JPH11285905A - Throw-away tip for rotary cutting tool - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve balance and to easily secure good balancing of a desired grade in using a throw-away tip as a rotary cutting tool by reducing a weight difference per a throw-away tip provided with CBN/PCD. SOLUTION: In this throw-away tip, its main body is formed of cermet, high-speed steel, or ceramic with a specific gravity of 9 or less. Instead of cemented carbide with a specific gravity of 14 approximately, cermet or the like with a specific gravity of 9 or less is used for forming the tip main body, so that a weight difference per a single tip can be reduced if sizing is carried out with the same allowable error in formation. Therefore, balance is greatly improved when the tip is used for a milling cutter or the like.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a throw-away insert, and more particularly, to a throw-away insert for a rotary cutting tool used for a rotary cutting tool such as a cutter for face milling (hereinafter also referred to as a throw-away insert or simply a tip). ).

[0002]

2. Description of the Related Art In rotary cutting tools such as cutters for face milling (hereinafter also referred to as cutting tools), those having a throw-away type cutting edge have become mainstream like cutting tools used for turning and the like. . And for indexable inserts used in such rotary cutting tools,
Depending on the processing conditions, such as the type of work material, a cubic boron nitride (hereinafter, also referred to as CBN) or a polycrystalline carbide nitride may be used instead of a conventional cemented carbide chip body (base material). Ultra-high pressure sintered bodies such as crystalline diamond (hereinafter, referred to as PCD) are brazed. Further, even in such a chip with an ultra-high pressure sintered body, 800 m / mi has recently been used to improve productivity and the like.
There is a demand for use in a high-speed cutting speed region of n or more or 1000 m / min or more, and in some cases, an ultra-high cutting speed region of several thousand m / min or more.

[0003] In a rotary cutting tool such as a face milling cutter, it is extremely important how to improve the balance (rotation balance). This is because, if the rotational balance is poor, the centrifugal force due to the imbalance increases as the rotation speed increases or the blade diameter increases, causing vibrations or, in extreme cases, chip movement or popping out (scattering). It is extremely dangerous. Therefore, the cutting tool body on which the chip is clamped (mounted) is machined and manufactured with strict dimensional accuracy (allowable dimensional error), and is adjusted so that a desired grade of good balance is obtained. Here, the good balance is an amount indicating the degree of balance of the rigid rotor defined in JIS B 0905 (rotating machine-good balance of rigid rotor), and indicates the ratio between the unbalance and the specified angular velocity. Product (mm / s).

On the other hand, when such a high-speed rotary cutting tool is of a throw-away type, even if the cutting tool main body (cutter main body) is well balanced, the difference in weight between individual chips (individuals) clamped on the cutting tool main body (cutter main body) (see FIG. Error) affects the balance. That is, such errors are basically slight, but the higher the rotation speed, the better the balance. Such a weight error depends on an allowable error in the dimensional accuracy (polishing accuracy) of the insert. In the standard of the Carbide Tool Association, which defines this type of insert, one of the throw-away inserts is used. Strict dimensional accuracy (permissible error) is specified for each.

[0005]

The main body (base material) for forming a chip with CBN or a chip with PCD is:
As described above, the cemented carbide is formed of a cemented carbide, but such cemented carbide has a specific gravity of 14.2 to 14.6, which is considerably larger than steel materials such as high-speed steel. Therefore, the maximum weight difference occurring within the allowable error, that is, the difference between the chip weight (maximum weight) at the maximum allowable dimension and the chip weight (minimum weight) at the minimum allowable dimension is small, Indeed, this causes reduction or impairment of the rotational balance.

[0006] That is, although such a weight difference is very small, its influence on the balance is not small at high speed rotation. Therefore, when it is used for a high-speed rotating cutting tool such as a face mill (high-speed rotating cutting tool). In
It is required to reduce the weight difference in one chip as much as possible. The present invention has been made in view of such problems, and an object of the present invention is to reduce the difference in the weight of one insert in a CBN or a throwaway insert with a PCD so that the weight of one insert does not easily appear. It is an object of the present invention to make it easier to improve the balance or to obtain a desired grade of balance when used.

[0007]

In order to solve the above-mentioned problems, the present invention provides an indexable insert body in which an ultrahigh-pressure sintered body such as cubic boron nitride or polycrystalline diamond is joined as a cutting edge. The indexable insert for a rotary cutting tool is characterized in that its main body is formed from a material having a specific gravity of 9 or less. Here, the main body is formed of a material having a specific gravity of 9 or less. By doing so, the weight difference of one chip main body can be reduced to such an extent that the good balance is remarkably improved. This is because the cermet can also be included in the material forming the main body, but the material forming the main body is preferably any of high-speed steel and ceramic.

