Drilling method using a core cutter

Abstract

To provide a boring method using a core cutter which is capable of preventing cutting chips from hindering boring operation.SOLUTION: A boring method uses a core cutter, and the core cutter has: a cylindrical base body; an attachment part to a rotary driving device provided on a base end side of the base body; a plurality of blade parts which are provided at a plurality of parts at an end of the base body with gaps from each other in a peripheral direction and at least whose ends protrude from the end of the base body; and a discharge groove which is provided between adjacent blade parts among the plurality of blade parts and discharges cutting chips cut by the blade parts to the base end side. The method has: a first step which bores a smaller hole than an area planned to be bored so as to include a part of an area planned to be cut that is an outer edge part in the area planned to be bored; and a second step which bores the area planned to be bored by cutting the area planned to be cut with the plurality of blade parts after the first step is performed.SELECTED DRAWING: Figure 6

Description

Technical Field

[0001] The present disclosure relates to a drilling method using a core cutter.

Background Art

[0002] Conventionally, a drilling method using a core cutter has been known. Such a drilling method has been proposed, for example, in Patent Document 1. The core cutter described in Patent Document 1 includes a cylindrical base body, a mounting portion on the side of a rotation drive device provided on the proximal end side of the base body, and a plurality of portions provided at a plurality of locations at intervals in the circumferential direction at the tip of the base body, at least the tip of which protrudes from the tip of the base body, and the outer surface of which is located radially outside the outer surface of the base body, a blade portion, and a discharge groove provided between adjacent blade portions among the plurality of blade portions for discharging the cutting chips cut by the blade portion to the proximal end side. In Patent Document 1, while rotating the base body of the core cutter by a rotation drive device, a part of the object to be drilled is drilled by pressing the plurality of blade portions against the object to be cut.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In Patent Document 1, there was a case where the cutting chips were not appropriately discharged from the discharge groove. In such a case, a problem occurred in that the cutting chips hindered the drilling operation.

[0005] Therefore, an object of the present disclosure is to provide a drilling method using a core cutter that can prevent cutting chips from hindering the drilling operation.

Means for Solving the Problems

[0006] In order to solve the above problems, a drilling method according to one aspect of the present disclosure is a drilling method using a core cutter, wherein the core cutter includes a cylindrical base body, a mounting portion on the side of a rotary drive device provided on the proximal end side of the base body, a plurality of blade portions provided at a plurality of positions spaced apart from each other in the circumferential direction at the tip of the base body, with at least the tips thereof protruding from the tip of the base body, a discharge groove provided between the adjacent blade portions among the plurality of blade portions for discharging the cutting chips cut by the blade portions to the proximal end side, and includes a first step of drilling a small hole smaller than the planned drilling area so as to include a part of a planned cutting area which is an outer edge portion of the planned drilling area, and a second step of drilling the planned drilling area by cutting the planned cutting area with the plurality of blade portions after performing the first step.

[0007] According to the above configuration, the cutting chips are segmented by the small hole drilled so as to include a part of the planned cutting area. As a result, the cutting chips are appropriately discharged from the discharge groove, so that the problem that the cutting chips hinder the drilling operation is solved.

Advantages of the Invention

[0008] According to the present disclosure, it is possible to provide a drilling method using a core cutter that can prevent cutting chips from hindering the drilling operation.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

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Figure 4

Figure 5A

Figure 5B

Figure 6

Figure 7A

Figure 7B

Figure 8

Figure 9A

Figure 9B

Figure 9C

Figure 9D

Figure 10

Embodiments for Carrying Out the Invention

[0010] (Structure of Core Cutter) FIG. 1 is a perspective view showing the overall structure of a core cutter used in a drilling method according to the first to third aspects of the present disclosure. FIG. 2 is an enlarged perspective view of the tip portion of the base portion and a plurality of blade portions of the core cutter shown in FIG. 1. FIG. 3 is a view of the core cutter shown in FIG. 1 as seen from the tip side. As shown in FIGS. 1 to 3, the core cutter A includes a cylindrical base body 1, a mounting portion 1A on the side of a rotation driving device 50 (see FIG. 4) provided on the proximal end side of the base body 1, a plurality of blade portions 2 provided at a plurality of positions spaced apart from each other in the circumferential direction at the tip of the base body 1, and at least the tips of which protrude from the tip of the base body 1, and a discharge groove 3 provided between adjacent blade portions 2 among the plurality of blade portions 2 for discharging the cutting chips cut by the blade portions 2 to the proximal end side.

