JPH11138233A - Formation of female screw and device therefor, and formed product - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve production efficiency of a female screw. SOLUTION: A prepared hole 24 and a gathering part 26 of excess thickness located in a surrounding wall around the prepared hole 24 are formed in a work 4. By opening the opening-closing tap 7 in the direction of radius of the prepared hole 24 under the condition that an opening-closing tap 7 in closed state is inserted into the direction parallel to the axis line, a screw thread part 12 of the opening-closing tap 7 is transferred to the prepared hole 24 to form a female screw 5, and at the same time an excess thickness generated by the transfer of the screw thread part 12 is made to escape into the gathering part 26 of excess thickness.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for forming an internal thread, and to a formed article, and more particularly, to a method and an apparatus for forming an internal thread and an formed article capable of improving the production efficiency of an internal thread. It is about.

[0002]

2. Description of the Related Art When a female screw is formed on a workpiece, conventionally, a pilot hole is first formed in the workpiece, and then a rod-shaped tap having a thread on the outer periphery is screwed into the pilot hole. By inserting while inserting, the inner peripheral surface of the prepared hole is cut with a tap to form a female screw, and finally, by reversely rotating the tap, the tap is extracted from the formed female screw I have.

[0003]

However, the means for forming the female screw has the following problems.

[0004] That is, since the tapping and removing steps of the tap into the prepared hole formed in the workpiece involve the rotation of the tap, the processing speed is limited, and it is difficult to increase the production efficiency. Was. In addition, it is necessary to switch between forward rotation and reverse rotation of the tap, in which the tapping process is forward rotation and the tapping process is reverse rotation, which further reduces the production efficiency.

[0005] Further, in a cutting step in which a tap is screwed into a through hole formed in a workpiece, lubrication for cutting is required, and scattering of cutting powder is inevitable.

SUMMARY OF THE INVENTION In view of the above circumstances, an object of the present invention is to provide a method and apparatus for forming a female screw and a formed product capable of improving the productivity of the female screw.

[0007]

Means for Solving the Problems In order to solve the above problems, the present invention is as follows.

That is, according to the first aspect of the present invention, a pilot hole and a surplus pocket located on a peripheral wall portion of the pilot hole are formed in the work.
When the closed tap is inserted into the lower hole of the workpiece from a direction parallel to the axial direction, and the tap is opened in the radial direction of the pilot hole, the thread of the tap is transferred to the pilot hole. And forming a female screw, and allowing the excess thickness generated by the transfer of the thread portion to escape to the excess thickness pool.

According to a second aspect of the present invention, in the first aspect, the excess pocket formed on the peripheral wall of the pilot hole of the work is formed as a groove extending in the axial direction.

According to a third aspect of the present invention, in the first or second aspect, the installation number of the surplus reservoir is a multiple of the number of divisions of the opening and closing tap, and the installation position of the excess reservoir is determined by the dividing position of the opening and closing tap. I try to match.

Further, according to a fourth aspect of the present invention, in any one of the first to third aspects, the pilot hole is formed by burring.

According to a fifth aspect of the present invention, there is provided a semiconductor device comprising:
A tap that can be opened and closed in the radial direction of the pilot hole in a state where the pilot hole is inserted into the pilot hole having a surplus pool in the peripheral wall portion in a direction parallel to the axial direction of the pilot hole, and a tap that opens and closes the tap in the radial direction of the pilot hole An internal thread forming apparatus is provided with an opening mechanism and a press apparatus mold.

According to a sixth aspect of the present invention, in the fifth aspect, the tap opening mechanism presses the opening operation guide surface formed at the end of the opening and closing tap in a tapered opening direction in the axial direction of the pilot hole. Thus, the opening and closing tap is constituted by a core insert that opens in the radial direction of the pilot hole.

According to a seventh aspect of the present invention, according to the fifth or sixth aspect, the dividing position of the opening / closing tap is adjusted to the installation position of the excess pocket.

The invention according to claim 8 is a female screw having a thread portion transferred to a lower hole by an opening / closing tap, and a surplus portion formed by being transferred to a surplus pool formed in a peripheral portion of the lower hole. Are provided on the product body to form a female screw.

According to a ninth aspect of the present invention, in the ninth aspect, the product main body has a plate shape.

