JP2009072870A - Broken screw removing method and centering tool to be used for the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problems on a conventional broken screw removing method that labor is required for setting a tool and it is difficult to accurately drive a punch into the center of the broken end face of a broken screw or the center of a screw hole. <P>SOLUTION: This broken screw removing method comprises inserting the cylindrical front end of a centering tool between the inner peripheral face of the screw hole and the outer peripheral face of the broken screw, applying a fitting space portion of the centering tool onto the outer periphery of the broken end of the broken screw protruded outside the screw hole, or applying the cylindrical front end of the centering tool onto the outer periphery of the broken end of the broken screw and inserting the cylindrical front end of the centering tool between the inner peripheral face of the screw hole and the outer peripheral face of the broken screw, inserting the punch into a punch insertion hole passing through the center of the centering tool, forming a recessed portion at the front end of the punch where the broken end face of the broken screw is located to be the center of the screw hole, and using a drill or an extractor for removing the screw from the screw hole with the recessed portion as a center. The centering tool is one which is used in the above various methods. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a broken screw removing method for removing a screw remaining in a screw hole by folding the screw hole in or out of the screw hole at the time of tightening to or removing from the screw hole, and a broken screw. The present invention relates to a centering tool for forming a concave portion at the center of the screw hole or at the center of the bent end surface of the folding screw.

  Conventionally, a screw sometimes breaks in and out of a screw hole when tightening to or removing from the screw hole. In particular, screws that have rusted over the years since tightening are easy to break when removed. As a method for removing the broken screw that removes screws (such as bolts and screws) remaining in the screw holes (hereinafter collectively referred to as “screws”) from the screw holes, an extractor (extracted) There is a method to remove the screw by removing the folding screw by screwing it back in reverse, but the rust screw is not rotatable, so it is often impossible to remove it using an extractor. Moreover, even if an extractor is used, a recessed portion of a reservoir for inserting the extractor, an insertion hole, or the like is required, and these must be formed at the center of the folding end surface of the folding screw.

  Conventionally, a tool as described in Patent Document 1 has been used to form a recess at the center of the folded end surface. This tool includes a shaft portion that can be screwed into or inserted into a screw hole, and a nut that can be screwed into a folding screw, and is used by combining the shaft portion and the nut. A punch insertion hole through which a punch can be inserted and penetrated is passed through the shaft portion.

JP 2000-505363 A.

When forming a recessed part using the tool of the said patent document 1, and removing a folding screw, there exist the following subjects.
(1) When setting a tool to a broken screw or screw hole, it is necessary to screw the shaft portion into the screw hole or to screw the nut to the broken screw, so that it takes time to set the tool.
(2) When the screw hole or the broken screw is rusted, it is difficult to screw the shaft portion into the screw hole or screw the nut to the broken screw.
(3) Even if the shaft portion can be screwed into the screw hole or the nut can be folded and screwed into the screw hole, the slight clearance generated between the screwed male screw and female screw. In addition, it is difficult to accurately position the punch insertion hole at the center portion of the bent end surface of the bent screw or the center portion of the screw hole at the bent end surface of the bent screw. For this reason, the concave portion cannot be formed in the central portion of the screw hole, and the screw hole may be damaged when the broken screw is pulled out or scraped off. Since a damaged screw hole cannot be reused, a new screw hole must be drilled. Since the new screw hole is always larger than the previous screw hole, it may be difficult or impossible to make a new screw hole depending on the location.

  In the present invention, a concave portion is accurately formed at a central portion of a folding screw end surface or a folding screw end surface and a central portion of a screw hole, and the folding screw is securely secured by an extractor or a drill blade. The present invention provides a method for removing a broken screw that can be removed, and a centering tool used therefor.

