Rotary tool and drilling bit tool

Abstract

To provide a rotary tool which makes a portion of a connection structure less likely to be damaged even when a diameter of a bit is 5 mm or smaller.SOLUTION: In a rotary tool, a bit 10, in which a grind stone 16 having a diameter of 5 mm or smaller is joined to a tip of a base metal 11 having a lubrication water passage, is detachably connected to a cylindrical shank 1 to use the rotary tool. The bit includes: the base metal having a joint part 12, to which the grind stone is joined, at one end side; a first screw 15 located at the other end of the base metal; and a first inclined surface 14 formed adjacent to the first screw. The shank includes: a second screw 5 located at one end and configured to engage with the first screw; and a second inclined surface 4 which is formed adjacent to the second screw and contacts with the first inclined surface.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a rotary tool and a drill bit for drilling holes in materials such as tiles, grout, concrete, etc. [Background technology]

[0002] Conventionally, drilling devices have been proposed for drilling materials such as concrete, high-strength concrete, tiles, and stone (see Patent Documents 1-4). In the drilling device described in Patent Document 4, a bit for drilling the material is attached to the tip of the shank by a screw structure. Therefore, in the drilling device, if the bit at the tip becomes worn or damaged, the drilling operation can be continued by replacing it with a new bit via the screw structure of the bit. It is also known that drilling devices perform drilling operations while supplying lubricating water to the work surface (see Patent Document 4, etc.). There is a demand for such drilling devices to be able to operate even when the hole diameter that can be drilled becomes smaller. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-261203 [Patent Document 2] Japanese Patent Application Laid-Open No. 2003-245919 [Patent Document 3] Japanese Patent Application Laid-Open No. 2010-052215 [Patent Document 4] Japanese Patent Application Laid-Open No. 2013-067023 Summary of the Invention [Problem to be solved by the invention]

[0004] However, with conventional drilling devices, as the diameter of the drilled hole becomes smaller, the diameters of the bit and shank also become smaller, and since the shank is cylindrical and requires lubrication while working, the threaded structure connecting the shank and the bit is prone to breakage. In particular, if a portion of the bit connection part that connects the shank to the bit deteriorates due to wear, that wear can cause large cracks and shorten the service life of the shank.

[0005] Therefore, for bits with a small diameter of 4 to 5 mm, the shank and bit are brazed together, and when the bit wears out, the entire shank must be replaced. Therefore, for bits with small diameters, the economic burden is significant, and improvements are needed. The present invention was devised in consideration of the above-mentioned demand, and its object is to provide a rotary tool and a drill bit tool that have a connecting structure that is less likely to break and has an extended service life, even when the bit diameter is reduced to 5 mm or less. [Means for solving the problem]

[0006] In order to solve the above problem, the rotary tool of the present invention is a rotary tool that uses a bit having a grinding wheel with a diameter of 5 mm or less attached to the tip of a base metal having a flow path for lubricating water, which is detachably connected to a cylindrical shank, and the bit comprises the base metal having a joining portion at one end for joining the grinding wheel, a first screw at the other end of the base metal, and a first inclined surface formed adjacent to the first screw, and the shank comprises a second screw at one end that engages with the first screw, and a second inclined surface formed adjacent to the second screw and abutting the first inclined surface.

[0007] In addition, in order to solve the above problem, the boring bit tool of the present invention includes the above-mentioned rotary tool, an output shaft to which the shank is detachably connected, and an electric drive motor that rotates the output shaft. [Effects of the Invention]

