JP2002219616A - Tap - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a tap for working a material hard to be cut such as a metal matrix composite(MMC) into a screw hole and remarkably improved in a service life thereof and formed into a shape hard to be broken by forming the tap into a shape capable of reducing the cutting resistance and forming a diamond film or a diamond-like carbon film hard to be peeled at a cutting part. SOLUTION: The cutting blade part is formed of an imperfect thread shape chamfer part and a perfect thread shape screw part, and this cutting blade part is coated with the diamond film or the diamond-like carbon film. The cutting blade part is divided into four or more linear grooves in the circumferential direction, or the cutting blade part is provided with a spiral groove. Furthermore, a cutting angle of the cutting blade is set from -1 degree to -10 degree, desirably, from -3 degree to -5 degree.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tap for processing a female screw, and more particularly to a tap for processing a difficult-to-cut material such as a composite material of metal and ceramics.

[0002]

2. Description of the Related Art In recent years, a metal-based composite material (hereinafter referred to as MMC), which is a composite material of metal and ceramics, has been used as a new material. Since this material is lighter and more rigid than conventional metal materials, it is expected to be widely used as a material for precision equipment and devices such as semiconductor manufacturing equipment, machine tools, and liquid crystal manufacturing equipment. . When screw holes are formed in this material, taps are used in the same manner as a normal metal material. Usually, the tap is provided with about 20 to 30 pitches of the complete screw portion of the cutting edge, and a groove is provided to form a rake face of the cutting edge,
For example, M3 to M10 taps have three grooves, and M12 and above have four grooves. However, since MMC disperses ceramic particles, tool wear is remarkable due to the ceramic particles, and it is an extremely difficult-to-cut material. For this reason, screw hole processing is not easy, and the tapping may often be broken due to increased cutting resistance.

[0003] MMC uses, for example, an aluminum alloy as a matrix material in which SiC, Al ₂ O ₃ , AlN
Such as dispersed ceramic particles such as
These may also have numerous pores. Before drilling with taps, drill holes are drilled. However, in the case of difficult-to-cut materials, drilling of pilot holes often occurs.
MC has ceramic particles dispersed as described above,
Since the hardness difference between the ceramic particles and the matrix material is large, the pilot hole is easily bent. When a tap hole is formed in the bent prepared hole with a tap, a force for bending the tap is applied, and a problem that the tap is easily broken occurs.

[0004]

As a tap for forming a screw hole in an MMC, there is a tap described in Japanese Patent Application Laid-Open No. 11-221716. In this tap, the cutting edge portion is composed of a bite portion which is an incomplete thread portion and a complete thread portion in which a cutting edge of 1 pitch or more and 3 pitches or less is formed, and this cutting edge portion is coated with a diamond film. is there. It is said that the thickness of the diamond film may be about 2-3 μm.

[0005] However, even with the above tap, there is a problem that the diamond film is easily peeled off depending on the shape of the cutting edge portion because the cutting resistance is high when the MMC thread hole is drilled. When the diamond film is peeled off, particularly the rake face side of the cutting edge portion of the tap causes crater wear at an early stage, so that it does not function as a cutting edge and the cutting resistance further increases. In addition, when the crater wear is increased, the diamond film on the flank of the cutting edge portion is also peeled off in a chain, and the cutting chips are welded, the cutting resistance is further increased, and the tap breaks.

The present invention solves the above problems, and proposes a tap in which a hard film such as a diamond film is hardly peeled off and hardly broken even when a threaded hole of an MMC is machined. .

[0007]

SUMMARY OF THE INVENTION A first feature of the tap of the present invention is that a cutting edge portion formed by a partially threaded bite portion and a completely threaded completely threaded portion is provided. The cutting part has a diamond film or a diamond-like carbon film coated on the surface of the cutting part, and the cutting part is divided by four or more linear grooves in the circumferential direction.

Another feature of the tap having a different shape from the above is that a cutting edge portion formed by a bite portion having an incomplete thread shape and a complete screw portion having a full thread shape, and at least the cutting edge portion of the cutting edge portion. It has a diamond film or a diamond-like carbon film coated on the surface, and the cutting edge portion is provided with a spiral groove.

As a second feature, the rake angle of the cutting edge is -1 ° to -10 °.

A third feature is that the rake angle of the cutting edge is further limited to -3 ° to -5 °.

A fourth feature is that the diamond film has a thickness of 5 to 20 μm.