According to a tenth aspect of the present invention, in the eighth or ninth aspect, the pilot hole is formed by burring.

According to the eleventh aspect of the present invention, the number of provisions of the surplus pool is set to a multiple of the number of divisions of the opening and closing taps, and the installation position of the excess pocket is matched with the division position of the opening and closing taps.

According to the above means, the following effects can be obtained.

First, a plate-shaped work or the like in which a pilot hole and a surplus wall are formed on the peripheral wall of the pilot hole is prepared in advance, and the work is set on a mold of a press device, and simultaneously formed on the work. The prepared hole is inserted into the opening and closing tap incorporated in the mold, and the prepared hole is aligned with the opening and closing tap.

At this time, a work in which the periphery of the pilot hole is formed by burring may be used.

Next, the press device is driven. Then, since the core insert is inserted into the tapered opening operation guide surface formed at the axial center position of the upper or lower end of the opening / closing tap, the opening / closing tap constantly urged in the closing direction is rotated by the wedge effect. It is expanded radially around the center position.

As described above, the thread portion formed on the outer periphery of the opening and closing tap is pressed and transferred to the lower hole of the work, and the female screw is formed.

When the thread is transferred to the lower hole, excess thickness is generated. However, since the excess thickness is formed on the peripheral wall of the lower hole, the excess thickness is released to the excess thickness accumulation. . On this occasion,
Since the surplus pocket is formed in a groove shape extending in the axial direction of the pilot hole, it is possible to properly escape the residual thickness of the entire pilot hole.

[0025] The number of strips of the surplus pool is set to the number or a multiple of the number of divisions of the opening and closing taps.
By adjusting to the division position of the opening / closing tap, it becomes possible to allow the excess thickness to escape to a position where the thread portion when the opening / closing tap is opened is not transferred. The surplus fled to the surplus pool is then threaded when a bolt or the like is screwed into the female screw, and the threaded portion cuts into the bolt, thus exhibiting an anchoring effect that makes it difficult for the bolt to come off. As a result, the female screw has a strong fastening force.

When the female screw is transferred to the pilot hole, the core insert is pulled away from the tapered opening operation guide surface at the upper end or lower end of the opening / closing tap, and the opening / closing tap is closed.

As described above, the female screw can be formed on the work only by pressing without any rotational movement, so that the productivity of the female screw can be remarkably improved.

Further, since there is no cutting step of screwing a tap into a prepared hole formed in a work, lubrication for cutting can be made unnecessary, and cutting powder is scattered and accumulates in the mold to frequently form the mold. This makes it possible to prevent problems such as the necessity of cleaning.

Further, the prepared hole of the work is formed by a burring process so as to form a thickened portion having a substantially frustoconical shape, so that a desired number of effective threads can be ensured even if the work is a thin plate. .

[0030]

Embodiments of the present invention will be described below with reference to the drawings.

FIGS. 1 to 6 show a first embodiment of the present invention. FIG. 1 is a partially enlarged side sectional view of a mold apparatus provided with an opening / closing tap, and FIG. FIG. 3 is a partially enlarged side sectional view similar to FIG. 1 showing a state in which a screw is being transferred; FIG. 3 is a view showing a state in which an opening / closing tap is closed after a female screw is formed;
4 (a) is a partially enlarged plan view of the work, FIG. 4 (b) is a partially enlarged side view of the work,
FIG. 5A is a partially enlarged plan view of another burring work, FIG. 5B is a partially enlarged side view of the burring work, and FIG. 6A is another groove shape. FIG. 6B is a partially enlarged side view of a work having another groove shape.

First, as shown in FIGS. 1 to 3, a lower die 2 is placed on a base plate 1, and a work holder 3 is opposed to the lower die 2 via a slide (not shown) so as to be able to move up and down. A mold apparatus 6 is provided, which is arranged so that the work 4 placed on the lower mold 2 is held by the work presser 3 and the female screw 5 can be pressed.

In addition, in addition to the above, there is a width direction press in which a die is reciprocated in a horizontal direction to perform a press, and such a width direction press may be used. In the present embodiment, as an example, a case of a press device that reciprocates a work holder 3 in a vertical direction will be described.

An opening / closing tap 7 is attached to the lower mold 2 of the mold apparatus 6.

