JPH06262434A - Thread cutting machine for steel pipe and thread cutting work method using this machine - Google Patents

Abstract

PURPOSE:To provide a thread cutting machine for a steel pipe and a thread cutting work method of using this machine. CONSTITUTION:By using a thread cutting machine for symmetrically mounting at least by each quantity the first tool holder 21 of mounting a forming tool 12 for grinding a seal part on a die head 20 and the second tool holder 22 of mounting a turning tool 14 for performing work before threading and a chaser 13 for thread cutting work, thread cutting work can be performed in high cutting accuracy.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thread cutting machine for thread cutting a steel pipe such as an oil well pipe having a special seal portion at the pipe end, and a thread cutting method using the same.

[0002]

2. Description of the Related Art Conventionally, oil well pipe screws used for oil drilling and the like have extremely strict requirements in terms of manufacturing and applications, and therefore, for example, API screw joints have been developed. However, oil wells in recent years have become deeper, and joint strength and airtightness are required to be improved more than API threaded joints. For this reason, the joints are made more sealed with metal surfaces, and the thread shape is made square and In the meantime, joints with Teflon rings have been developed.

As shown in FIG. 5, for example, a screw of an oil country tubular good having a special seal portion has an inner surface seal portion 2 provided from an end surface 1a of a pipe end 1 to an inner surface 1b and an outer surface seal portion 3 provided on an outer surface 1c. Similarly, the screw portion 4 provided on the outer surface 1c is formed by cutting. Conventionally, the process of cutting such a screw is performed as shown in FIG.
It consists of processes. That is, (a) a step of cutting the end surface 1a of the pipe end 1 using the cutting tool 6a attached to the holder 5 and further forming a rough seal portion 2a on the inner surface 1b thereof, (b) using the cutting tool 6b A rough seal portion 3a is formed on the outer surface 1c of the pipe end 1, and then the screw lower taper outer diameter portion 3b is formed.
, (C) a step of cutting the coarse screw 4a on the screw taper outer diameter part 3b using the cutting tool 6c, (d) a step of finishing the pipe end inner surface 1b using the cutting tool 6d, (e) There are 7 steps of finishing the inner and outer surface seal portions 2 and 3 by using the cutting tool 6e, and (f) finishing the threaded portion 4 twice by using the cutting tool 6f. One by one is selected by a turret (not shown) for each process, attached to the holder 5, and used in order for processing.

In addition, the machining of the rough inner and outer surface sealing portions of (a) and (b) and the finishing of the inner surface and inner and outer surface sealing portions of (d) and (e) should be performed by using a forming tool. It is possible to cut at the same time.

[0005]

However, in the conventional thread cutting process described above, one cutting tool is required for each process, so that simultaneous cutting or heavy cutting is required. Unable to cut,
It takes a considerably longer time than the processing time of a normal screw having no seal portion, and there is a problem that the productivity (production efficiency) of equipment is reduced.

By the way, as a means for solving the above-mentioned problems of the prior art, the present applicant has proposed a thread cutting method, for example, in Japanese Patent Laid-Open No. 3-270818. That is, the contents are a side blade portion 12a for cutting the inner and outer surface seal portions of the pipe end at the end portion of the tool holder 11 as shown in FIG. 7, and a lower blade portion for cutting the taper outer diameter portion of the screw lower portion.
Using a thread cutting tool configured by attaching a forming tool 12 provided with 12b and a checker 13 for cutting a thread portion, thread cutting of a steel pipe end is performed in a procedure as shown in FIG. It is a thing. (a) Bring the tool holder 11 close to the pipe end 1 of the steel pipe to be cut,
The side blade portion 12a of the forming tool 12 is aligned with the end portion 1a. (b) Next, the tool holder 11 or the steel pipe is rotated to machine the entire inner surface seal portion 2 and part of the outer surface seal portion 3 on the pipe end 1 to finish the end face. (c) Using the lower blade 12b of the general-purpose bite 12 to seal the outer surface 3
And the cutting of the taper outer diameter portion 3b of the screw lower portion are simultaneously performed. (d) The tool holder 11 is slightly advanced to position the screw cutting tool 13 on one end surface of the screw lower taper outer diameter portion 3b,
Cutting of the screw portion 4 is performed.