[0011] The mounting portion 1A is formed with a mounting recess 1a having a partially chamfered shape. When mounting to the rotation driving device 50, the tip of a fixing bolt disposed in the axial center direction of the mounting provided on the rotation driving device 50 side abuts against the mounting recess 1a, and the core cutter A is configured to be fixed to the rotation driving device 50 side. Instead of this mounting recess 1a, other types of fixing means may be used, and these are variously prepared depending on the configuration of the mounting means on the rotation driving device side.

[0012] Each of the plurality of blade portions 2 has its outer surface located radially outside the outer surface of the base body 1. In this aspect, the blade portions 2 are provided at six positions at equal intervals in the circumferential direction. The blade portion 2 is constituted by a single chip body. In this aspect, the blade portion 2 is obtained by sintering a cemented carbide. That is, this blade portion 2 is composed of a so-called sintered alloy chip body. The blade portion 2 is not limited to a cemented carbide in terms of material, and may be a metal of other materials suitable as a cutting blade portion, and the forming method of the blade portion 2 may also be manufactured by a processing method other than the sintering method, for example, casting or machining. That is, the blade portion 2 may be a chip body having an integral form.

[0013] In the direction from the front toward the base end in the rotational direction (see arrow R) of the cutting edge 2, a discharge groove 3 is formed adjacent to the cutting edge 2. Toward the tip of the discharge groove 3, garnets 4 are formed continuously with the discharge groove 3 and located in front of the cutting edge 2, respectively. The discharge groove 3 and the garnets 4 are formed between blade forming portions 5 that are formed with reduced thickness at a plurality of locations circumferentially spaced apart in a part of the base body 1 corresponding to the cutting edge 2. Therefore, the front ends in the rotational direction of the garnets 4 and the discharge groove 3 are adjacent to the back surface 5A of the blade forming portion 5 in front in the rotational direction. Also, the wall surface 3b at the rear end of the discharge groove 3 coincides with the front surface 5B of the blade forming portion 5.

[0014] FIG. 4 is a perspective view showing a state in which the core cutter shown in FIG. 1 is attached to a rotational drive device. As shown in FIG. 4, the rotational drive device 50 has a center pin 52 that extends along the axis of the base body 1 and protrudes from the opening at the tip of the base body 1 in a state where the core cutter A is attached. The center pin 52 has a spring member (elastic body) that is axially expandable and contractible on its base end side, and when an external force is applied in its axial direction, its tip moves relative to the base body 1 to at least the same position as the tip of the base body 1 in the axial direction. With such a structure, when performing a drilling operation on a workpiece using the rotational drive device 50 and the core cutter A, the center pin 52 does not create a hole in the center of the drilling planned area DA described later.

[0015] (Drilling method according to the first aspect) Based on FIGS. 5A - 5B and 6, the drilling method according to the first aspect of the present disclosure will be described. FIGS. 5A - 5B are schematic views showing the state after performing the first - second steps in the drilling method according to this first aspect. In this first aspect, a part (drilling planned area DA shown in FIG. 5A) of a workpiece (for example, a steel plate, etc.) is drilled using the core cutter A attached to the rotational drive device 50 shown in FIG. 4. Also, in this first aspect, the drilling planned area DA has a shape and size corresponding to a circle connecting the tips of a plurality of cutting edges 2.

[0016] First, as shown in FIG. 5A, a small hole SH smaller than the planned drilling area DA is drilled so as to include a part of the planned cutting area CA which is the outer edge of the planned drilling area DA ( "step S1-1" in FIG. 6). In this first aspect, this step S1-1 corresponds to the first step. In this first aspect, as shown in FIG. 5A, in this step S1-1, the small hole SH is drilled at one location including a part of the planned cutting area CA. Further, in this first aspect, the small hole SH is drilled by a drilling device provided separately from the rotary drive device 50 and the core cutter A. Note that this drilling device may have, for example, a structure including a rotary drive device having a center drill and a core cutter described later, or may have another structure.

[0017] Next, as shown in FIG. 5B, the planned drilling area DA is drilled by cutting the planned cutting area CA with a plurality of blade portions 2 ( "step S1-2" in FIG. 6). In this first aspect, this step S1-2 corresponds to the second step. In this first aspect, as described above, since the planned drilling area DA has a shape and size corresponding to a circle connecting the tips of the plurality of blade portions 2, while rotating the base body 1 by the rotary drive device 50, the plurality of blade portions 2 are pressed against the entire planned cutting area CA, whereby the planned cutting area CA can be cut and the planned drilling area DA can be drilled.