That is, a tap insertion hole 8 penetrating in the vertical direction is formed in the lower mold 2, and a shaft extending in the vertical direction with a smaller diameter than the tap insertion hole 8 is formed in the portion of the tap insertion hole 8 of the lower mold 2. An opening / closing tap 7 having a portion 9 is provided at the upper end of the shaft portion 9 with a lower mold 2.
Is mounted so as to protrude upward from the upper surface.

The opening / closing tap 7 includes a plurality of divided tap pieces 10 and 11 divided into a plurality in the circumferential direction (in the figure, the divided tap pieces are divided into two, but may be divided into three or more). Are arranged so that they can be freely opened and closed in the radial direction around the center. The work 4 is placed on the outer periphery of the shaft 9 of the opening and closing tap 7 at a position slightly above the upper surface of the lower mold 2.
A thread portion 12 for transfer is formed over a range substantially equal to the thickness dimension of the shaft portion 9, and a flange portion 13 is formed at a lower end portion of the shaft portion 9. The flange portion 13 is formed by the base plate 1 and the lower mold 2. The opening and closing tap 7 is fixed to the portion of the gap 14 formed between the lower die 2
To be held.

The mold apparatus 6 is provided with tap opening mechanisms 15 and 16 for opening the opening and closing tap 7 and a tap closing mechanism (not shown) for urging the opening and closing tap 7 to be always closed.

The tap opening mechanism 15 includes an inverted conical tapered upper opening operation guide surface 17 formed at the axial center position of the upper end of the opening and closing tap 7, and an opening and closing tap formed on the work holder 3 of the mold apparatus 6. An upper core insert 20 which is provided in a recess 18 for accommodating the upper end of the workpiece 7 so as to be able to advance and retreat and move up and down with respect to the work holder 3 and has a wedge-shaped portion 19 at the lower end which can be inserted into the upper opening operation guide surface 17 It is composed of

The similar tap opening mechanism 16 is provided with, for example, a conical tapered lower opening operation guide surface 21 formed at an axial center position of a lower end of the opening / closing tap 7, and moves up and down with respect to the base plate 1. It is provided with a lower core insert 23 which is freely provided and has a wedge-shaped portion 22 having a conical tapered shape which can be wedge-inserted into the lower opening operation guide surface 21 at the upper end.

Although it is sufficient to provide only one of the tap opening mechanisms 15 and 16, it is sufficient to provide both when the transfer of the thread 12 to the work 4 requires a large force. I do. And the tap opening mechanism 15, 1
When both 6 are provided, the lower core insert 23 and the upper core insert 20 are moved in close proximity to and separated from each other in synchronization.

The tap closing mechanism may be a spring mechanism that constantly biases each of the divided tap pieces 10 and 11 in the closing direction.
It is good also as something like a lever mechanism which closes 0,11.

Then, a work 4 that can be set in the mold apparatus 6 having the above-described opening / closing tap 7 is prepared.

As shown in FIGS. 4 to 6, the work 4 is formed with a shaft 9 of an opening / closing tap 7 in order to form a female screw 5.
And a through hole slightly larger in diameter than the threaded portion 12
And a surplus pool 26 formed on the peripheral wall of the pilot hole 24.

Further, a surplus pool 26 formed in the pilot hole 24.
Is preferably a groove extending in the axial direction of the pilot hole 24,
Further, it is preferable to provide a plurality of strips at the same pitch in the circumferential direction of the pilot hole 24. The volume of the surplus pool 26 is set in consideration of the volume of the surplus generated by the transfer of the thread portion 12.

Further, the number of lines of the excess wall space 26 is set according to the axial size and diameter of the pilot hole 24, the number of divisions of the opening and closing tap 7, and the like. For example, when the diameter of the pilot hole 24 is large, the number of the excess pockets 26 is increased, and when the diameter of the pilot hole 24 is small, the number of the excess pockets 26 is reduced.

When the opening / closing tap 7 is divided into two parts, the number of the excess pockets 26 is preferably a multiple of two, such as two or four, and the opening / closing tap 7 is divided into three parts. In this case, it is preferable to use three or six or so multiples of three.
It is preferable that the installation position of the surplus pool 26 is adjusted to the division position of the opening and closing tap 7.

