Drilling tools

Abstract

By adding a thickness measurement function to the drilling tool itself, we provide a drilling tool that can accurately measure the thickness dimension without damaging the material being drilled. [Solution] A drilling tool 1 is provided with a shaft portion 3 having a cutting portion 2 at its tip, and a tool attachment portion 4 at the rear end of the shaft portion 3, such that the outer diameter of the shaft portion 3 matches the maximum cutting diameter of the cutting portion 2. A recessed portion 6 is provided in a part of the shaft portion 3, forming an eccentric shaft portion 3a in the remaining part of the shaft portion 3. The recessed portion 6 is set such that the width of the eccentric shaft portion 3a is narrower than the diameter of the maximum cutting diameter of the cutting portion 2, and the length along the axial direction is such that it can fit to the thickness of the material to be drilled, thereby making the recessed portion 6 a thickness measuring fitting portion.

Description

Technical Field

[0001] The present invention relates to a drilling tool used for drilling through-holes in a pierced member made of a fragile material, and more particularly to a drilling tool for drilling a pilot hole for inserting a base metal fitting into a wall material when attaching various equipment and instruments to a wall material made of gypsum board serving as the pierced member, wherein the base metal fitting serves as a base for attachment; the drilling tool is capable of continuously and simultaneously performing the drilling of the pilot hole in the wall material and the checking of the thickness dimension of the wall material.

Background Art

[0002] When various equipment and instruments are to be attached to a wall surface using gypsum board, which is exemplified as the aforementioned fragile pierced member, as the wall material, the required fixing strength cannot be obtained if the instruments are directly fixed with screws or the like. Therefore, an attachment method has been adopted in which a base metal fitting capable of providing sufficient fixing strength, such as plugs and anchors, is used as the attachment base, fixed by inserting it into a pilot hole drilled in the wall material, and then various equipment and instruments are fixed to the base metal fitting. For this reason, when drilling a pilot hole for inserting the base metal fitting into the wall material, a special drilling tool having a structure corresponding to the fragility of the wall material is used.

[0003] In the conventional drilling tool described above, as disclosed in Patent Document 1 and Patent Document 2, a cutting portion is provided at the tip end of a shaft portion, and a mounting portion for a rotary tool is provided at the rear end end in a coaxial arrangement; a large-diameter flange for insertion restriction is provided between the rear end of the shaft portion and the mounting portion. The outer diameter of the shaft portion matches the maximum cutting diameter of the cutting portion, and the axial length is set to be capable of penetrating through the plate thickness of the gypsum board. Furthermore, a spiral groove for discharging cutting chips during drilling is formed on the outer peripheral surface. The drilling tool is mounted on a rotary tool via the mounting portion, and the cutting portion is pressed against the gypsum board and rotated to drill a pilot hole.

[0004] By the way, gypsum boards used as wall coverings come in various thicknesses, from thin to thick. Naturally, the base fittings used to fix these gypsum boards must be the same length as the thickness of the gypsum board. Therefore, there are as many types of base fittings as there are thicknesses of gypsum boards, and when using them, you must select the length that corresponds to the thickness of the gypsum board. For this reason, checking the thickness of the gypsum board is an essential requirement when using base fittings.

[0005] The conventional drilling tools described above allow drilling into materials ranging from thin to thick by setting the length of the shaft to correspond to the maximum thickness dimension of the gypsum board, but the drilling tool itself only has the function of drilling pilot holes.

[0006] By the way, when attempting to fix base brackets to an existing wall, it is impossible to determine the thickness of the gypsum board used as the wall material simply by looking at the surface of the wall.

