JP2004332848A - Blind bolt - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a blind bolt with high workability enabling the driving resistance of an insert pin into a bolt body, capable of providing a high fastening force by properly setting the balance of the size of an enlarged portion with the wall thickness of the bolt, and enabling the easy recognition of the timing of enlargement of a tip part and a nut tightening position. <P>SOLUTION: This blind bolt comprises a bolt body 2 having an expansion part 22 having a converging slit 24 dividing a tip part 2a into a plurality of parts along the axial direction and expanded in the radial direction, having a male screw part 23 for threading a nut 5 formed at a rear end part 2b, and having a through hole 21 extending in the axial direction and an insert pin 3 inserted into the through hole 21 of the bolt body 2. The outline shape of the bolt body 2 at the tip face is formed in a pseudo polygonal shape formed of a plurality of arcs, and the insert pin 3 is inserted into the through hole 21 and advanced to the inside of the slit. By this, the expansion part 22 of the tip part 2a is radially expanded to lock a fastened material X. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a blind bolt that can be fastened by operating one side when fastening another member to a member that cannot be reached inside or on the back side.
[0002]
[Prior art]
Conventionally, blind bolts have been used for fastening other members to places or members that cannot be accessed, such as inside a wall. For example, Japanese Unexamined Patent Publication No. 2000-154810 discloses a bolt with a retaining function which aims to fix a pin by driving a pin from one side surface and to enable retightening after the fixing (Patent Document 1). ). In this bolt with a retaining function, a center hole is drilled at the axis of the male screw rod to which the nut is screwed, and a slit-shaped “split” reaching the center hole is provided at the end of the male screw rod. The split portion is formed so as to be expandable by a pin which is forcibly fitted into the center hole. The member is fastened between the nut and the expanded portion expanded by the insertion of the pin.
[0003]
[Patent Document 1]
Japanese Patent Application Laid-Open No. 2000-154810
[Problems to be solved by the invention]
However, in the bolt with a retaining function described in JP-A-2000-154810, when the pin is fitted into the center hole, the tip of the pin comes into contact with the corner of the divided piece. Therefore, when the pin is driven into the center hole of the external thread rod, the pin advances in the axial direction while crushing the center corner of the divided piece. Therefore, there is a problem that the driving resistance of the pin is large.
[0005]
Further, in the conventional bolt having a retaining function, the end of the split portion is expanded and deformed in a tapered shape on the back side of the fastener, and the outer peripheral surface of the expanded portion is in sliding contact with the pilot hole of the fastener. The frictional force prevents the rod from coming off. However, the portion that is hooked on the fastener by the expanding deformation portion is very limited and small. Therefore, when a tensile force acts in the axial direction, the rod is likely to move in the axial direction, and the tightening may be loosened. In order to prevent such loosening, it is conceivable to further expand the expansion deforming portion, but in this case, in the conventional bolt configuration, a pin having a large outer diameter must be fitted, that is, the center It is necessary to make the hole larger, and as a result, the thickness of the external thread rod is reduced, and the strength of the entire bolt is significantly reduced, which is meaningless.
[0006]
Furthermore, in the conventional bolt with a retaining function, the timing of expanding the deformed portion is not known. In other words, it is unclear how much the male screw rod should be inserted into the pilot hole to be able to expand at the position where it is most likely to catch the pilot hole. Probably in reality, it is impossible to know the proper position unless the thickness of the fastener and the workpiece is accurately measured and the tightening position of the nut is determined in advance in accordance with this thickness. Would. This is very troublesome.
[0007]
Furthermore, in the above-mentioned bolt with a retaining function, the external thread rod and the pin are not integrally formed, but are formed separately. For this reason, storage and carrying are inconvenient. In particular, in the case of blind bolts having various outer diameters ranging from several mm to several tens of mm, a suitable pin must be searched each time, which is extremely troublesome.
[0008]
Further, in the conventional bolt with a retaining prevention function, the expansion deformation portion can prevent the bolt from coming off in the axial direction, but cannot prevent the nut from rotating in the circumferential direction when tightening the nut. If the rod co-rotates with the nut, there is a problem that a sufficient fastening force cannot be obtained, and the friction generated during the co-rotation causes the pilot hole to be shaved and loosened.
