angle is in the range of: 3. The length of the first cutting edge is approximately 5/6 or less with respect to the length of each side ridge, and the length of the second cutting edge is equal to the length of the first cutting edge. The throw-away tip according to claim 1 or 2, wherein the length of each side ridge portion is set to substantially 1/6 or more corresponding to the length. 4. A flat contact surface, which is capable of contacting a wall surface of a tip mounting seat formed on a milling tool main body, is formed on a side surface on which a flank surface is formed. Item 4. The indexable insert according to any one of Items 1 to 3. 5. A milling tool to which the indexable insert according to claim 1 is mounted.