[0008] With the rotary tool and boring bit according to the present invention, the rotary tool is less likely to break even when the bit diameter is 5 mm or less, such as 5 mm, 4.5 mm, or 4 mm, and its service life can be extended. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is an overall configuration diagram illustrating a schematic example of an entire lubricating water circulation drilling system including a drill bit tool equipped with a rotary tool according to an embodiment. FIG. [Figure 2] FIG. 1A is a cross-sectional view schematically showing a state in which a bit is connected to a shank in a rotary tool according to an embodiment, and FIG. 1B is a cross-sectional view schematically showing a state in which the bit is removed from the shank in a rotary tool according to an embodiment. [Figure 3] 3(a) is an enlarged cross-sectional view of part A in FIG. 2(a), (b) is an enlarged cross-sectional view of part B in FIG. 2(b), and (c) is a front view of the bit in FIG. 3(b). [Figure 4] 3(a) is an enlarged schematic diagram showing an enlarged view of part C in FIG. 3(a), (b) is an enlarged schematic diagram showing an enlarged view of part D in FIG. 3(b), and (c) is an enlarged schematic diagram showing an enlarged view of part E in FIG. 3. [Figure 5] 5(a) is a schematic diagram showing a state in which a portion of the shank of a conventional rotary tool is worn, and FIG. 5(b) is a schematic diagram showing a state in which a portion of the shank of a rotary tool according to an embodiment is worn, in comparison with FIG. 5(a). [Figure 6] FIG. 4 is a schematic view showing a first modified example of the rotary tool according to the embodiment. [Figure 7] 10(a), (b), and (c) are schematic views each showing a second modified example of the rotary tool according to the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] An example of using a rotary tool having a bit-and-shank connection structure according to an embodiment of the present invention in a lubricating water circulation drilling system will be described below with reference to the drawings. Note that in each figure, up, down, left, right, front, and back are shown only for illustrative purposes and do not indicate absolute directions. Also, some parts of each configuration may be exaggerated. Furthermore, the following description will be given as an example in which the tool is placed in concrete as the object to be drilled, and a predetermined position in the concrete is used as the drilling start surface. Also, in the enlarged portion of the shank 1 and bit 10 in Figure 1, the shank 1 and bit 10 are shown separated for ease of understanding, but of course, the screw is tightened during operation.

[0011] <Lubricant Circulation Drilling System> As shown in FIG. 1 , the lubricating water circulation drilling system 100 primarily includes a lubricating water circulation device 50 and a drilling bit 20 that receives a supply of lubricating water from the lubricating water circulation device 50 and performs drilling operations. The drilling bit 20 includes a rotary tool 30 having a shank 1 and a bit 10 connected via a connecting structure. The lubricating water circulation drilling system 100 preferably further includes a guide mechanism for linearly performing drilling operations, a vacuum pump for fixing the guide mechanism's fixing base to the installation surface, a dust collection drive unit for the lubricating water circulation device 50, a bubble blocking mechanism for the lubricating water circulation device 50, an air drive source for driving the drilling bit 20 with air, and a power supply device 40 that serves as the power source for the vacuum pump and the like, all of which are not shown. The drilling bit 20 will be described here as being driven by the power supply device 40.

[0012] <Drilling bit tool> As shown in FIGS. 1 and 2(a) and (b), the drill bit 20 is, for example, a tool that is held by a guide mechanism (not shown) or by an operator directly using a tool handle to drill concrete W. The drill bit 20 includes an electric drive motor 21 disposed within a drive body, an output shaft 22 of the electric drive motor 21, and a rotary tool 30 connected to the output shaft 22. The rotary tool 30 includes a shank 1 and a bit 10 connected to the shank 1. The shank 1 is cylindrical and hollow along its length, with a lubricating water flow path 8 for lubricating water. The shank 1 also includes a body connection portion 6 at the end opposite the end where the bit 10 is provided, and is configured to be detachably attached to the output shaft 22 with a screw.

[0013] The drill bit 20 also includes a water injection unit 23 on the side where the shank 1 is connected, for sending lubricating water into the lubricating water flow path 8 of the shank 1. The water injection unit 23 is attached to the tool so that the shank 1 can rotate freely, and has a protruding connection portion for connecting one end of a lubricating water supply hose. The drill bit 20 is driven by operating a drive switch via a power supply unit 40 to which an electric cord is connected, for example. The drill bit 20 is also configured so that when driven, lubricating water is supplied from a lubricating water circulation unit 50 via a supply hose 51, and sludge, a mixture of cuttings and lubricating water, is collected via a collection hose 52 while work is carried out.

[0014] As shown in Figures 2(a) and 2(b) and Figures 3(a) and 3(b), the bit 10 is configured to have an outer diameter of 5 mm or less, and grinding wheels 16 with diameters of 5 mm, 4.5 mm, 4 mm, etc. are used. Note that if the outer diameter of the bit 10 exceeds 5 mm, for example, 6 mm, 7 mm, 8 mm, etc., the thickness of the material at the bit connection portion 2 of the shank 1 becomes resistant to breakage, so here, bits of 5 mm or less are targeted. The bit 10 has a bit flow path 17 that penetrates approximately the center of the base metal 11 and supplies lubricating water to the tip end. The bit 10 is connected to the shank 1 using a threaded connection structure that allows it to be detachably attached.