[0009]
The present invention has been made in order to solve such a problem, and it is possible to reduce the driving resistance of an insertion pin to a bolt body, and to appropriately balance the size of an expanded portion and the thickness of a bolt. Blind with excellent workability, such as stable high fastening force can be obtained, and the timing of the expansion and the tightening of the nut by driving the insertion pin can be easily recognized and the co-rotation can be prevented. The purpose is to provide bolts.
[0010]
[Means for Solving the Problems]
The feature of the blind bolt according to the present invention is that it has a tapered slit that divides the front end into a plurality of parts along the axial direction, has a bulging portion that bulges in the radial direction, and screws a nut to the rear end. A bolt body having a through-hole extending in the axial direction and having a male screw portion formed therein, and an insertion pin inserted into the through-hole from a rear end of the bolt body; Is a pseudo-polygon made up of a plurality of arcs, and the insertion pin penetrates the through-hole and enters the slit, whereby the distal end is expanded, and the outer diameter of the expanded portion has a radius. It is at the point projected in the direction. At this time, it is preferable that the outer diameter of the expanded portion protrudes in the radial direction by about 30% from the outer diameter of the external thread portion.
[0011]
Further, in the present invention, in consideration of the size of the expanded portion at the bolt tip, the degree of expansion, and the thickness of the bolt, in order to optimize the balance between the fastening force and the overall strength, the expanded portion is The outer diameter is formed to be about 1.3 times the outer diameter of the male thread part, and the slit width of the male thread part is determined based on the difference between the outer diameter dimension of the expansion part and the pilot hole diameter of the fastener. The outer diameter is formed so as to be in a range of 0.21 to 0.27 times the outer diameter, and the swelling portion has an outer diameter that slides on the inner peripheral surface of the prepared hole when the fastener is inserted into the prepared hole. It is preferable that the distal end portion of the bolt body is previously reduced in diameter.
[0012]
Furthermore, in the present invention, in order to increase the tensile strength of the bolt body and prevent co-rotation at the time of fastening the nut, the outer diameter of a portion behind the expanded portion at the distal end is expanded by inserting an insertion pin. Then, it is preferable that the groove is formed to have a size protruding in the radial direction from the male screw portion and abutting against the prepared hole of the fastener, and to have a longitudinal groove for preventing co-rotation along the axial direction.
[0013]
Further, in the present invention, the insertion pin is integrally attached to the bolt main body, and when the blind bolt is inserted into the prepared hole, even if the insertion pin is hit, the insertion pin does not enter the through hole. In order to ensure that only the bolt body is inserted through the pilot hole, the pin insertion resistance force when inserting the insertion pin into the through hole is reduced by the bolt insertion resistance when the expansion portion is inserted through the pilot hole of the fastener. It is preferable that an insertion resistor for increasing the force is provided on the outer peripheral surface of the insertion pin. At this time, the insertion resistor includes an expansion resistance portion that is expanded in the radial direction at a position near the middle of the insertion pin in the longitudinal direction or at a position behind the insertion pin. May be formed such that a resistance groove is formed in the groove. Furthermore, the expansion resistance portion is formed in a tapered shape whose diameter decreases in the insertion direction, and the dimension on the front side in the insertion direction is set to an outside enough to fit in the through hole and prevent the insertion pin from coming off. It is also possible to form the outer diameter so that the pin insertion resistance due to friction with the through hole is larger than the bolt insertion resistance.
[0014]
Furthermore, in the present invention, the timing at which the expansion portion has completely passed through the pilot hole is easily sensed, so that the distal end portion of the bolt body is subjected to the compressive force applied to the expansion portion when the pilot hole of the fastener is inserted. It is preferable to use a material having an elastic force that reduces the diameter and restores in the radial direction after inserting the prepared hole.
[0015]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of a blind bolt according to the present invention will be described with reference to the drawings. FIG. 1 is a front view showing an embodiment of a blind bolt 1 according to the present invention, FIG. 2 is a side view seen from an arrow A in FIG. 1, and FIG. 3 is a cross-sectional view taken along line BB in FIG. It is.
