JPH11320255A - Cheser - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the screw cutting load of a blade part by increasing the screw cutting load toward the depth of a screw to be cut in a blade part. SOLUTION: In a rough cutting chaser 1A, a rough cutting blade part 1Aa performs the rough cutting to an oil well steel pipe, and a depth direction cutting blade part 1Ab performs the cutting in the depth direction, and a depth and cross direction cutting blade part 1Ac performs the cutting in the depth and cross direction. In a finish cutting chaser 1B, a depth direction cutting blade part 1Ba performs the cutting in the depth direction, and a depth and cross direction cutting blade part 1Bb performs the depth and cross direction cutting, and a finish cutting blade part 1Bc performs the finish cutting. With this structure, micro-chipping by a breakdown of a blade tip due to the excessive cutting and a lack of cutting and a heat crack by the friction heat can be prevented, and the lifetime of a blade can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a trapezoidal screw (so-called A-type) for use in, for example, oil-weld pipes and the like, which is used for cutting threaded joints requiring high precision.
PI buttress), a square screw, a key screw and the like.

[0002]

2. Description of the Related Art A trapezoidal screw will be described below as an example. For example, thread cutting to a steel pipe for an oil country tubular good and a coupling (coupling) for connecting the pipes to each other requires high-precision processing and high productivity. Instead, a different shape is used for each cutting step, such as a cheese 31 in which a plurality of blade portions are arranged in series as shown in FIG. 3, and a finish cutting cheser 41A and a rough cutting chezer 41B as shown in FIG. In FIG. 2, reference numeral 21a denotes a finishing blade, and in FIG.
1a shows a finishing blade portion, 31b shows a rough cutting blade portion, and in FIG. 4, 41a shows a finishing blade portion.

However, in recent years, the environment of oil wells has become severe, and as gas wells and deep wells have progressed, demand for high-strength materials and hard-to-cut materials such as corrosion-resistant Cr steel as oil well pipe materials has increased, and the life of cutting tools and cheeses has been reduced. And the productivity has decreased.

[0004] Thread cutting is more difficult than general cutting.
Its substantial feed rate is high, and in order to form a trapezoidal screw, the bottom and crest of the screw shape are long, and the contact length with the chip, that is, the length of the substantial cutting blade is extremely long, It is known that the load on the cutting blade increases.

Further, as described above, it is known that the frequency of chipping of the cutting edge increases extremely when the cutting depth in the depth direction is increased to 0.3 mm or more with the increase in the strength of the material to be cut.
In addition, since emphasis is placed on the finish roughness of the screw surface, if the cutting depth in the depth direction of the blade portion is reduced to 0.15 mm or less, micro chipping due to the brittleness of the coating occurs, thereby causing the screw surface It is known that it leads to the generation of roughness defects.

Under the circumstances described above, the following chaser and thread cutting methods have been proposed for the purpose of improving the life and productivity of the chaser for difficult-to-cut materials. For example, a coated cemented carbide cheser disclosed in Japanese Patent Application Laid-Open No. Sho 60-172403 is a coated cemented carbide chezer in which the coating thickness near the cutting edge is partially thinned, thereby preventing a decrease in toughness. In addition, micro chipping due to a decrease in toughness is prevented, and the life of the blade is improved.

Further, a method for cutting a high-alloy oil country tubular good as disclosed in Japanese Patent Application Laid-Open No. 60-197317 discloses a method for reducing the content of Cr by 8 wt%.
When performing high alloy thread cutting including the above,
The coating, the cutting edge treatment method, and the shape of the cheese (rake angle) are optimized, and thereby, high alloy screw cutting can be performed smoothly, and the tool life is improved eight times.

The pipe threading tip and the manufacturing apparatus disclosed in Japanese Patent Application Laid-Open No. 5-277809 are an improved method of processing (honing) a coated cheese with a cutting edge, thereby providing sharpness and chipping resistance. Performance and abrasion resistance are improved.

[0009]

In the cutting of a trapezoidal screw, as shown in FIG. 5, the cutting depth c in the depth direction of the thread and the width direction are usually determined by the angles α and β of the side surfaces of the blade. Are different from each other, so that the depth of cut c and the width of cut a, b in the depth direction with respect to the entire surface of the cutting edge.
It was extremely difficult to limit the diameter to 0.15 to 0.3 mm and to improve the life of the cheese.

