JPH08232933A - Structure for reducing loosening torque of bolt and loosening method - Google Patents

Abstract

PURPOSE: To reduce the torque for loosening work by screwing a first auxiliary bolt until being engaged with a locking stepped part, screwing a second auxiliary bolt until being abutted on the first auxiliary bolt, and screwing the bolt to a fitting body through a work to be tightened. CONSTITUTION: A first auxiliary bolt 121 is screwed into a first threaded hole part 10 until being abutted on a locking stepped part 9, a second auxiliary bolt 131 is screwed into a second threaded hole part 11 until a head part 161 is abutted on the bolt 121 , and a bolt B passing through a work 5 to be tightened is tightened to a fitting body 5. Tension is applied to the bolts B, 131 . To loosen the bolt B, the bolts 131 , 121 are removed from the bolt B, and the tension borne by the bolt 131 is borne by the bolt B to allow the bolt B to be further elongated. The bolt 131 is screwed into the second threaded hole part 11 until the head part 161 is opposite to the locking stepped part 9 with interval therebetween, and the bolt 121 is tightened into the first threaded hole part 10 to allow the bolt B to be further elongated, and to allow the tightening force to be applied to the work 4 to be tightened from the bolt B to be further reduced. Thus, the bolt B can be loosened with small torque.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bolt loosening torque reducing structure and a bolt loosening structure for holding an object to be fastened with a mounting body to reduce a loosening torque of a bolt screwed to the mounting body. Regarding the method.

[0002]

2. Description of the Related Art It is sometimes necessary to remove a bolt for disassembly, repair, etc. when the object to be fastened is firmly fastened to a mounting body using a bolt, but the threaded portion of the bolt may become rusted. , The bolt may not be easily loosened due to seizure.

In this case, conventionally, a large loosening torque is applied to the bolt to loosen it, or if it still does not loosen, the head of the bolt is scraped off with a cutter or burned off with a burner.

[0004]

However, when the above-mentioned conventional method is used, not only is the bolt loosening work extremely troublesome, but the work may damage the object to be fastened. It may be necessary to repair the fastened object later, or in some cases it may not be possible to reuse the fastened object, resulting in low work efficiency and high cost as a whole, and waste of resources. It was

The present invention has been made in view of the above circumstances, and a bolt loosening torque reducing structure and a bolt loosening method which solve the above problems by allowing bolt loosening work to be performed easily and quickly with a small loosening torque. The purpose is to provide.

[0006]

In order to achieve the above object, the present invention according to claim 1 provides a loosening torque for a bolt which is screwed to an attachment body by sandwiching an object to be fastened with the attachment body. In the bolt loosening torque reduction structure to reduce,
The bolt has an insertion hole portion at least a portion of which corresponds to the object to be fastened, and an outer end of which is formed on one end surface of the bolt in the axial direction to have a diameter larger than that of the insertion hole portion. A first screw hole portion that forms a locking step portion with one end of the hole portion and a second screw hole portion that is continuous with the other end of the insertion hole portion are coaxially provided, and a rotary tool member is provided at one end portion in the axial direction. A head that is screwed into the first screw hole portion and rotatably accommodated in the first screw hole portion until a first auxiliary bolt having a mating portion and having a through hole extending in the axial direction contacts the locking step portion. The second auxiliary bolt, which has a portion and is inserted into the through hole and the insertion hole, is screwed into the second screw hole until the head is brought into contact with the first auxiliary bolt, and the bolt is fastened. It is characterized in that it penetrates an object and is screwed into the mounting body.

The invention according to claim 2 is the above-mentioned claim 1.
In addition to the configuration of the invention described above, the rotary tool engaging portion provided on the first auxiliary bolt is formed as a recess that can accommodate a part of the head of the second auxiliary bolt.

Further, in loosening the bolt according to the first or second aspect of the invention, after loosening and removing the first and second auxiliary bolts from the bolt, the head of the second auxiliary bolt is engaged. Loosen the bolt while screwing it into the second screw hole of the bolt to a position facing the stop with a gap, and further tightening the first auxiliary bolt by screwing it into the first screw hole. Characterize.