[0007] Therefore, when checking the thickness of gypsum board used as a wall material in an existing wall, using the pre-drilled hole has the advantage of not causing unnecessary damage to the wall material. Specific methods include simply looking into the pre-drilled hole to make a judgment, or inserting a thin rod-shaped object along the inner surface of the pre-drilled hole and sliding it along, checking the insertion length by the change in feel when the tip of the rod reaches the back side, and separately, using a dedicated thickness measuring tool to insert a thin rod-shaped object into the pre-drilled hole after removing the drilling tool to measure the thickness. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] Japanese Patent Publication No. 2001-79783 [Patent Document 2] Utility Model Registration No. 3081613 Gazette [Patent Document 3] Japanese Patent Publication No. 2018-112428 [Overview of the project] [Problems that the invention aims to solve]

[0009] In the thickness measurement methods described above, the former method of looking into the pilot hole or using a rod-shaped object cannot accurately determine the thickness, which can lead to errors in selecting the base fitting. Attempting to install a base fitting that is unsuitable for the thickness can result in damage to the pilot hole in the plasterboard or make it impossible to secure the base fitting itself.

[0010] Furthermore, conventional measuring tools used in the latter measurement method, as shown in Publication 3, have a structure in which a rod-shaped body extends in a straight line has a tip that has elasticity to bend laterally and return to a fixed position, and a contact part is provided at the tip of the rod-shaped body to contact the back of the gypsum board, and the rod-shaped body is marked with a thickness indicator scale. The rod-shaped body is inserted into a pilot hole, the contact part is passed through to the back of the gypsum board, and the rod-shaped body is pulled towards the surface of the wall to engage the contact part with the back of the gypsum board, and the thickness dimension of the gypsum board can be determined by checking the scale on the rod-shaped body on the surface of the gypsum board.

[0011] However, using the thickness measuring tool described above requires a separate measurement operation after the drilling process, where the drilling tool is removed from the pilot hole. Since drilling and thickness measurement are separate operations, this increases the number of work steps and reduces efficiency. Furthermore, it incurs additional costs for purchasing the thickness measuring tool and the hassle of managing the tool, in addition to the drilling tool itself.

[0012] Furthermore, in the above-mentioned thickness measuring tool, the contact portion provided at the tip of the rod-shaped body has a structure that provides elasticity to return to its fixed position. Therefore, when the contact portion is inserted into the pilot hole, it scrapes the inner surface of the pilot hole, and when it is forcibly removed, it scrapes the inner surface of the pilot hole. As a result, there is a concern that the area around the drilled pilot hole in the gypsum board may be damaged, reducing the fixing strength of the base fitting to the gypsum board.

[0013] Therefore, the objective of this invention is to provide a drilling tool that adds a thickness measuring function to the drilling tool itself, thereby enabling accurate measurement of thickness dimensions without damaging the material to be drilled, improving the efficiency of installation work for various equipment, and eliminating the need for a separate dedicated thickness measuring tool, thereby saving on purchase costs and management effort associated with such a tool. [Means for solving the problem]

[0014] To solve the above-mentioned problems, the invention of claim 1 provides a drilling tool in which a tool attachment portion is provided at the rear end of a shaft portion having a cutting portion at its tip, and the outer diameter of the shaft portion is adapted to the maximum cutting diameter of the cutting portion, wherein a recessed portion is provided in a part of the shaft portion for fitting onto the thickness of the material to be drilled, the remaining part of the shaft portion relative to the recessed portion is formed into an eccentric shaft portion, the conditions of the recessed portion are set such that the width of the eccentric shaft portion corresponding to the bottom surface of the recessed portion is narrower than the diameter of the maximum cutting diameter of the cutting portion, and the length along the axial direction of the shaft portion is set to a length dimension that can fit onto the thickness of the material to be drilled, and a first end surface is formed at the end of the recessed portion on the cutting portion side for contacting the back surface of the material to be drilled, thereby making the recessed portion a thickness measuring fitting portion.

[0015] The invention of claim 2 is configured such that the positional relationship between the thickness measuring fitting portion and the cutting portion is such that the rear end of the cutting blade formed in the cutting portion faces the front end of the thickness measuring fitting portion, and the cutting portion is perpendicular to the width direction on the inner surface of the thickness measuring fitting portion.

[0016] The invention of claim 3 is characterized in that the first end surface, which is provided to contact the back surface of the member to be drilled at the tip side of the thickness measuring fitting portion, is formed by the rear end edge of the cutting portion.