  The broken screw removing method of the present application is the broken screw removing method in which the screw remaining inside the screw hole after being broken inside the screw hole or outside the screw hole is removed from the screw hole. Insert the cylindrical tip of the centering tool between the surface and the outer peripheral surface of the folding screw in the screw hole, or cover the fitting space portion of the centering tool on the outer periphery of the folding end of the folding screw protruding out of the screw hole, Alternatively, the cylindrical tip of the centering tool is put on the outer periphery of the bent end of the folding screw protruding outside the screw hole, and the cylindrical tip of the centering tool is inserted between the inner peripheral surface of the screw hole and the outer peripheral surface of the bent screw, A punch is inserted into the punch hole insertion hole that is penetrated through the center of the centering tool, and a concave portion is formed at the center of the screw hole at the tip of the punch and at the center of the screw hole. The folding screw as the center By cutting with Lil, or set the extractor is reversely rotated the screw broken by rotating the extractor counterclockwise in the recess, and the broken screw to be removed from the screw hole.

  The centering tool of the present application is a centering tool for removing a screw remaining in the screw hole after being broken in the screw hole or outside the screw hole. The punch insertion hole is penetrated, and a cylindrical tip part or fitting space part covering the outer periphery of the folding end of the folding screw is formed at one or / and both ends of the centering tool in the opening direction of the punch insertion hole. The outer peripheral wall of the cylindrical tip is tapered so that it can be inserted along the inner peripheral surface of the screw hole between the inner peripheral surface of the screw hole and the outer peripheral surface of the folding screw, and the fitting space portion is fitted along the outer peripheral surface of the folding screw. The inner diameter can be adjusted.

  Another centering tool of the present application is a centering tool for removing a screw remaining in the screw hole after being broken in the screw hole or outside the screw hole. The punch insertion hole is penetrated in the center of the center of the centering tool, and the punching hole is opened at one end in the opening direction to cover the outer periphery of the bent end of the screw. Between the inner peripheral surface of the screw hole and the outer peripheral surface of the screw screw, A tapered cylindrical tip that can be inserted along the outer periphery of the folding screw is formed at the other end, and a fitting space that covers the outer periphery of the folding screw is formed at the other end. The fitting space can be covered along the outer peripheral surface of the folding screw. The inner diameter was taken.

The broken screw removing method of the present application has the following effects.
(1) Since the cylindrical tip of the centering tool is inserted along the inner peripheral surface of the screw hole where the folding screw remains, the punch inserted into the centering tool is the folding end surface of the folding screw and the center of the screw hole. A concave portion can be accurately formed at a location to be a portion. For this reason, if the center of the drill is set in the recess and the broken screw is cut and removed, the broken screw can be reliably removed from the screw hole, and the screw hole remains intact without being damaged. A new screw can be screwed in and the original hole can be reused. For this reason, it is not necessary to make a new hole.
(2) By setting the extractor in the recess and rotating the extractor counterclockwise, the folding screw can be reversely rotated to remove the folding screw from the screw hole, so that the folding screw can be removed easily and reliably. In this case, the original hole remains as it is, so that the screw hole can be reused, and there is no need to open a new screw hole.
(3) In addition to inserting the cylindrical tip of the centering tool along the inner peripheral surface of the screw hole in which the folding screw remains, the centering tool is placed on the outer periphery of the folding end of the folding screw protruding out of the screw hole. The centering tool can be easily and accurately set at a predetermined position even when the folding screw protrudes long out of the screw hole. A concave portion can be easily and accurately formed at a location that becomes the central portion of the screw hole.
(4) The centering tool can be put on the outer periphery of the bent end of the folding screw protruding outside the screw hole, and the cylindrical tip of the centering tool can be inserted between the inner peripheral surface of the screw hole and the outer peripheral surface of the folding screw. Therefore, even when the folding screw protrudes out of the screw hole shortly, the centering tool can be easily and accurately inserted into the predetermined position, and is the folding end surface of the folding screw and the center of the screw hole Therefore, it is possible to form the recess easily and accurately.