[0009]

According to the configuration of the invention described in claim 1, the first
When the bolt that penetrates the object to be fastened with the second auxiliary bolt tightened is screwed into the mounting body, a tensile force along the axial direction acts on the bolt and the second auxiliary bolt. Thus, when the first and second auxiliary bolts are loosened and removed from the bolts, the bolts will also share the tensile force that the second auxiliary bolts shared, which corresponds to at least the object to be fastened. The bolt extends axially at the part where Also, when the first auxiliary bolt is tightened so that it is received by the second auxiliary bolt located at the position where the head is opposed to the locking step with a space, the bolt further extends in the axial direction and is loosened. The torque is further reduced. Moreover, since the first and second auxiliary bolts are also screwed into the bolts when tightening the bolts, it is not necessary to prepare both auxiliary bolts necessary for the loosening work when the bolts are loosened.

Further, according to the structure of the invention described in claim 1, the head portion of the second auxiliary bolt is accommodated in the rotary tool engaging portion of the first auxiliary bolt, whereby the axial length of the head portion of the bolt is increased. Can be made relatively small.

According to the invention of claim 3, the second aspect
Then, the loosening work of the first auxiliary bolt, the screwing work of the second auxiliary bolt, and the tightening work of the first auxiliary bolt are sequentially performed to loosen the bolt with the loosening torque of the bolt reduced, thereby reducing the size of the bolt. It becomes possible to loosen easily and quickly with the loosening torque.

[0012]

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

FIGS. 1 to 3 show a first embodiment of the present invention. FIG. 1 is a sectional view showing a fastening state of an object to be fastened by bolts, and FIG. 2 is a view in which first and second auxiliary bolts are removed. 1 is a cross-sectional view corresponding to FIG. 1 in a state in which the second auxiliary bolt is re-screwed into the bolt after it has been bent, and FIG. 3 is a cross-sectional view corresponding to FIG.

First, in FIG. 1, in a bolt B, an engaging portion 1 formed into a substantially regular hexagonal cross section so that a rotary operating tool such as a wrench can be engaged is integrally connected to one end of a shaft portion 2. A male screw 3 is provided on the outer periphery of at least the other end of the shaft portion 2. The object to be fastened 4 is fastened to the mounting body 5 by the bolt B, the mounting body 5 is provided with a screw hole 6, and the object to be fastened 4 is a through hole through which the shaft portion 2 of the bolt B is inserted. A hole 7 is provided. Then, the male screw 3 of the shaft portion 2 inserted in the through hole 7 is screwed into the screw hole 6 and tightened, whereby the object to be fastened 4 is engaged with the engaging portion 1 of the bolt B and the mounting body 5.
It is sandwiched between them, whereby the object to be fastened 4 is fastened to the mounting body 5.

The bolt B has an insertion hole 8 having a circular cross section.
And the outer end is formed to have a diameter larger than that of the insertion hole portion 8 by opening the outer end of the bolt B in the axial direction one end surface (the end surface of the engaging portion 1 in this embodiment) and the one end of the insertion hole portion 8. Locking step 9
And a second screw hole portion 11 that is continuous with the other end of the insertion hole portion 8 and opens at the other end of the bolt B are provided coaxially. Moreover, the range A in which the insertion hole portion 8 is provided is set such that at least a part of the insertion hole portion 8 along the axial direction corresponds to the object to be fastened 4. Further, the first and second screw hole portions 10 and 11 are formed in reverse threads to each other.

The bolt B has the first and second auxiliary bolts 1
2 ₁ and 13 ₁ are coaxially screwed together. First auxiliary bolt 12
₁ is intended to be screwed into the first screw hole portion 10 of the bolt B, and the axial end portion, transverse MenTadashi hexagonal rotary tool (not shown) in the first threaded holes 10. As can be engaged A rotary tool engaging portion 14 ₁ formed in a shape is provided. Moreover, the through hole 15 ₁ is provided coaxially over the entire axial length of the first auxiliary bolt 12 ₁ .

Further, the second auxiliary bolt 13 ₁ is rotatably accommodated in the first screw hole portion 10 and has a head 16 ₁ capable of abutting and engaging with the locking step portion 9 in the second screw hole portion. A male screw 17 screwed into the portion 11 is integrally provided at the other end of a shaft portion 18 having an outer circumference on one end side, and the head portion 16 ₁ is
It is formed in a regular hexagonal cross section so that a rotary tool (not shown) can be engaged.