The groove shape of the surplus pool 26 is shown in FIG.
-As shown in FIG. 5, it may be a rectangular cross section, a semicircular cross section as shown in FIG. 6, or a cross sectional shape other than the above.

The work 4 may be made of any material that can be subjected to plastic working such as metal or resin, but a plate-like material is particularly suitable.

Further, when the work 4 is a thin plate, FIG.
As shown in FIG. 6, at the same time that the pilot hole 24 is formed by burring, a thickened portion 27 is formed on one surface of the work 4 so as to secure a desired number of effective threads around the pilot hole 24. You can also.

Next, the operation will be described.

First, a plate-like work 4 or the like in which a pilot hole 24 and a surplus pool 26 are formed on the peripheral wall of the pilot hole 24 is prepared in advance, and as shown in FIG. 2 and at the same time, the pilot hole 24 formed in the work 4 is inserted through the opening / closing tap 7 protruding from the tap insertion hole 8 of the lower die 2, and the pilot hole 24 is aligned with the opening / closing tap 7. State.

At this time, as shown in FIGS. 5 and 6, the thickening portion 27 is formed around one end of the pilot hole 24 by burring.
May be used.

Next, as shown in FIG. 2, the press device is driven to lower the work presser 3, and the upper surface of the work 4 is pressed by the work presser 3.

Next, the upper core insert 20 provided in the concave portion 18 of the work holder 3 descends, and the wedge-shaped portion 22 at the lower end of the upper core insert 20 is inverted at the axial center of the upper end of the opening / closing tap 7. Since the split tap pieces 10 and 11 of the opening / closing tap 7 are inserted in the conical tapered upper opening operation guide surface 17, the split tap pieces 10 and 11 are expanded in the radial direction around the axial center position.

At the same time, the lower core insert 23 is moved upward from the base plate 1 in synchronization with the upper core insert 20, and the wedge-shaped portion 22 at the upper end of the lower core insert 23 is opened and closed.
The split tap pieces 10 and 11 of the opening / closing tap 7 are inserted into the conical tapered lower opening operation guide surface 21 formed at the lower center axis position, and are expanded in the radial direction about the center position. .

As described above, the thread portion 12 formed on the outer periphery of the shaft portion 9 of the opening / closing tap 7 slightly above the upper surface of the lower die 2 is pressed and transferred to the lower hole 24 of the work 4, The female screw 5 is formed.

When transferring the threaded portion 12 to the pilot hole 24, extra thickness is generated. However, since the extra wall 26 is formed on the peripheral wall of the preliminary hole 24, the extra thickness is reduced. Escape to the pool 26. At this time, since the excess thickness reservoir 26 is formed in a groove shape extending in the axial direction of the prepared hole 24, the excess thickness of the entire prepared hole 24 can be properly escaped.

Further, the number of installation steps of the surplus pool 26 is set to the number or a multiple of the number of divisions of the opening and closing tap 7,
By setting the installation position of the opening and closing tap 7 to the division position of the opening and closing tap 7, the excess thickness is allowed to escape to a position where the thread 12 between the split tap pieces 10 and 11 is not transferred when the opening and closing tap 7 is opened. It is possible to do so. The surplus meat that escaped to the surplus pool 26 is then threaded when a bolt or the like is screwed into the female screw 5, and the threaded portion cuts into the bolt, thereby providing an anchoring effect that makes it difficult for the bolt to come off. Thus, the female screw 5 having a strong fastening force is obtained.

When the female screw 5 is transferred to the pilot hole 24 in this way, the work holder 3 is raised and the wedge-shaped portion 22 of the upper core insert 20 is inverted conically tapered at the upper end of the opening / closing tap 7 as shown in FIG. The lower core insert 23 is immersed in the base plate 1 at the same time, and the wedge-shaped portion 22 of the lower core insert 23 is opened at the lower end of the conical taper at the lower end of the opening / closing tap 7. The opening / closing tap 7 is pulled away from the operation guide surface 21 and is closed by a tap closing mechanism (not shown).

As described above, the female screw 5 can be formed on the work 4 only by pressing without any rotational movement, so that the productivity of the female screw 5 can be significantly improved. Become.

Further, since there is no cutting step of screwing a tap into the prepared hole 24 formed in the work 4, lubrication for cutting can be made unnecessary, and cutting powder is scattered and accumulated in the lower mold 2. It is possible to prevent problems such as the need to frequently clean the lower mold 2.