That is, in the present invention, since the main body is formed from a material having a specific gravity of 9 or less, when the main body is formed with the same allowable error, the main body is more balanced than that made of a cemented carbide having a specific gravity of about 14. The difference in weight of one chip main body can be remarkably reduced by an amount corresponding to the ratio to the extent that the goodness is remarkably improved. Therefore, when the insert having such a main body is used by being clamped to a rotary cutting tool, the good balance is remarkably improved, and it is easy to secure the desired grade of good balance. It is unlikely to occur. The indexable insert for a rotary cutting tool in any of the above means is suitable for use as a tool for a high-speed rotary cutting tool. The rotary cutting tool according to the present invention is exemplified by a milling cutter and an end mill, but may be other tools.

[0009]

Next, an embodiment of such a throw-away tip will be described in detail with reference to FIG. In the figure, reference numeral 1 denotes a throw-away tip, in which a material forming a main body 2 joining an ultrahigh-pressure sintered body 3 forming a cutting edge thereof is any of cermet, high-speed steel, or ceramic. It is. Each of these has a specific gravity of 9 or less. Specifically, the cermet is about 8.1 and the high speed is about 7.9. For the ceramic, for example, Al2 O3 + TiC is about 4.3, A
l2 O3 + SiCw is about 3.7, Si3 N4 is about 3.2
It is. In each case, the specific gravity is considerably smaller than that of the cemented carbide having a specific gravity of 14.4. However, the ceramic having the composition of Al2 O3 + TiC in the ceramic exemplified here and the ceramic having the composition of Al2
With the composition of O3 + SiCw, the composition weight ratio is
Al2 O3 is about 70% by weight, TiC or SiCw
Is about 30% by weight. Therefore, when the chip 1 made of such a material and the main body 2 has the same dimensional tolerance, the variation in weight (weight difference) corresponds to the specific gravity as compared with the cemented carbide main body. It can be made smaller.

Thus, when the tip 1 having such a small weight difference is used by being clamped to a rotary cutting tool body (cutter body) such as a face mill, the unbalance is small, and therefore, good balance at high speed rotation is achieved. Can be significantly improved. When joining the ultrahigh-pressure sintered body 3 to the main body 2 made of such a material, although not shown in detail, for example, this is formed as a sintered body having a two-layer structure with the cemented carbide layer 4. Then, brazing may be performed via the cemented carbide layer 4. In this case, if the main body 2 is made of cermet or ceramic, Ti-based active solder (Ag-Cu-
Ti-based brazing, Ag-Ti-based brazing, or the like, or the joining surface (brazing surface) of the main body 2 is metallized, and Ag
What is necessary is just to braze with a system braze (Ag-Cu system braze etc.).

Hereinafter, when the chip body 2 is formed from each of the above-mentioned materials, the tip body 2 is clamped to a cutter (see FIG. 2) as described below, and when the chip body 2 is rotated at high speed, good balance is obtained. (A cemented carbide body). However, the type and size of the tip used here were CNGA43 (with a tip inscribed circle dimension tolerance of ± 0.025 mm) in the standard of the Carbide Tool Association. This is a diamond-shaped chip, and the length of one side on the rake face is 12.7m.
m, thickness 4.76 mm, cutting edge corner angle 80 degrees, hole diameter for set screw 5.16 mm, which is clamped to a cutting tool body (see FIG. 2) described below and 20,000 r.
pm. The results are as shown in Table 1.

Incidentally, as shown in FIG.
No. 1 has a blade outer diameter (D = 2r) of 80 mm, a weight (F) of 0.73 kg, and the number of tips to be clamped is 6
(The arrangement is θ = 60 degrees equiangular spacing). However, in the calculation, the allowable maximum weight difference (Δm) of the chip body 2 made of each material (material), that is, the difference between the chip weight (maximum weight) at the maximum allowable dimension and the chip weight (minimum weight) at the minimum allowable dimension is obtained. , And the maximum unbalance and good balance (G). In this case, assuming that the balance is the worst (the balance is most broken with six blades), as shown in FIG. 2, the three adjacent chips 1a to 1a are set to the maximum weight and the remaining chips are left. The three chips 1b to 1b were set as the minimum weight, and the maximum unbalance and the good balance were calculated. In calculating the maximum weight difference (the maximum value of Δm) of one chip body,
Considering only chip inscribed circle size tolerance ± 0.025mm, tolerance of chip thickness ± 0.13mm, tolerance of corner height ± 0.025mm, and for ultra-high pressure sintered body joints The existence of pockets (recesses) is not considered in this calculation example.

