JP2001030113A - Cutting work method for tapered square screw - Google Patents

Abstract

PROBLEM TO BE SOLVED: To grind a tapered square screw of a pipe end such as an oil well pipe having a specific sealed part by using roughly working and finishing chasers. SOLUTION: Rough screw working is applied to a tapered square screw, having the acute angle of reverse pipe end side angles α1 and α2 to the axis of the screw joint of the play and pressure side flanks of a screw thread, by using a rough working chaser 3 having three or more crests A-D of saw tooth screw state cutting edges having obtuse or right angles of a reverse pipe end side angle β2 to the axis of the screw joint of the follow side flank 2 of a cutting edge, and having an acute angle of a reverse pipe end side angle β1 to the axis of the screw joint of a lead side flank 1. Finishing screw working is applied by using a finishing working chaser 13 having one or more crests E and F of screw thread type cutting edges having a same shape as the finishing angular screw having an acute angle of reverse pipe end side angles γ1 and γ2 to the axis of the screw joint of the lead and follow side flanks of the cutting edge.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for cutting a tapered square thread into a steel pipe such as an oil country tubular good having a special seal portion at a pipe end.

[0002]

2. Description of the Related Art Oil well pipe screws used for drilling of oil and natural gas are extremely demanding in terms of production and application. For example, buttress screws of API standard have been developed. However, oil wells in recent years have become extremely deep, and there is a demand for improved joint strength and airtightness over buttress screws of the API standard. For this reason, special extreme line square screws for oil and natural gas wells that require greater strength and leakage prevention have been developed and standardized.

[0003] For example, in the case of a male thread, this extreme line square thread has a play-side flank 53 and a pressure-side flank 54 of a thread 52 at the end of a steel pipe 51 as shown in FIGS. Angles α ₁ and α ₂ opposite to the pipe end with respect to the axis of the threaded joint are acutely tapered rectangular screw shapes. Such cutting of the thread of the extreme line square threaded joint, after machining the tapered outer diameter portion under the thread, as shown in FIG.
By using a chaser 71 having several thread-shaped cutting edges X and Y formed into a finish screw shape, several passes, for example, by performing three-pass screw cutting as shown in FIG. , Had been screw cutting.

[0004] Further, as another method of cutting a screw or a cutting tool of a screw, a tool with a side cutting portion and a lower cutting portion provided in a tool holder and a screw cutting tool are arranged at a predetermined interval. A method for threading a steel pipe having a special seal portion at the pipe end using a cutting tool integrally provided with a step, wherein the seal portion is formed by using a side cutting portion of the full-form bite. A step of cutting the end face and the outer surface, a step of cutting the tapered outer diameter portion under the screw using the lower blade portion of the forming tool, and a step of screwing the tapered outer diameter portion under the screw using the screw cutting tool. A thread cutting method for steel pipes in which the step of performing cutting and the series of operations are performed continuously (Japanese Patent Publication No. 6-102)
No. 285), in a combination tool used for a tool rotation type steel pipe end face processing machine, a tool body detachably provided with various chips, and a direction transverse to the spindle axis direction at a chuck side end face corner of the tool body. A triangular or quadrangular tip mounted so as to form an apex angle toward each other, and a chaser provided on the main shaft axis direction inward from the tip mounting position of the tool main body. A combination tool that chamfers the end face of steel pipes, inner and outer surfaces, outer diameter processing, and threading with a chaser.
No. 921) has been proposed.

[0005]

In the thread cutting of a steel pipe using the conventional chaser, a single chaser is used, and for example, thread cutting is performed by three-pass screw cutting. If the chaser is lost due to winding around a product being processed, the product will be defective. Moreover, in this method, since a single chaser is used to perform several pass screw cutting, there is a problem that the threaded cutting edge of the chaser wears quickly and the life of the chaser is short.

[0006] Further, in order to improve the thread cutting efficiency,
Although it is necessary to reduce the number of screw cutting passes, if only one chaser is used as in the past, the cutting load on the chaser per pass increases,
The life of the chaser was significantly reduced.

[0007] Even when two chasers for roughing and finishing are used, the chaser for roughing has an acute angle with respect to the axis of the threaded joint of the trailing flank and the leading flank of the cutting edge with respect to the axis of the threaded joint. When a thread-shaped cutting edge with a square cross-section screw shape is adopted, as shown in Fig. 8, when grinding the chaser 81, the side faces of the thread-shaped cutting edges X and Y escape to an acute angle surface with respect to the axis of the threaded joint. Since the angle θ is required, as shown in FIG. 9, it is necessary to grind each chaser 81 with the grinder 82. For this reason, chaser grinding requires many man-hours, and has a problem that the chaser 81 becomes expensive.