The centering device of the present application has the following effects.
(1) A tapered tube which can be inserted along the inner peripheral surface of the screw hole between the inner peripheral surface of the screw hole and the outer peripheral surface of the bent screw. Since the tip portion is formed, the centering tool can be set without being screwed into the screw hole. For this reason, it is easy to attach to and remove from the screw hole, and it is possible to accurately form a concave portion at the end of the folding screw, which is the center of the screw hole. In this case, there is no risk of damaging the screw hole, the screw can be reliably and smoothly folded, and the screw hole can be reused.
(2) Since the fitting space that covers the outer periphery of the folding end of the folding screw is formed, the centering tool can be set without screwing it with the folding screw. Therefore, it can be easily attached to and detached from the folding screw, and a concave portion can be accurately formed at the central portion of the folding end surface of the folding screw, and the folding screw can be removed securely and smoothly without damaging the screw hole. In addition, the screw holes can be reused.
(3) When one end is a cylindrical tip and the other end is a fitting space, depending on the unfolded state of the folding screw, the end to be used is switched and various unfolded states can be achieved with a single centering tool. A recess can be formed in the folding screw.

(Embodiment 1 of the broken screw removing method)
An example of the embodiment of the broken screw removing method of the present invention will be described below with reference to FIGS. The broken screw removing method of this embodiment is a method of removing screws such as bolts and screws (hereinafter referred to as “folded screws”) left unfastened when tightening into or removing from the screw holes from the screw holes. When the bent end 2 of the folding screw 1 remains in the screw hole 3 (FIG. 2a), the bent end 2 slightly protrudes outward from the screw hole 3 (FIG. 2b). This is a method that can remove the folding screw 1 in any case where the end 2 protrudes outward from the screw hole 3 and remains (FIG. 3). The broken screw removal method of the present invention can remove any broken screw 1 when it is broken when tightened into the screw hole 3 or when it is broken when removed from the screw hole 3.

  As shown in FIG. 1, the broken screw removing method of the present embodiment has a cylindrical main body 5 having a punch insertion hole 6 in the center and a punch longer than the main body 5 inserted into the punch insertion hole 6. 7 is used. As shown in FIGS. 2A and 2B, the centering tool 4 is formed such that one end of the main body 5 is formed on the inner side and a covering space portion 8 is formed to cover the bent end portion 2 of the screw 1 and the outer periphery thereof is tapered. Thus, a cylindrical tip portion 10 that can be fitted into a clearance 9 between the inner peripheral surface of the screw hole 3 and the outer peripheral surface of the folding screw 1 is formed, and the other end of the main body 5 covers the outer periphery of the folding end portion 2 of the folding screw 1. A fitting space portion 11 having an inner diameter is formed, and the outer side of the fitting space portion 11 is a covering portion 12 that covers the outer peripheral surface of the folding screw 1.

(When the broken end face of the broken screw remains in the screw hole)
As shown in FIGS. 2 (a, 2 b), when the screw hole 3 is tightened or removed from the screw hole 3, the broken screw 2 is folded and the folded end 2 remains in the screw hole 3. A method of removing 1 from the screw hole 3 will be described. In this case, first, as shown in FIGS. 2A and 2B, the cylindrical tip portion 10 of the main body 5 is inserted into the clearance 9 between the inner peripheral surface of the screw hole 3 and the outer peripheral surface of the folding screw 1. When the main body 5 is set, the punch insertion hole 6 of the main body 5 is arranged right above the position that is the bent end portion 2 of the folding screw 1 and the center portion of the screw hole 3. When the main body 5 is set, the punch 7 is inserted into the punch insertion hole 6 from above and penetrated, and the tip end (lower end) 13 of the punch 7 is the folding end portion 2 of the folding screw 1 and the screw hole 3. A concave portion is formed at a location that becomes the central portion. The broken screw 1 is cut and removed with a drill slightly smaller than the diameter of the screw hole 3 around the formed recess. Alternatively, the extractor can be removed from the screw hole 3 by setting an extractor in the recess and rotating the folding screw 1 in the reverse direction. Before setting the extractor, it is possible to make the extractor easy to screw by making a hole around the recess.