[0018] (Effect of the drilling method according to the first aspect) In the drilling method according to this first aspect, the cutting chips are segmented by the small hole SH drilled so as to include a part of the planned cutting area CA and are appropriately discharged from the discharge groove 3. Thereby, for example, it is possible to prevent the cutting chips from becoming relatively long and not being appropriately discharged from the discharge groove 3, getting entangled with the core cutter A, and hindering the rotational operation of the core cutter A. Further, it is possible to prevent the cutting chips from blocking the discharge groove 3, and the heat generated during drilling is appropriately released from the discharge groove 3. Therefore, for example, even when coolant oil cannot be used, the drilling method according to this first aspect can be effectively utilized. Since it is as described above, by using the drilling method according to this first aspect, it is possible to prevent the cutting chips from interfering with the drilling operation.

[0019] In the drilling method according to this first aspect, since a small hole SH is drilled at one location including a part of the planned cutting area CA, step S1-1 (the first step) can be easily performed.

[0020] (Drilling method according to the second aspect) Based on FIGS. 7A-7B and 8, the drilling method according to the second aspect of the present disclosure will be described. FIGS. 7A-7B are schematic views showing the state after performing the first and second steps in the drilling method according to this second aspect. In this second aspect, step S2-1 shown in FIG. 8 corresponds to step S1-1 and the first step shown in FIG. 6. Also, in this second aspect, step S2-2 shown in FIG. 8 corresponds to step S1-2 and the second step shown in FIG. 6. The drilling method according to this second aspect is the same as the drilling method according to the above-described first aspect, except that three small holes SH are drilled in step S2-1 as shown in FIG. 7A. Therefore, the same reference numerals are assigned to the same parts, and the same explanations will not be repeated.

[0021] In this second aspect, as shown in FIG. 5A, in step S2-1, small holes SH are drilled at three locations including a part of the planned cutting area CA. The three small holes SH are drilled at equal intervals from each other in the circumferential direction of the planned cutting area CA.

[0022] (Effect of the drilling method according to the second aspect) In the drilling method according to this second aspect, since small holes SH are drilled at three locations including a part of the planned cutting area CA, compared with the drilling method according to the above-described first aspect, the cutting chips are more fragmented and discharged more appropriately from the discharge groove 3. Other effects are the same as those of the drilling method according to the above-described first aspect.

[0023] (Drilling method according to the third aspect) Based on FIGS. 9A - 9D and 10, the drilling method according to the third aspect of the present disclosure will be described. FIGS. 9A - 9D are schematic views showing the state after performing the first, third - fifth steps in the drilling method according to this third aspect. In this third aspect, similar to the above - described first and second aspects, a core cutter A attached to the rotational drive device 50 shown in FIG. 4 is used to drill a part (drilling planned area DA' shown in FIG. 9A) of the workpiece (for example, a steel plate, etc.).

[0024] In this third aspect, the cutting planned area CA' includes a cutting planned area CAa (first cutting planned area) that includes at least a part of the small hole SH, a cutting planned area CAb (second cutting planned area) adjacent to the cutting planned area CAa and sharing a part of the cutting planned area CAa, and a cutting planned area CAo (third cutting planned area) adjacent to the cutting planned area CAa from the opposite side of the cutting planned area CAb and sharing a part of the cutting planned area CAa. In this third aspect, the cutting planned area CA' further includes a cutting planned area CAc (fourth cutting planned area) adjacent to the cutting planned area CAb from the opposite side of the cutting planned area CAa and sharing a part of the cutting planned area CAb, and a cutting planned area CAn (fourth cutting planned area) adjacent to the cutting planned area CAo from the opposite side of the cutting planned area CAa and sharing a part of the cutting planned area CAo.