[0010] Furthermore, in order to cope with cutting of difficult-to-cut materials, in order to avoid cutting edge defects, the depth of cut c in the depth direction of the thread is reduced and the number of cutting passes is increased.
The cutting depths a and b in the width direction of the thread become extremely small,
In addition to the micro-chipping of the coating, there has been a problem that the cutting edge is broken due to the heat crack due to the frictional heat, and the thread cutting productivity and the life of the cheese are reduced. Note that none of the above-mentioned conventional devices solves the above problem by optimizing the cut depth.

SUMMARY OF THE INVENTION The present invention has been made in order to solve the above-mentioned problems. In a chaser having a plurality of blades, a depth of cut of a thread of each blade and a depth of cut in a width direction are provided. It is possible to optimize the amount, prevent micro chipping due to excessive cutting and insufficient cutting due to micro chipping and heat crack due to frictional heat, improve the service life, and carry out thread cutting using each cutting edge efficiently. The purpose is to provide a cheser that can be used.

[0012]

In order to achieve the above object, according to the present invention, at least one of the plurality of blades is increased in the depth direction of a screw to be cut. By doing so, the thread cutting load on the blade portion can be reduced, and the efficiency of thread cutting and the life of the cheese can be prolonged.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A finishing blade 21 as shown in FIG.
In the case of thread cutting using the conventional blade 21 having one peak a, as shown in FIG. 6, depending on the angles α and β of the side surfaces of the blade portion of the blade 21, several times, for example, 4 in the illustrated state. The cutting was performed at a constant depth of cut c over the times. Now, for example, when the cut amount c in the depth direction is fixed at 0.3 mm, the cut amounts a and b in the width direction are a + b.
In this case, only about 0.07 mm can be secured, so that microchipping and heat cracks due to frictional heat occur to shorten the life of the cether.

Further, as shown in FIG. 7, since the cheese having a plurality of blades is designed to have a thread depth and a cut amount in the width direction with respect to all the blades.
When creating a trapezoidal screw, the depth of cut can be controlled by the shape of the cutting edge, but the amount of cut in the width direction tends to be small (for example, 0.1 mm or less) due to the angle of the side surface of the blade. In the same manner as described above, micro chipping and heat cracks occur to shorten the service life of the chaser.

Further, in the case of the above-mentioned conventional cheese having a plurality of blade portions, since all the blade portions are cut in both the thread depth direction and the width direction, the blade edge rigidity is secured, so that the width is reduced. It was difficult to increase the depth of cut in the direction.

Therefore, in the present invention, at least one of the plurality of blades arranged in series is enlarged in the depth direction of the screw to be cut, and is cut only in the depth direction of the screw. I did it.

According to the above configuration, the blade portion enlarged in the depth direction of the screw to be cut is screw-cut only in the depth direction of the thread, so that the load on the cutting edge is reduced. Then, by adjusting the cut amount in the width direction with another blade portion, it is possible to set an appropriate cut amount of 0.15 to 0.3 mm.

Further, by adopting the configuration of the present invention, the cutting portion that cuts only in the depth direction of the thread does not need to cut in the width direction, so that the actual cutting edge length is shortened. As described above, the cutting load is reduced, whereby the depth of cut in the depth direction can be increased to about 1.5 times the normal depth.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIG. FIG. 1A shows a side view of a chaser according to the present invention, and FIGS. 1B and 1C show a thread cutting state by the chaser according to the present invention.

In the drawing, 1A is a plurality of blades,
For example, it is a rough cutting chaser having a rough cutting blade portion 1Aa, a depth direction cutting blade portion 1Ab, and a depth and width direction cutting blade portion 1Ac from the left in the drawing. 1B is a depth direction cutting blade 1B as a plurality of blades, for example, from the left in the drawing.
a, depth and width direction cutting blade 1Bb, finishing cutting blade 1
Bc. Then, the cheese of the present invention cuts, for example, a trapezoidal thread for a joint on a steel pipe used for, for example, an oil country tubular good by using the rough cutting cheese 1A and the finish cutting cheese 1B.