(When the folded end face of the broken screw protrudes slightly outside the screw hole)
As shown in FIG. 2 (c), when the screw hole 3 is tightened or removed from the screw hole 3, it is bent outside the screw hole 3, and the bent end 2 slightly protrudes outside the screw hole 3 and remains. A method of removing the broken screw 1 from the screw hole 3 will be described. Also in this case, first, as shown in FIG. 2C, the cylindrical tip portion 10 of the main body 5 is inserted into the clearance 9 between the inner peripheral surface of the screw hole 3 and the outer peripheral surface of the folding screw 1. At this time, the covering space 8 is placed on the outer periphery of the folding end 2 of the folding screw 1. When the main body 5 is set, the punch insertion hole 6 of the main body 5 is arranged right above the position that is the bent end portion 2 of the folding screw 1 and the center portion of the screw hole 3. When the main body 5 is set, the punch 7 is inserted into the punch insertion hole 6 from above and penetrated, and at the tip end portion 13 of the punch 7, the folding end portion 2 of the folding screw 1 and the center portion of the screw hole 3 A recess is formed at the location. After the recess is formed, the folding screw 1 can be removed from the screw hole 3 using a drill or an extractor with the formed recess as the center, as in the case described above. This method is used when the protruding length of the bent end portion 2 from the screw hole 3 is shorter than the depth of the covering space portion 8. When the protruding length of the bent end portion 2 from the screw hole 3 is longer than the depth of the covering space portion 8, a method of covering the bending screw 1 with the covering portion 12 as shown in FIG.

(When the folded end face of the broken screw protrudes outside the screw hole)
As shown in FIG. 3, when the screw hole 3 is tightened or removed from the screw hole 3, it is bent outside the screw hole 3, and the folded screw 1 when the bent end 2 protrudes outside the screw hole 3 and remains. A method of removing from the screw hole 3 will be described. In this case, first, as shown in FIG. 3, the body 5 is set on the folding screw 1 by covering the outer periphery of the folding end portion 2 of the folding screw 1 with the covering portion 12 of the centering tool 4. This method is used when the protruding length of the bent end portion 2 from the screw hole 3 is longer than the depth of the covering space portion 8 as shown in FIG. When the main body 5 is set, the punch insertion hole 6 of the main body 5 is disposed immediately above the location that is the center of the folding end 2 of the folding screw 1. When the main body 5 is set, the punch 7 is inserted into the punch insertion hole 6 from above and penetrated, and the front end portion 13 of the punch 7 forms a recess at the center of the folded end portion 2. After the recess is formed, the folding screw 1 can be removed from the screw hole 3 by using an extractor or a drill around the formed recess as in the case described above.

(Embodiment 2 of the broken screw removing method)
Another example of the embodiment of the broken screw removing method of the present invention will be described with reference to FIG. As shown in FIG. 4, this broken screw removal method is such that when the screw hole 3 is tightened or removed from the screw hole 3, it is bent outside the screw hole 3, and the bent end 2 protrudes outside the screw hole 3. This is a method that can be used for the broken screw 1 when it remains. In this embodiment, as shown in FIG. 4, as the centering tool 4, a fitting space portion 11 having an inner diameter capable of covering the outer peripheral surface of the folding screw 1 is formed at one end of the main body 5. What the outer side is made into the coating | coated part 12 which covers the outer peripheral surface of the folding screw 1 is used. The fitting space portion 11 is formed so as to widen the end portion. The other end of the main body 5 is not provided with a fitting space 11 or the like. Since the fitting space portion 11 of the main body 5 is formed so as to widen the end portion, one main body 5 can be set with respect to various folding screws 1 having different diameters (see the one-dot chain line portion in FIG. 4). About the folding screw 1, a recessed part can be formed in the center part of the folding end part 2. FIG. After the recess is formed, the folding screw 1 can be removed from the screw hole 3 by using an extractor or a drill around the formed recess as in the first embodiment.