[0016]
As shown in FIGS. 1 to 3, the blind bolt 1 of the present embodiment includes a bolt main body 2 having a through-hole 21 formed on an axis, and an insertion pin 3 inserted into the through-hole 21. ing. A slit 24 and a swelling portion 22 are formed at a front end portion 2a of the bolt main body 2, and a male screw portion 23 is formed at a rear end portion 2b. The nut 5 is screwed into the male screw portion 23 via the washer 4, and the object Y is fastened to the fastener X by the nut 5 and the expansion portion 22.
[0017]
Explaining each component of the present embodiment in more detail, a bulging portion 22 bulging in the radial direction is formed at the tip 2 a of the bolt body 2. A slit 24 is formed in the distal end portion 2 a including the expanding portion 22 along the axial direction, and the slit 24 communicates with the through hole 21. As shown in FIG. 2, the distal end portion 2a of the bolt body 2 is divided into four substantially in a cross shape by the slits 24.
[0018]
The tip 2a of the bolt body 2 has a diameter reduced so as to be tapered, and its outer peripheral surface is tapered toward the tip. Thus, the width of the slit 24 gradually decreases toward the tip. Further, as shown in FIG. 2, the expanding portion 22 is formed in a pseudo-rectangular shape having a contour of a tip end surface formed of four arc-shaped divided pieces 22a, 22a,.
[0019]
The diameter of the expanded portion 22 is reduced to such an extent that when it is inserted into the prepared hole h of the fastener X and the workpiece Y, it slides on the inner peripheral surface thereof and can be inserted with a light resistance. In the present embodiment, the expanded portion 22 is formed to have an outer diameter that is about 30% larger than the outer diameter (reference dimension) of the external thread portion 23, and then the diameter is reduced to such an extent that it penetrates the prepared hole h with a light resistance. In consideration of this, the width of the slit 24 is formed to be approximately 0.21 to 0.27 times the outer diameter of the male screw portion 23. Thus, the diameter of the divided pieces 22a, 22a,. Note that the width of the slit 24 is determined within a range of about 0.21 to 0.27 times the outer diameter of the male screw part 23 based on the difference in diameter between the expanded part 22 and the prepared hole h. You. Normally, the pilot hole h is drilled 0.5 mm to 1.0 mm larger than the bolt diameter (outer diameter of the male screw portion 23), and the final slit width is determined in consideration of the deviation of the pilot hole diameter. Is done.
[0020]
The reason why the size is set to such a size is to take into consideration the balance between the size of the expanded expansion portion 22 and the width of the slit 24 for reducing the diameter. Of course, the larger the expanded portion 22 is, the larger the area to be locked to the fastener X when expanded is preferable. However, conversely, the degree of diameter reduction must be increased in order to insert the hole into the prepared hole h. However, for this purpose, it is necessary to increase the width of the slit 24 for cutting. Furthermore, in order to increase the degree of expansion, a large-diameter insertion pin 3 must be inserted, and a large through-hole 21 has to be formed. For this reason, the thickness of the bolt body 2 is reduced. It will be thin. As a result of trial and error of the size of the bulging portion 22 required for the locking force and the thickness of the bolt body 2 required for the strength, the numerical value considered to be optimal is within the above range.
[0021]
The portion of the tip end 2a behind the swelling portion 22 is a co-rotation preventing portion 25. The co-rotation preventing portion 25 is formed to be approximately 0.7 mm larger than the outer diameter of the male screw portion 23, and is expanded by the insertion pin 3 from the reduced diameter as shown in FIG. Are expanded in the radial direction and come into contact with the prepared hole h of the fastener X. A longitudinal groove 25a is formed in the outer circumferential surface of the co-rotation preventing portion 25 by knurls in the axial direction, so that the frictional force with the pilot hole h can be increased. Thereby, the vertical groove 25a prevents the blind bolt 1 from rotating together when the nut 5 is tightened.
[0022]
The distal end portion 2a composed of the swelling portion 22 and the co-rotation preventing portion 25 is reduced in diameter with respect to the compressive force applied to the swelling portion 22 when the prepared hole X of the fastener X is inserted. It is formed of a material having an elastic force that restores in the radial direction after the hole h is inserted. For example, it may be an annealed iron or a plastic material.
[0023]
Next, the insertion pin 3 will be described. The insertion pins 3 are inserted into the through holes 21 of the bolt body 2 to radially expand the divided pieces 22a, 22a,. Therefore, the insertion pin 3 as a whole has a smaller diameter than the through hole 21 and is formed slightly longer than the bolt body 2. The tip of the insertion pin 3 is formed in a tapered shape so as to reduce the driving resistance when entering the slit 24.