[0025] In this third aspect, the planned cutting area CA´ includes a planned cutting area CAd that is adjacent to the planned cutting area CAc from the opposite side of the planned cutting area CAb and shares a part of the planned cutting area CAc, and a planned cutting area CAm that is adjacent to the planned cutting area CAn from the opposite side of the planned cutting area CAo and shares a part of the planned cutting area CAn. In this third aspect, the planned cutting area CA´ further includes a planned cutting area CAe that is adjacent to the planned cutting area CAd from the opposite side of the planned cutting area CAc and shares a part of the planned cutting area CAd, and a CAl that is adjacent to the planned cutting area CAm from the opposite side of the planned cutting area CAn and shares a part of the planned cutting area CAm. In this third aspect, the planned cutting area CA´ further includes a planned cutting area CAf that is adjacent to the planned cutting area CAe from the opposite side of the planned cutting area CAd and shares a part of the planned cutting area CAe, and a planned cutting area CAk that is adjacent to the planned cutting area CAl from the opposite side of the planned cutting area CAm and shares a part of the planned cutting area CAl.

[0026] In this third aspect, the planned cutting area CA´ further includes a planned cutting area CAg that is adjacent to the planned cutting area CAf from the opposite side of the planned cutting area CAe and shares a part of the planned cutting area CAf, and a planned cutting area CAj that is adjacent to the planned cutting area CAk from the opposite side of the planned cutting area CAl and shares a part of the planned cutting area CAk. In this third aspect, the planned cutting area CA´ further includes a planned cutting area CAh that is adjacent to the planned cutting area CAg from the opposite side of the planned cutting area CAf and shares a part of the planned cutting area CAg, and a planned cutting area CAi that is adjacent to the planned cutting area CAj from the opposite side of the planned cutting area CAk and shares a part of the planned cutting area CAj. The planned cutting area CAi is adjacent to the planned cutting area CAh from the opposite side of the planned cutting area CAg and shares a part of the planned cutting area CAh.

[0027] In this third aspect, the outer edge of the planned drilling area DA´ includes a planned drilling area DAa (first planned drilling area) with the outer edge of the planned cutting area CAa, a planned drilling area DAb (second planned drilling area) with the outer edge of the planned cutting area CAb, and a planned drilling area DAc with the outer edge of the planned cutting area CAc. Also, in this third aspect, the outer edge of the planned drilling area DA´ further includes planned drilling areas DAd - DAo with the outer edges of the planned cutting areas CAd - CAo. In this third aspect, the planned drilling area DAo corresponds to the third planned drilling area, and the planned drilling areas DAc and DAl correspond to the fourth planned drilling area.

[0028] In this third aspect, the planned drilling area DA´ is circular and larger than the circle connecting the tips of the plurality of cutting edges 2. Specifically, as shown in Fig. 9A, the planned drilling area DA´ is circular and includes a perfect circle with a diameter φ. As shown in Fig. 9A, the planned cutting areas CAa - CAo are arranged in parallel on this perfect circle. Also, in this third aspect, the planned drilling areas DAa - DAo respectively have shapes and sizes corresponding to the circles connecting the tips of the plurality of cutting edges 2.

[0029] First, as shown in Fig. 9A, a small hole SH smaller than the planned drilling area DA´ is drilled so as to include a part of the planned cutting area CA´ which is the outer edge of the planned drilling area DA´ ( "step S3 - 1" in Fig. 10). In this third aspect, this step S3 - 1 corresponds to the first step. In this third aspect, as shown in Fig. 9A, in this step S3 - 1, a small hole SH is drilled at one location including a part of the planned cutting area CA´. In this third aspect, the small hole SH is drilled radially outside the perfect circle with a diameter φ by a drilling device provided separately from the rotary drive device 50 and the core cutter A.

[0030] Next, as shown in Fig. 9B, while rotating the base body 1 by the rotary drive device 50, the plurality of cutting edges 2 are pressed against the entire planned cutting area CAa to cut the planned cutting area CAa and drill the planned drilling area DAa ( "step S3 - 2" in Fig. 10). In this third aspect, this step S3 - 2 corresponds to the third step.

[0031] Next, as shown in FIG. 9C, while rotating the base body 1 by the rotary drive device 50, the plurality of blade portions 2 are pressed against the entire cutting planned area CAb, thereby cutting the cutting planned area CAb and drilling the drilling planned area DAb (in FIG. 10, "step S3-3"). In this third aspect, this step S3-3 corresponds to the fourth step.

[0032] Next, while rotating the base body 1 by the rotary drive device 50, the plurality of blade portions 2 are pressed against the entire cutting planned area CAc, thereby cutting the cutting planned area CAc and drilling the drilling planned area DAc (in FIG. 10, "step S3-4"). In this third aspect, this step S3-4 corresponds to the sixth step.

