Cutting assist device and cutting method

Abstract

To provide a cutting auxiliary device capable of solving problems in prior arts, namely, capable of cutting a steel pipe without penetrating in a thickness direction, and to provide a cutting method using the device.SOLUTION: A cutting auxiliary device is a device which is used for forming a cutting groove on a part of a steel pipe using a hole saw, the cutting auxiliary device comprises: a main body plate on which a main body opening is formed; an arrangement guide fitted to the main body plate; and a control collar on which a collar opening is formed. In a state of arranging the control collar on the main body opening and arranging the cutting blade of the hole saw on the collar opening part, when the cutting blade cuts the steel pipe, a part of the hole saw contacts a top face of the control collar, thereby forming a cutting groove which does not penetrate in the steel pipe.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The invention of the present application relates to a technique for providing an opening in a part of a steel pipe. More specifically, for example, it relates to a cutting auxiliary device capable of cutting a steel pipe so as not to damage a cable housed therein, and a cutting method using the same.

Background Art

[0002] In a power plant, electricity of several thousand to several tens of thousands of volts is generated. However, in order to avoid losses due to electrical resistance, it is transmitted at an ultra-high voltage of about several hundred thousand volts. Then, the voltage is gradually lowered at each substation such as an ultra-high voltage substation, a primary substation, a secondary substation, and a distribution substation, and then supplied to a factory or the like. Further, the voltage is lowered by a pole-mounted transformer or the like and supplied to a household. In any case, the electricity generated at the power plant is supplied to users via transmission lines and distribution lines (hereinafter, these are collectively referred to as "transmission lines, etc.") using electric wires, cables, and the like. Naturally, a huge amount of transmission lines, etc. are arranged throughout the country, and there are some relatively new transmission lines, etc. and some transmission lines, etc. that have passed a considerable period of time.

[0003] Among the transmission lines, etc., there are overhead transmission lines, etc. (overhead transmission lines and overhead distribution lines) erected on power poles and underground transmission lines, etc. (underground transmission lines and underground distribution lines) buried underground. Among these, the underground transmission lines, etc. are generally housed in a galvanized steel pipe or the like and then buried underground. Therefore, when performing maintenance work on aging underground transmission lines, etc. or when connecting other cables to the underground transmission lines, etc., a so-called "pipe cutting operation" of removing a part of the galvanized steel pipe is performed. Hereinafter, the conventional procedure until the galvanized steel pipe is partially cut will be described with reference to FIG. 9.

[0004] First, as shown in Figure 9(a), an opening window is formed on the surface of the galvanized steel pipe. After forming the opening window, the underground power lines etc. housed inside are checked, and then, as shown in Figure 9(b), the opening is further expanded using the opening window as a guide, and the exposed underground power lines etc. are protected with a resin protective sheet. Next, as shown in Figure 9(c), a portion of the galvanized steel pipe is cut, and the underground power lines etc. that can now be handled are subjected to the prescribed work.

[0005] Regarding techniques for cutting steel pipes containing cables and the like, various techniques have been proposed to date. For example, Patent Document 1 proposes a technique that prevents the scattering of cut pieces and enables cutting in the axial direction of the pipe. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Utility Model Registration No. 3192120 Gazette [Overview of the Initiative] [Problems that the invention aims to solve]

[0007] Previously, opening windows were formed by using a disc grinder to penetrate the galvanized steel pipe and extracting (or dropping into) a rectangular section, for example, about 5cm x 5cm. This meant that the cutting with the disc grinder was done by feel without knowing the condition of the power lines inside, and there was a risk of unintentionally cutting the power lines. Furthermore, since the opening windows were formed by penetrating the galvanized steel pipe, there was a risk that sparks from the cutting with the disc grinder could damage the power lines. However, no effective technology has been proposed to form opening windows on the surface of a galvanized steel pipe while avoiding cutting power lines or causing damage from sparks.

[0008] The object of the present invention is to solve the problems of the prior art, namely, to provide a cutting aid that can cut a steel pipe without penetrating it in the thickness direction, and a cutting method using the same. [Means for solving the problem]

[0009] The present invention focuses on the fact that, when creating an opening window in a part of a steel pipe, the opening window is created by forming a cutting groove without penetrating the steel pipe, and is based on an unprecedented idea.