Further, as shown in FIGS. 5 and 6, a pilot hole 24 is formed by burring,
When the work 4 having the thickened portion 27 formed around the prepared hole 24 on one side is used, it is possible to secure a desired number of effective threads even with the work 4 having a thin plate shape.

FIG. 7 shows a second embodiment of the present invention, in which a long work such as a coil material is continuously processed by a transfer press device while being rewound to form a product having an internal thread. FIG. 8A is a plan view showing a process, FIG. 8A is a plan view showing a pilot hole formed in the work of FIG. 7, and FIG.
8A is a side view showing a pilot hole different from FIG. 8A formed in the workpiece, FIG. 9A is a plan view showing the shape of the formed product,
FIG. 9B is a side view showing the shape of the formed product.
(C) is another side view showing the shape of the product formed by burring.

When a long work 4 such as a coil material that has been rewound is sent to a transfer press device, first, in a first stage (a), a pilot pilot hole is made in the work 4 and a pilot pilot hole is formed. 28 is formed, and a tap pilot hole is formed to form a pilot hole 24. As shown in FIGS. 8A and 8B, the excess hole 26 is also formed in the prepared hole 24 at the same time. 8A, for example, as shown in FIG. 8A, even if four lines are formed at a pitch of 90 degrees in the circumferential direction as shown in FIG.
As shown in (b), three stripes may be formed at a pitch of 120 degrees in the circumferential direction.

Next, in the second stage (b), the pilot punch 29 is inserted into the pilot pilot hole 28 so that the work 4
Pilot (positioning and fixing) of the pilot hole 24
Then, tapping is performed on the lower hole 24, and chamfering or the like is performed on the lower hole 24. At this time, it is also possible to form a thickened portion 27 on one surface of the prepared hole 24 by inserting a punch into a prepared small hole (not shown) and performing burring if necessary.

Further, at the third stage (c), a pilot punch 29 is inserted into the pilot pilot hole 28 to
And the tapping is performed on the prepared hole 24 to form the female screw 5.

Finally, at the fourth stage (d), the pilot 4 is inserted into the pilot pilot hole 28 to perform the pilot of the work 4 and the outer shape of the work 4 is removed. ), (B) or (c), a product 31 having the female screw 5 in the product body 30 is obtained.

As shown in FIG. 9B, the product 31 does not have the thickened portion 27 formed by burring, or the product 31 has the thickened portion 27 formed by burring as shown in FIG. 9C. Either one can be formed.

As described above, by passing the long work 4 through the four stages (a) to (d), the preparation of the pilot hole, the tapping of the pilot pilot hole, the formation of the female screw 5, and the removal of the outer shape of the product main body 30 are continuous. It is possible to efficiently produce the product 31 having the female screw 5.

It should be noted that the present invention is not limited to the above-described embodiment, and the opening / closing tap 7 may be incorporated in the upper mold instead of the lower mold 2 of the mold apparatus 6. Of course, various changes can be made without departing from the spirit of the present invention.

[0071]

As described above, according to the female screw forming method and apparatus of the present invention and the formed product, the following excellent effects can be obtained. 1) Since a female screw can be formed on a work only by press working without any rotational movement, the productivity of female screw production can be remarkably improved.

2) Since there is no cutting step of screwing a tap into the prepared hole formed in the work, lubrication for cutting can be made unnecessary, and cutting powder is scattered and accumulates in the mold to frequently form the mold. This makes it possible to prevent problems such as the necessity of cleaning.

3) When transferring the thread portion to the pilot hole,
The excess wall is formed, but since the excess wall is formed on the peripheral wall of the pilot hole, the excess wall is released to the excess wall. At this time, since the excess thickness reservoir is formed in a groove shape extending in the axial direction of the pilot hole, it is possible to properly escape the excess thickness of the entire pilot hole.

4) When the opening and closing tap is opened by setting the installation number of the surplus pool to be a multiple of the number of divisions of the opening and closing tap, and setting the installation position of the excess pocket to the division position of the opening and closing tap. It is possible to allow the excess thickness to escape to a position where the thread portion is not transferred. The surplus fled to the surplus pool is then threaded when a bolt or the like is screwed into the female screw, and the threaded portion cuts into the bolt, thus exhibiting an anchoring effect that makes it difficult for the bolt to come off. As a result, the female screw has a strong fastening force.