[0033] Next, while rotating the base body 1 by the rotary drive device 50, the plurality of blade portions 2 are pressed against the entire cutting planned area CAc, thereby cutting the cutting planned area CAc and drilling the drilling planned area DAc (in FIG. 10, "step S3-4"). In this third aspect, this step S3-4 corresponds to the sixth step.

[0034] Furthermore, by sequentially cutting the cutting planned areas DAd - DAl, the drilling planned areas CAa - CAl are sequentially drilled (in FIG. 10, "step S3-5" to "step S3-15". To avoid visual complexity, these steps are indicated by "···").

[0035] Finally, while rotating the base body 1 by the rotary drive device 50, the plurality of blade portions 2 are pressed against the entire cutting planned area CAo, thereby cutting the cutting planned area CAo and drilling the drilling planned area DAc, and drilling the drilling planned area DA' (in FIG. 10, "step S3-16"). In this third aspect, this step S3-16 corresponds to the fifth step.

[0036] (Effect of the drilling method according to the third aspect) In the drilling method according to this third aspect, by performing the drilling operation as described above, the drilling area can be enlarged as compared with the circle connecting the tips of the plurality of blade portions 2. Other effects are the same as those of the drilling methods according to the above-described first and second aspects.

[0037] (Modification example) From the above description, many improvements and other embodiments of the present disclosure will be apparent to those skilled in the art. Therefore, the above description should be construed as illustrative only and is provided for the purpose of teaching those skilled in the art the best mode of carrying out the present disclosure. Without departing from the spirit of the present disclosure, the details of its structure and / or function can be substantially changed.

[0038] The drilling methods according to the above-described first to third aspects have been described for the case where they are performed using the core cutter A described with reference to FIGS. 1 to 4. However, the present disclosure is not limited to this case. For example, the drilling may be performed using a core cutter having a structure different from that of the core cutter A, such that the outer surfaces of the plurality of blade portions 2 are respectively arranged at the same position in the radial direction as the outer surface of the base body 1.

[0039] In the drilling method according to the above-described first to third aspects, the case where the small hole SH is drilled by a drilling device provided separately from the rotation driving device 50 and the core cutter A in the first step has been described. However, the present disclosure is not limited to this case. For example, when the rotation driving device 50 has a center drill instead of the center pin 52, the small hole SH may be drilled by this center drill. Here, the center drill is different from the center pin 52 and does not have a spring member (elastic body) that can expand and contract in its axial direction. Even if an external force is applied in its axial direction, it does not move relative to the base body 1 in its axial direction. With such a structure, when performing a drilling operation on a workpiece using a rotation driving device having a center drill and a core cutter, a hole will be formed at the center of the planned drilling area by the center drill. By performing the drilling method according to the present disclosure using the rotation driving device and the core cutter as described above, the above-described first and second steps can be performed using the same device, thereby improving convenience.

[0040] In the drilling method according to the second aspect described above, the case where small holes SH are drilled at three positions in the first step has been described. However, the present invention is not limited to this case. For example, depending on the material and shape of the object to be drilled, the small holes SH may be drilled at two positions or four or more positions.

[0041] In the drilling method according to the third aspect described above, the case where a small hole SH is drilled at one position in the first step has been described. However, the present invention is not limited to this case. For example, depending on the material and shape of the object to be drilled, the small holes SH may be drilled at a plurality of positions. Further, in the drilling method according to the third embodiment described above, the case where the small hole SH is drilled outside the radial direction of the perfect circle with diameter φ has been described. However, the present invention is not limited to this case, and the small hole SH may be drilled inside the radial direction of the perfect circle with diameter φ, or the small hole SH may be drilled on the perfect circle with diameter φ.

[0042] In the drilling method according to the third aspect described above, the case where the cutting planned areas CA´ include fifteen cutting planned areas CAa - CAo arranged in parallel with each other has been described. However, the present invention is not limited to this case, and the cutting planned areas CA´ may include three or more and fourteen or less or sixteen or more cutting planned areas arranged in parallel with each other.

[0043] In the drilling method according to the third aspect described above, the case where the drilling planned area DA´ is circular has been described. However, the present invention is not limited to this case. By appropriately changing the number or parallel arrangement mode of the cutting planned areas CAa - CAo, the drilling planned area DA´ may be, for example, any polygon, star shape, and other shapes.