[0017] The invention of claim 4 is such that the inner surface of the eccentric shaft portion, which corresponds to the bottom surface of the thickness measuring fitting portion, is divided by a helical groove with a recessed portion, and both side edges of the helical groove have a shape in which the peaks and valleys of the helical groove are arranged alternately, and the width direction of this inner surface is formed into an arc-shaped surface that bulges inward into the recessed portion.

[0018] The invention of claim 5 is characterized in that a second cutting blade is provided at the base of the cutting blade in the cutting section, having a drilling diameter that matches the maximum drilling diameter made by the cutting section.

[0019] Here, the shaft portion has a cylindrical shaft portion at the rear end located on the fitting side, with an outer diameter that matches the maximum cutting diameter of the cutting portion, and this cylindrical shaft portion is located for a length of about one pitch of the helical groove. This cylindrical shaft portion, the mounting portion, and the tip of the cutting portion are aligned coaxially, the arcuate outer diameter of the eccentric shaft portion matches the outer diameter of the cylindrical shaft portion, and the end face of the cylindrical shaft portion facing the recessed portion becomes a second end face that determines one of the lengths of the recessed portion. [Effects of the Invention]

[0020] According to this invention, in a drilling tool for drilling pilot holes in a fragile material, the thickness measurement of the material to be drilled can be performed simultaneously with drilling the pilot hole, before removing the drilling tool from the pilot hole at the end of the pilot hole drilling process. Compared to when pilot hole drilling and thickness measurement are performed separately, the number of work steps is reduced, thereby improving work efficiency.

[0021] Furthermore, by incorporating a thickness measurement function into the drilling tool, the need to prepare a separate thickness measuring device is eliminated, resulting in reduced costs associated with thickness measuring devices and simplification of tool management.

[0022] Furthermore, for measuring the thickness dimension, the drilling tool that has drilled the pilot hole can be moved laterally and in the pulling-out direction without being pulled out, and after measurement, it can be returned to the original position by lateral movement and then pulled out. Therefore, thickness measurement can be performed without causing damage or breakage to the inner circumference and the periphery of the pilot hole. Moreover, since the thickness can be measured based on the protruding state from the wall surface, the thickness can be measured accurately, and the occurrence of inconveniences caused by selecting a base bracket incompatible with the thickness of the member to be drilled can be prevented. Brief Description of the Drawings

[0023] [Figure 1] Front view of the drilling tool according to the present invention [Figure 2] Left side view of the same [Figure 3] Right side view of the same [Figure 4] Rear view of the same [Figure 5] Longitudinal sectional side view taken along arrow A-A in Fig. 1 [Figure 6] Perspective view showing the external shape of the above drilling tool [Figure 7] Cross-sectional view taken along arrow B-B in Fig. 1 [Figure 8] Cross-sectional side view taken along arrow C-C in Fig. 1 [Figure 9] Cross-sectional plan view showing a thickness measurement state after a pilot hole is drilled by the drilling tool, in a case where the thickness of a gypsum board is 9.5 mm [Figure 10] Cross-sectional plan view showing a thickness measurement state after a pilot hole is drilled by the drilling tool, in a case where the thickness of a gypsum board is 12 mm [Figure 11] Cross-sectional plan view showing a thickness measurement state after a pilot hole is drilled by the drilling tool, in a case where the thickness of a gypsum board is 15 mm [Figure 12] Cross-sectional plan view showing a thickness measurement state after a pilot hole is drilled by the drilling tool, in a case where the thickness of a gypsum board is 21 mm Mode for Carrying Out the Invention

[0024] Hereinafter, embodiments of this invention will be described in detail based on the attached drawings.

[0025] As shown in the figure, the drilling tool 1 is used to drill a pilot hole b in a gypsum board a, which is a fragile wall material such as gypsum board a, in order to fix the base fitting that will serve as the mounting base for various equipment. The tool is formed by a shaft portion 3 having a cutting portion 2 at its tip, and a mounting portion 4 of a well-known structure that fits onto a rotary tool at the rear end of the shaft portion 3, and a flange 5 that restricts the drilling stroke between the rear end of the shaft portion 3 and the mounting portion 4. The mounting portion 4 is attached to a rotary tool, and the cutting portion 2 is pressed against the gypsum board a and rotated to drill the pilot hole b with the cutting portion 2.

