JPH07217627A - Forming method for screw - Google Patents

Abstract

PURPOSE:To eliminate the generation of burr when a screw is forming-worked by means of a screwing chip by forming the screw in a screw part base mold by a screw forming chip after a groove for cutting a position near the cross point of the outline of the screw and a taper part is formed in a ring shape. CONSTITUTION:The screw part for forming a screw is cut in a cylindrical shape having a prescribed outer shape and length, and the base mold 6 of the screw part is formed. A plurality of grooves 8 which are formed in a triangular shape in cross sectional view is formed in a ring shape at constant intervals on the taper part 6b of the screw part base mold 6 by a groove drilling chip. Namely, a triangular part whose taper part 6b having a constant length including the cross point P of the outline 7a of a screw 7 and the taper part 6b is formed in a slant side, is cut in a ring shape as groove 8a, 8b, 8c. It is thus possible to eliminate burr cutting.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a method for forming a threaded portion for connecting a valve, a threaded portion for a pipe joint, a threaded portion for connecting a pipe end, and the like.

[0002]

2. Description of the Related Art Generally, a threaded portion such as a valve or a pipe joint is first finished by cutting a base material formed by casting with an NC machine tool or the like, and then the finished prototype. It is formed by performing thread processing on the thread portion of the thread using a thread cutting tip.

For example, a T having an external screw A as shown in FIG.
When the mold joint B is formed, as shown in a partially enlarged cross-sectional view of FIG. 7, a screw portion 11 (hereinafter referred to as a screw portion prototype) of a prototype formed of a cylindrical portion 11a and a tapered portion 11b formed by prototype finishing. Thread processing is performed using a thread cutting tip, and the screw part prototype 1 is formed along the outline 12a of the screw 12.
The screw 12 is formed by cutting off the one-dot chain line portion 1.

By the way, when thread cutting is carried out by the conventional threading method as described above, burrs 13 frequently occur near the boundary between the taper portion 11b of the screw part prototype 11 and the cylindrical portion 11a and the taper portion 11b. Observing the occurrence state of the burrs 12, as shown in FIG. 7, burrs 13 frequently appear in the vicinity of the intersection P between the outline 12a of the screw 12 and the taper portion 11b formed in the cross-sectional view. It is practically impossible to eliminate the occurrence of burrs.

Therefore, in the processing of threaded portions such as valves and joints, the burr 13 is removed by retreating the threading tip after forming the screw to remove the burr 13 or buffing after forming the thread. A measure is applied to remove the burr 13. However, in the actual production of valves and fittings, 1/1000 ~
With a probability of 1/2000, burrs 13 that have an adverse effect as described below remain, and it is difficult to completely remove burrs by the above-described deburring method.

If the burr 13 remains on the threaded portion 12 of the valve or the joint, the worker may damage his / her hand when the sealing tape is wound in the piping work, or the threaded portion 12 may be damaged.
When the screw is tightened, seizure occurs in the screw part, which makes it difficult to dissociate the screw connection part later, or the screw part 12 is damaged when the screw connection part is dissociated and leaks when reconnecting. .

[0007]

DISCLOSURE OF THE INVENTION The present invention is unavoidable with the above-mentioned problem in the conventional method for forming threads of valves and joints, that is, burrs are unavoidable, and the post-treatment for deburring is troublesome. It is difficult to eliminate the residual burr even if deburring is performed, and seizure of the screw part and injury of workers are 1/1000 to 1 of the number of products.
This is to solve the problems such as occurring at a probability of about / 2000, and does not remove the burr that has occurred after forming the screw, but does not generate the burr itself when forming the screw with the thread cutting tip. The present invention provides a method for forming such a screw.

[0008]

According to the first aspect of the present invention, a screw part prototype 6 having a cylindrical portion 6a and a taper portion 6b is formed on a base material 5, and the taper portion 6b has a sectional view. After forming the groove 8 that cuts out in the vicinity of the intersection P between the outer shape line 7a of the screw 7 and the taper portion 6b formed in a ring shape, the screw 7 is formed on the screw portion prototype 6 by the screw forming tip. This is a basic configuration of the invention.

