JP2003001512A - Cutting insert and cutting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce cutting resistivity and also to keep good exhaustibility of chips, and to heighten edge strength. SOLUTION: The clearance angle α of the flank 23A of a main cutting edge is set to be α<0 deg. and also the clearance angle β of the flank 23B of a minor cutting edge is set to be β=0 deg.. The length of a ridge line of which the flank 23B of the minor cutting edge is orthogonal to a bottom face 21 is made longer than that of the minor cutting edge 25. The area of the bottom face 21 is made larger than that of a top face 22. A breaker is formed on the top face 22. A cutting insert 20 is equipped so that its radial rake can be made to be negative to the body 30 of a tool. The bottom face 21 of the cutting insert 20 is restricted by making seat on the bottom face of a mounting seat for the insert and by abutting the flank 23B of the minor cutting edge against the restricting face of the mounting seat for the insert.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cutting insert mounted on a cutting tool such as a face mill and used, and a cutting tool equipped with this cutting insert.

[0002]

2. Description of the Related Art Generally, in order to realize high-efficiency machining in a cutting tool such as a face milling machine, it is necessary to reduce the cutting resistance to suppress the vibration generated in the tool body and to maintain the good chip discharging property. Importantly, this is done by using positive type cutting inserts to make both the true rake angle and the cutting edge tilt angle positive. As an example of such a positive type cutting insert, FIG.
There is something like 0. This cutting insert 1
Has a substantially square flat plate shape, and has a main cutting edge 5 and a sub cutting edge 6 at the ridge line where the upper surface 3 (rake surface) facing the lower surface 2 (seating surface) and the side surface 4 (flank surface) intersect. Are formed. In addition, the side surface 4 (flank surface) inclines inward from the upper surface 3 toward the lower surface 2, that is, the main cutting edge 5
The clearance angles of the flank 4A and the flank 4B connected to the auxiliary cutting edge 6 are both positive, and the area of the lower surface 2 is the upper surface 3
Is smaller than the area.

The cutting insert 1 as described above is shown in FIG.
It is used by being attached to a cutting tool such as a face mill as shown in FIG. Note that FIG. 11 shows a state in which only one cutting insert 1 is mounted on the face milling cutter. This face mill has a tool body 10 that can be rotated about an axis O, and a plurality of chip pockets 11 are formed on the outer periphery of the tip end thereof, and insert mounting seats 12 are formed in the chip pockets 11. . The insert mounting seat 12 is composed of a bottom surface 13 that faces the front side in the tool rotation direction T, and constraining surfaces 14 and 14 that are made up of two wall surfaces that stand upright from the bottom surface 13 and face the tip end side of the tool body.

Then, the positive type cutting insert 1 described above is seated on the insert mounting seat 12 with its lower surface 2 seated on the bottom surface 13 of the insert mounting seat 12 and is continuous with the two adjacent main cutting edges 5. Flank 4A, 4
A is attached to the restraining surfaces 14, 14 of the insert mounting seat 12 so that the main cutting edge 5 is projected to the outer peripheral side of the tool body with a corner angle, and the auxiliary cutting edge 6 is attached to the axial line. It is projected toward the tool body tip side so as to extend in a direction orthogonal to O. At this time, in the cutting insert 1, the axial rake is set to be positive, the inclination angle of the cutting edge of the main cutting edge 5 is positive, and the radial rake is set to be positive. The true rake angle of 5 is positive.

[0005]

However, in the positive type cutting insert 1 as described above, the cutting edge angle is inevitably small, the cutting edge strength is reduced, and the cutting edge is apt to be damaged. . Moreover, since the area of the lower surface 2 forming the seating surface is smaller than the area of the upper surface 3, the cutting resistance received by the cutting insert 1 is locally reduced through the lower surface 2 of this small area to the back metal of the tool body 10. In addition, this back metal is small because both the axial rake and the radial rake of the cutting insert 1 are positive, and the strength of the tool body 10 is reduced, and the cutting resistance cannot be fully received. The tool body 10 is easily damaged. Therefore, when performing high-efficiency machining that increases the cutting amount of the work, not only the cutting edge of the cutting insert is damaged but also the tool body is damaged, which is important for achieving high-efficiency machining. It was a big problem in.