However, in the thread cutting method disclosed in Japanese Patent Laid-Open No. 3-270818, the lower taper outer diameter portion 3b of the screw lower portion is cut by the lower blade portion 12b located at the jaw portion of the forming tool 12 for processing the outer surface seal portion 3. Therefore, there is a restriction that the forming tool 12 and the checker 13 must be separated by a predetermined distance L or more. Since it is necessary to secure the predetermined distance L, the length of the tool holder 11 becomes long and the size becomes large. Therefore, especially when the tool holder 11 is applied to a thread cutting machine of a type in which a tool is rotated and cut, centrifugal force becomes large. It was found that there are potential problems such as the accuracy of the screw part becoming poor, and the rigidity needs to be increased in consideration of this centrifugal force, and the entire equipment becomes large and uneconomical.

The present invention has been made in order to solve the above-mentioned problems of the prior art, and provides a threading machine for steel pipes capable of cutting in a short time and a threading method using the same. With the goal.

[0009]

The steel pipe threading machine of the present invention is a threading machine for steel pipes having a special metal seal portion at the end of the oil well pipe by rotating a die head incorporating a plurality of tool holders. At least one of the tool holders is a first tool holder to which a shaping tool for cutting a seal portion is attached, and at least one of the tool holders is a turning tool for screwing down and a checker for threading. Is a second tool holder to which is attached.

The steel pipe thread cutting method of the present invention is characterized in that the end face of the seal portion of the steel pipe is machined and then screwed or the end face of the seal portion is machined by using the screw machine.

[0011]

According to the thread cutting machine of the present invention, at least one of the first tool holder having the forming tool attached thereto and the second tool holder having the turning tool and the checker attached thereto are symmetrically assembled to the die head. Since this is done, the centrifugal force can be reduced and thread processing can be performed with high cutting accuracy.

Further, according to the thread cutting method of the present invention, the end surface of the seal portion may be processed and then threaded, or the end surface of the seal portion may be processed after threading, so that the thread can be processed with high accuracy. It can be carried out.

[0013]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a front view showing an embodiment of a thread cutting machine of the present invention, in which a first tool holder 21 and a second tool holder 22 are symmetrically arranged on a die head 20. Of these tool holders, the first tool holder 21 is, as shown in FIG.
There is provided a forming tool 12 having only a side blade portion 12a for cutting the blade and a checker 13 for cutting the screw portion 4.
Further, as shown in FIG. 2B, the second tool holder 22 is provided with a turning tool 14 for cutting the screw lower taper outer diameter portion 3b and a checker 13 for cutting the screw portion 4.

The length a of each of the first and second tool holders 21 and 22 described above is set to about 1 / 1.5 of that of the conventional example.
In addition, the checker 13 and turning tool of the second tool holder 22
The positional relationship with 14 is shown in FIG.
The distance b between the valley point S of 13 and the lowermost point P of the turning tool 14 is approximately 1/5 of the distance L of the conventional example.
The height of the valley S point of 13 is c from the point P (usually 0.1 to 1.0
The appropriate range is mm). Further, the slope θ of the surface of the valley portion is set to a value such that the cutting surface of the lower tapered outer diameter portion 3b can escape from the cutting surface of the screw portion 4 (for example, a range of 1/32 to 1/16 mm is appropriate). To be done.

When thread cutting of the end portion of the steel pipe is carried out by using the thread cutting machine having the above-mentioned structure, the following steps are carried out as shown in FIG. (a) First, a roughing machine (pre-machine, not shown) cuts the diagonal line portion R of the pipe end 1 of the steel pipe, and then supplies it to the threading machine (see FIG. 4 (a)). (b) In the screw cutting machine, as shown in FIG.
The tool holder 21 of is brought close to the pipe end 1 and the side blade portion 12a of the shaping tool 12 is aligned with the end portion 1a, and the die head 20 is rotated to move forward, while the pipe end 1 is entirely covered with the inner surface seal portion. And part of the outer surface seal is processed to finish the end surface. (c) The die head 20 is retracted to align the turning tool 14 of the second tool holder 22 with the finished surface of the outer seal portion 3, and the height position of the first tool holder 21 is adjusted to the second tool holder. After adjusting the checker 13 to the finishing screw diameter in synchronization with 22, the die head 20 is rotated and moved forward while simultaneously machining the outer surface seal and cutting the taper outer diameter of the screw lower part and further cutting the thread. Perform (see Figure 4 (c)). (d) After screw cutting, the first and second tool holders 21,
After letting 22 escape in the radial direction, the die head 20 is retracted (see FIG. 4 (d)).

