JP3016127B2 - Thread cutting method for steel pipe - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of threading an end of a steel pipe such as a threaded steel pipe such as an oil country tubular good.

[0002]

2. Description of the Related Art For example, when thread cutting is performed on the end of a steel pipe, as shown in FIG. 2 (a), a taper is formed on the end of the steel pipe 1 in a rotating state using a cutting tool 3 as shown in FIG. As shown in FIG. 2 (b), the threaded cutting tool 2 having a thread shape is cut from the pipe end to the center of the pipe from the pipe end as shown by an arrow. As shown in FIG. 2 (c), a predetermined threading process is performed by adding the amount and moving the steel tube. Is turned to the left, and when turning left, the steel pipe is turned to the right.

At this time, in order not to damage the finished surface,
It is a point in quality control that the chips 1b are discharged in the direction of travel of the blade, and a chucking device (hereinafter, abbreviated as "chuck") 5 for fixing the steel pipe 1 is provided in the direction of travel. Therefore, there is a problem that the chips 1b are entangled with the chuck 5 and the thread cutting blade 2 is chipped accordingly.

[0004] In the above-described thread cutting,
In order to reduce the number of cutting passes and increase the efficiency by sharing the cutting amount in a well-balanced manner, for example, a three-threaded cutting tool 2 is used.
When cutting a special screw having a seal portion 1a at the tip of the steel pipe 1, it is indispensable to adjust the penetration angle α of the thread cutting blade 2 in order to prevent the seal portion 1a from being damaged. If the penetration angle α is poorly adjusted,
As for the second peak, the balance of the cutting amount is lost, and the cutting conditions become extremely unstable, which may lead to deterioration of the screw quality. The arrows in FIGS. 2 and 3 indicate the traveling directions of the blade 3 and the threaded blade 2.

Therefore, for example, Japanese Patent Application Laid-Open No. 61-288956
No. 6, in a die head type (knife rotating type) threading machine, a projection is installed inward at the entrance and exit of the steel pipe in the die head cover that covers the die head, and after the end of the steel pipe is threaded, the die head is threaded. When retracting to the origin position of the above, the scraps wound around the steel pipe by the projections are scraped and dropped into a shooter below the die head.
In 337737, by forming the outer end face of a blade holder attached to the tip of the rotating body for attaching a cutting blade arranged to surround the steel pipe so as to be inclined outward toward the rotating body, A device that does not allow chips to remain around the blade holder has been proposed.

[0006]

However, when the end of a steel pipe is threaded by using a threading machine proposed in the above-mentioned Japanese Patent Application Laid-Open No. 61-288956, if chips are always wound around the steel pipe. In some cases, chips may not be removed by hooking the projections. Also, if the chips do not wind well around the steel pipe during thread cutting,
There is also a problem that the chips fall into the die head cover or the shooter with a large volume, causing clogging and entanglement with the die head.

Further, even when the end of a steel pipe is threaded by using a threading machine proposed in Japanese Patent Application Laid-Open No. 5-337737, chips are not entangled with the outside of the blade holder.
It does not always fall from the blade holder.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional problems. The present invention has been made in consideration of the above-described problems, and it is possible to effectively process chips during thread cutting. It is an object of the present invention to provide a thread cutting method for a steel pipe, which can stabilize the quality of a screw even when machining a special screw having the following characteristics.

[0009]

In order to achieve the above-mentioned object, a method for threading a steel pipe according to the present invention is to move a threaded cutting tool to a rotating steel pipe while giving a predetermined cut. A method of performing thread cutting on the end of a steel pipe by rotating the steel pipe in the same direction as the spiral of the screw to be processed, and for this steel pipe, using a thread cutting tool having a plurality of ridges having substantially the same shape. In this state, the steel pipe is moved from the center side to the end side in a state of being arranged substantially parallel to the pipe axis.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The thread cutting method for a steel pipe according to the present invention is performed in the same direction as the spiral of the screw to be machined, for example, clockwise rotation for a right-hand thread and left-hand rotation for a left-hand thread. In order to rotate the steel pipe, for the steel pipe in this rotating state, a thread cutting blade having a plurality of ridges of substantially the same shape,
In a state where the steel pipe is arranged substantially parallel to the pipe axis, the steel pipe is moved from the center side to the end side while giving a predetermined cut, and the steel pipe end is subjected to thread cutting.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A method for thread cutting a steel pipe according to the present invention will be described below with reference to an embodiment shown in FIG. 1A and 1B are explanatory views of a method for thread cutting a steel pipe according to the present invention, wherein FIG. 1A is a diagram showing a cutting state, and FIG.

