JP2006130579A - Chaser - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To lengthen the life of a blade part in high-speed cutting by properly determining the number of blade parts and the shape of each blade part. <P>SOLUTION: In this chaser 1, two blade parts, a roughening blade 2 for cutting a thread and a finishing blade 3 are formed in series. The respective clearance angles γ1 to γ3 of side cutting edges 2b, 2c and 3b, 3c and front cutting edges 2a and 3a in the roughening blade 2 and the finishing blade 3 are set to 2 to 10°. The area of the roughening blade 2 is set to 80 to 95% of that of the finishing blade 3. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a chaser used for thread cutting that requires high accuracy, such as when a trapezoidal screw (so-called API buttress) or a square screw of a threaded joint is cut at the end of an oil well pipe. It is.

Hereinafter, a case where a trapezoidal screw is cut at the end of the oil well pipe will be described.
In order to cut the thread of the coupling (coupling) for connecting the oil well pipes, not only the chaser 11 having one blade portion 11a as shown in FIG. 3, but also as shown in FIG. A chaser having a plurality of blade portions is used, such as a chaser 21 in which five blade portions 21a to 21e are arranged in series.

  Thread cutting using such a chaser has a substantially higher feed rate than general cutting. In addition, when cutting a trapezoidal screw, the bottom and thread of the screw are longer than when cutting a general thread, so the contact length with the chip, that is, the substantial blade Becomes longer, and the load acting on the blade becomes larger.

  In recent years, the demand for difficult-to-cut materials such as high-strength materials and corrosion-resistant Cr steel as oil well pipe materials has increased as the oil well environment has become severe, and gas wells and deep wells have advanced. There is a problem of a decrease in life and productivity.

Therefore, for the purpose of improving the service life and productivity of such a chaser, in order to improve the tool life, for example, in a coated cemented carbide alloy chaser, the coating film thickness in the vicinity of the cutting blade is partially thinned to reduce toughness. There are proposals to prevent this.
JP 60-172403 A

In addition, there has been proposed a pipe threading tip that has improved sharpness, chipping resistance, and wear resistance by improving the cutting edge processing (honing) method of the coated chaser.
JP-A-5-277809

  However, in the cutting of the trapezoidal screw, as shown in FIG. 5, the cutting depth c in the depth direction of the thread and the cutting depths a and b in the width direction are different depending on the angles α and β of the blade side surface. Therefore, when cutting difficult-to-cut materials, the cutting depth c in the depth direction of the thread is reduced and the number of cutting passes is increased in order to avoid chipping of the cutting edge. The amount of cuts a and b in the width direction becomes extremely small compared to the amount of cut c in the depth direction of the thread, and the problem arises that the cutting edge wears early due to frictional heat and the life of the chaser is reduced. The technique proposed in the patent document was the same.

  The problem to be solved by the present invention is that the number of blade portions and the shape of each blade portion are not appropriate in the conventional chaser, and the life is reduced by frictional heat during high-speed cutting.

The chaser of the present invention
In order to prevent life reduction due to frictional heat during high-speed cutting,
A chaser in which two or three rough blades for cutting a screw and a finishing blade are formed in series,
The most important feature is that the clearance angles of the side cutting ridge and the front cutting ridge of the rough blade and the finishing blade are 2 to 10 °.

  In the case of a chaser with a plurality of blade portions formed in series, if the cutting amount of the entire chaser is the same, the cutting amount per blade portion is reduced and cutting resistance is reduced. Cutting becomes possible.

However, if the number of blades is increased too much, even though the cutting resistance per blade can be reduced, the cutting resistance of the entire chaser increases, so that the dimensional accuracy of the product deteriorates.
Therefore, in the present invention, two or three blade portions for cutting a screw are used in consideration of high speed cutting and production accuracy.

  Thus, in the present embodiment of the present invention in which the blade portion has two or three rough blades and a finishing blade, the clearance angles of the side cutting ridge and the front cutting ridge of the rough blade and the finishing blade are set to 2 to 10 °. This is because, when these clearance angles are less than 2 °, the increase in resistance at the time of cutting is increased by rubbing the flank with the respective clearance surfaces of the side surface cutting ridge and the front cutting ridge of the blade portion. On the other hand, if the clearance angle exceeds 10 °, the tip of the blade portion is too sharp and defects are likely to occur during cutting. According to the inventors' experiments, the best results were obtained when the clearance angle was 5-6 °.

  In addition, since the cutting resistance acting on each blade portion differs depending on the number of blade portions formed on the chaser, the optimum range of the clearance angle differs when the blade portion is other than two or three rough blades and a finishing blade. Needless to say.

  In the above-described chaser according to the present invention, when cutting is completed in one pass, the rough blade immediately before the finishing blade and the finish are finished so that the area of the rough blade immediately before the finishing blade is 80 to 95% of the area of the finishing blade. Although it is desirable to determine the area of the blade, when cutting is completed in a plurality of passes, the ratio of the area of the rough blade and the finishing blade immediately before the finishing blade varies depending on the cutting amount of each pass. In addition, in this invention, the area of a blade means the value which multiplied the front cutting edge and the side cutting edge.

  According to the experiments by the inventors, when cutting is completed in one pass, if the area of the rough blade immediately before the finishing blade is less than 80% of the area of the finishing blade, the cutting area of the finishing blade increases and wears. Also, if it exceeds 95%, the cutting area of the finishing blade becomes too small and wear is accelerated by frictional heat, and pitch deviation tends to occur for each pass.