Further, the main cutting edge 5 is arranged with a corner angle as described above, and the flank 4A continuous with the main cutting edge 5 is formed.
When restraining the tool body 10 by the restraining surface 14 of the insert mounting seat 12, it is necessary to form the tool body 10 so as to wrap around the tool body outer peripheral side of the cutting insert 1. There is also a problem that the outer diameter is increased and the weight is increased, and the centrifugal force is influenced by the high speed rotation.

Further, in the positive type cutting insert 1 as described above, a positive clearance angle is given to the clearance surface 4A which is continuous with the main cutting edge 5 which abuts on the restraining surface 14 of the insert mounting seat 12. Therefore, as shown in FIG. 12, the cutting insert 1 rises along the restraining surface 14 of the insert mounting seat 12 by the cutting resistance (white arrow in the drawing) received during the cutting of the workpiece, and the positioning of the cutting edge is performed. There was a possibility that it would not be stable.

On the other hand, when a negative type cutting insert is used to secure the strength of the cutting edge, the cutting resistance cannot be reduced, and excessive power is required for the machine tool for rotating the tool body. As a result, the machining efficiency is limited by the ability of the machine tool. Also,
There is a negative type cutting insert as disclosed in Japanese Patent Publication No. 2000-516152, but even if such a cutting insert is used, the area of the lower surface forming the seating surface on the tool body becomes small. Because
The fear of damage to the tool body could not be eliminated.

The present invention has been made in view of the above problems, and provides a cutting insert having a high cutting edge strength, a good chip discharge property, a high cutting edge strength, and a high strength cutting tool. With the goal.

[0010]

[Means for Solving the Problems] By solving the above problems,
In order to achieve such an object, the cutting insert of the present invention has a substantially polygonal plate shape, and has an upper surface facing a lower surface forming a seating surface and a side surface crossing the upper surface forming a flank surface. A cutting insert in which a main cutting edge and a sub cutting edge are formed on a ridge line, a breaker is formed on the upper surface, and a clearance angle α of a flank that is continuous with the main cutting edge is set to α <0 °. And the clearance angle β of the flank that continues to the secondary cutting edge
Is set to α <β, and the length of the ridgeline at which the flank that continues to the sub cutting edge and the lower surface intersect is longer than the length of the sub cutting edge. Further, the cutting tool of the present invention has a plurality of chip pockets formed on the outer periphery of the tip of the tool body rotated around the axis, and the insert mounting seat formed in the chip pockets has a cutting insert of the present invention. Is a cutting tool equipped with
The cutting insert is mounted so that the radial rake is negative.

According to the present invention, the cutting insert is mounted on the tool body so that the radial rake of the cutting insert is negative, so that a positive cutting edge inclination angle can be obtained. Moreover, since the breaker is formed on the upper surface, it is possible to obtain a positive true rake angle, so that it is possible to reduce cutting resistance while maintaining good chip discharge performance. On the other hand, since the clearance angle α of the flank surface that is continuous with the main cutting edge of the cutting insert is negative α <0 °, it is possible to sufficiently secure the edge strength of the main cutting edge.

Further, since the cutting insert is attached to the tool body so that the radial rake becomes negative, the back metal of the tool body becomes large and a tool body having higher strength can be obtained. At this time, when the area of the lower surface that is the seating surface of the cutting insert to the tool body is formed larger than the area of the upper surface, the stress transmitted from the cutting insert to the tool body that receives cutting resistance is It can be distributed to the tool body via the lower surface of the tool.

Further, since the length of the ridgeline between the flank and the lower surface connected to the sub cutting edge is longer than the length of the sub cutting edge, the flank connected to the sub cutting edge has a certain area. The lower surface of the cutting insert is seated on the bottom surface of the insert mounting seat that faces the front side in the tool rotation direction, and the flank that is connected to the auxiliary cutting edge is constrained by a restraining surface that stands upright from the bottom surface of the insert mounting seat. Thus, the cutting insert can be mounted. In this way, if the flanks that are connected to the secondary cutting edge are constrained by the constraining surface of the insert mounting seat, when mounting the cutting insert with the main cutting edge having a corner angle, the tool body It is not necessary to form the tool body so as to go around to the outer peripheral side, and accordingly, the outer diameter of the tool body is also reduced, and the weight can be reduced. Also, by restraining the cutting insert with the flank of the auxiliary cutting edge,
Regardless of the shape of the flank that is continuous with the main cutting edge, cutting inserts with various blade shapes for the same tool body, for example, the main cutting edge is configured with a convex curve or the relief of the main cutting edge It is also possible to use a cutting insert having a multi-sided surface.