On the other hand, a driving portion 31 having a large diameter is formed at the rear end of the insertion pin 3.
[0024]
The insertion pin 3 is held while being inserted into the bolt body 2. That is, when the tip of the insertion pin 3 reaches the tip 2 a in the through hole 21, an insertion resistor 32 that can fit into the through hole 21 at the rear end of the bolt body 2 is formed on the outer peripheral surface of the insertion pin 3. Have been. As shown in FIG. 1, the insertion resistor 32 is formed as a tapered expansion resistance portion 32 a gradually expanding toward the rear end, and a resistance groove 33 is formed along the longitudinal direction. I have. The resistance groove 33 may be formed obliquely with respect to the longitudinal direction of the insertion pin 3 so as to generate a higher resistance.
[0025]
The external dimensions of the expansion resistance portion 32a are such that the front portion in the insertion direction is formed to have an outside diameter that can be fitted into the through hole 21 to prevent the insertion pin 3 from coming off, and the rear portion in the insertion direction is formed. Are formed to have an outer diameter such that the pin insertion resistance force to be inserted into the through hole 21 is larger than the bolt insertion resistance force. In other words, the front side of the expansion resistance portion 32a in the insertion direction fulfills the function of preventing the pin from coming off, and the rear side in the insertion direction fulfills the function of preventing the pin from inserting.
[0026]
The expansion resistance portion 32a may not be formed on the entire circumference of the insertion pin 3 but may be formed radially at appropriate intervals. In addition, the insertion resistor 32 may be configured such that a protrusion having an appropriate height is formed on the insertion pin 3 to increase the resistance.
[0027]
Next, the operation of the blind bolt 1 according to the present embodiment having such a configuration will be described with reference to FIGS.
[0028]
When fastening the fastened object Y to the fastened object X that cannot be reached inside, a pilot hole h is drilled in the fastened object X and the fastened object Y. The insertion pin 3 is inserted into the through hole 21 of the bolt main body 2, and is held by the expansion resistance portion 32 a so as not to fall out of the through hole 21.
[0029]
Then, the tip 2a of the blind bolt 1 is inserted into the prepared hole h, and the driving portion 31 of the insertion pin 3 is lightly hit with a hammer. At this time, since the insertion resistance of the insertion pin 3 is larger than the bolt insertion resistance due to the pin insertion prevention function of the expansion resistance portion 32a, the blind bolt 1 is inserted into the pilot hole h without the insertion pin 3 being inserted. Can be inserted. Further, while being inserted through the pilot hole h, the distal end 2a of the bolt body 2 is compressed in the axial direction by the pilot hole h, but is elastically deformed by the elastic force of the distal end 2a (see FIG. 6). , While sliding on the prepared hole h (see FIG. 7).
[0030]
When the bolt body 2 is further driven, the expanded portion 22 completely passes through the pilot hole h, and the contact state with the pilot hole h is released. At this time, the frictional force generated on the contact surface between the bulging portion 22 and the pilot hole h disappears, so that the operator senses that the bulging portion 22 has completely passed through the pilot hole h. Further, since the bolt body 2 is formed of a material having elasticity, the expansion portion 22 expands in the radial direction and is restored (see FIG. 8). As a result, the fastening position of the blind bolt 1 is determined, so that the operator can know the timing of starting the driving of the insertion pin 3.
[0031]
At this position, the washer 4 is brought into contact with the workpiece Y, and the nut 5 is temporarily tightened. This prevents the bolt main body 2 from being inserted deeper into the pilot hole h from that position. When the insertion pin 3 is strongly driven in this state, since the bolt body 2 is fixed by the nut 5, the expansion resistance portion 32a enters the through hole 21 while being crushed. Further, as shown in FIG. 9, the insertion pin 3 enters the gap between the slits 24 to expand the distal end portion 2a (see FIG. 9). At this time, since the slit 24 is formed so as to be tapered with a gentle inclination from a portion communicating with the through hole 21, the insertion pin 3 easily expands the distal end portion 2a. As shown in FIG. 4, the swelling portion 22 of the distal end portion 2a is expanded outward more than the pilot hole h, and the co-rotation preventing portion 25 of the distal end portion 2a contacts the inner peripheral surface of the pilot hole h. .