5) When using a work in which a thickened portion is formed around a pilot hole on one side of the work by burring, a desired number of effective threads is ensured even for a work having a thin plate shape. It becomes possible.

[Brief description of the drawings]

FIG. 1 is a partially enlarged side sectional view of a mold apparatus provided with an opening / closing tap according to a first embodiment of the present invention.

FIG. 2 is a partially enlarged side sectional view similar to FIG. 1, showing a state in which an opening / closing tap is opened and a female screw is transferred.

FIG. 3 is a partially enlarged side sectional view similar to FIG. 1 showing a state in which an opening / closing tap is closed after a female screw is formed.

FIG. 4A is a partially enlarged plan view of a work, and FIG. 4B is a partially enlarged side view of the work.

5A is a partially enlarged plan view of another work, and FIG.
Is a partially enlarged side view of another work.

6A is a partially enlarged plan view of another work, and FIG.
Is a partially enlarged side view of another work.

FIG. 7 shows a step of forming a product having a female screw by continuously processing with a transfer press device while unwinding a long workpiece such as a coil material according to a second embodiment of the present invention. It is a top view.

8A is a plan view showing a pilot hole formed in the work of FIG. 7, and FIG. 8B is a plan view showing another pilot hole formed in the work of FIG.

9A is a plan view showing the shape of the formed product 31, FIG. 9B is a side view showing the shape of the formed product, FIG.
(C) is a side view showing another shape of the formed product.

[Explanation of symbols]

 2 type (lower type) 4 work 5 female screw 6 press device 7 opening / closing tap 12 thread part 15,16 tap opening mechanism 17,21 (upper and lower) open operation guide surface 20,23 (upper and lower) core insertion Gold 24 Preparatory hole 26 Surplus pool 27 Increased thickness 30 Product body

Claims (11)

[Claims] 1. A lower hole and a surplus pool located on a peripheral wall portion of the lower hole are formed in a work, and a closed opening / closing tap is inserted into the lower hole of the work in a direction parallel to an axial direction. By opening the opening / closing tap in the radial direction of the pilot hole in a state inserted from the above, the thread portion of the opening / closing tap is transferred to the pilot hole to form a female screw, and the thread portion is transferred. A method for forming a female screw, comprising: letting excess material generated by the above process escape into the excess material reservoir. 2. The female screw forming method according to claim 1, wherein the excess pocket formed on the peripheral wall of the pilot hole of the work is a groove extending in the axial direction. 3. The installation number of the excess paddle is the number of divisions of the opening and closing tap, and the installation position of the excess padding is adjusted to the division position of the opening and closing tap. Or the method for forming a female screw according to 2. 4. The method according to claim 1, wherein the pilot hole is formed by burring. 5. An opening / closing tap which can be opened / closed in a radial direction of the pilot hole while being inserted into a pilot hole formed in the workpiece and having a surplus pocket in a peripheral wall portion in a direction parallel to the axial direction of the pilot hole. And a tap opening mechanism for opening the opening / closing tap in the radial direction of the pilot hole in a mold of a press device. 6. The tap opening mechanism includes a tapered opening operation guide surface formed at an end portion of the opening and closing tap, and the opening and closing tap being pushed by pushing the opening operation guide surface in an axial direction of the pilot hole. The female screw forming device according to claim 5, further comprising a core insert that opens in a radial direction of the pilot hole. 7. The female screw forming device according to claim 5, wherein a dividing position of the opening / closing tap is adjusted to an installation position of a surplus pool. 8. A product body comprising: a female screw having a thread portion transferred to a lower hole by an opening / closing tap; and a surplus formed by being transferred to a surplus pool formed in a peripheral portion of the lower hole. A female screw forming product comprising: 9. The female screw forming product according to claim 8, wherein said product main body is plate-shaped. 10. The female screw formed product according to claim 8, wherein the pilot hole is formed by burring. 11. The method according to claim 11, wherein the setting number of the excess paddle is the number of divisions of the opening / closing tap, and the installation position of the excess padding is adjusted to the dividing position of the opening / closing tap. An internal thread formed product according to any one of 8 to 10.