Here, the clearance angle β of the flank that is continuous with the auxiliary cutting edge
When is set to β ≦ 0 °, the intersection angle between the bottom surface of the insert mounting seat and the restraining surface standing upright from this bottom surface is 90 degrees.
The cutting insert will not rise along the restraint surface of the insert mounting seat even if the cutting resistance exerts a great influence on the cutting insert during cutting, so the cutting edge position accuracy must be kept high. You can In particular, when the clearance angle β of the flank connecting to the secondary cutting edge is set to β = 0 °, the crossing angle between the bottom surface of the insert mounting seat and the restraining surface standing upright from this bottom surface becomes 90 °, Processing for forming the mounting seat is facilitated.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the accompanying drawings. 1 is a perspective view of a cutting insert according to a first embodiment of the present invention, FIG. 2A is a plan view of the cutting insert, FIG. 2B is a view in the direction A in FIG. 11A is a sectional view taken along line I-I in FIG. 9A, FIG. 8D is a sectional view taken in the direction of arrow B in FIG. 14A, and FIG.

Cutting insert 2 according to the first embodiment
As shown in FIGS. 1 and 2, 0 has a substantially square flat plate shape, and the lower surface 21 forming the seating surface is a flat surface.
Four main cutting edges 24 each having a linear shape are formed on a ridge line forming each side where an upper surface 22 facing 1 and a side surface 23 (flanking surface) connecting the upper and lower surfaces 22, 21 intersect with each other.
At the intersection of the four main cutting edges 24, four linear cutting edges 25 are also formed. The main cutting edge 24 and the sub cutting edge 25 are located on the same virtual imaginary plane parallel to the lower surface 21, and have the same height from the lower surface 21. As a result, corner indexing is performed according to wear and the like, and a pair of adjacent main cutting edge 24 and auxiliary cutting edge 25
By using properly, one cutting insert can make a total of 4
It is designed so that it can be reused once.

The side surface 23 is inclined outward from the upper surface 22 toward the lower surface 21, and the area of the lower surface 21 is an area of the upper surface 21 (a virtual edge surrounded by four main cutting edges 24 and four sub cutting edges 25). Larger than the area of the plane),
The cutting insert 20 according to the first embodiment is a negative type. At this time, the flank (side surface 23) continuous with the main cutting edge 24, that is, the main cutting edge flank 23A
Is a plane, and the clearance angle α is α <0 °
Is set to (in the first embodiment, α = −
15 °). In addition, the flank (side surface 2) continuous with the auxiliary cutting edge 25
3) That is, the sub cutting edge flank 23B is also formed by a flat surface, and the clearance angle β is set to α <β ≦ 0 ° (β = 0 ° in the first embodiment). .
(Although it appears as α> 0 ° in FIG. 2, in the present embodiment, positive and negative clearance angles are taken into consideration based on the regulation of JIS B 4120, and in reality α <0.
It is shown as °. The same applies to FIGS. 8 and 9 described later. Therefore, the length L2 of the ridgeline where the sub cutting edge flank 23B and the lower surface 21 intersect is longer than the length L1 of the sub cutting edge 25.

Further, a breaker is formed on the upper surface 22, so that the rake surface 22A of the main cutting edge 24 and the rake surface 22B of the auxiliary cutting edge 25 are moved away from each cutting edge toward the center. It is a flat surface that gradually inclines so as to approach the lower surface 21 side. These rake faces 22A, 2
2B are formed to have substantially the same width, and the upper surface 22
Is connected to a flat surface 22C parallel to the lower surface 21 located in the central portion of the. Since the breaker is formed on the upper surface 22,
A positive rake angle θa (θa = 20 ° in the first embodiment) is given to the rake face 22A of the main cutting edge 24, and a positive rake angle θ is given to the rake face 22B of the auxiliary cutting edge 25.
b (θb = 15 ° in the first embodiment) is given. At this time, the cutting edge angle φa of the main cutting edge 24 is set to 85 ° (= 90 ° -α-θa), and the auxiliary cutting edge 25
The blade edge angle φb of is set to 75 ° (= 90 ° -β-θb). In addition, the central portion of the upper surface 22, that is, the flat surface 22C
A through hole 26 for screw clamping that penetrates to the lower surface 22 is formed in the central portion of the.