  However, when cutting a trapezoidal screw, as described above, the cutting depth in the width direction is smaller than the depth cutting depth, and wear due to frictional heat increases. As for the amount, it is desirable to determine the shape of the coarse blade so that the depth of cut of the screw thread is smaller than the total depth of cut.

  Since the number of blade parts and the shape and area of each blade part are appropriately determined in the chaser according to the present invention, the life of the blade part can be extended while enabling both high-speed cutting and manufacturing accuracy.

Hereinafter, the best mode for carrying out the present invention will be described with reference to FIGS. 1 and 2. FIG.
FIG. 1 is a view showing an example of the inventive chaser for cutting a trapezoidal screw, and FIG.

  Reference numeral 1 denotes a chaser according to the present invention for cutting a trapezoidal screw of a threaded joint formed at the end of an oil well pipe. For example, as shown in FIGS. 1 (a) and 1 (c), a roughly similar rough blade 2 and a finishing blade 3 two blade parts are formed in series.

  In this way, by forming the two blade portions of the rough blade 2 and the finishing blade 3 in series, the cutting resistance acting on each of the blade portions can be reduced, and the increase in the cutting resistance acting on the entire chaser 1 can be suppressed. Therefore, both high-speed cutting and improved cutting accuracy are achieved.

  And in this invention, the front cutting ridges 2a and 3a which cut the screw bottom part of the trapezoidal screw, and the side cutting ridges 2b and 2c which cut the screw side face, The clearance angles γ1, γ2, and γ3 of the front cutting ridges 2a and 3a and the side cutting ridges 2b, 2c and 3b and 3c are set to 5 °, for example. Reference numerals 2d to 2f and 3d to 3f denote flank faces of the front cutting ridges 2a and 3a and the side cutting ridges 2b, 2c and 3b, 3c.

  In this way, by setting the clearance angles γ1 to γ3 of the cutting edges 2a to 2c and 3a to 3c to, for example, 5 °, it is possible to effectively prevent an increase in cutting resistance during cutting and a loss of each blade portion. I have to.

  Further, since this example shows the chaser 1 when cutting is completed in one pass, the area of the rough blade 2 (front cutting ridge 2a × side cutting ridge 2b or 2c) is set to the area of the finishing blade 3 (front cutting ridge). 3a × side cutting edge 3b or 3c), for example, 88%, for example, 88% of the total cutting area when cutting is completed is cut by the coarse blade 2, and the remaining 12% (hatched in FIG. 2) The portion shown) is cut with the finishing blade 3 so as to prevent the finishing blade 3 from being worn as much as possible even when high-speed cutting is performed.

  In the case of the chaser 1 shown in FIGS. 1 and 2 that cuts such a trapezoidal screw, the cutting amount of the finishing blade 3 is set in the depth direction of the thread in order to prevent an increase in wear due to frictional heat. It is desirable that the cutting amount c be smaller than the sum b + c of the cutting amounts a and b in the width direction.

  For example, in the example shown in FIG. 2, the cutting depth c in the thread depth direction of the finishing blade 3 is 0.1 mm, and the cutting depths a and b in the thread width direction are each 0.08 mm. . However, it goes without saying that the optimum amount of cutting varies depending on the material to be cut, the material of the chaser to be used, surface processing, and the like.

  The chaser 1 of the present invention having the above-described configuration can effectively prevent wear due to frictional heat caused by excessive cutting, particularly chipping of the finishing blade 3 or insufficient cutting due to excessive cutting. Can be improved.

  In addition, in the above example, the chaser 1 of the present invention has been described as being applied when cutting a trapezoidal screw for an oil well pipe. However, the present invention is not limited to this, and is used for cutting other square screws, for example. Also good.

  Moreover, although said example demonstrated what formed two blade parts in series, what formed three blade parts in series may be sufficient. In this case, the rough blade refers to the first and second blade portions, and the finishing blade refers to the third blade portion that is the final blade following the first and second blade portions. Therefore, in this case, in the invention according to claim 2, the second blade portion is the second blade portion so that the area of the second blade portion that is the rough blade is 80 to 95% of the area of the third blade portion that is the finishing blade. The areas of the coarse blade and the third finishing blade are determined. In addition, the area ratio of the 1st blade part and the 2nd blade part also makes the area of the 1st blade part become 80 to 95% of the area of the 2nd blade part similarly to the above. It is desirable to decide on.

  Although the best mode for carrying out the present invention has been described above, the present invention is not limited to these exemplifications, and can be appropriately changed within the scope of the technical idea shown in the claims. Needless to say.

  The present invention described above can be applied to any cutting tool as long as it cuts a workpiece, without being limited to a chaser that performs thread cutting on an end portion of an oil well pipe.

It is the figure which showed an example of the chaser of this invention which cuts the trapezoidal screw of the threaded joint formed in an oil well pipe, (a) is a front view of a chaser, (b) is a top view of (a), (c) is It is a right view of (a). It is the detailed view which looked at the blade part of the chaser of FIG. 1 from the front. It is a front view which shows the conventional chaser which has one pile of blade parts. It is a front view which shows the conventional chaser which has five blade parts. It is a figure explaining the cutting amount by the conventional chaser which has one blade part.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Chezer 2 Coarse blade 2a Front cutting edge 2b, 2c Side cutting edge 3 Finishing blade 3a Front cutting edge 3b, 3c Side cutting edge

Claims (2)

A chaser in which two or three rough blades for cutting a screw and a finishing blade are formed in series,
A chesser characterized in that a clearance angle of each of the side cutting ridge and the front cutting ridge of the rough blade and the finishing blade is 2 to 10 °. The area of the rough blade immediately before the finishing blade is 80 to 95% of the area of the finishing blade.

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