[0026] The shaft portion 3 of the drilling tool 1 has a recessed portion 6 in a part thereof, and the remaining portion that is left over from the recessed portion 6 becomes the eccentric shaft portion 3a, and the bottom surface of the recessed portion 6 corresponds to the inner surface 6a of the eccentric shaft portion 3a. Regarding the depth and length of the recessed portion 6, the depth condition is set so that the width of the inner surface 6a of the eccentric shaft portion 3a is narrower than the diameter of the maximum cutting diameter of the cutting portion 2, and the length condition along the axial direction of the shaft portion 3 is set so that it can fit to the thickness dimension of the gypsum board a, so that the recessed portion 6 becomes a thickness measuring fitting portion.

[0027] In the shaft portion 3 described above, the basic structure before the recessed portion 6 was provided was a circular shaft with a diameter matching the maximum cutting diameter of the cutting portion 2, and its axis was coaxial with the cutting portion 2 and the mounting portion 4, with a helical groove 7 for discharging chips provided along its entire length on the outer surface.

[0028] As shown in Figures 7 and 8, by providing a recessed portion 6 to the circular shaft which is the basic structure of the shaft portion 3, the portion of the shaft portion 3 that remains after being cut out by the recessed portion 6 becomes an eccentric shaft portion 3a with a cross-sectional shape that is slightly narrower than a semicircle. As shown in Figure 2, both side edges of the inner surface 6a of this eccentric shaft portion 3a, which corresponds to the bottom surface of the recessed portion 6, are divided by the spiral groove 7, resulting in a structure where the peaks 7a and valleys 7b of the spiral groove 7 are arranged alternately along the axial direction. As shown in Figure 3, the arc-shaped outer surface of the eccentric shaft portion 3a where the outer surface of the circular shaft remains has the divided spiral groove 7 remaining, thereby maintaining the chip discharge function.

[0029] Furthermore, in the eccentric shaft portion 3a, the inner surface 6a corresponding to the bottom surface of the notch portion 6 may be a simple flat surface, but as shown in Figures 7 and 8, it may be formed as an arc-shaped surface that bulges in the width direction toward the recessed portion 6, thereby increasing the cross-sectional area of ​​the eccentric shaft portion 3a and improving its strength.

[0030] In the illustrated example, a cylindrical shaft portion 3b is provided between the rear end of the recessed portion 6 of the shaft portion 3 and the flange 5, leaving the basic shaft portion intact, for a length of approximately one pitch in the peak portion 7a of the helical groove 7. This cylindrical shaft portion 3b is aligned coaxially with respect to the axis connecting the tip of the mounting portion 4 and the cutting portion 2, and its end face facing the recessed portion 6 is designated as the second end face 3c. This second end face 3c is substantially the rear end of the recessed portion 6 and serves as the judgment end for visual confirmation during thickness measurement when fitting the recessed portion 6 to the thickness of the gypsum board a. However, apart from this embodiment, the use of the cylindrical shaft portion 3b may be omitted, and the flange 5 may be directly positioned at the rear end of the eccentric shaft portion 3a, with the front surface of the flange 5 serving as the second end face 3c, which serves as the judgment end for visual confirmation during thickness measurement.

[0031] Furthermore, the cutting portion 2 located at the tip of the eccentric shaft portion 3a has a pointed shape with one side being flat and the other side being conical, resembling a triangular pyramid divided in two. The flat surface is located on the axis of the shaft portion 3, and the sharp end is positioned to coincide with the axis. The tip of the eccentric shaft portion 3a extends directly from this cutting portion 2. As shown in Figure 1, the short axis 3d of the valley diameter located at the tip of the eccentric shaft portion 3a connects to the flat surface side at the base of the cutting portion 2. Also, as shown in Figure 4, the tip of the peak portion 7a located at the tip of the eccentric shaft portion 3a connects to the extension portion 3e on the conical surface side at the base of the cutting portion 2. The tip of this extension portion 3e has an inclined edge 3f that slopes upward towards the tip, and the outer circumference of this extension portion 3e is in a condition that corresponds to part of the basic structure of the shaft portion 3.