That is, in the rough cutting cheese 1A and the finish cutting cheese 1B of the present invention, at least one of the plurality of blades, that is, the depth direction cutting blade 1
Ab and the depth direction cutting blade portion 1Ba are enlarged in the depth direction of the screw to be cut so that the cutting is performed only in the depth direction of the screw.

The thread cutting by the rough cutting cheese 1A and the finish cutting cheese 1B having the above-described configuration is as follows.
As shown in FIG. 1 (b), in the rough cutting cheese 1A, rough cutting is performed on the oil well steel pipe by the rough cutting blade 1Aa, and the depth direction is cut by the depth direction cutting blade 1Ab. The depth and width direction are further cut by the width direction cutting blade portion 1Ac. Then, as shown in FIG. 1 (b), the finish cutting chaser 1B is further cut in the depth direction by the depth direction cutting blade portion 1Ba, and the depth and width direction are cut by the depth and width direction cutting blade portion 1Bb. Cutting is performed, and finish cutting is performed by the finish cutting blade portion 1Bc.

Next, the effect of the present invention will be described in comparison with a conventional one. Table 1 below shows the conventional FIG.
FIG. 6 shows a comparison result when a screw cutting operation is performed using each of the blade and the cheese shown in FIGS. 3 and 4 and the cheese of the present invention. In Table 1, the number of passes indicates how many times the steel pipe was cut with a cutting tool or a chaser. The tool life indicates how many steel pipes have been finished.

[0024]

[Table 1]

As shown in Table 1, it can be seen that the conventional one has a short life because it is broken by micro chipping on the side surface of the blade. Also, when the number of passes is increased,
Since the cutting edge loss ratio does not decrease, this cutting edge loss
Rather than due to excessive cutting load in the thread depth direction,
It can be presumed that this is due to a heat crack on the side surface of the blade. On the other hand, the service life of the cether according to the present invention has been improved about twice or more, and the reasons for disposal due to wear have increased.

From the above results, it is possible to prevent the chipper of the present invention from chipping due to excessive cutting or micro-chipping due to insufficient cutting and heat crack due to frictional heat, to prolong the service life of the cutting tool, and to improve the life of each cutting edge. It can be used efficiently to perform thread cutting. In addition,
In the above embodiment, the chaser of the present invention is applied to cutting a trapezoidal screw for an oil country tubular good. However, the present invention is not limited to this, and may be applied to, for example, cutting of another square screw or a key screw.

[0027]

As described above, according to the present invention, at least one of the plurality of blades arranged in series is enlarged in the depth direction of the screw to be cut, so that the depth of cut can be reduced. Can be made appropriate, and it is possible to prevent cutting edge loss due to excessive cutting and micro chipping and heat cracking due to insufficient cutting, and therefore, it is possible to carry out thread cutting using each cutting edge efficiently. At the same time, the life of the blade can be improved.

[Brief description of the drawings]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows a cheese of the present invention, in which (a) is a side view of a rough-cutting cheese and a finish-cutting cheese; It is a figure showing a situation.

FIG. 2 is a side view showing a conventional cutting tool having one finishing blade portion.

FIG. 3 is a side view showing a conventional cheese having three blades.

FIG. 4 is a side view showing a conventional rough cutting chaser having a plurality of blade portions and a finish cutting chaser.

FIG. 5 is a view for explaining a cutting amount by a conventional blade having one blade portion.

FIG. 6 is a diagram showing a conventional thread cutting state using a blade having one crest.

7 (a) shows a conventional rough cutting chaser having a plurality of blade portions and a finish cutting chaser, FIG. 7 (b) shows a thread cutting situation by the rough cutting chaser, and FIG. 7 (c) shows a conventional cutting chaser. It is a figure showing a screw cutting situation.

[Explanation of symbols]

 1A Rough Cutting Cheser 1Ab Depth direction cutting blade 1B Finish Cutting Chaser 1Bb Depth direction cutting blade

Claims (1)

[Claims] 1. A checker in which a plurality of blades for cutting a screw are arranged in series, wherein at least one of the plurality of blades is enlarged in a depth direction of the screw to be cut. A chaser characterized by cutting only in the depth direction of the screw.