As another fourth feature, the diamond-like carbon film has a thickness of 1 to 20 μm.

A fifth feature is that the tap is used for drilling a screw hole in a metal-based composite material.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION The tap of the present invention has an incompletely shaped biting portion at the tip as a cutting edge portion, and a full threaded full thread portion is provided continuously to this.
The cutting edge portion is divided by a linear groove in the circumferential direction, and the number of the grooves is four or more. A diamond film or a diamond-like carbon film is formed on the cutting edge by a method such as a vapor phase synthesis method. As a material for the base material, a cemented carbide is suitable. More preferably, the number of grooves is 4 or more for M3 to M10,
M12 or more is preferably 5 or more grooves.

For example, in the case of machining with an M3 tap, four or more cutting edges are used during one rotation of the tap. The number of the cutting edges is four or more.
This is because the diamond film or the diamond-like carbon film is hardly peeled off by reducing the cutting amount per piece. In addition, when the cutting amount of one cutting edge is reduced, the amount of chips is reduced, and the size of the groove can be reduced. Even if the groove is shallow, there is no problem that the discharge of the chip is deteriorated. Therefore, the diameter (d in FIG. 1) of the portion where the diameter of the base material becomes the smallest can be increased, and the substrate can be hardly broken by thrust at the time of screw hole processing. This is particularly effective in the case of a material having a large cutting resistance such as MMC because the axial strength can be increased. Further, by increasing the number of grooves and shortening the circumferential length of the blade, that is, the land width (l in FIG. 1), cutting chips are easily discharged and cutting resistance is reduced. Thus, the present inventors have found that a slight increase in the diameter has an unexpected effect.

Further, as a different shape from the above, the shape of the groove provided in the cutting edge portion can be spiral.
The spiral shape has a chip discharge effect equal to or greater than that of the above-described linear groove, and the groove can be made shallower, so that the diameter of the portion where the diameter of the base material becomes narrowest (d in FIG. 1) is further increased. It can be made large, which is also effective against tap breakage. In consideration of the amount of chips discharged, the size of the groove, the minimum diameter of the base material, and the like, the number is preferably three or more.

Regarding the rake angle of the cutting edge, -1 ゜ to-
Set between 10 °. To make -1 to -10 ゜,
The diamond film or diamond-like carbon film is less likely to peel off when bitten during cutting, and the negative rake angle secures the cutting edge strength. Make it good. More preferably, it is set to -3 ° to -5 °, but in combination with the above-mentioned four or more grooves, when a screw hole is formed in a difficult-to-cut material such as MMC, a diamond film or a diamond-like carbon film is formed. Can be effectively prevented from peeling off.

The thickness of the diamond film is 5 to 20 μm. The reason for setting the thickness to 5 μm or more is that if the thickness of the film is thin, the strength of the film is weak, so that cracks are apt to be formed during the processing, and the film is separated from the crack. Further, depending on the method of forming the film, even if an attempt is made to form a film having a thickness of less than 5 μm, diamond particles are scattered and the film is not formed. It is also possible to form a diamond film of less than 5 μm by seeding with diamond powder or the like. However, in this method, the adhesion to the substrate is weakened, and the diamond film is easily peeled off. Not suitable for tools. The reason why the thickness is set to 20 μm or less is that if the thickness is more than this, the radius of the cutting edge of the cutting edge portion becomes large and the action as a cutting edge is reduced, and the difference in thermal expansion coefficient between the base material and the film when these films are formed. Due to the residual stress
This is because the film is easily peeled.

The thickness when forming the diamond-like carbon film is 1 to 20 μm. The thickness of 1 μm or more is necessary to prevent the base material from being exposed when these films are worn by cutting, and to maintain the cutting edge function as a cutting tool to a minimum. Is
If the thickness is more than this, the radius of the cutting edge of the cutting edge portion becomes large and the action as a cutting edge decreases, and furthermore, when these films are formed, residual stress caused by the difference in thermal expansion coefficient between the substrate and the film causes This is because they are easily peeled off.

When the shape of the groove dividing the cutting edge portion is linear, it is preferable that the groove is linear in parallel with the axis of the tap. This is suitable for efficiently discharging chips, and facilitates processing of the tap base material. When the workpiece is MMC as in the present invention, the chips are not continuous but powdery. In order to discharge such powdery chips, it is suitable to make them into a straight shape in consideration of cost.