[0032] In the cutting section 2 described above, the cutting edge 2a has a forward inclined edge in the screwing rotation direction of the flat surface, and the cutting edge 2a reaches the base where the maximum cutting diameter is located. As shown in Figure 4, the conical surface is provided with a groove 2b that extends from the semicircular part on the base side toward the sharp end, and the rear edge of this groove 2b in the screwing rotation direction becomes an auxiliary cutting edge 2c. The groove 2b is connected to the tip of the valley 7b in the helical groove 7 of the eccentric shaft section 3a, ensuring smooth chip evacuation.

[0033] As shown in Figures 1 and 2, the positional relationship between the recessed portion 6 and the cutting portion 2 is such that the rear end of the cutting blade 2a formed in the cutting portion 2 faces the tip of the recessed portion 6, and the flat surface of the cutting portion 2 is set to be perpendicular to the width direction of the inner surface 6a, which is the bottom of the recessed portion 6. The length of the lower edge of the cutting portion 2 in a triangle becomes the maximum drilling diameter, and the portion of this lower edge on the recessed portion 6 side protrudes perpendicular to the axial direction of the shaft portion 3. This portion substantially forms the tip end of the recessed portion 6, i.e., the first end surface 2d for contact with the back surface of the gypsum board a. Therefore, the recessed portion 6 forms a thickness measuring fitting portion with the first end surface 2d and the second end surface 3c.

[0034] As described above, the positional relationship between the recessed portion 6 and the cutting portion 2 on the shaft is set such that the rear edge of the cutting portion 2 faces the tip of the recessed portion 6, and the flat surface having the cutting blade 2a is perpendicular to the width direction of the inner surface 6a of the recessed portion 6. By making the first end face 2d and the rear end of the cutting blade 2a the same, the cutting surface side of the cutting portion 2 and the interior of the recessed portion 6 are connected, and the chips generated when the cutting portion 2 drills the pilot hole b can be quickly guided into the recessed portion 6, thus enabling efficient drilling.

[0035] At the base of the cutting blade 2a of the cutting section 2, a sharp second cutting blade 8 is provided, which protrudes to an intermediate position toward the tip of the cutting blade 2a by the outer edge of the extension 3e located on the conical surface. The straight portion of its outer edge becomes a cutting edge 8a with a drilling diameter that matches the maximum drilling diameter of the cutting section 2, and the inner circumferential surface of the pilot hole b drilled by the cutting section 2 is finished smoothly by the cutting edge 8a. Furthermore, if there is a material attached to the surface of the gypsum board a such as cloth or wallpaper, the second cutting blade 8 cuts through the attached material during drilling, preventing a decrease in drilling accuracy or damage to the attached material due to torn pieces of the attached material getting caught.

[0036] Here, in order to form a second cutting blade 8 in the cutting section 2, an extension 3e of the shaft section 3 is provided on the conical surface side of the cutting section 2. This extension 3e has a semicircular cross-section and an inclined edge 3f that faces the tip. By selecting the lead angle of the inclined edge 3f, the length of the second cutting blade 8 is changed. Therefore, by making the lead angle steeper and extending the tip of the second cutting blade 8, the start time of cutting the attached material can be set earlier. Furthermore, by aligning the rear end surface of the extension 3e with the rear end edge of the cutting section 2 to form the first end surface 2d, a flat area can be secured on the first end surface 2d. This prevents the first end surface 2d from digging into and damaging the gypsum board a when it comes into contact with the back surface of the gypsum board a.

[0037] Furthermore, the first end face 2d formed on the lower edge of the cut portion 2 and the second end face 3c facing the recessed portion 6 of the cylindrical shaft portion 3b face each other at both ends along the length of the recessed portion 6, along the axial direction of the shaft portion 3. The distance between the opposing surfaces of the first end face 2d and the second end face 3c is substantially equal to the length of the recessed portion 6. Therefore, the thickness measuring fitting portion fits over the thickness of the gypsum board a between the first end face 2d and the second end face 3c.