(Another embodiment of the broken screw removing method)
In the broken screw removal method of the present invention, as the centering tool 4, a covering space portion 8 is formed at one end of the main body 5 so as to cover the folded end portion 2 of the folding screw 1 as in FIGS. The outer peripheral surface of the space portion 8 is tapered to form a cylindrical tip portion 10 that can be fitted into the clearance 9 between the inner peripheral surface of the screw hole 3 and the outer peripheral surface of the folding screw 1. A space portion is not provided, or one having a covering space portion and a cylindrical tip portion having different diameters from the covering space portion 8 and the cylindrical tip portion 10 on one end side can be used. In this case, only the folding screw 1 when the folded end surface of the folding screw remains in the screw hole (see FIG. 2b) and when the folded end surface of the folding screw slightly protrudes out of the screw hole (see FIG. 2c). Can be removed from the screw hole 3.

  In the folding screw removing method of the present invention, as the centering tool 4, a fitting space portion 11 having an inner diameter capable of covering the outer peripheral surface of the folding screw 1 is formed at one end of the body 5 as in FIGS. The outer side of the fitting space portion 11 is a covering portion 12 that covers the outer peripheral surface of the folding screw 1, and the fitting space portion is not provided at the other end, or the fitting space portion on one end side. The thing provided with the fitting space part and coating | coated part from which a diameter and a shape differ from 11 and the coating | coated part 12 can also be used. The shape of the fitting space portion 11 may be a straight tube shape shown in FIGS. 2 and 3, or may be an end portion spread shown in FIG. In this case, when the screw hole 3 is bent or removed from the screw hole 3 at the time of tightening or removing from the screw hole 3 and the bent end portion 2 protrudes outside the screw hole 3 (see FIGS. 3 and 4). .)) Only the broken screw 1 can be removed from the screw hole 3.

(Embodiment 1 of centering tool)
An example of an embodiment of the centering tool of the present invention will be described with reference to FIGS. The centering tool 4 is an instrument for forming a recess in the folded end 2 of the folding screw 1 when the folding screw removing method is performed. As shown in FIGS. 1 to 3, the centering tool 4 of the present invention is cylindrical and has a main body 5 having a punch insertion hole 6 in the center thereof, and is inserted into the punch insertion hole 6. And a punch 7 longer than the round bar-shaped main body 5 sharpened to form a recess. One end side of the main body 5 is formed with a covering space portion 8 covering the bent end portion 2 of the screw 1 on the inner side, and the outer peripheral surface thereof is tapered to be formed between the inner peripheral surface of the screw hole 3 and the outer peripheral surface of the bent screw 1. The cylindrical tip portion 10 can be fitted into the clearance 9. The other end side of the main body 5 is formed with a fitting space portion 11 having an inner diameter that can cover the outer peripheral surface of the folding screw 1, and the outer side of the fitting space portion 11 is a covering portion 12 that covers the outer peripheral surface of the folding screw 1. . The main body 5 and the punch 7 can be formed of an arbitrary material, but it is preferable that the main body 5 and the punch 7 are made of metal having a hardness capable of forming a concave portion in the bent end portion 2 of the folding screw 1 such as steel.

  The punch insertion hole 6 provided in the axial direction of the main body 5 is opened to a diameter that allows the punch 7 to be inserted and slidable.

  As shown in FIG. 2 (b), the cylindrical tip portion 10 is folded in the screw hole 3 when tightened to the screw hole 3 or removed from the screw hole 3, and the folded end portion 2 is in the screw hole 3. When remaining, it can be fitted into the clearance 9 between the outer peripheral surface of the folding screw 1 and the inner peripheral surface of the screw hole 3. When the cylindrical tip portion 10 is fitted and set in the clearance 9, the punch insertion hole 6 is disposed just above the portion that is the folded end portion 2 of the folding screw 1 and becomes the central portion of the screw hole 3. In this state, the punch 7 is inserted into the punch insertion hole 6 from above and penetrated, and the folding end portion 2 of the folding screw 1 is struck by the front end portion (lower end portion) 13 of the punch 7 to break the folding screw 1. A recess can be formed at the end 2 and at the center of the screw hole 3.