[0021]

1 shows a tap according to the invention. In this embodiment, the tap of M3 will be described as an example. A material processed into the shape shown in FIG. 1 using a cemented carbide as a material of the base material 4 was prepared. The cutting edge 2 is formed at the tip of the base material 4. In this cutting edge portion 2, the number of ridges of the biting portion 2a is four, the angle of the biting portion 2a is 10 ° with respect to the axis of the tap, and the number of ridges of the completely threaded portion 2b is 25. -1 ゜ to -3 ゜, -3 ゜ to -5 ゜, -8 ゜ to -1
Three kinds of 0% were prepared. A diamond film is formed on the cutting edge 2 by a vapor phase synthesis method, and the thickness is about 15 μm.
m. The grooves 3 for dividing the cutting edge portion 2 were four linear ones.

As comparative examples, taps having the shape shown in FIG. 1 and having a rake angle in the range of 3 ° to 0 ° and taps having three grooves 3 as shown in FIG. 2 were prepared. The rake angle of the tap having three grooves 3 is the same as that of the present invention.
Ones of ゜ to -5 ゜ and 3 ゜ to 0 ゜ were prepared.

Using these taps, a threaded hole was formed in the MMC material, and a test was conducted to determine the state of peeling of the diamond film. The composition of the MMC material is 30% Si
Those containing C particles were used. 100 holes were machined at each tap, and the number of peaks from which the diamond film was peeled was measured. Table 1 shows the results of these tests.

[0024]

[Table 1]

As can be seen from Table 1, the tap of the present invention has a very small number of peaks from which the diamond film is peeled off. The number increases, and when the number of grooves becomes three, the number of peaks to be peeled increases remarkably. From the above, the tap of the present invention causes less peeling of the diamond film, which leads to a longer life of the tap. In the present embodiment, the one coated with a diamond film is used, but the same effect can be obtained with a diamond-coated carbon film.

[0026]

As described above, the tap according to the present invention has four or more linear grooves for dividing the cutting edge portion when threading a difficult-to-cut material such as MMC material. Alternatively, by using a spiral groove, the resistance applied to the cutting edge during cutting can be reduced, and the sharpness is good, so that the diamond film or the diamond-like carbon film does not easily peel off. Further, by setting the rake angle to a negative rake angle of -1 ° to -10 °, the cutting resistance can be further reduced, and the diamond film or the diamond-like carbon film can be prevented from peeling. Furthermore, since the cutting resistance is reduced by the shape and the diamond film or diamond-like carbon film can be prevented from peeling and increasing the cutting resistance, the breakage of the tap can be prevented, the tool wear is reduced, and the service life is greatly reduced. extend.

[Brief description of the drawings]

FIG. 1A is a front view showing a tap of the present invention,
(B) is a side view.

FIG. 2A is a front view showing a conventional tap, and FIG.
Is a side view.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Tap 2 Cutting edge part 2a Biting part 2b Perfect cutting edge part 2c Rake surface 3 Groove 4 Base material

Continued on the front page (72) Inventor Katsunori Tomari 2-chome, Horikita-cho, Sakai-shi, Osaka Arai Material Osaka Seisakusho Co., Ltd. Material Osaka Works (72) Inventor Keiji Yamabe 3-37-9, Higashi-Ueno, Taito-ku, Tokyo Inside Selangx Corporation

Claims (7)

[Claims] 1. A cutting edge portion formed by an incompletely threaded biting portion and a completely threaded completely threaded portion, and a diamond film or a diamond-like carbon film coated on at least the surface of the cutting edge portion. Wherein the cutting edge portion is divided by four or more linear grooves in the circumferential direction. 2. A cutting edge portion formed by an incompletely threaded biting portion and a completely threaded completely threaded portion, and a diamond film or a diamond-like carbon film coated on at least the surface of the cutting edge portion. And a spiral groove is provided in the cutting edge portion. 3. The rake angle of the cutting edge is from -1 ° to -1.
The tap according to claim 1, wherein the tap is 0 °. 4. The rake angle of the cutting edge is -3 ° to -5.
The tap according to claim 1, wherein the tap is ゜. 5. The film thickness of the diamond film is 5 to 20.
The tap according to claim 1, wherein the tap is μm. 6. The film thickness of the diamond-like carbon film is 1
The tap according to claim 1, wherein the thickness is from 20 μm to 20 μm. 7. The tap according to claim 1, wherein the tap is used for forming a screw hole in a metal matrix composite.