[0044] (Summary) In order to solve the above problems, a drilling method according to an aspect of the present disclosure is a drilling method using a core cutter, where the core cutter includes a cylindrical base body, a mounting portion provided on the proximal end side of the base body for attachment to a rotary drive device, a plurality of blade portions provided at a plurality of locations spaced apart from each other in the circumferential direction at the tip of the base body, with at least the tips thereof protruding from the tip of the base body, and a discharge groove provided between adjacent ones of the plurality of blade portions for discharging the cutting chips cut by the blade portions toward the proximal end side. The method includes a first step of drilling a small hole smaller than the planned drilling area so as to include a part of the planned cutting area which is the outer edge of the planned drilling area, and a second step of drilling the planned drilling area by cutting the planned cutting area with the plurality of blade portions after the first step.

[0045] According to the above configuration, the cutting chips are segmented by the small hole drilled so as to include a part of the planned cutting area. As a result, the cutting chips can be appropriately discharged from the discharge groove, so that it is possible to prevent the cutting chips from interfering with the drilling operation.

[0046] In the first step, the small hole may be drilled at one location including a part of the planned cutting area.

[0047] According to the above configuration, the first step can be easily performed.

[0048] In the first step, the small hole may be drilled at a plurality of locations including a part of the planned cutting area.

[0049] According to the above configuration, the cutting chips can be discharged more appropriately from the discharge groove.

[0050] The rotation driving device has a center pin that extends along the axis of the base body within the internal space of the base body and protrudes from the opening at the tip of the base body. The center pin has an elastic body that can expand and contract in its axial direction. When an external force is applied in the axial direction, its tip moves relative to the base body to at least the same position as the tip of the base body in the axial direction. In the first step, the small hole is drilled by a drilling device provided separately from the rotation driving device and the core cutter.

[0051] For example, each of the plurality of blade portions may have an outer surface located radially outside the outer surface of the base body.

[0052] The planned drilling area has a shape and size corresponding to a circle connecting the tips of the plurality of blade portions. In the second step, while rotating the base body by the rotation driving device, the plurality of blade portions may be pressed against the entire cutting planned area to cut the cutting planned area and drill the planned drilling area.

[0053] According to the above configuration, the second step can be easily performed.

[0054] The planned cutting area includes a first planned cutting area that includes at least a part of the small hole, a second planned cutting area that is adjacent to the first planned cutting area and shares the first planned cutting area and a part thereof, and a third planned cutting area that is adjacent to the first planned cutting area from the opposite side of the second planned cutting area and shares the first planned cutting area and a part thereof. The outer edge of the planned drilling area includes a first planned drilling area with the first planned cutting area as the outer edge, a second planned drilling area with the second planned cutting area as the outer edge, and a third planned drilling area with the third planned cutting area as the outer edge. The planned cutting area is larger than a circle connecting the tips of the plurality of cutting edges. The first to third planned drilling areas respectively have shapes and sizes corresponding to the circle connecting the tips of the plurality of cutting edges. The second step may include a third step of cutting the first planned cutting area and drilling the first planned drilling area by pressing the plurality of cutting edges against the entire first planned cutting area while rotating the base by the rotational drive device, a fourth step of cutting the second planned cutting area and drilling the second planned drilling area by pressing the plurality of cutting edges against the entire second planned cutting area while rotating the base by the rotational drive device after performing the third step, and a fifth step of cutting the third planned cutting area and drilling the third planned drilling area and drilling the planned drilling area by pressing the plurality of cutting edges against the entire third planned cutting area while rotating the base by the rotational drive device after performing the fourth step.

[0055] According to the above configuration, the drilling area can be enlarged as compared with the circle connecting the tips of the plurality of cutting edges.

[0056] The planned cutting area is adjacent to at least one of the second and third planned cutting areas from the opposite side of the first planned cutting area, and further includes a fourth planned cutting area that shares a part with at least one of the second and third planned cutting areas. The outer edge of the planned drilling area further includes a fourth planned drilling area with the fourth planned cutting area as the outer edge. The fourth planned drilling area has a shape and size corresponding to a circle connecting the tips of the plurality of blade parts. After performing the fourth step and before performing the fifth step, the second step may further include a sixth step of pressing the plurality of blade parts against the entire fourth planned cutting area while rotating the base body by the rotational drive device, thereby cutting the fourth planned cutting area and drilling the fourth planned drilling area.

[0057] According to the above configuration, the drilling area can be made even larger compared to the circle connecting the tips of the plurality of blade parts.