Before tightening the bolt B to fasten the object to be fastened 4 to the mounting body 5, the first auxiliary bolt 12 ₁ is inserted into the first screw hole portion 10 until it comes into contact with the locking step portion 9. The second auxiliary bolt 13 _{1 that} is screwed and is inserted into the through hole 15 _{1 of} the first auxiliary bolt 12 ₁ and the insertion hole portion 8 until the head 16 ₁ of the second auxiliary bolt 13 ₁ contacts the first auxiliary bolt 12 ₁ . The bolt B, which is screwed into the two-screw hole portion 11 and penetrates the object to be fastened 4 in that state, is screwed into the mounting body 5 and tightened. Thus the bolt B and a second auxiliary bolt 13 _1, the tensile force along the axial direction are both applied.

In loosening the bolt B, the second auxiliary bolt 13 ₁ is loosened and removed from the bolt B, and then the first auxiliary bolt 12 ₁ is loosened and removed from the bolt B. Thus, even minute tensile force second auxiliary bolt 13 ₁ had shared now bolt B is to bear, thus extending the bolt B by axially pulling force increases, which acts on the bolt B. Moreover, since the range A in which the insertion hole 8 of the bolt B is provided is set so that at least a part thereof corresponds to the object to be fastened 4, the locking step 9 of the bolt B and the second
By extending the space between the screw holes 11 in the axial direction, the bolt B
Therefore, the fastening force acting on the article 4 can be reduced.

Then, as shown in FIG. 2, the second auxiliary bolt 13 ₁ is screwed into the second screw hole portion of the bolt B until the head 16 _{1 of} the second auxiliary bolt 13 ₁ faces the locking step portion 9 with a gap. 11
Screw into. Then, as shown in FIG.
The first auxiliary bolt 12 ₁ is screwed into the screw hole portion 10 and tightened. Then, the first auxiliary bolt 12 ₁ is received by the head 16 ₁ of the second auxiliary bolt 13 ₁ , and the first auxiliary bolt 12 1
_The bolt B further extends in the axial direction by the tightening force of _{1, and} the tightening force acting from the bolt B on the object to be fastened 4 can be further reduced.

Therefore, even when the bolt B is not easily loosened by the normal loosening torque due to rusting or seizure of the male screw 3, the bolt B can be loosened easily and quickly with a relatively small loosening torque. It will be possible. That is, the loosening and removing work of the first and second auxiliary bolts 12 ₁ and 13 ₁ is followed by the screwing work of the second auxiliary bolt 13 ₁ and the first auxiliary bolt 13 1.
By performing the tightening operation auxiliary bolts 12 _1, bolt B to reduce the fastening force acting on the fastened object 4 from the bolt B stretched axially, whereby the engagement portion 1 and the fastened object of bolt B The frictional force acting between the bolts 4 and the frictional force acting on the threaded portion between the shaft portion 2 of the bolt B and the screw hole 6 of the mounting body 5 are reduced, so that the bolt B can be easily moved with a relatively small loosening torque. Can be loosened. Therefore, it becomes possible to easily and quickly loosen the bolt B without damaging the object to be fastened 4 during the operation.

When tightening the first auxiliary bolt 12 ₁ that is in contact with the head 16 ₁ of the second auxiliary bolt 13 ₁ , the first screw hole portion 10 into which the first auxiliary bolt 12 ₁ is screwed is Since the second auxiliary bolt 13 ₁ has a reverse thread to the second screw hole portion 11 with which the second auxiliary bolt 13 ₁ is screwed, the second auxiliary bolt 13 ₁ does not rotate in the tightening direction when the first auxiliary bolt 12 ₁ is tightened. .

Moreover, the object to be fastened 4 is attached by the bolt B.
When tightening the body 5, the first and second auxiliary bolts 12₁,
13₁Are both screwed to the bolt B,
When loosening the bolt B, the first and
Second auxiliary bolt 12₁, 13 ₁Need to prepare a new
Absent.

Further, the first and second auxiliary bolts 12 ₁ , 1
If 3 ₁ is made of a material having higher strength than the bolt B, the second auxiliary bolt 13 ₁ can bear the axial force accompanying the fastening of the object to be fastened 4, so that the second auxiliary bolt 13 ₁ can be provided. bolt 13 ₁ by the action of a large axial force in the bolt B by loosening to increase the elongation of the bolt B, the it is possible to further reduce the release torque of bolt B.

FIGS. 4 and 5 show a second embodiment of the present invention, in which parts corresponding to those of the first embodiment are designated by the same reference numerals.