The negative type cutting insert 20 configured as described above is used by being attached to a cutting tool such as a face milling cutter as shown in FIG. Note that FIG. 3 shows a state in which only one cutting insert 20 is mounted on the face milling cutter. This front milling cutter has a tool body 30 that can be rotated about an axis O.
And a plurality of chip pockets 31 are formed on the outer peripheral portion of the tip at substantially equal intervals in the circumferential direction, and the wall surface of the chip pocket 31 facing the tool rotation direction T front side is located on the tool rotation direction T rear side. The insert mounting seat 32 is formed so as to be retracted by one step. Insert mounting seat 32
Is composed of a bottom surface 33 that faces the front side in the tool rotation direction T, and constraining surfaces 34 and 34 that are made up of two wall surfaces that stand upright from the bottom surface 33 and face the tool body outer peripheral side and the tool body tip side.

The negative type cutting insert 20 described above is seated on the insert mounting seat 32 with the lower surface 21 thereof seated on the bottom surface 33 of the insert mounting seat 32.
Moreover, the two auxiliary cutting edge flanks 23B, 23B adjacent to each other with the main cutting edge flank 23A in between are brought into contact with the restraining surfaces 34, 34 of the insert mounting seat 32, and are mounted by a clamp screw (not shown). ing. As a result, the main cutting edge 24 of the cutting insert 20 is projected to the outer peripheral side of the tool body with a corner angle (45 ° in the first embodiment), and the sub cutting edge 25 extends in the direction orthogonal to the axis O. It is arranged so as to be extended and projected toward the tip side of the tool body.

At this time, the cutting insert 20 has a negative axial rake in the range of -5 ° to -15 ° (in the first embodiment, the axial rake has a negative -1).
0 °) and the radial rake is negative in the range of −5 ° to −30 ° (in the first embodiment, the radial rake is −25 °).

Such a face mill has a tool body 31.
While being rotated around the axis O and being fed in the direction orthogonal to the axis O, the main cutting edge 24 protruding to the outer peripheral side of the tool main body performs the main cutting of the work, while The surface of the workpiece to be machined is finished by the protruding secondary cutting edge 25.

In the first embodiment having the above-mentioned structure, the cutting insert 20 is mounted on the tool body 30 so that the radial rake of the cutting insert 20 is negative.
Even though the cutting insert 20 is of a negative type, it is possible to give the main cutting edge 24 a positive cutting edge inclination angle. As shown in the explanatory view of FIG. 4, when the radial rake is increased to the negative angle side, the main cutting edge 24 arranged with a corner angle is located on the base end side of the tool body 30 in the axis O direction. This is based on the idea that the inclination angle of the cutting edge increases toward the regular angle side by inclining to the rear side in the tool rotation direction T as it goes. The cutting edge inclination angle is preferably set to 10 ° or more in consideration of cutting resistance and chip discharging property.

Further, since the breaker is formed on the upper surface 22 of the cutting insert 20 and the rake surface 22A of the main cutting edge 24 is provided with a positive rake angle, the cutting insert 20 is mounted on the tool body 30. When this is done, the radial rake takes a negative value, but the true rake angle can be made positive. Accordingly, in the first embodiment,
Both the inclination angle of the cutting edge and the true rake angle become positive, cutting resistance can be reduced, and good chip discharge performance can be maintained.

In the cutting insert 20, the clearance angle α of the main cutting edge flank 23A is α <0 °, and the clearance angle β of the auxiliary cutting edge flank 23B is β = 0 °. Further, since the blade is a negative type, the cutting edge angle thereof does not become a sharp acute angle, and sufficient cutting edge strength can be obtained.

Further, the area of the lower surface 21 forming the seating surface of the cutting insert 20 on the tool body 30 is larger than the area of the upper surface 21, and the cutting resistance received by the cutting insert 20 is larger than that of the large area. It can be dispersed via the lower surface 22 and transmitted to the tool body 30. in addition,
Since the cutting insert 20 is attached to the tool body 30 so that both the axial rake and the radial rake are negative, it is possible to secure a large back metal of the tool body 30 that supports the cutting insert 20. The tool body 30 having high strength can be obtained by the synergistic effect of.