Explanation of Signs

[0058] A Core Cutter 1 Base 1A Mounting Part 1a Mounting Recess 2 Blade Part 3 Discharge Groove 50 Rotational Drive Device 52 Center Pin SH Small Hole CA, CA´, CAa - CAo Planned Cutting Area DA, DA´, DAa - DAo Planned Drilling Area

Claims

1. A drilling method using a core cutter, comprising: the core cutter includes a cylindrical base body, a mounting portion provided on the proximal end side of the base body for attachment to a rotary drive device, a plurality of blade portions provided at a plurality of locations on the tip of the base body with a circumferential interval therebetween, at least the tips of which protrude from the tip of the base body, and a discharge groove provided between adjacent ones of the plurality of blade portions for discharging the cutting chips cut by the blade portions to the proximal end side; the rotary drive device has a center drill that extends along the axis of the inner space of the base body and protrudes from the opening at the tip of the base body, and does not move relative to the base body in the axial direction even when an external force is applied in the axial direction; a first step of drilling a small hole smaller than the planned drilling area with the center drill so as to include a part of a cutting planned area that is an outer edge of the planned drilling area; a second step of drilling the planned drilling area by cutting the cutting planned area with the plurality of blade portions after performing the first step. The drilling method is characterized by comprising the above steps.

2. The drilling method according to claim 1, wherein in the first step, the small hole is drilled at one location including a part of the cutting planned area.

3. The drilling method according to claim 1, wherein in the first step, the small holes are drilled at a plurality of locations including a part of the cutting planned area.

4. In the drilling method according to any one of claims 1 to 3, each of the plurality of blade portions has an outer surface located radially outside the outer surface of the base body.

5. The planned drilling area has a shape and size corresponding to a circle connecting the tips of the plurality of blade portions. In the second step, while rotating the base body by the rotary drive device, the plurality of blade portions are pressed against the entire cutting planned area, thereby cutting the cutting planned area and drilling the planned drilling area. The drilling method according to any one of claims 1 to 4.

6. The planned cutting area includes a first planned cutting area including at least a part of the small hole, a second planned cutting area adjacent to the first planned cutting area and sharing a part of the first planned cutting area therewith, a third planned cutting area adjacent to the first planned cutting area from the opposite side of the second planned cutting area and sharing a part of the first planned cutting area therewith, and a plurality of fourth planned cutting areas located between the second planned cutting area and the third planned cutting area so as to connect the second planned cutting area and the third planned cutting area. Among the plurality of the fourth planned cutting areas, the fourth planned cutting areas adjacent to each other share a part of each other. The fourth planned cutting area adjacent to the second planned cutting area among the plurality of the fourth planned cutting areas shares a part of the second planned cutting area therewith. The fourth planned cutting area adjacent to the third planned cutting area among the plurality of the fourth planned cutting areas shares a part of the third planned cutting area therewith. The outer edge of the planned drilling area includes a first planned drilling area with the first planned cutting area as the outer edge, a second planned drilling area with the second planned cutting area as the outer edge, a third planned drilling area with the third planned cutting area as the outer edge, and a plurality of fourth planned drilling areas with the plurality of the fourth planned cutting areas as the outer edges. The planned cutting area is larger than a circle connecting the tips of the plurality of cutting edges. The first to third planned drilling areas and the plurality of fourth planned drilling areas each have a shape and size corresponding to the circle connecting the tips of the plurality of cutting edges. The second step is a third step of cutting the first planned cutting area and drilling the first planned drilling area by pressing the plurality of cutting edges against the entire first planned cutting area while rotating the base by the rotational drive device; a fourth step of cutting the second planned cutting area and drilling the second planned drilling area by pressing the plurality of cutting edges against the entire second planned cutting area while rotating the base by the rotational drive device after performing the third step; a fifth step of cutting the third planned cutting area and drilling the third planned drilling area and drilling the planned drilling area by pressing the plurality of cutting edges against the entire third planned cutting area while rotating the base by the rotational drive device after performing the fourth step; After performing the fourth step and before performing the fifth step, while rotating the base body by the rotary drive device, by pressing a plurality of the blade portions against the entirety of any one of the plurality of fourth planned cutting regions, any one of the plurality of fourth planned cutting regions is cut and any one of the plurality of fourth planned punching regions is punched repeatedly, and a sixth step of cutting a plurality of the fourth planned cutting regions and punching a plurality of the fourth planned punching regions is included. The punching method according to any one of claims 1 to 4.

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