The invention according to claim 5 of the present application is the taper part 6 of the screw part prototype 6 according to the invention of claim 1.
In addition to the groove 8 formed in b, the cylindrical portion 6a adjacent thereto
In addition, the basic configuration of the invention is to form the groove 8 for cutting out the vicinity of the apex Q of the thread ridge of the screw 7 to be formed in a ring shape.

[0010]

[Function] The thread cutting tip is used to attach the screw 7 to the screw type master 6
When forming the, a large amount of burrs remains in the vicinity of the intersection P between the outer shape line 7a of the screw 7 to be formed and the taper portion 6b in a sectional view. In the present invention, the groove 8 is formed to pre-cleave a region of the threaded portion prototype 6 where burrs are likely to remain, so that no burrs are produced when a screw is formed by the thread cutting tip. Become.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a process diagram of a screw forming method according to the present invention, in which 1 is a base material forming process, 2 is a master forming process, 3 is a grooving process, and 4 is a thread cutting process.

In the base material forming step 1, the metal raw material is formed by forging, casting, or the like into a shape substantially similar to the outer shape of the product. The base material (for example, valve box or joint member) 5 formed in the base material forming step 1 is subsequently machined in the prototype forming step 2, and the joint member or the like is provided with a through hole or a screw. The thread portion for forming the is cut into a cylindrical shape having a predetermined outer shape and length, and the prototype 6 of the thread portion is formed.

When the master 6 of the screw portion is formed in the master forming step, next, in the grooving step 3, grooving is performed at a predetermined position of the screw master 6. FIG. 2 is a partially enlarged cross-sectional view of a screw part prototype 6 of a joint or a valve body.
Is a cylindrical portion, 6b is a tapered portion, 7 is a screw cut and formed by a thread cutting tip, and 7a is an outline of the screw.

In the grooving step 3, as shown by the alternate long and short dash line in FIG. 2, a plurality of triangular grooves 8 in a sectional view are formed on the taper surface 6b of the screw part master 6 by a grooving tip. It is formed in a ring shape at intervals. That is, in a cross-sectional view, the intersection P of the outline 7a of the screw 7 and the taper portion 6b
The triangular portion having the taper portion 6b having a constant length as a hypotenuse is cut into a ring shape as the grooves 8a, 8b, 8c.

Incidentally, in this embodiment, the taper portion 6b is formed.
Although the three grooves 8a, 8b, and 8c are formed in a ring shape, the groove 8 may be formed only at the uppermost position where the adverse effect of residual burr is greatest.

Further, in this embodiment, the groove 8 is a triangular groove having a fixed length of the tapered surface portion 6b as a hypotenuse in a sectional view, but as shown in FIG. It is also possible to form the rectangular groove 8 having one side as the tapered portion 6b having a constant length including the intersection point P of the portion 6b and the outline 7a of the screw.

Further, in this embodiment, the groove 8 is formed in the taper portion 6b.
Although it is provided only in the groove 8, the groove 8 of the tapered portion 6b is provided.
Alternatively, the groove 8 may be provided in the cylindrical portion 6a near the taper portion 6b to cut out the vicinity of the screw 7 including the thread crest Q. In addition, the lateral width of the groove 8 is preferably about 1/5 to 1/3 of the screw pitch, and the depth of the groove 8 is preferably about 1/8 to 1/4 of the thread height. This is because if the width and depth of the groove 8 are larger than the above-mentioned values, the smoothness of screwing the threaded portion is reduced.

After the formation of the groove 8 in the grooving step 3 is completed, in the thread cutting step 4, a screw 7 having a predetermined pitch and thread is formed using a thread cutting tip.

4 and 5 show partially enlarged cross sections of the screw 7 formed according to the present invention. FIG. 4 shows the screw 7 formed by the manufacturing method of FIG. 2 and FIG. 5 shows the screw 7 formed by the manufacturing method of FIG. Is shown. As is clear from FIGS. 4 and 5, the screw 7 according to the present invention has the first three threads and the shape thereof is slightly different from the shape of the conventional screw 7 of this kind. Since the vicinity of the intersection point P of the outline 7a of the screw 7 and the taper portion 6b where burrs are likely to remain during thread cutting with a tip is pre-cleaved in the grooving step 3, the burrs are formed in the thread cutting step 4. There is nothing to cause.