  As shown in FIG. 2C, the cylindrical tip portion 10 includes an outer peripheral surface of the folding screw 1 when the bent end portion 2 slightly protrudes outside the screw hole 3 and an inner peripheral surface of the screw hole 3. Can also be inserted into the clearance 9 between the two. The protruding folded end 2 is covered with the covering space 8. In this case as well, a concave portion can be formed at a location that is the folded end portion 2 of the folding screw 1 and that is the central portion of the screw hole 3.

  As shown in FIG. 3, the covering portion 12 can cover the outer peripheral surface of the folding screw 1 when the folded end portion 2 protrudes outside the screw hole 3 by the inner fitting space portion 11. The fitting space 11 is formed in a cylindrical shape having an inner diameter slightly larger than the diameter of the folding screw 1 that can cover the folding screw 1 so that the main body 5 set on the folding screw 1 does not rattle. When the folding screw 1 is covered with the covering portion 12 and the main body 5 is set, the punch insertion hole 6 is disposed immediately above the center portion of the folding end portion 2 of the folding screw 1. In this state, the punch 7 is inserted into the punch insertion hole 6 from above and penetrated, and the folded end portion 2 of the folding screw 1 is struck by the front end portion 13 of the punch 7 so that the folded end portion 2 of the folding screw 1 A recess can be formed in the center.

(Embodiment 2 of centering tool)
Another example of the embodiment of the centering device of the present invention will be described with reference to FIG. As shown in FIG. 4, the centering tool 4 is formed with a fitting space portion 11 having an inner diameter capable of covering the outer peripheral surface of the folding screw 1 at one end of the main body 5, and the outside of the fitting space portion 11 is folded. The covering portion 12 covers the outer peripheral surface of the screw 1 and the fitting space portion 11 is formed so as to expand the end portion. The other end of the main body 5 is not provided with a fitting space 11 or the like. Since the fitting space portion 11 of the main body 5 is formed so as to widen the end portion, one main body 5 can be set with respect to various folding screws 1 having different diameters (refer to the alternate long and short dash line portion in FIG. 4). With respect to the folding screw 1, a concave portion can be formed at the center of the folded end 2.

(Embodiment 3 of centering tool)
In the centering tool described in the first embodiment, the fitting space 11 at one end of the main body 5 is formed to widen the end face (see the broken line portion in FIG. 2a and FIG. 3), and the single main body 5 has various folding screws having different diameters. 1 can be set.

(Other Embodiments of Centering Tool)
In the centering device of the present invention, a covering space portion 8 that covers the bent end portion 2 of the folding screw 1 is formed at one end of the main body 5 similarly to FIGS. 1 and 2, and the outer peripheral surface of the covering space portion 8 is tapered. Formed into a cylindrical tip portion 10 that can be fitted into the clearance 9 between the inner peripheral surface of the screw hole 3 and the outer peripheral surface of the folding screw 1, and the other end is not provided with a covering space portion, or The covering space portion 8 and the cylindrical tip portion 10 on one end side may be provided with a covering space portion and a cylindrical tip portion having different diameters. In this case, the folded end surface 2 of the folding screw 1 remains in the screw hole 3 (see FIG. 2b) and the folded end surface 2 of the folding screw 1 slightly protrudes outside the screw hole 3 (see FIG. 2c). ) In the bent end portion 2 of the folding screw 1 and the central portion of the screw hole 3 can be formed.