In FIG. 1, reference numeral 5 denotes a chuck for holding a portion near the end of the steel pipe 1. The steel pipe 1 held by the chuck 5 can be rotated in both forward and reverse directions. Reference numeral 4 denotes a thread cutting tool applied to the thread cutting method of the present invention, and has, for example, three ridges 4a having substantially the same shape. The threaded cutting tool 4 is arranged to face the outer peripheral surface of the end of the steel pipe 1 so as to be movable in the axial direction and the radial direction with respect to the end of the steel pipe 1.

In the thread cutting method for a steel pipe according to the present invention, as described above, the steel pipe 1 held by the chuck 5 is rotated in the same direction as the spiral of the screw to be machined, for example, clockwise in the case of a right-hand thread, or In the case of a left-handed screw, it is turned so that it turns counterclockwise. On the other hand, the above-mentioned threaded cutting tool 4 is arranged substantially parallel to the pipe axis of the steel pipe 1.

Then, a threaded cutting tool 4 arranged substantially in parallel with the pipe axis of the steel pipe 1 is provided on the steel pipe 1 in the rotating state as described above. Then, the steel pipe 1 is moved while giving a predetermined cut while being substantially parallel to the pipe axis of the steel pipe 1, and the end of the steel pipe is subjected to thread cutting.

That is, in the thread cutting method of the present invention, the steel pipe 1 is rotated in a direction opposite to that of the conventional thread cutting method, and the thread cutting blade 4 is moved from the center side of the steel pipe 1 to the end side. The chips 1b are also discharged toward the pipe end, and the chips 1b are not entangled with the chuck 5 and the like, so that the processing of the chips 1b can be easily performed.

Further, in the thread cutting method of the present invention, the thread cutting blade 4 has, for example, three ridges 4a of substantially the same shape.
This is moved in the axial direction and the radial direction with respect to the end of the steel pipe 1 in a state substantially parallel to the pipe axis of the steel pipe 1, so that the cutting amount can be shared in a well-balanced manner, and the seal portion 1a is provided at the tip. Even when machining a special screw having, the blade retreat angle β corresponding to the blade penetration angle α of the conventional method is smaller than the blade penetration angle α of the conventional method.
Even for the second mountain, thread cutting can be performed with a stable cutting amount.

By the way, the outer diameter is 244.5 mm and the wall thickness is 1
An API standard buttress screw (trapezoidal screw) and a special screw with a seal portion were thread-cut at the end of a 3.84 mm oil country tubular good (API standard L80 grade) by the method of the present invention. As shown in the figure, the chips could be discharged in a very good condition and all items of the screw element passed. In particular, the cutting surface of the first and second hills and the tapered surface of the seal part,
It was more stable than when threading was performed by the conventional method.

[0018]

As described above, according to the thread cutting method for steel pipes of the present invention, the chip processing at the time of thread cutting is greatly improved by simple equipment improvement. The chip processing work that has occurred when the method is applied and the stoppage time due to chip entanglement can be omitted or reduced, and work can be reduced and cost can be reduced. Further, the quality of a special screw having a seal portion at the tip can be improved.

[Brief description of the drawings]

FIG. 1 is an explanatory view of a method for thread cutting a steel pipe according to the present invention;
(A) is a figure which shows a cutting situation, (b) is a principal part enlarged view of (a).

FIG. 2 is an explanatory view of a conventional method of thread cutting a steel pipe;
(A) is a figure which shows a pre-processing state, (b) is a figure which shows a thread cutting state, (c) is a figure which shows the steel pipe end part after thread cutting.

FIG. 3 is an explanatory diagram of a case where a special screw having a seal portion at a tip is subjected to thread cutting.

[Explanation of symbols]

 Reference Signs List 1 steel pipe 4 thread cutting blade 4a blade

Claims (1)

(57) [Claims] 1. A method of performing a thread cutting process on an end of a steel pipe by moving a thread cutting blade with a predetermined cut to a steel pipe in a rotating state. While rotating in the same direction as the helix, the steel pipe is moved from the center side to the end side of the steel pipe in a state in which a thread cutting blade having a plurality of ridges of substantially the same shape is arranged substantially parallel to the pipe axis. A method for thread cutting a steel pipe.