[0010] The cutting assist device of the present invention is used when forming a cutting groove in a part of a steel pipe using a hole saw, and comprises a main body plate with a main body opening, an arrangement guide attached to the main body plate, and a control collar with a collar opening. The arrangement guide is arc-shaped in cross-section, and its inner diameter is approximately the same as (including being the same as) the outer diameter of the steel pipe. The arrangement guide is positioned along the surface of the steel pipe, the control collar is placed in the main body opening, and the cutting blade of the hole saw from which the center drill has been removed is placed in the collar opening. When the cutting blade cuts the steel pipe, a part of the hole saw comes into contact with the upper surface of the control collar, thereby forming a cutting groove that does not penetrate the steel pipe.

[0011] The cutting assist device of the present invention may also be equipped with multiple types of placement guides with different inner diameters. In this case, a desired placement guide can be selected according to the outer diameter of the steel pipe, and the placement guide can be attached to the main body plate in an interchangeable manner.

[0012] The cutting assist device of the present invention may further include a housing with an insertion hole formed therein. In this case, the housing can be attached to the main body plate so as to cover the upper part of the main body opening, with the rotation axis of the hole saw, in which the cutting blade is positioned within the collar opening, inserted through the insertion hole.

[0013] The cutting assist device of the present invention may further be equipped with a fixing belt. In this case, the main body plate can be fixed to the steel pipe by wrapping the fixing belt around the main body plate and the steel pipe, that is, by tightening the fixing belt.

[0014] The cutting assist device of the present invention is a method for forming an opening window in a part of a steel pipe using the cutting assist device of the present invention and a hole saw, and comprises an assist device placement step, a cutting step, and a window formation step. In the assist device placement step, the cutting assist device is positioned so that the placement guide follows the surface of the steel pipe, and a control collar is placed in the opening of the main body. In the cutting step, the cutting blade of the hole saw from which the center drill has been removed is placed in the collar opening, and the steel pipe is cut with the cutting blade to form a cutting groove. In the window formation step, an opening window is formed in a part of the steel pipe. In the cutting step, a part of the hole saw contacts the upper surface of the control collar to form a cutting groove that does not penetrate the steel pipe, and in the window formation step, the opening window is formed by removing the part of the steel pipe surface surrounded by the cutting groove. [Effects of the Invention]

[0015] The cutting assist device and cutting method of the present invention have the following effects. (1) For example, an opening can be safely installed in the steel pipe without damaging the cables housed inside. (2) Even those without advanced skills or considerable experience can easily and reliably create openings in steel pipes. (3) By selecting an appropriate placement guide, it can be applied to steel pipes of various outer diameters, and by selecting an appropriate plate thickness control collar, it can be applied to steel pipes of various wall thicknesses. [Brief explanation of the drawing]

[0016] [Figure 1] A schematic perspective view showing the cutting assist device of the present invention. [Figure 2] (a) is a schematic side view of the cutting assist device, and (b) is a schematic top view of the cutting assist device. [Figure 3] Perspective view schematically showing the cutting assistance device of the present invention before the hole saw is set. [Figure 4] Perspective view schematically showing the cutting assistance device of the present invention with the hole saw set. [Figure 5] (a) is a model diagram schematically showing the situation before the cutting edge is placed in the color opening, and (b) is a model diagram schematically showing the situation of cutting by the cutting edge. [Figure 6] Cross-sectional view schematically showing the placement guide placed on the surface of the steel pipe. [Figure 7] (a) is a cross-sectional view schematically showing the cutting groove formed on the surface of the steel pipe, (b) is a plan view schematically showing the cutting groove formed on the surface of the steel pipe, and (c) is a plan view schematically showing the opening window formed by extracting the inside of the cutting groove. [Figure 8] Flow chart showing the main steps of the cutting method of the present invention. [Figure 9] Step diagram schematically showing the procedure until the steel pipe is partially removed in order to perform work on the underground cable housed in the steel pipe.

Embodiments for Carrying Out the Invention

[0017] An example of an embodiment of the cutting assistance device and the cutting method of the present invention will be described based on the drawings.

[0018] 1. Cutting Assistance Device The cutting assistance device of the present invention will be described in detail with reference to the drawings. The cutting method of the present invention is a method of forming an opening window in a steel pipe (for example, a galvanized steel pipe) using the cutting assistance device of the present invention. Therefore, first, the cutting assistance device of the present invention will be described, and then the cutting method of the present invention will be described in detail.

[0019] Figure 1 is a schematic perspective view of the cutting assist device 100 of the present invention, Figure 2(a) is a schematic side view of the cutting assist device 100 viewed from the side, and Figure 2(b) is a schematic plan view of the cutting assist device 100 viewed from above. As shown in these figures, the cutting assist device 100 of the present invention is composed of a main plate 110, a control collar 120, and an arrangement guide 130, and may also be composed of a housing 140 and a fixing belt 150.