  In the centering tool of the present invention, a fitting space portion 11 having an inner diameter capable of covering the outer peripheral surface of the folding screw 1 is formed at one end of the main body 5, and the outer side of the fitting space portion 11. Is a covering portion 12 that covers the outer peripheral surface of the folding screw 1, and the other end is not provided with a fitting space portion, or the fitting space portion 11 and the covering portion 12 on one end side have a diameter. It is also possible to provide a fitting space portion and a covering portion having different shapes. The shape of the fitting space portion 11 may be a straight tube shape shown in FIGS. 2 and 3, or may be an end portion spread shown in FIG. In this case, when the screw hole 3 is bent or removed from the screw hole 3 at the time of tightening or removing from the screw hole 3 and the bent end portion 2 protrudes outside the screw hole 3 (see FIGS. 3 and 4). .)) Can be formed at the center of the bent end 2 of the folding screw 1.

  The folding screw removing method of the present invention and the centering tool used therefor are not limited to the removing operation of the folding screw from the screw hole, but can be used for various operations such as a drilling operation for accurately forming a hole at the center of the object. it can.

The perspective view which shows an example of embodiment of the centering tool of this invention. (A) is sectional explanatory drawing which shows a mode that the cylindrical front-end | tip part of the main body of the centering tool shown in FIG. 1 is set to a screw hole. (B) (c) is sectional explanatory drawing which shows a mode that the cylindrical front-end | tip part was fitted in the clearance between a screw hole inner peripheral surface and a broken screw outer peripheral surface. Cross-sectional explanatory drawing which shows a mode that the folding screw was coat | covered with the coating | coated part of the main body of the centering tool shown in FIG. Cross-sectional explanatory drawing which shows another example of embodiment of the centering tool of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Folding screw 2 Folding end part 3 Screw hole 4 Centering tool 5 Main body 6 Punch insertion hole 7 Punch 8 Covering space part 9 Clearance 10 Cylindrical tip part 11 Fitting space part 12 Covering part 13 Tip part

Claims (3)

  In the method of removing a broken screw in which the screw remaining inside the screw hole after being broken inside or outside the screw hole is removed from the screw hole, the tube of the centering tool is interposed between the inner peripheral surface of the screw hole and the outer peripheral surface of the broken screw in the screw hole. Insert the tip of the ring or place the fitting space of the centering tool on the outer periphery of the bent end of the bent screw protruding out of the screw hole, or on the outer periphery of the bent end of the bent screw protruding out of the screw hole. Cover the cylindrical tip of the centering tool and insert the cylindrical tip of the centering tool between the inner peripheral surface of the screw hole and the outer peripheral surface of the folding screw, and punch into the punch hole insertion hole that penetrates the center of the centering device. And then forming a recess at the center of the screw hole at the tip of the punch, and cutting the folding screw with a drill around the recess, or extra in the recess. The broken thread by sets ter rotate the extractor counterclockwise rotated in the reverse direction, the bending fold screw removal method is characterized by removing the screw from the screw hole.   In the centering device for removing the screw remaining in the screw hole after being broken in the screw hole or outside the screw hole, the punch insertion hole is penetrated in the center of the centering device, and the punch insertion hole of the centering device At one or / and both ends in the opening direction, a cylindrical tip portion or a fitting space portion covering the outer periphery of the bent end portion of the folding screw is formed, and the outer peripheral wall of the cylindrical tip portion is connected to the inner peripheral surface of the screw hole. A centering tool characterized in that it is tapered so that it can be inserted along the inner peripheral surface of the screw hole between the outer peripheral surfaces of the folding screw, and the fitting space portion has an inner diameter that can be fitted along the outer peripheral surface of the folding screw.   A centering tool for removing the screw remaining in the screw hole after being broken in the screw hole or outside the screw hole. The punch insertion hole is penetrated through the center of the centering tool. A tapered cylindrical tip that can be inserted along the inner peripheral surface of the screw hole is formed between the inner peripheral surface of the screw hole and the outer peripheral surface of the bent screw. A centering tool characterized in that a fitting space portion is formed to cover the outer periphery of the bent end of the folding screw, and the fitting space portion has an inner diameter that can be covered along the outer circumferential surface of the folding screw.

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