[0015] The bit 10 has a grinding wheel 16 joined to a connecting portion 12 on one side of a base metal 11 by brazing or sintering. The bit also has a first inclined surface (hereinafter referred to as the base metal inclined surface) 14 formed on the other side of the base metal 11 via a step portion 13 (hereinafter referred to as the base metal inclined surface), and a first screw (hereinafter referred to as the male screw) 15 formed adjacent to the base metal inclined surface 14. The connecting portion 12 of the base metal 11 is one end surface of a cylindrical portion, and the base metal inclined surface 14 is formed on the other end surface via the step portion 13. The grinding wheel 16 is formed in a cylindrical shape and has an arc-shaped notch 18 in part thereof. The grinding wheel 16 is made of a general material used for this type of drilling, such as a material containing diamond abrasive grains. The shape of the grinding wheel 16 is not particularly limited.

[0016] As shown in FIGS. 3(a) to 4(c), the base metal 11 has a base metal inclined surface 14 formed continuously on the opposite side of the connection portion 12 with a step portion 13 interposed therebetween. The base metal inclined surface 14 is the portion that abuts against the second inclined surface (hereinafter referred to as the shank inclined surface) 4 of the shank 1, which will be described later. The base metal inclined surface 14 is a peripheral surface in the shape of a truncated cone, which is formed so that the diameter decreases from the step portion 13 toward the male thread 15. The base metal inclined surface 14 is formed to a length that is 30 to 40% of the diameter of the grinding wheel 16. As an example, if the diameter of the grinding wheel 16 is 4 mm, the base metal inclined surface 14 is preferably formed in the range of 1.2 mm to 1.6 mm. If the length of the base metal inclined surface 14 is 1.2 mm (30% of the diameter of the grinding wheel 16) or less, the effect of the inclined surfaces abutting against each other cannot be achieved.

[0017] Furthermore, if the length of the base metal inclined surface 14 exceeds 1.6 mm (40% of the diameter of the grinding wheel 16), the structural balance of the bit 10 will be poor. The inclination angle of the base metal inclined surface 14 is in the range of 10 to 45 degrees. If the inclination angle of the base metal inclined surface 14 is less than 10 degrees, the force in the direction in which the inclined surfaces abut against the shank inclined surface 4 will be weak. If the inclination angle of the base metal inclined surface 14 exceeds 45 degrees, the contact area between the bit 10 and the shank 1 will be small when the shank 1 wears, resulting in a shorter lifespan. It is more preferable that the base metal inclined surface 14 and the shank inclined surface 4 be in the range of 15 to 40 degrees, and even more preferably in the range of 20 to 35 degrees.

[0018] The male screw 15 detachably engages with the second screw (hereinafter referred to as the female screw) 5 of the shank 1. The male screw 15 is formed so that the tightening direction of the male screw 15 is opposite to the rotation direction of the shank 1 during drilling. The male screw 15 is formed adjacent to the base metal inclined surface 14. As an example, the male screw 15 is formed so as to continue to the base metal inclined surface 14. Also, as shown in FIG. 4, it is preferable that a threaded portion 15a that becomes part of the male screw 15 is formed up to a part of the base metal inclined surface 14. In other words, it is also possible to form a portion on the base metal inclined surface 14 where the spacing between the crests and valleys of the screw is gradually reduced, continuing from a portion where the spacing between the crests and valleys of the screw is constant, as the threaded portion 15a. It is preferable that the threaded portion 15a is in the range of 5 to 10% of the base metal inclined surface 14. By making the threaded portion 15a continuous with the male thread 15 up to the portion that becomes part of the base metal inclined surface 14, the degree of contact between the shank inclined surface 4 of the shank 1 and the base metal inclined surface 14 is improved, making it easier to prevent damage to the bit connection portion 2 side.

[0019] The shank 1 is cylindrical and includes a main body connection portion 6 connected to the drill bit 20 at one end and a bit connection portion 2 connected to the bit 10 at the other end. The shank 1 has a lubricating water flow path 8 extending continuously in the longitudinal direction, which sends lubricating water to the bit 10. The shank 1 is also cylindrical, with the main body connection portion 6 side having a larger diameter than the bit connection portion 2 side. The longitudinally central portion of the shank 1 adjacent to the main body connection portion 6 is formed so that at least two opposing points on the cylindrical shape are parallel to each other, allowing the shank 1 to be connected to the drill bit 20 using a tool such as a wrench. The main body connection portion 6 of the shank 1 has a female thread formed on the inside of its cylindrical body, allowing it to be detachably connected to the output shaft 22 of the drill bit 20. The main body connection portion 6 rotates in the opposite direction to the rotation of the shank 1 during drilling.

[0020] The bit connection portion 2 of the shank 1 includes an end face abutment portion 3 formed on the open end face on one end side, a shank inclined surface 4 formed continuously from the end face abutment portion 3, and a female thread 5 formed adjacent to the shank inclined surface 4. The end face abutment portion 3 is the portion that abuts against a step portion 13 of the bit 10. The end face abutment portion 3 is formed so as to be perpendicular to the axial direction of the shank 1. The end face abutment portion 3 abuts against the step portion 13 of the bit 10 by a surface, and together with the shank inclined surface 4, it is possible to reduce vibration of the shank 1 during operation.