[0038] The drilling tool 1 of this invention has the configuration described above and is used to drill a pilot hole b for inserting a base fitting into a fragile material to be drilled, such as a gypsum board a, and to measure the thickness dimension of the gypsum board a during drilling. The drilling tool 1 is attached to a rotary tool with the mounting part 4, and first, the tip of the cutting part 2 is pressed against the front surface of the gypsum board a and the tool is rotated to drill, and when the cutting part 2 of the drilling tool 1 penetrates to the back surface of the gypsum board a, the rotation of the drilling tool 1 is stopped.

[0039] Next, before completely removing the drilling tool 1 from the pilot hole b, pull the drilling tool 1 out until the cylindrical shaft portion 3b is removed, move it laterally in the radial direction of the pilot hole b, and once the recessed portion 6 is fitted onto the thickness of the gypsum board a, pull the drilling tool 1 slightly forward, bring the first end face 2d into contact with the back side of the gypsum board a, and check the position of the recessed portion 6 on the front side of the gypsum board a to confirm the thickness dimension of the gypsum board a.

[0040] Furthermore, if the drilling tool 1 cannot be moved laterally during the lateral movement operation described above, it can be determined that the thickness of the gypsum board a is greater than the length of the recessed portion 6, because the recessed portion 6 does not fit into the thickness of the gypsum board a.

[0041] Here, in the case of wall materials, there are several types of thicknesses for gypsum board a. Examples of thicknesses actually used include 9.5 mm, 12.5 mm, 15 mm, and 21 mm. However, 12.5 mm gypsum board a is commonly used as wall material in general buildings. In contrast, if the drilling tool 1 is to be used exclusively for measuring each thickness, the length of the recessed portion 6 provided on the shaft portion 3 should be individually manufactured to match each thickness dimension. To elaborate on the measurement of thickness using a drilling tool 1 of this structure, when the recessed portion 6 is fitted onto the thickness of the gypsum board a by lateral movement, the gypsum board When the second end face 3c coincides with the surface of a, the thickness of the gypsum board a can be determined to be the set thickness of the drilling tool 1. When the drilling tool 1 is pulled forward, movement occurs, causing the second end face 3c to protrude forward relative to the surface of the gypsum board a, and it can be determined that the thickness of the gypsum board a is thinner than the set thickness of the drilling tool 1. Furthermore, when lateral movement is not possible, it can be determined that the thickness of the gypsum board a is thicker than the set thickness of the drilling tool 1. After measuring the thickness of the gypsum board a in this manner, the drilling tool 1 is returned to the radial direction of the pilot hole b, the recessed portion 6 is separated from the thickness portion of the gypsum board a, and the drilling tool 1 is removed from the pilot hole b.

[0042] Next, in order to determine the four thickness dimensions described above with a single drilling tool 1, this can be achieved by setting the length dimension along the axial direction of the eccentric shaft portion 3a of the recessed portion 6, that is, the distance in the longitudinal direction of the recessed portion 6, which is the dimension between the first end face 2d and the second end face 3c, to 15 mm.

[0043] In other words, under the condition that the drilling tool 1, which has drilled the pilot hole b, is moved laterally, the recessed portion 6 is fitted onto the thickness of the gypsum board a, and the first end face 2d on the tip side is engaged with the back surface of the gypsum board a, if the thickness of the gypsum board a is 9.5 mm, the amount of protrusion of the recessed portion 6 on the surface side of the gypsum board a, that is, the distance between the surface of the gypsum board a and the second end face 3c, will be 40% of the total length of the recessed portion 6, and it can be determined that the thickness is 9.5 mm because this amount of protrusion is large.

[0044] Similarly, if the thickness of gypsum board a is 12.5 mm, the amount of protrusion of the recessed portion 6 relative to the surface side of gypsum board a will be 15-30%, and the small amount of protrusion allows us to determine that the thickness is 12.5 mm.