[0020] The cutting assist device 100 of the present invention is used when cutting a part of the surface of a steel pipe GP, such as a galvanized steel pipe, and is particularly suitable for cutting a steel pipe GP that houses electric wires or cables. When a steel pipe GP is cut using the cutting assist device 100, the cutting does not penetrate the steel pipe GP in the thickness direction, but is limited to the middle of the thickness, so to speak, and a groove (hereinafter referred to as a "cutting groove" for convenience) is formed on the surface of the steel pipe GP. If the steel pipe GP is cut all the way through in the thickness direction, there is a risk of damaging cables etc. housed inside the steel pipe GP, but by limiting the cutting to the formation of a cutting groove, it is possible to easily create an opening window using the cutting groove without damaging the cables etc.

[0021] Furthermore, as shown in Figures 3 and 4, the cutting assist device 100 is used when forming cutting grooves in the steel pipe GP using the hole saw 200. Figure 3 is a schematic perspective view showing the cutting assist device 100 before the hole saw 200 is set, and Figure 4 is a schematic perspective view showing the cutting assist device 100 with the hole saw 200 set. The procedure for setting the hole saw 200 in the cutting assist device 100 will be described below.

[0022] As shown in Figures 1 and 2, before attaching the cutting assist device 100 to the steel pipe GP, the state is changed from that shown in Figure 3 to that shown in Figure 4. Specifically, the control collar 120 is placed in the main body opening 110H provided in the main body plate 110, and the cutting blade 210 of the hole saw 200 is placed in the collar opening 120H provided in the control collar 120. Then, the housing 140 is attached to the main body plate 110 using the housing fixing bolts 141. At this time, the rotating shaft 220 of the hole saw 200 is inserted through the insertion hole 140H provided in the housing 140 before attachment.

[0023] The following will provide a detailed explanation of each of the main elements constituting the cutting assist device 100 of the present invention.

[0024] (Main panel) The main body plate 110 is, so to speak, the base component of the cutting assist device 100, and is generally plate-shaped. The main body plate 110 is provided with a main body opening 110H and a placement guide mounting fixture 111. The main body opening 110H is an opening for housing the control collar 120, and therefore the inner diameter of the main body opening 110H is slightly larger (in particular, just slightly larger) than the outer diameter of the control collar 120. The placement guide mounting fixture 111 is a jig for attaching the placement guide 130, which will be described later, to the main body plate 110. It is desirable that the placement guide mounting fixture 111 be structured so that the placement guide 130 can be attached to the main body plate 110 in a replaceable manner, for example, by using bolts, pins, or magnets.

[0025] (Control Color) The control collar 120 is a component that restricts the cutting blade 210 of the hole saw 200 from advancing in the thickness direction of the steel pipe GP during cutting. As described above, the control collar 120 is housed in the main body opening 110H of the main body plate 110, so it is preferable that the shape of the control collar 120 be approximately similar (including similar) to the shape of the main body opening 110H. For example, in Figure 3, both the control collar 120 and the main body opening 110H are circular.

[0026] The control collar 120 is also provided with a collar opening 120H for accommodating the cutting blade 210 of the hole saw 200. The cutting blade 210 of a typical hole saw 200 is hollow and ring-shaped (annular), with a circular outer shape. Therefore, the collar opening 120H should have an inner diameter slightly larger than the outer diameter of the cutting blade 210 and be roughly circular in shape. In particular, making the inner diameter of the collar opening 120H slightly larger than the outer diameter of the cutting blade 210, in other words, minimizing the clearance between the collar opening 120H and the cutting blade 210, allows the cutting blade 210 to be supported by the control collar 120 (and further supported by the main plate 110 that supports the control collar 120), enabling it to rotate without wobbling, which is preferable.

[0027] Figure 5 is a schematic model diagram illustrating how the control collar 120 restricts the movement of the cutting blade 210 during cutting. (a) shows the situation before the cutting blade 210 is positioned in the collar opening 120H, and (b) shows the situation during cutting by the cutting blade 210. A typical hole saw 200 is equipped with a center drill, but this center drill should be removed when using the hole saw 200 according to the present invention. The hole saw 200 also has a cutting blade 210, a rotating shaft 220, and a flange 230, of which the flange 230 is formed with dimensions larger than the outer diameter of the cutting blade 210, and at least the flange 230 has a portion that protrudes (overhangs) from the cutting blade 210 in a plan view.