The first auxiliary bolt 12 ₂ screwed into the first screw hole portion 10 of the bolt B has one end in the axial direction, in which a rotary tool (not shown) can be engaged in the first screw hole portion 10 so as to have a normal cross section. A rotary tool engaging portion 14 ₂ formed in a hexagonal shape is provided, and a rotary tool engaging portion 19 capable of engaging a rotary tool (not shown) at the other axial end has a regular hexagonal cross section. It is provided as a recess. Moreover, the first auxiliary bolt 12 ₂
A through hole 15 ₂ is provided coaxially over the entire length in the axial direction.

On the other hand, the second auxiliary bolt 13 ₂ has a circular cross section for accommodating a part thereof in the rotary tool engaging portion 19 of the first auxiliary bolt 12 ₂ and has an outer end surface for engaging a rotary tool (not shown). The head 16 ₂ provided with the locking recess 20 is
A male screw 17 screwed into the screw hole portion 11 is integrally provided at the other end of a shaft portion 18 having an outer circumference on one end side.

Then, the bolt B is tightened to fasten the object 4 to be fastened.
Before tightening to the mounting body 5, as shown in FIG.
Auxiliary bolt 12₂Is the rotary tool engaging portion 14₂The locking step
When it is screwed into the first screw hole portion 10 until it comes into contact with the portion 9.
Both, the first auxiliary bolt 12 ₂Through hole 15₂And insert
Second auxiliary bolt 13 inserted into the through hole 8₂Is its head
16₂The first auxiliary bolt 12₂On the rotary tool engaging part 19
First auxiliary bolt 12 so as to accommodate a part₂To
It is screwed into the second screw hole portion 11 until it comes into contact with it.
In this state, the bolt B that penetrates the object to be fastened 4 is screwed into the mounting body 5.
It is tightened together.

In loosening the bolt B, the second auxiliary bolt 13 ₂ is loosened and removed from the bolt B, and then the first auxiliary bolt 12 ₂ is loosened and removed from the bolt B. further,
As shown in FIG. 5, the second auxiliary bolt 13 ₂ is screwed into the second screw hole portion 11 of the bolt B until the head portion 16 ₂ of the bolt B is located at a position facing the locking step portion 9 with a gap. After that, the first auxiliary bolt 12 ₂ with the rotary tool engagement portion 19 facing the head portion 16 ₂ side is screwed into the first screw hole portion 10 and tightened.

According to the second embodiment, the same effect as that of the first embodiment can be obtained, and the object to be fastened 4 by the bolt B can be obtained.
The head 16 ₂ of the second auxiliary bolt 13 ₂ when tightening the
Since it is possible to accommodate a part of the _second auxiliary bolt 12 _{2 in} the rotary tool engaging portion 19 of the first auxiliary bolt 122, even if the axial length of the engaging portion 1 of the bolt B is relatively short, Since 13 ₂ does not project from the bolt B, the bolt B can be downsized.

As another embodiment of the present invention, the rotary tool engaging portion 14 of the first auxiliary bolt 12 ₂ in the second embodiment described above.
₂ may be omitted, and in that case, when loosening the bolt B, the first auxiliary bolt 12 ₂ is
The first screw hole portion 10 is screwed and tightened in a direction in which 9 is an axially outward position.

FIG. 6 and FIG. 7 show a third embodiment of the present invention, and the portions corresponding to the respective embodiments described above are designated by the same reference numerals.

The bolt B has an insertion hole 8 and an insertion hole 8
First screw hole portion 10 that forms a locking step portion 9 between one end and
And a second screw hole portion 11 ′ that is continuous with the other end of the insertion hole portion 8 are provided coaxially, and the first and second screw hole portions 10 and 11 ′ are provided.
The directions of the screws in are the same.

A rotary tool assembly formed as a recess having a regular hexagonal cross section so that a rotary tool (not shown) can be engaged with one axial end of the first auxiliary bolt 12 ₃ screwed into the first screw hole portion 10. The joint portion 19 is provided, and the first auxiliary bolt 12 ₃
Through holes 15 ₃ are provided coaxially over the entire length in the axial direction.

On the other hand, the second auxiliary bolt 13 ₁ has a head 16 ₁ having a regular hexagonal cross section which can be partially engaged with the rotary tool engaging portion 19 of the first auxiliary bolt 12 ₃ , and has a second screw hole. Part 11
Shaft 1 having a male screw 17 screwed to the ‘
It is integrally provided at the other end of 8.