[0016] The standard is API-L80 grade with an outer diameter of 139.7 mm,
When the outer surface screw having the special seal portion is applied to the oil well pipe having the wall thickness of 9.17 mm, the threading machine of the present invention in which the first tool holder 21 and the second tool holder 22 are symmetrically attached one by one is used. . The weight of each tool holder attached to the die head 20 of the thread cutting machine of the present invention is 1370 kg / 1 set including the die head, which is 65% lighter than the conventional tool holder weight (1850 kg / 1 set). I was able to

Standard deviation σ of the standoff (screw gauge fitting) of the screw cut by the threading machine of the present invention.
Was 0.14 mm, and it was confirmed that the σ of the conventional example was 0.22 mm, which was improved by about 40%. From this, it can be seen that the reduction in the weight of the tool holder directly leads to the reduction of the centrifugal force applied to the die head. In addition,
Regarding the number of tool holders to be attached to the die head 20 in the above embodiment, the first tool holder 21 with the forming tool 12 attached thereto and the second tool holder 22 with the turning tool 14 attached thereto are symmetrically attached one by one. However, the present invention is not limited to this.
The number of the second tool holders 22 is set to 2 to 5 with respect to the number of the first tool holders 21, or the number of the first tool holders 21 is set to 2.
The cutting efficiency can be further improved by making it into individual pieces.

In the above-mentioned embodiment, the checker 13 is attached to all the tool holders, but the checker 13 may be attached only to a part of the tool holders.

[0019]

As described above, according to the thread cutting machine of the present invention, the first tool holder having the shaping tool attached thereto and the second tool holder having the turning tool and the checker combined therein are attached to the die head. Since at least one piece is symmetrically assembled, the centrifugal force can be reduced to perform threading with high cutting accuracy, and the efficiency of thread cutting can be greatly improved.

Further, according to the thread cutting method of the present invention, the end surface of the seal portion may be processed and then threaded, or the end surface of the seal portion may be processed after threading, thereby performing thread processing with high accuracy. It can be carried out.

[Brief description of drawings]

FIG. 1 is a front view showing an embodiment of a thread cutting machine of the present invention.

FIG. 2 is a side view of a tool holder used in the thread cutting machine of the present invention.

FIG. 3 is a partially enlarged side view illustrating a relationship between a turning bite and a checker.

FIG. 4 is an explanatory diagram of an operation procedure of the thread cutting machine of the present invention.

FIG. 5 is a partial sectional view showing a special screw shape of a conventional oil country tubular good.

FIG. 6 is a diagram showing a conventional example of a thread processing process for an oil country tubular good.

FIG. 7 is a side view showing a cutting tool proposed in JP-A-3-270818.

8 is a diagram showing a thread processing step of the oil country tubular good using the cutting tool of FIG.

[Explanation of symbols]

 1 Pipe end 2 Inner surface seal part 3 Outer surface seal part 4 Threaded part 12 General-purpose tool 13 Chesher 14 Turning tool 20 Die head 21 1st tool holder 22 2nd tool holder

Claims (2)

[Claims] 1. A steel pipe threading machine having a special metal seal portion at the end of an oil well pipe by rotating a die head incorporating a plurality of tool holders, wherein at least one of the tool holders has a seal portion. A first tool holder to which a shaping tool for cutting is attached, and at least one of the tool holders is a second tool holder to which a turning tool for screw down machining and a checker for thread cutting are attached. A characteristic steel pipe thread cutting machine. 2. The thread cutting method for a steel pipe using a thread cutting machine according to claim 1, wherein the end surface of the seal portion of the steel pipe is machined and then threaded or the end surface of the seal portion is machined.