[0028] When the hole saw 200, with the center drill removed, is used to cut the steel pipe GP, the cutting blade 210 advances in the direction of the thickness of the steel pipe GP. After cutting to a certain extent, as shown in Figure 5(b), a part of the flange material 230 (especially the lower surface) comes into contact with the upper surface of the control collar 120, preventing the cutting blade 210 from advancing in the direction of the thickness of the steel pipe GP. In other words, the control collar 120 restricts the cutting blade 210 from advancing in the direction of the thickness of the steel pipe GP. To put it another way, the control collar 120 prevents the cutting blade 210 from cutting all the way through the steel pipe GP, and only forms a cutting groove. To achieve the state shown in Figure 5(b), it is necessary to form the collar opening 120H with dimensions and a shape that prevents the flange material 230 from passing through. Furthermore, the thickness of the control collar 120 must be set so that the sum of the thickness of the steel pipe GP and the thickness of the control collar 120 is greater than the dimensions of the cutting blade 210 (the vertical length in Figure 5). On the other hand, there are various hole saws 200 with different dimensions of cutting blades 210, and various steel pipes GP with different wall thicknesses. Therefore, in order to accommodate various hole saws 200 and steel pipes GP, it is advisable to prepare control collars 120 having collar openings 120H of various dimensions and shapes, as well as control collars 120 with various wall thickness dimensions.

[0029] (Placement Guide) When cutting steel pipe GP with a hole saw 200, the cutting assist device 100 is installed on the steel pipe GP as shown in Figures 1 and 2. During cutting, it is desirable that the cutting assist device 100 is firmly installed so that it does not detach from the steel pipe GP and does not swing (wobble). The placement guide 130 is a component that provides a more secure installation of the cutting assist device 100 when positioning it on the steel pipe GP. In these figures, the placement guide 130 is provided in two places on the main plate 110, but it is not limited to this, and the placement guide 130 can be provided in only one place, or in three or more places.

[0030] The placement guide 130 should be positioned as close to the steel pipe GP as possible (fitted) to prevent the cutting assist device 100 from oscillating during cutting. Figure 6 is a schematic cross-sectional view showing the placement guide 130 placed on the surface of the steel pipe GP. As shown in this figure, the steel pipe GP is generally cylindrical, meaning its cross-sectional shape is circular. Therefore, the placement guide 130 should be arc-shaped in cross-section, and the inner diameter of the arc should be approximately the same as (or identical to) the outer diameter of the steel pipe GP. Since various types of steel pipe GP with different outer diameters exist, it is advisable to prepare placement guides 130 with various inner diameters to accommodate each type of steel pipe GP. That is, the placement guide 130 that matches the outer diameter of the steel pipe GP is selected, and the cutting assist device 100 is positioned on the steel pipe GP after the placement guide 130 is attached. Therefore, the placement guide mounting device 111 in this case is designed to allow the placement guide 130 to be attached to the main plate 110 in a replaceable manner, as described above.

[0031] (housing) The housing 140 is a component that houses the cutting blade 210 during cutting, the control collar 120, and the main body opening 110H, and is attached to the main body plate 110 using housing fixing bolts 141, etc. The housing 140 attached to the main body plate 110 covers the upper part of the main body opening 110H and houses the cutting blade 210 during cutting, thereby preventing the scattering of cutting fragments and other debris generated during cutting, and preventing cuts from the rotating part during cutting.

[0032] The housing 140 is a hollow box-shaped structure with a through-hole 140H on its upper surface (top surface). When cutting steel pipe GP with the hole saw 200, the rotating shaft 220 of the hole saw 200 is inserted through this through-hole 140H, as shown in Figures 1 and 2. The inner diameter of the through-hole 140H should be slightly larger (in particular, just slightly larger) than the outer diameter of the hole saw 200. This allows the rotating shaft 220 to be supported by the through-hole 140H (i.e., the housing 140) and rotate without wobbling.

[0033] (Securing belt) The fixing belt 150, like the placement guide 130, is a component that firmly secures the cutting assist device 100 to the steel pipe GP. As shown in Figures 1 and 2, after the cutting assist device 100 is placed on the steel pipe GP, the fixing belt 150 wraps around the main plate 110 and the steel pipe GP together, that is, the fixing belt 150 tightens the main plate 110 and the steel pipe GP, thereby more firmly securing the cutting assist device 100. It is desirable that the fixing belt 150 be made of a highly elastic material such as nylon or rubber, and it can be in the shape of an endless loop, or it can be made into a shape with both ends by providing connecting means such as hook-and-loop fasteners.

