JPH0720202U - Throw-away tip - Google Patents

Abstract

(57) [Summary] [Purpose] To improve the chipping resistance of the throw-away insert with a core down. [Structure] The land of the indexable indexable insert is ground in a direction not parallel to the cutting edge. Compressive residual stress is imparted by grinding, and fracture resistance is improved. The grinding range may be limited to the range corresponding to the cutting.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a throw-away tip used for cutting, and particularly to improving the tool life of a die that is embossed.

[0002]

[Prior art]

 The main forming methods of the throw-away chip having breaker grooves are: (a) the entire surface of the chip (including the breaker groove) is ground (b) the boss surface and land of the chip are ground simultaneously ( c) Grinding the boss surface of the chip. (d) Embossing as it is without grinding.

Of these, the above-mentioned (b) is often applied to a breaker groove having a boss surface and a cutting edge on the same plane and constituted only by a concave portion. In most cases (c), the cutting edge is located at a lower position than the boss surface, and has a breaker groove formed of a complicated curved surface having a concave or concave shape. The boss surface is ground so that the flatness is increased and the stability when fixed to the chip seat is increased. (D) is basically the same as (c), but the manufacturing process is improved and the boss surface is not ground.

[0004]

[Problems to be solved by the device]

 Conventionally, in the throw-away tip having a shape in which the cutting edge is down-centered as in the above (c) and (d), the land is not ground. However, in the throw-away tip of the present invention, this land is ground so that the tool life especially relating to fracture resistance is extended more than ever.

[0005]

[Means for Solving the Problems]

 The feature of the present invention is that the land portion of the indexable insert with a breaker groove of the core-down type is subjected to the grinding process. The grinding process applied to the land may be performed over its entire length, or alternatively, the range may be limited to a part corresponding to the cutting edge length actually involved in cutting. At this time, the boss surface may be a ground surface or a non-ground surface before sintering.

Further, it is preferable that the land is ground in a direction not parallel to the cutting edge.

[0007]

[Action]

 In the cutting process, tensile stress usually acts on the rake face of the chip. In order to resist this tensile stress, it is preferable that a compressive residual stress exists on the chip rake face side, and the larger the residual stress, the greater the effect. It is noted that the throw away tip of the present invention gives compressive residual stress to the surface to be ground during grinding, and the land of the core-falling tip is subjected to a grinding process that has not been performed in the past. It is made to remain. This compressive residual stress effectively acts to improve defects caused by mechanical impact.

[0008]

【Example】

 Next, an embodiment of the throw-away tip of the present invention will be described with reference to the drawings.

FIG. 1 is a front view showing an embodiment of a throw-away tip of the present invention, and FIG. 2 is an enlarged sectional view of the vicinity of a cutting edge portion thereof. The rake face of the throw-away tip 1 having an equilateral triangle shape is composed of a boss face 2, a breaker groove 3 and a narrow land 4, and a hole 5 for attachment is bored in the center thereof. The line of intersection formed by the land 4 and the flank 6 becomes the cutting edge 7.

In this embodiment, the breaker groove 3 has the most basic arcuate cross section. As shown in FIG. 2, the cutting edge 7 is lower than the boss surface 2 and is so-called center-down. The land 4 is ground, but the other surface is still sintered.

The surface configured as described above may be only the upper surface or may be the upper and lower surfaces, and the chip shape may be a negative chip or a positive chip.

Now, the performance of the above throw-away tip will be introduced below. The tip shape is an equilateral triangular negative tip, and the tool material is P20 equivalent cemented carbide.

FIG. 3 is a conceptual diagram showing the state of the land. Fig. 3 (a) shows the tip according to the present invention, which has a grinding surface with arcuate grinding marks that are not parallel to the cutting edge processed by the grindstone with shaft, and Fig. 3 (b) is parallel to the cutting edge processed by the flat grindstone. It is a ground surface with grinding marks. FIG. 3C is an as-sintered one, which was used for comparison.

Table 1 shows the results of measuring the residual stress in the land of the above three types of chips. An X-ray stress measuring device is used for the measurement, and the measured value is an average value from the surface to a depth of about 10 μm. As a result of the measurement, the compressive stress remained in each of the chips, but the size was larger than that of the as-sintered two types. Further, in the comparison between the two types of ground chips, the magnitude of the compressive residual stress was the same regardless of the grinding direction.

[0015]

[Table 1] Next, we will introduce the results of actual cutting using these chips.

For cutting, a material having four grooves parallel to the shaft center is used on the outer circumference of the round bar, and the cutting edge is mechanically impacted four times during one rotation. It was FIG. 5 is a diagram in which the number of impacts leading to a defect is plotted on a Weibull probability sheet. The ground insert shown in FIG. 3 (a) has significantly improved fracture resistance compared to the sintered insert shown in FIG. 3 (c), and is approximately four times as high as the comparison with a cumulative loss probability of 50%. In addition, since the former curve is upright, it can be seen that there is no variation in fracture resistance and the reliability of the chip is high.

On the other hand, the grinding tip shown in FIG. 3B has a sawtooth-shaped cutting edge because it has a grinding surface parallel to the cutting edge even though the compressive residual stress is large. The result was that the life was inferior to that of the sintered chip of 3 (c).

FIG. 4 shows another embodiment of the present invention applied to a throw-away tip having the same shape as that of FIG. 1, and the same parts are designated by the same reference numerals. In this example, the cutting edge 7 grinds only the area a of the land 4 corresponding to the area a in which the cutting edge 7 actually participates in cutting, but the effect is not different from the above.

[0019]

[Effect of device]

 As described above, by performing grinding on the land of the core-down chip in a direction that is not parallel to the cutting edge, the compressive residual stress of the land part increases, and as a result, the fracture resistance related to mechanical impact is improved. However, the tool life can be extended.

[Brief description of drawings]

FIG. 1 is a front view showing an embodiment of a throw-away tip of the present invention.

FIG. 2 is an enlarged cross-sectional view taken along the line AA of the throw-away tip shown in FIG.

FIG. 3 is a conceptual diagram showing a surface state of a land. (A) is a grinding tip which is an embodiment of the present invention, (b) is a grinding tip parallel to a cutting edge, and (c) is a sintered tip. It shows a chip.

FIG. 4 is another embodiment of the throw-away tip of the present invention,
It is a front view which shows the chip which grind | polished a part of land.

FIG. 5 is a diagram showing results of a cutting test relating to fracture resistance.

[Explanation of symbols]

 1 Throw-away tip 2 Boss surface 3 Breaker groove 4 Land 7 Cutting edge

Claims (3)

[Scope of utility model registration request] 1. A polygonal flat plate or a circular flat plate such as a triangular plate, a quadrangular plate, etc., on the periphery of which a land 4 and a breaker groove 3 are formed along a cutting edge 7, and the cutting edge 7 is a boss surface. In the throw-away tip 1 made of a super-hard tool material such as cemented carbide or cermet, which is lower than 2, the throw-away tip 1 is formed by embossing and is sintered, and at least the land A throw-away tip characterized in that 4 is ground. 2. The grinding process applied to the land 4 is limited to the land portion corresponding to the length of the cutting edge where the cutting edge 7 is actually involved in the cutting. Throw-away tip described in. 3. The throw-away tip according to claim 1 or 2, wherein a grinding direction of the grinding process applied to the land 4 is a grinding direction which is not parallel to the cutting edge.