Then, the bolt B is tightened to fasten the object 4 to be fastened.
Before tightening on the mounting body 5, as shown in FIG.
Auxiliary bolt 12₃Positions the rotary tool engaging portion 19 at the outer position.
As a result, the first screw hole portion 10 is screwed until it comes into contact with the locking step portion 9.
Together with the first auxiliary bolt 12₃Through hole 15
₃And the second auxiliary bolt 13 inserted through the insertion hole portion 8 ₁
Is the head 16₁The first auxiliary bolt 12₃Rotary tool
Partial engagement with the mating part 19 so that it is housed
Bolt 12₃Screw it into the second screw hole 11 'until it contacts
Bolts that are fitted and that penetrate the object to be fastened 4 in that state
B is screwed onto the mounting body 5 and tightened.

[0037] When loosening the bolt B is operated to rotate a loosening direction by engaging the rotary tool to a second auxiliary bolt 13 ₁ of the head 16 _1. Then, since the head 16 ₁ is engaged with the rotation tool engagement portion 19 of the first auxiliary bolt 12 _3, the second auxiliary bolt 13 ₁ and the first auxiliary bolt 12 ₃
Can be simultaneously loosened and removed from the bolt B. Thereafter, as shown in FIG. 7, the second auxiliary bolt 13 ₁ is screwed into the second screw hole portion 11 ′ of the bolt B until the head portion 16 ₁ thereof is located at a position spaced from the locking step portion 9. In addition, the first auxiliary bolt 12 ₃ with the rotary tool engaging portion 19 set to the outer position
Is screwed into the first screw hole portion 10 and tightened.

According to the third embodiment, the same effect as that of the second embodiment can be obtained, and the first and second auxiliary bolts 12 ₃ and 13 ₁ can be simultaneously removed from the bolt B. It is possible to more quickly loosen the bolt B.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, and various design changes can be made without departing from the present invention described in the claims. It is possible.

For example, the second screw hole portions 11 and 11 'may be provided on the engaging portion 1 side of the bolt B.

[0041]

As described above, according to the first aspect of the present invention, the bolt has an insertion hole portion at least a portion of which extends along the axial direction corresponding to an object to be fastened, and an outer end of the bolt shaft. The first screw hole portion that is formed to have a diameter larger than that of the insertion hole portion and is formed on one end face in the direction, and that forms a locking step portion with one end of the insertion hole portion, and is connected to the other end of the insertion hole portion. The first screw hole is provided coaxially with the second screw hole portion, has a rotary tool engaging portion at one end portion in the axial direction, and has a through hole extending in the axial direction until the first auxiliary bolt comes into contact with the locking step portion. A second auxiliary bolt that is screwed into the first portion and that is rotatably accommodated in the first screw hole portion and that is inserted into the through hole and the insertion hole portion contacts the head portion with the first auxiliary bolt. While being screwed into the second screw hole until it comes into contact, the bolt penetrates the object to be fastened and is screwed into the mounting body. Therefore, by loosening the first and second auxiliary bolts and removing them from the bolts, the bolts are extended in the axial direction at least at the portion corresponding to the object to be fastened, and the first screw is spaced apart from the locking step portion. By tightening the first auxiliary bolt so that it is received by the second auxiliary bolt screwed into the hole, it is possible to further extend the bolt in the axial direction and reduce the loosening torque, making it easy and quick with a small loosening torque. It becomes possible to loosen.

According to the second aspect of the present invention, the rotary tool engaging portion provided on the first auxiliary bolt is formed as a recess capable of accommodating a part of the head portion of the second auxiliary bolt. By accommodating the head portion of the second auxiliary bolt in the rotary tool engaging portion of the first auxiliary bolt, the axial length of the head portion of the bolt can be made relatively small, which contributes to downsizing of the bolt. it can.

According to the third aspect of the invention, when the bolt is loosened, the first and second auxiliary bolts are loosened and removed from the bolt, and then the second auxiliary bolt is connected to the head portion and the locking step portion. The second of the bolts up to the spaced position
Since the bolt is loosened in a state where it is screwed into the screw hole portion and further the first auxiliary bolt is screwed into the first screw hole portion and tightened,
By loosening the second and first auxiliary bolts, removing work, screwing the second auxiliary bolts, and tightening the first auxiliary bolts in order, loosening the bolts with the bolt loosening torque reduced The bolt can be loosened easily and quickly with a small loosening torque.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a fastening state of an object to be fastened with a bolt according to a first embodiment.