[0034] (Example of use) The following describes an example of forming cutting grooves in a steel pipe GP using the cutting assist device 100.

[0035] When forming a cutting groove in a steel pipe GP using the cutting assist device 100, first determine the outer diameter and wall thickness of the target steel pipe GP. Then, select a placement guide 130 that matches the outer diameter of the steel pipe GP and attach the placement guide 130 to the main plate 110. In addition, select an appropriate control collar 120 according to the hole saw 200 to be used (especially the dimensions of the cutting blade 210) and the wall thickness of the steel pipe GP, and remove the center drill from the hole saw 200 to be used. When selecting the control collar 120, select one such that the sum of the wall thickness of the control collar 120 and the wall thickness of the steel pipe GP is greater than the dimensions (height) of the cutting blade 210.

[0036] When the placement guide 130 is attached to the main plate 110, the main plate 110 is placed on the surface of the steel pipe GP. At this time, as shown in Figures 1 and 2, the placement guide 130 is positioned so that it is aligned with the surface (circumferential direction) of the steel pipe GP, and the longitudinal direction of the main plate 110 is aligned with the axial direction of the steel pipe GP. Next, the selected control collar 120 is placed in the main opening 110H, and the cutting blade 210 of the hole saw 200 is placed in the collar opening 120H. Then, the rotating shaft 220 of the hole saw 200 is inserted through the insertion hole 140H, and the housing 140 is attached to the main plate 110 using the housing fixing bolt 141, and then the main plate 110 and the steel pipe GP are wrapped together with the fixing belt 150.

[0037] Once the preparations are complete, the main body of the hole saw 200 is attached to the rotating shaft 220, and the cutting blade 210 is rotated by rotating the rotating shaft 220, thereby cutting the steel pipe GP. As shown in Figure 5(b), when the cutting is advanced until a part of the flange material 230 contacts the upper surface of the control collar 120, the cutting operation by the hole saw 200 is stopped. As a result, the cutting blade 210 does not penetrate the steel pipe GP, and a cutting groove CG is formed on the surface of the steel pipe GP as shown in Figure 7(a). Also, since the cutting blade 210 is hollow and ring-shaped, a roughly circular cutting groove CG is formed as shown in Figure 7(b). Then, by removing (or punching out) the inside of the cutting groove CG, an opening window OW is formed as shown in Figure 7(c). The cutting groove CG of the steel pipe GP is, so to speak, weakened (thinned), so the opening window OW can be easily formed by utilizing this cutting groove CG.

[0038] 2.Cutting method Next, the cutting method of the present invention will be explained in detail with reference to the figures. The cutting method of the present invention is a method of forming an opening window OW in a steel pipe GP (for example, a galvanized steel pipe) using the cutting assist device 100 described so far. Therefore, explanations that overlap with those described for the cutting assist device 100 will be avoided, and only the content specific to the cutting method of the present invention will be explained. In other words, the content not described here is the same as that described in "1. Cutting Assist Device".

[0039] Figure 8 is a flowchart showing the main steps of the cutting method of the present invention. When forming an opening window OW in a steel pipe GP using the cutting assist device 100, predetermined preparatory work is performed first. Specifically, the outer diameter and wall thickness of the target steel pipe GP are determined, a placement guide 130 that fits the outer diameter of the steel pipe GP is selected, and the placement guide 130 is attached to the main plate 110. In addition, an appropriate control collar 120 is selected according to the hole saw 200 to be used (especially the dimensions of the cutting blade 210) and the wall thickness of the steel pipe GP, and the center drill is removed from the hole saw 200 to be used.

[0040] After attaching the placement guide 130 to the main body plate 110, the main body plate 110 is placed on the surface of the steel pipe GP, the selected control collar 120 is positioned in the main body opening 110H, and the cutting blade 210 of the hole saw 200 is positioned in the collar opening 120H. Then, the rotating shaft 220 of the hole saw 200 is inserted through the insertion hole 140H, the housing 140 is attached to the main body plate 110 using the housing fixing bolt 141, and the main body plate 110 and the steel pipe GP are wrapped together with the fixing belt 150 (Step 301 in Figure 8).