Although the so-called straight type external thread is formed in the embodiments shown in FIGS. 1 to 5, it goes without saying that the external thread may be a taper thread. Further, in each of the above-mentioned embodiments, the outer thread is formed, but it is needless to say that this may be an inner thread, and when the formed thread is an inner thread, the taper portion 6b has an outer end. It becomes a taper part whose diameter gradually increases toward the part.

[0021]

According to the present invention, a groove cutting step is provided before the thread cutting step, and the intersection point P between the outline of the screw and the taper portion of the screw portion prototype is prone to burrs during thread cutting with a chip.
The vicinity of is cut from the pre-screw screw prototype. As a result, no burrs are left on the threaded portion during the thread cutting process using the tip, eliminating the need for labor-intensive and highly accurate deburring as before, and tightening due to burrs remaining No seizure of screws occurs. Further, according to the present invention, a groove cutting process is required in the process of forming a screw, but since a complicated and highly accurate deburring process as in the past is not required, the screw forming cost does not increase. The present invention has excellent practical utility as described above.

[Brief description of drawings]

FIG. 1 is a process drawing of a screw according to the present invention.

FIG. 2 is a partial enlarged cross-sectional view showing a groove formation state in the groove forming step of the present invention.

FIG. 3 is a partially enlarged cross-sectional view showing a state of forming another groove in the groove making step.

FIG. 4 is a partially enlarged sectional view showing an example of a screw formed according to the present invention.

FIG. 5 is a partially enlarged sectional view showing another example of the screw formed according to the present invention.

FIG. 6 shows an example of a conventional T-type threaded joint.

FIG. 7 is a partially enlarged cross-sectional view showing a formation state of a thread portion of a conventional T-type threaded joint.

[Explanation of symbols]

1 is a base material forming step, 2 is a master forming step, 3 is a grooving step, 4 is a thread cutting step, 5 is a base material, 6 is a screw part prototype, 6
a is a cylindrical portion, 6b is a tapered portion, 7 is an external thread, 7a is a screw outline, 8 is a groove, P is an intersection of the outline of the screw 7 and the tapered portion, and Q is a screw thread formed on the cylindrical portion. Mountain top.

Claims (5)

[Claims] 1. A screw part prototype (6) having a cylindrical part (6a) and a tapered part (6b) is formed on a base material (5), and is formed on the tapered part (6b) in a cross-sectional view. A groove (8) for cutting out the vicinity of the intersection P between the outer shape line (7a) of the screw (7) and the taper portion (6b) is formed in a ring shape, and then the screw part prototype (6) is screwed with a screw cutting tip (6). 7) A method for forming a screw, characterized in that 2. The method for forming a screw according to claim 1, wherein the groove (8) has a triangular shape having a taper portion (6b) having a constant length including an intersection point P as a hypotenuse in a cross-sectional view. 3. The method of forming a screw according to claim 1, wherein the groove (8) has a quadrangular shape having a taper portion (6b) of a constant length including an intersection point P as one side in a sectional view. 4. The thread formation according to claim 1, claim 2 or claim 3, wherein the groove (8) is provided only in a portion including an intersection point P located at an uppermost position of the tapered portion (6b). Method 5. A screw part prototype (6) having a cylindrical part (6a) and a tapered part (6b) is formed on a base material (5), and is formed on the tapered part (6b) in a sectional view. A groove (8) for cutting out in the vicinity of an intersection P between the outer shape line (7a) of the screw (7) and the tapered portion (6b) is formed in a ring shape, and a cylindrical portion (6a) adjacent to the tapered portion (6b). To
A groove (8) for cutting out the vicinity of the apex Q of the thread of the screw (7) formed in a sectional view is formed in a ring shape, and thereafter,
Screws (7) to the thread prototype (6) with the thread-forming tip
Forming method for forming screw