Since the length L2 of the ridgeline between the sub cutting edge flank 23B and the lower surface 21 is longer than the length L1 of the sub cutting edge 25, the sub cutting edge flank 23B is wide to some extent. Of the insert mounting seat 3
The second restraining surface 34 makes it possible to restrain the auxiliary cutting edge flank 23B of the cutting insert 20.

As described above, when the auxiliary cutting edge flank surface 23B is restricted by the restriction surface 34 of the insert mounting seat 32, the main cutting edge 24 is provided with a corner angle to the cutting insert 20 and the tool main body. It is sufficient to restrain the two auxiliary cutting edge flanks 23B, 23B with the two restraint surfaces 34, 34 facing the outer circumferential side and the tip end side of the tool body, and the tool body 30 reaches the tool body outer circumferential side of the cutting insert 20. It does not need to be formed so as to wrap around. Therefore, the tool body 3
Since the outer diameter of 0 can be reduced and the weight can be reduced, and there is no fear of being affected by the centrifugal force generated by the high-speed rotation state during cutting, the tool body 30 suitable for high-speed rotation can be obtained.

Further, as shown in FIG. 5, when the cutting insert 20 is attached to the tool body 30, the auxiliary cutting edge is orthogonal to the axis O and seen in a section passing through the auxiliary cutting edge flank 23A. Since the clearance angle β of the clearance surface 23A is set to β = 0 °, the bottom surface 3 of the insert mounting seat 32 is
The angle of intersection between 3 and the constraining surface 34 is 90 °. therefore,
The bottom surface 33 and the constraining surface 34 reliably receive the cutting resistance (white arrow in the figure) received by the cutting insert 20, so that the cutting surface along the constraining surface 34 as in the case of using the positive type cutting insert. As a result, the cutting insert 20 does not rise up, the position accuracy of the cutting edge can be kept high, and the effect that the fixing rigidity of the cutting insert 20 is excellent can be obtained. Further, if the intersection angle between the bottom surface 33 of the insert mounting seat 32 and the restraining surface 34 is 90 °, the processing for forming the insert mounting seat 21 becomes easy.

Here, as shown in FIG. 6, by setting the radial rake of the cutting insert 20 to a negative value, a large chip pocket 31 for releasing chips generated by the cutting work of the work 40 is formed. Even if the chip pocket 31 is not provided, a good chip discharging property can be obtained, so that the chip pocket 31 can be made small. As a result, in addition to the large back metal, the number of cutting inserts 20 that can be mounted on the tool body 30 can be increased by about 20 to 70% compared to the conventional face milling cutter. By doing so, it is possible to reduce the load on the individual cutting inserts 20 mounted on the tool body 30 to extend the service life and improve the machining efficiency.

Similarly, by setting the radial rake of the cutting insert 20 to a negative value, as shown in FIG. 7, S point contact, that is, the S point having the weakest strength among the cutting edges (for cutting) The area in contact with the work 40 from the provided intersection of the main cutting edge 24 and the auxiliary cutting edge 25) becomes small, and a large area (non-S point contact area) where safe cutting can be performed can be taken. it can. Therefore, it is not necessary to change the tool or lower the processing conditions according to the size of the work 40 or the processing width.

As described above, according to the first embodiment, a positive cutting edge inclination angle and a positive true rake angle can be obtained even with the negative type cutting insert 20 having a high cutting edge strength. The cutting resistance can be reduced to maintain good chip discharge performance, and moreover, the cutting insert 20
It is possible to improve the strength of the tool body 30 to which is attached. Therefore, even if the feed amount of the tool body 30 at the time of cutting is increased to increase the cut amount of the work to about twice as large as the conventional amount, no problem occurs and high efficiency machining can be achieved. it can.

Next, a second embodiment of the present invention will be described, but the same parts as those of the first embodiment described above will be denoted by the same reference numerals and the description thereof will be omitted. FIG. 8A shows the second embodiment of the present invention.
The top view of the cutting insert by embodiment, (b) is the C direction arrow view in (a), (c) is the III-III sectional view taken on the line in (a), (d) is the D direction arrow in (a). FIG. 6E is a sectional view taken along line IV-IV in FIG.