[0008] An object of the present invention is to solve the above-mentioned problems of the prior art, and to prevent the occurrence of defective products even if a defect occurs in a roughing chaser during machining, and to reduce the machining allowance in the roughing chaser. And a thread cutting method using the chaser for rough machining, which can grind a plurality of pieces at the same time, and the chaser for finish machining.

[0009]

SUMMARY OF THE INVENTION According to the present invention, there is provided a method of cutting a tapered square thread according to the present invention, wherein after machining an outer diameter portion of a tapered bottom thread, a play flank of a thread and a pressure flank are opposed to a shaft of a threaded joint. When cutting a thread with a tapered square thread shape with acute pipe end angles α ₁ and α ₂ , the opposite end angle β _{2 of} the cutting edge with respect to the axis of the threaded joint of the trailing flank of the cutting edge is obtuse or right angle. It proceeds counter-tube end angle beta ₁ with respect to the axis of the side flanks of the threaded joint with Cheza for rough machining with a cutting edge of an acute buttress thread shape 3 mountain above, to provide one or more crude threading. Then, the finishing process having one or more thread-shaped cutting edges having the same angle as the above-mentioned finished square thread shape in which the opposite pipe end angles γ ₁ , γ ₂ of the leading edge flank and the leading flank of the cutting edge with respect to the axis of the threaded joint are acute. One or more finishing screws are processed using a chaser.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The method for cutting a tapered square thread according to the present invention is characterized in that, after machining a tapered outer diameter portion under a thread, an angle β ₂ opposite to a pipe end of a trailing flank of a cutting edge with respect to a shaft of a threaded joint. a There obtuse or right angle, and Cheza for rough machining counter tube end angle beta ₁ with respect to the axis of the stabbing flank of the screw joint has a cutting edge of an acute buttress thread shape 3 mountain above, follow flank of the cutting edge and In order to use two chasers for finishing, which have one or more threads with the same thread-shaped cutting edge as the finished square thread shape with the acute angle γ ₁ and γ ₂ with respect to the axis of the threaded joint of the leading flank. In addition, even if the roughing chaser is damaged during the processing, it can be cut by the finishing chaser and the occurrence of defective products can be prevented.

[0011] In addition, the method of cutting a tapered square screw according to the present invention can reduce the number of times of finishing chasers required for machining by cutting most of the screws with a chaser for rough machining. The service life of the chaser can be extended.

[0012] Furthermore, since the chaser for rough machining has a large width in the axial direction of the threaded joint to be machined and has three or more cutting edges, a large allowance for thread groove machining per pass can be obtained, and the threading of the thread can be reduced. The number of grinding passes required for cutting can be reduced,
Screw cutting efficiency can be improved.

[0013] Furthermore, the chaser for rough machining has an angle β opposite to the pipe end with respect to the axis of the threaded joint of the trailing flank of the cutting edge.
₂ adopts an obtuse or right-angled saw-tooth screw-shaped cutting edge, eliminating the need for a relief angle on the trailing flank.When grinding chasers, several chasers for roughing can be ground at the same time. Man-hours can be reduced, and as a result, a chaser for roughing can be obtained at a low price.

[0014]

[Embodiment] As shown in FIG.
The angle β on the opposite end to the axis of the threaded joint₁Is an acute angle,
Angle on the opposite side to the axis of the threaded joint of the trailing flank 2
β _TwoWith four cutting edges A to D in the form of sawtooth screw
As shown in FIG. 1 (b), the chaser 3 for machining
Shaft of threaded joint of flank 11 and trailing flank 12
Angle γ₁, Γ_TwoIs an acute angle cross section square screw type
Finishing chain with two thread-shaped cutting edges E and F
Seamless with outer diameter 244.48mm and wall thickness 13.84mm
After processing the tapered outer diameter part under the thread on the pipe end of the steel pipe,
As shown in 2, one pass with roughing chaser 3 and finishing
1-pass thread cutting with chaser 13 for
A test was conducted in which a square screw with a pad was formed at the pipe end.

For comparison, as shown in FIG. 7A, as a conventional method, as shown in FIG. 7 (a), the angle between the leading flank 72 and the trailing flank 73 of the cutting edge with respect to the axis of the threaded joint with respect to the axis of the threaded joint is acute. Using one machining chaser 71 having two thread-shaped cutting edges X and Y, and machining the tapered outer diameter portion under the thread at the pipe end, as shown in FIG. The cutting of the screw was performed in three passes, and a test was performed to form a tapered square screw at the pipe end.