[0032]
Then, when the nut 5 is tightened, the bolt body 2 is pulled in the direction opposite to the direction in which the bolt 5 is inserted (see FIG. 10). Thereby, the expansion part 22 abuts on the inner wall of the fastener X, and further tightens the nut 5 to fasten the workpiece Y to the fastener X. When the nut 5 is tightened, the bolt body 2 receives a rotational force in the circumferential direction due to the rotational torque. However, the vertical groove 25a of the co-rotation preventing portion 25 cuts into the inner peripheral surface of the pilot hole h to suppress the rotation. Prevent rotation. Thereby, a strong fastening force is obtained.
[0033]
According to the above-described embodiment, when the insertion pin 3 is inserted into the through hole 21, the insertion pin 3 expands while abutting on the tapered surface of the slit 24 formed so as to be tapered. Can be reduced. Also, instead of preventing the insertion pin 3 from coming off due to the frictional force between the outer peripheral surface of the distal end portion 2a and the pilot hole h, the expansion portion 22 projects about 30% in the radial direction from the outer diameter of the screw portion 23. As a result, a high fastening force can be obtained because it comes into contact with the inner wall of the fastener X.
[0034]
Further, the outer diameter of the swelling portion 22 is formed to be approximately 1.3 times the outer diameter of the male screw portion 23, and the width of the slit 24 is formed to be 0.21 to 0.27 times the outer diameter of the male screw portion 23. Therefore, when the distal end portion 2a is expanded, the fastening force and the bolt strength suitable for the blind bolt 1 can be obtained in a well-balanced manner.
[0035]
Furthermore, since the co-rotation prevention portion 25 contacts the pilot hole h, the pulling resistance after fastening can be increased, and the co-rotation can be prevented to obtain a strong fastening force.
[0036]
Further, the expansion pin 32a formed on the insertion pin 3 allows the insertion pin 3 to be held in the through hole 21 of the bolt body 2 so as not to fall off. The tip 2a of the bolt body 2 is prevented from being erroneously expanded in order to prevent the inside of the bolt.
[0037]
Further, the time when the blind bolt 1 passes through the pilot hole h can be easily detected by the degree of diameter reduction of the expanding portion 22 of the bolt main body 2 and the elastic force of the distal end portion 2a. You can know. Thereby, the trouble of accurately measuring the thickness of the fastener X and the workpiece Y is released, and the expanding operation and the fastening operation at the wrong position are not performed.
[0038]
【Example】
Next, a specific example of the blind bolt 1 of the present embodiment will be described. In each example, optimal values of the expansion diameter, the slit width, the insertion pin diameter, and the pilot hole diameter were obtained for each of the blind bolts M6, M8, M10, M12, M16, M20, and M24 having different bolt diameters. The numerical values are shown in FIG.
[0039]
The blind bolt 1 shown in FIG. 11 assumes that the diameter of the pilot hole h is larger than the diameter of the external thread portion 23 by 0.5 mm. According to the blind bolt 1 as described above, the driving resistance is reduced and high fastening performance is exhibited. For example, the M12 blind bolt 1 exhibits a breaking strength of about 39.2 kN.
[0040]
In addition, the blind bolt 1 according to the present invention is not limited to the above-described embodiment, and can be appropriately changed.
[0041]
For example, in the present embodiment, the slit 24 is formed to have a substantially cruciform cross section to divide the tip 2a of the bolt body 2 into four equal parts. However, the present invention is not limited to this. It may be appropriately divided into three equal parts, six equal parts, and the like.
[0042]
【The invention's effect】
As described above, according to the present invention, the driving resistance of the insertion pin can be reduced, and a stable high fastening force can be obtained by appropriately setting the balance between the size of the expanded portion and the thickness of the bolt. . In addition, it is possible to easily recognize the timing of expanding the expanding portion and the tightening position of the nut, to prevent co-rotation with the nut, and to improve the workability.
[Brief description of the drawings]
FIG. 1 is a front view showing an embodiment of a blind bolt according to the present invention.
FIG. 2 is a side view as viewed from an arrow A in FIG.