[0041] Once the preparations are complete, the main body of the hole saw 200 is attached to the rotating shaft 220, and the cutting blade 210 is rotated by rotating the rotating shaft 220, thereby cutting the steel pipe GP (Step 302 in Figure 8). Cutting is continued until a part of the flange material 230 contacts the upper surface of the control collar 120, at which point the cutting operation by the hole saw 200 is stopped. As a result, a cutting groove CG is formed on the surface of the steel pipe GP (Step 303 in Figure 8). Then, the opening window OW is formed by removing (or punching out) the inside of the cutting groove CG (Step 304 in Figure 8). At this time, the inside of the cutting groove CG can be knocked out using a hammer and chisel, or the removed part can be peeled up and removed using a crowbar to prevent it from falling into the steel pipe GP.

[0042] Once the opening window OW is formed, the opening is expanded starting from the opening window OW (Step 305 in Figure 8), and then a "cutting" operation is performed to partially remove the steel pipe GP (Step 306 in Figure 8). Once the steel pipe GP is cut, predetermined operations are performed on the housed cables, for example. [Industrial applicability]

[0043] The cutting assist device and cutting method of the present invention can be particularly suitably used when creating opening windows in steel pipes containing various contents, including steel pipes housing cables and electric wires. Considering that the present invention reduces the need to cut cables and electric wires, and thus contributes to a stable supply of electricity, it is an invention that can be expected to make a significant contribution not only industrially but also socially. [Explanation of symbols]

[0044] 100 Cutting assist device of the present invention 110 (Main body plate of cutting aid device) 110H (Main body opening of the main body panel) 111 (Main plate) Placement guide mounting device 120 (Cutting aid device) control collar 120H (Control color) color aperture 130 (Placement guide for cutting aids) 140 (Cutting aid device) housing 140H (Housing) Through Hole 141 (Housing) Fixing bolts for housing 150 (Cutting assist device) fixing belt 200 Hole Saw 210 (Hole saw) cutting blade 220 (Hole saw) rotation axis 230 (Hole saw) flange material CG cutting groove GP steel pipe OW opening window

Claims

1. A device used when forming a cutting groove in a part of a steel pipe using a hole saw, A plate-shaped main body plate with an opening formed therein, A placement guide attached to the main body plate, A plate-shaped control collar having a color opening formed therein, The aforementioned arrangement guide is arc-shaped in cross-section, and its inner diameter is the same as or approximately the same as the outer diameter of the steel pipe. The aforementioned placement guide is positioned along the surface of the steel pipe, the control collar is positioned to be housed in the opening of the main body, and the cutting blade of the hole saw from which the center drill has been removed is positioned in the opening of the collar. As the cutting blade cuts through the steel pipe, a portion of the hole saw comes into contact with the upper surface of the control collar, thereby forming the cutting groove that does not penetrate the steel pipe. A cutting assist device characterized by the following features.

2. The arrangement guide is provided at two locations on the main body plate, The two placement guides are positioned so as to sandwich the main body plate, and the placement guides are then attached to the main body plate. The cutting assist device according to feature 1.

3. The housing further comprises a through hole formed therein. With the rotating shaft of the hole saw, in which the cutting blade is positioned within the collar opening, inserted through the insertion hole, the housing can be attached to the main body plate so as to cover the upper part of the main body opening. The cutting assist device according to feature 1.

4. The steel pipe on which the main plate is arranged is further provided with a fixing belt that can be wrapped around it. The main plate is fixed to the steel pipe by tightening the aforementioned fixing belt. The cutting assist device according to feature 1.

5. A method for forming an opening window in a part of a steel pipe using a cutting assist device and a hole saw, The cutting assist device comprises a plate-shaped main body plate with a main body opening formed therein, an arrangement guide attached to the main body plate, and a plate-shaped control collar with a collar opening formed therein. The aforementioned arrangement guide is arc-shaped in cross-section, and its inner diameter is the same as or approximately the same as the outer diameter of the steel pipe. An auxiliary device arrangement step involves arranging the cutting auxiliary device so that the arrangement guide follows the surface of the steel pipe, and arranging the control collar so that it is housed in the opening of the main body, A cutting step in which the cutting blade of the hole saw, from which the center drill has been removed, is placed in the collar opening, and the steel pipe is cut with the cutting blade to form a cutting groove, The process includes a window forming step of forming the opening window in a part of the steel pipe, In the cutting process, a portion of the hole saw contacts the upper surface of the control collar to form the cutting groove that does not penetrate the steel pipe. In the window forming step, the opening window is formed by removing the portion of the steel pipe surface surrounded by the cutting groove. A cutting method characterized by the following:

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