Then, the chaser life, the thread cutting efficiency, and the basic unit of the chaser of the method of the present invention and the conventional method were investigated. The results are shown in FIGS. In addition, the chaser life is the number of threaded pipe ends per chaser for finishing, and the thread cutting efficiency is the number of threaded pipe ends per hour,
The basic unit of the chaser is the price of the chaser per service life, and is indicated by an index using the conventional method as 100.

As shown in FIGS. 3 to 5, in the method of the present invention, the chaser life is extended about three times as compared with the conventional method, and the thread cutting efficiency is improved by about 11% as compared with the conventional method. As a result, the basic unit of the chaser was reduced by about 30% compared with the conventional method.

[0018]

Cutting method of tapered square screw of the present invention exhibits anti pipe end side angle beta ₂ with respect to the axis of the threaded joint follow flank cutting edge an obtuse angle or a right angle, the stabbing flank of the threaded joint anti tube end angle beta ₁ with respect to the axis is to perform rough threading of one or more times with Cheza for rough machining with a cutting edge of an acute buttress thread shape 3 mountain above. And, for the finishing process having one or more thread-shaped cutting edges having the same angle as the finished square thread shape in which the opposite end angles γ ₂ and γ ₁ of the cutting edge with respect to the axis of the threaded joint of the trailing flank and the leading flank are sharp. By performing finishing screw processing at least once using the chaser described above, the thread cutting efficiency can be improved, the average life of the chaser can be extended, and the basic unit of the screw chaser can be reduced.

[Brief description of the drawings]

BRIEF DESCRIPTION OF DRAWINGS FIG. 1 shows a chaser according to the method of the present invention used in an example, in which (a) is a roughing chaser and (b) is a side view of a finishing chaser.

FIG. 2 is a detailed explanatory diagram of a method of cutting a screw in two passes by a chaser of the method of the present invention used in an example.

FIG. 3 is a graph showing a comparison of the chaser life between the method of the present invention and the conventional method in Examples.

FIG. 4 is a graph showing a comparison of the thread cutting efficiency between the method of the present invention and the conventional method in Examples.

FIG. 5 is a graph showing a comparison between the unit of the chaser according to the method of the present invention and the unit of the conventional method in Examples.

6A and 6B are explanatory views of a tapered square screw; FIG. 6A is a schematic cross-sectional view of a tube-end tapered square screw portion; and FIG. 6B is a cross-sectional explanatory view of the square screw.

7A and 7B are explanatory views of a conventional chaser and screw cutting method, in which FIG. 7A is a side view of the chaser, and FIG. 7B is a detailed explanatory view of a screw cutting method in three passes.

FIG. 8 is a detailed explanatory view of a conventional chaser, in which (a) is a side view, (b) is a front view, and (c) is a bottom view.

9A and 9B are explanatory views of a conventional method of grinding a chaser with a grinder, wherein FIG. 9A is a side view and FIG. 9B is a bottom view.

[Explanation of symbols]

 1, 11, 72 Leading side 2, 12, 73 Follow-up side 3 Chaser for roughing 13 Chaser for finishing 51 Steel pipe 52 Thread 53 Playing flank 54 Pressure flank 71, 81 Chaser 82 Grinder A, B, C, D , X, Y Cutting edge E, F, X, Y Thread cutting edge θ Clearance angle

Claims (1)

[Claims] 1. A method of cutting a thread of a threaded threaded joint product having a tapered square thread shape in which the non-tube end side angles α ₁ and α ₂ with respect to the axis of the threaded joint of the play side flank and the pressure side flank of the thread are acute. , after processing the untapped tapered outer diameter, counter-tube end angle beta ₂ is obtuse or a right angle relative to the axis of the threaded joint follow flank of the cutting edge, anti pipe end side with respect to the axis of the stabbing flank of the threaded joint After the angle beta ₁ is subjected to one or more coarse threaded with rough machining Cheza having cutting edges sharp buttress thread shape 3 mountain above, the cutting edge leading side flank and follow the side flanks of the threaded joint Applying one or more finishing screws using a finishing chaser having at least one thread-shaped cutting edge having the same thread angle cutting edge as the above-mentioned finished rectangular screw shape in which the opposite pipe end angles γ ₁ and γ ₂ with respect to the shaft are acute angles. Features of tapered square screw Cutting processing method.