A calculation example is shown in the case where the tip body is a cemented carbide (specific gravity 14.4) (comparative example). In this case, the maximum weight difference (Δm) of one chip body is 0.044 g, and the maximum unbalance and the good balance (G) are obtained as follows. Maximum unbalance = unbalance weight × cutter radius = (Δm + 2Δmcos60 °) r = 2rΔm = 2 × 80/2 × 0.044 = 3.48 mmg Good balance = 1 / 9.55 × unbalance / F × N / 1000 = 1/9 .55 × 3.48 / 0.73 × 20,000 / 1000 = 10 mm / s

[0014]

[Table 1]

[0015] From the "balance ratio to carbide" in Table 1, under the above conditions, the balance (G) indicates that the chip of the body made of cermet or high speed steel is different from the case of using the chip of the body made of cemented carbide. Is improved by 1.7 times or more when ceramic is used (Al2 O3 + TiC, Al2 O3
It can be seen that the improvement is 3 to 5 times when a chip having a main body made of + SiCw, Si3 N4) is used. That is, even when finished with the same dimensional difference, when using a chip with a super-high-pressure sintered body of a chip body made of cermet, high-speed steel, or ceramic, a chip with a super-high-pressure sintered body of a cemented carbide body is used. It can be seen that the good balance is remarkably improved as compared with the case where it is used.

However, such an improvement in the balance can be achieved even if the conditions such as the diameter of the cutter body, the weight of the cutter body, the number of chips, and the maximum number of revolutions are different from those described above.
If a fixed chip is used, the same can be obtained.

The indexable insert for a rotary cutting tool of the present invention can be said to be suitable not only for milling but also for a wide range of rotary cutting tools such as end mills, especially as a cutting tool used for high-speed rotating cutting tools. Naturally, the present invention can be embodied irrespective of the type, such as the shape and size of the chip. Further, the material forming the throw-away tip body according to the present invention may have a specific gravity of 9 or less,
Therefore, it is not limited to cermet, high-speed steel, or ceramic.However, if these materials are used, even if trouble such as chipping occurs in the ultra-high pressure sintered body due to its own high hardness and high wear resistance, it is possible to take a measure. This is preferable because cutting performance is expected. Note that the chip according to the present invention can also be applied to a chip having a configuration in which an ultrahigh-pressure sintered body is joined to a plurality of corners.

[0018]

As is clear from the above description, according to the indexable insert according to the present invention, the tip main body is formed of a cermet or the like having a specific gravity of about 14 instead of a cemented carbide having a specific gravity of about 14. Is formed with the same tolerance, the difference in weight of one chip body is reduced by an amount corresponding to the ratio to such an extent that the balance is remarkably improved as compared with that of a cemented carbide having a specific gravity of about 14. it can. Therefore, when the tip provided with such a main body is used by being clamped to a rotary cutting tool such as a face milling cutter, the balance is greatly improved. In addition, it is easy to secure the desired balance of the desired grade, and the deviation is less likely to occur. Thus, when the insert according to the present invention is used, higher-speed (cutting speed) processing can be performed, which not only contributes to the improvement of the processing efficiency, but also improves the finished surface roughness (accuracy), and also has the effect of extending the life of the chip. Is done.

[Brief description of the drawings]

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

FIG. 2 is a schematic bottom view of a six-blade cutter main body.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Throw-away tip 2 Throw-away tip main body 3 Ultra-high pressure sintered body 11 Cutting tool main body (cutter main body)

Claims (3)

[Claims] An indexable insert for a rotary cutting tool comprising an indexable insert body and an ultra-high pressure sintered body such as cubic boron nitride or polycrystalline diamond as a cutting edge, wherein the specific gravity of the indexable body is 9 or less. Indexable inserts for rotary cutting tools, characterized by being formed from a material of the type described above. 2. The indexable insert for a rotary cutting tool according to claim 1, wherein the material forming said main body is any one of cermet, high speed steel and ceramic. 3. The indexable insert for a rotary cutting tool according to claim 1, wherein the indexable insert for a rotary cutting tool is for a high-speed rotary cutting tool.