Cutting insert 5 according to the second embodiment
As shown in FIG. 8, 0 has substantially the same configuration as that of the first embodiment, but the difference is that the main cutting edge flank has a multi-step surface shape. That is, the main cutting edge flank surface is a main cutting edge first flank surface 53A continuous with the main cutting edge 24,
The main cutting edge first flank 53A and the main cutting edge second flank 53B connecting the lower surface 21 are formed by two planes. Here, the clearance angle α1 of the first flank 53A of the main cutting edge
Is set to α1 = −15 ° (α1 <0 °) and the clearance angle α2 of the main cutting edge second flank 53A is α2.
It is set to = 0 °.

Then, such a cutting insert 50 is used.
Is the same tool body 30 as described in the first embodiment.
Used by being attached to. The restraint surface 34 of the insert mounting seat 32 is the auxiliary cutting edge flank 23B of the cutting insert 50.
By constraining, the shape of the main cutting edge flank is not questioned, and the same tool body 30 as in the first embodiment,
Even if the cutting insert 50 in which the main cutting edge flank has a multi-step surface shape as in the second embodiment is mounted, no problem occurs. In this way, when the main cutting edge flank has a multi-step surface shape, in addition to the effects as described above, the main cutting edge 23
Therefore, it is possible to give a proper clearance angle to the blade, and it is possible to give a width to the axial rake when the cutting insert 50 is mounted on the tool body 30.

Next, a third embodiment of the present invention will be described, but the same parts as those of the first and second embodiments described above will be designated by the same reference numerals and the description thereof will be omitted. FIG. 9A is a plan view of a cutting insert according to a third embodiment of the present invention,
(B) is a VV line sectional view in (a).

Cutting insert 6 according to the third embodiment
As shown in FIG. 9, 0 has substantially the same structure as that of the first and second embodiments, except that the main cutting edge 6 is different.
4 has a convex curve shape, and the main cutting edge flank 63A has a convex curved surface shape. That is, the main cutting edge 64 is formed in the shape of a convex curve having a gentle radius of curvature that is convex toward the outside of the cutting insert 60, and the main cutting edge that is a flank that is continuous with the main cutting edge 64. Blade flank 63A
Is formed by a smooth convex curved surface that is convex toward the outside of the cutting insert 60. Here, the clearance angle α of the main cutting edge flank 63A is α = −15 ° (α <0 °)
Is set to.

Then, such a cutting insert 60
Is the same tool body 30 as described in the first embodiment.
Used by being attached to. The restraint surface 34 of the insert mounting seat 32 is the auxiliary cutting edge flank 23B of the cutting insert 50.
By restraining the main cutting edge 64 and the main cutting edge flank 6
It does not matter what the shape of 3A is, and for the same tool body 30 as in the first embodiment, the main cutting edge 6 as in the third embodiment is used.
Even if the cutting insert 60 having a convex curved line 4 and the main cutting edge flank 63A having a convex curved surface is mounted, no problem occurs. In this way, since the main cutting edge 64 is configured by the convex curve, in addition to the effects described above, the cutting edge gradually bites into the work during cutting, so the main cutting edge 64 The impact strength does not act on 64, and the cutting edge strength can be kept high. Therefore, it becomes effective when particularly high cutting edge strength is required, such as when cutting a difficult-to-cut material such as a heat-resistant alloy or stainless steel. Further, since the main cutting edge flank 63A is formed by the convex curved surface, the cutting insert 60
It is also possible to obtain the effect that it becomes possible to keep the rigidity of the higher.

In each of the above embodiments, the face milling cutter is used as the cutting tool, but the cutting tool is not limited to this and other cutting tools may be used.
It is also possible to apply the present invention to a cutting insert having another polygonal flat plate shape instead of the substantially square flat plate shape.

[0040]

EFFECTS OF THE INVENTION According to the present invention, although the cutting insert has a high cutting edge strength with a negative clearance angle of the main cutting edge,
By mounting the tool body such that the radial rake becomes negative, a positive cutting edge inclination angle can be obtained. Moreover, since the breaker is formed on the upper surface, a positive true rake angle can be obtained. Further, since the cutting insert is attached to the tool body so that the radial rake becomes negative, the back metal of the tool body becomes large, and a tool body having higher strength can be obtained. therefore,
While securing the strength of the cutting edge, cutting resistance is reduced to maintain good chip discharge performance, and a tough tool body can be obtained, so the feed amount of the tool body during cutting can be increased, It is possible to increase the cutting amount of and to achieve high efficiency machining.