[0045] Next, if the thickness of the gypsum board a is 15 mm, the total length of the recessed portion 6 matches the thickness of the gypsum board a. As a result, the rear end of the recessed portion 6 aligns with the surface of the gypsum board a, resulting in a protrusion of 0%. The absence of this protrusion allows us to determine that the thickness is 15 mm.

[0046] Furthermore, if the thickness of the gypsum board a is 21 mm, the recessed portion 6 will not fit into the thickness of the gypsum board a, making it impossible to move the drilling tool 1 sufficiently laterally, and thus it can be determined that the thickness is 21 mm.

[0047] In measuring the thickness of gypsum board a as described above, if the difference in protrusion of the recessed portion 6 relative to the surface of gypsum board a is considered small for thicknesses of 9.5 mm and 12.5 mm, marking a point 9.5 mm behind the first end face 2d located at the tip on the inner surface 6a of the recessed portion 6 will allow for accurate determination of the thickness dimension by checking this mark.

[0048] Furthermore, if the thickness of the gypsum board a to be drilled by the drilling tool 1 is a maximum of 21 mm, the length of the shaft portion 3 of the drilling tool 1, that is, the distance from the rear end of the cutting portion 2 to the flange 5, can be set to a corresponding distance to accommodate drilling of materials ranging from thin to thick. In addition, to address cases where the gypsum board a used as a wall material has wallpaper or wall coverings on its surface, the length of the recessed portion 6 may be made about 1 mm longer than the dimensions exemplified above to account for the increased thickness. [Explanation of Symbols]

[0049] 1. Drilling tool 2 Cutting part 2a cutting blade 2b Groove 2c auxiliary cutting blade 2d First end face 3. Shaft section 3a Eccentric shaft part 3b Circular shaft part 3c Second end face 3d short axis 3e extension 3f Elevated edge 4. Mounting part 5 Flange 6 Notch 6a Inside surface 7 Spiral groove 7a Yamabe 7b Tanibe 8. Second cutting edge 8a Cutting edge a. Gypsum board b Pilot hole

Claims

1. A drilling tool comprising a shaft having a cutting portion at its tip, with a tool attachment portion at the rear end, wherein the outer diameter of the shaft is adapted to the maximum cutting diameter of the cutting portion, wherein a recessed portion is provided in a part of the shaft for fitting onto the thickness of the material to be drilled, the remaining portion of the shaft relative to the recessed portion is formed into an eccentric shaft, the conditions of the recessed portion are set such that the width of the eccentric shaft portion corresponding to the bottom surface of the recessed portion is narrower than the diameter of the maximum cutting diameter of the cutting portion, and the length along the axial direction of the shaft is set to a length dimension that can fit onto the thickness of the material to be drilled, and a first end surface is formed at the end of the recessed portion on the cutting portion side for contact with the back surface of the material to be drilled, thereby making the recessed portion a thickness measuring fitting portion.

2. The drilling tool according to claim 1, characterized in that the positional relationship between the thickness measuring fitting portion and the cutting portion is set such that the rear end of the cutting blade formed in the cutting portion faces the front end of the thickness measuring fitting portion, and the cutting portion is perpendicular to the width direction on the inner surface of the thickness measuring fitting portion.

3. The drilling tool according to claim 1 or 2, characterized in that the first end surface, which is provided to contact the back surface of the member to be drilled at the tip side of the thickness measuring fitting portion, is formed by the rear end edge of the cutting portion.

4. The inner surface of the eccentric shaft portion, which corresponds to the bottom surface of the thickness measuring fitting portion, is divided by a helical groove formed by a recessed portion, so that both side edges of the helical groove have alternating peaks and valleys, and the width direction of this inner surface is formed into an arc-shaped surface that bulges inward into the recessed portion, as described in claim 1 or 2.

5. The drilling tool according to claim 1 or 2, characterized in that a second cutting blade having a drilling diameter matching the maximum drilling diameter made by the cutting section is provided at the base of the cutting blade in the cutting section.

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