FIG. 2 shows the second auxiliary bolt after removing the first and second auxiliary bolts.
It is sectional drawing corresponding to FIG. 1 in the state which re-threaded the auxiliary bolt to the bolt.

FIG. 3 is a sectional view corresponding to FIG. 1 in a state where a bolt is loosened.

FIG. 4 is a sectional view corresponding to FIG. 1 of the second embodiment.

5 is a cross-sectional view corresponding to FIG. 4 in a state where the second auxiliary bolt is screwed into the bolt again.

FIG. 6 is a sectional view corresponding to FIG. 1 of the third embodiment.

FIG. 7 is a cross-sectional view corresponding to FIG. 6 in a state where a bolt is loosened.

[Explanation of symbols]

4 ... Object to be fastened 5 ... Mounting body 8 ... Insertion hole 9 ... Locking step 10 ... First screw hole 11, 11 '... Second screw hole 12 ₁ , 12 ₂ , 12 ₃ ... First auxiliary bolt 13 ₁ , 13 ₂ ... Second auxiliary bolt 14 ₁ , 14 ₂ , 19 ... Rotating tool engaging portion 15 ₁ , 15 ₂ , 15 ₃ ... .... Through holes 16 ₁ , 16 ₂ ... Head 20 ... Second auxiliary bolt B ... Bolt

Front page continued (72) Inventor Haruyuki Watanabe 238 Nakaya Higashi, Gifu City, Gifu Prefecture (72) Manabu Naoi 3-7 Suhara Shineicho, Kakamigahara City, Gifu Prefecture

Claims (3)

[Claims] 1. An article to be fastened (4) between the attachment body (5) and the attachment body (5).
Of the bolt (B) which is clamped and screwed into the mounting body (5).
Loosening torque reduction mechanism for bolts to reduce the loosening torque
The bolt (B), at least
Insertion hole (8) with a part of it corresponding to the object to be fastened (4)
Insert the outer end of the bolt (B) by opening it at one end face in the axial direction.
The insertion hole is formed with a diameter larger than that of the through hole (8).
First step to form locking step (9) between one end of (8)
A second continuous hole (10) and the other end of the insertion hole (8)
The screw holes (11, 11 ') are provided coaxially, and the axial direction
The rotary tool engaging portion (14₁, 14
₂, 19) and has a through hole (1
5₁, 15₂, 15₃) With a first auxiliary bolt (12)
₁, 12₂, 12₃) Abuts the locking step (9)
The first screw hole, which is screwed into the first screw hole portion (10)
A head (16) rotatably housed in the part (10)₁, 1
6₂) Has a through hole (15₁, 15₂, 15₃) And
And the second auxiliary bolt (1) inserted through the insertion hole (8).
Three₁, 13₂) Is the head (16₁, 16 ₂) Is the first supplement
Auxiliary bolt (12₁, 12₂, 12₃) Until it contacts
While being screwed into the second screw hole portion (11, 11 '),
The bolt (B) penetrates the object to be fastened (4) and the mounting body (5)
Bolt loosening torque, characterized by being screwed into
Construction. 2. A first auxiliary bolts (12 _2, 12 ₃₎ rotating tool engagement portion provided in (19), a second auxiliary bolt (13 _1, 13 ₂₎ of the head (16 _1, 16 ₂₎ 2. The bolt loosening torque reduction structure according to claim 1, wherein the structure is formed as a recess capable of accommodating a part of the bolt. 3. The first and second auxiliary bolts (1) for loosening the bolt (B) according to claim 1 or 2.
2 ₁ , 12 ₂ , 12 ₃ ; 13 ₁ , 13 ₂ ) is loosened and removed from the bolt (B), then the second auxiliary bolt (13 ₁ , 1 2
3 ₂₎ and its head (16 _1, 16 ₂₎ are locking stepped portion (9)
Screw the bolts (B) into the second screw hole portions (11, 11 ') up to the opposite positions, and further attach the first auxiliary bolts (12 ₁ , 12 ₂ , 12 ₃ ) to the first screw holes. Division (10)
A method for loosening a bolt, characterized in that the bolt (B) is loosened in a state where the bolt (B) is screwed into and tightened.