[Brief description of drawings]

FIG. 1 is a perspective view of a cutting insert according to a first embodiment of the present invention.

2A is a plan view of the cutting insert according to the first embodiment of the present invention, FIG. 2B is a view taken in the direction of arrow A in FIG. 2A, and FIG. 2C is a sectional view taken along line I-I in FIG. Figure,
(D) is a view in the direction of arrow B in (a), (e) is (a).
11 is a sectional view taken along line II-II in FIG.

FIG. 3 is a side view of a cutting tool on which the cutting insert according to the first embodiment of the present invention is mounted.

FIG. 4 is an explanatory diagram showing a relationship between a cutting edge inclination angle of a main cutting edge and a radial rake of the cutting insert according to the first embodiment of the present invention.

FIG. 5 is an explanatory diagram showing a cutting resistance applied to the cutting insert according to the first embodiment of the present invention.

FIG. 6 is an explanatory view showing a state of a chip pocket of a cutting tool on which the cutting insert according to the first embodiment of the present invention is mounted.

FIG. 7 is an explanatory view showing a state of S point contact of the cutting tool equipped with the cutting insert according to the first embodiment of the present invention.

8A is a plan view of a cutting insert according to a second embodiment of the present invention, FIG. 8B is a view in the direction C in FIG. 8A, and FIG. 8C is a sectional view taken along line III-III in FIG. 8A. The figure, (d) is the D direction arrow line view in (a), (e) is the IV-IV sectional view taken on the line in (a).

9A is a plan view of a cutting insert according to a third embodiment of the present invention, and FIG. 9B is a V-V view in FIG. 9A.
It is a line sectional view.

FIG. 10 is a perspective view showing a conventional positive type cutting insert.

FIG. 11 is a side view showing a cutting tool equipped with a conventional positive type cutting insert.

FIG. 12 is an explanatory view showing a cutting resistance applied to a conventional positive type cutting insert.

[Explanation of symbols]

20,50,60 Cutting insert 21 Lower surface 22 upper surface 23 sides 23A, 63A Main cutting edge flank 23B Sub cutting edge flank 24,64 Main cutting edge 25 Sub cutting edge 53A Main cutting edge first flank 53B Main cutting edge 2nd flank

Claims (7)

[Claims] 1. A main cutting edge and a sub-cutting edge are formed on a ridge line of a substantially polygonal flat plate-shaped upper surface facing a lower surface which forms a seating surface and a side surface which intersects the upper surface and forms a flank. In the cutting insert described above, a breaker is formed on the upper surface, and a clearance angle α of a flank that is continuous with the main cutting edge is set to α <0 °, and a flank that is continuous with the sub cutting edge is formed. The clearance angle β is set to α <β, and the length of the ridgeline at which the flank that is continuous with the sub cutting edge and the lower surface intersect is longer than the length of the sub cutting edge. Cutting insert. 2. The cutting insert according to claim 1, wherein the area of the lower surface is larger than the area of the upper surface. 3. The cutting insert according to claim 1 or 2, wherein a clearance angle β of a clearance surface continuous with the auxiliary cutting edge is set to β ≦ 0 °. insert. 4. The cutting insert according to any one of claims 1 to 3, wherein a flank that is continuous with the main cutting edge has a multi-step surface shape. 5. The cutting insert according to any one of claims 1 to 4, wherein the main cutting edge has a convex curve. 6. A plurality of chip pockets are formed on a tip outer peripheral portion of a tool body rotated about an axis, and
In the insert mounting seat formed in this tip pocket,
A cutting tool equipped with the cutting insert according to any one of claims 1 to 5, wherein the cutting insert is installed so that its radial rake is negative. Cutting tools. 7. The cutting tool according to claim 6, wherein the lower surface of the cutting insert is seated on a bottom surface of the insert mounting seat that faces the tool rotation direction front side.
Further, the cutting tool is characterized in that a flank that is continuous with the auxiliary cutting edge is constrained and mounted by a constraining surface that stands upright from a bottom surface of the insert mounting seat.