FIG. 3 is a sectional view taken along line BB of FIG. 2;
FIGS. 4A and 4B are a front view and a left side view, respectively, showing a state in which an insertion pin is inserted into a through hole of a bolt body and a distal end portion is expanded in the embodiment.
FIG. 5 is a view showing a state before the blind bolt according to the embodiment is fitted into a pilot hole.
FIG. 6 is a view showing a state in which the tip of the blind bolt of the present embodiment is elastically deformed.
FIG. 7 is a view showing a state where the blind bolt of the present embodiment is inserted into a pilot hole.
FIG. 8 is a view showing a state in which an expanded portion of the blind bolt according to the present embodiment has passed through a pilot hole.
FIG. 9 is a view showing a state in which the insertion pin of the blind bolt according to the embodiment is driven.
FIG. 10 is a view showing a state in which a nut of the blind bolt according to the embodiment is tightened.
FIG. 11 is a table showing optimum values of examples in the embodiment.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Blind bolt 2 Bolt main body 2a Tip part 2b Rear end part 3 Insertion pin 4 Washer 5 Nut 21 Through hole 22 Expansion part 22a Dividing piece 23 Male screw part 24 Slit 25 Co-rotation prevention part 25a Vertical groove 31 Driving part 32 Insertion Resistor 32a Expansion / expansion resistance part 33 Resistance groove h Prepared hole X Fastener Y Fastened object

Claims (8)

It has a tapered slit that divides the tip into a plurality along the axial direction, has a swelling portion that is swelled in the radial direction, and forms an external thread portion for screwing the nut to the rear end portion. A bolt body having a through hole extending in the axial direction;
An insertion pin inserted into the through hole from the rear end of the bolt body,
The contour shape of the tip end surface of the bolt body is a pseudo polygon composed of a plurality of arcs,
A blind bolt, wherein the insertion pin is inserted through the through-hole and enters the slit, whereby the distal end is expanded, and the expanded portion is projected in the radial direction. 2. The blind according to claim 1, wherein, when the distal end portion of the bolt body is expanded by the insertion pin, the outer diameter of the expanded portion protrudes radially by about 30% from the outer diameter of the external thread portion. bolt. The outer diameter of the bulging portion according to claim 1 or 2, wherein the outer diameter of the bulging portion is formed to be about 1.3 times the outer diameter of the male screw portion, and the slit width is set to the outer diameter of the bulging portion and the prepared hole diameter of the fastener. It is formed so as to be in a range of 0.21 to 0.27 times the outer diameter of the external thread portion based on the difference from the dimension, and while the insertion portion is inserted into the prepared hole of the fastener, the expanded portion is located below the expanded portion. A blind bolt, wherein a front end portion of the bolt body is previously reduced in diameter so as to receive resistance by sliding contact with an inner peripheral surface of the hole. In any one of claims 1 to 3, the outer diameter of a portion of the distal end portion behind the expanded portion protrudes in the radial direction more than the external thread portion when the insertion pin is inserted and expanded. A blind bolt having a size that abuts a prepared hole and a longitudinal groove for preventing co-rotation along an axial direction. In any one of claims 1 to 4, the pin insertion resistance force when inserting the insertion pin into the through hole is larger than the bolt insertion resistance force when inserting the expansion portion into the prepared hole of the fastener. A blind resistor provided on the outer peripheral surface of the insertion pin. 6. The insertion resistance element according to claim 5, wherein the insertion resistance element includes an expansion resistance part expanded in the radial direction at a position near the middle of the insertion pin in the longitudinal direction or a position behind the insertion pin. A blind bolt, characterized in that a resistance groove is formed on the surface of the blind bolt. In claim 6, the expansion resistance portion is formed in a tapered shape whose diameter decreases in the insertion direction, and the dimension on the front side in the insertion direction is set to such a degree as to fit in the through hole to prevent the insertion pin from coming off. A blind bolt having an outer diameter formed in such a manner that the pin insertion resistance due to friction with the through-hole is larger than the bolt insertion resistance. In any one of claims 1 to 7, the distal end portion of the bolt body is reduced in diameter by a compressive force applied to the expanding portion when the pilot hole of the fastener is inserted, and is radially inserted after the pilot hole is inserted. A blind bolt characterized by being formed of a material having elasticity that restores to its original state.

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