[0021] As shown in Figures 3(a) to 4(c), the shank inclined surface 4 is the portion that abuts against the base metal inclined surface 14 of the bit 10. When connected to the bit 10, the shank inclined surface 4 tightly abuts against the base metal inclined surface 14, thereby reducing deterioration due to vibration during shank rotation. It also reduces damage to the shank's bit connection portion 2 due to wear. The abutment of the shank inclined surface 4 against the base metal inclined surface 14 reduces damage due to friction, and can, for example, extend the lifespan by more than two times compared to a bit without an inclined surface. For example, a bit without an inclined surface, with a grinding wheel 16 having a diameter of 5 mm, would need to be replaced after 300 holes drilled into concrete W, whereas a structure in which the shank inclined surface 4 abuts against the base metal inclined surface 14 allows for 600 holes drilled. Furthermore, if the diameter of the grinding wheel 16 is 4 mm, it will need to be replaced after drilling 100 holes in the concrete W, but if the shank inclined surface 4 abuts the base metal inclined surface 14, it will be possible to drill 200 holes.

[0022] The shank inclined surface 4 is formed so that its inclination angle and formed length are the same as those of the base metal inclined surface 14. Furthermore, when the thread portion 15a continues to a portion of the base metal inclined surface 14, a portion of the shank inclined surface 4 also has a portion that continues to the female thread 5 and becomes a continuous female thread portion 5a. The continuous female thread portion 5a is formed on a portion of the shank inclined surface 4 to an extent that it can face and engage with the thread portion 15a that becomes part of the base metal inclined surface 14. The continuous female thread portion 5a provides the continuous female thread portion 5a, which engages with the thread portion 15a, thereby strengthening the tight contact between the shank inclined surface 4 and the base metal inclined surface 14. Therefore, the shank 1 makes it easier to prevent damage to the bit connection portion 2.

[0023] The female thread 5 engages with the male thread 15 of the bit 10. The female thread 5 is formed so that the direction in which the male thread 15 is tightened is opposite to the direction in which the shank 1 rotates during drilling. The female thread 5 is formed adjacent to the shank inclined surface 4. As an example, the female thread 5 is formed so as to be continuous with the shank inclined surface 4. It is also preferable that a continuous female thread portion 5a, which becomes part of the female thread 5, is formed on part of the shank inclined surface 4. It is preferable that the continuous female thread portion 5a formed on the shank inclined surface 4 be in the range of 5 to 15%, which is the same as the base metal inclined surface 14.

[0024] The power supply unit 40 operates the drill bit tool 20, the lubricating water circulation device 50, etc. The power supply unit 40 may be a general power supply unit used to operate tools of this type. The lubricating water circulation device 50 includes a dust collection drive unit therein, which, for example, creates negative pressure in the air inside the lubricating water circulation device 50 to collect sludge from the collection hose 52. The dust collection drive unit collects sludge by arranging an electric suction pump inside the housing of the lubricating water circulation device 50. If an ejector is used to create an air flow inside the housing to collect dust, a compressor may also be used.

[0025] The lubricating water circulation device 50 sends lubricating water to be supplied from the lubricating water flow path 8 of the shank 1 via the water injection unit 23 to the drilling position of the bit 10. The sludge collected through the drainage flow path, which is the gap between the outside of the shank 1 and the inner surface of the drilled hole, is collected, filtered, and resupplied. The lubricating water circulation device 50 includes a housing, a pump (gear pump, tube pump, vacuum pump, or ejector) for collecting sludge provided within the housing, a supply pump for supplying lubricating water provided within the housing, a filter for filtering sludge provided within the housing, and a storage unit for storing the lubricating water filtered by the filter. The lubricating water circulation device 50 supplies the lubricating water from the storage unit to the shank 1 via a supply hose 51 and collects the sludge via a recovery hose 52. The lubricating water circulation device 50 also preferably includes a bubble blocking mechanism that blocks bubbles generated by the filter before they reach the dust collection drive unit. The foam blocking mechanism has a configuration such as disposing a mesh scrubbing brush in the space up to the dust collection drive unit, and can block the bubbles by bursting them.

[0026] An example of drilling concrete via a lubricating water circulator 50 using the drill bit tool 20 equipped with the rotary tool having the above-described configuration will be described below. As shown in FIG. 1 , first, the supply hose 51 of the lubricating water circulation device 50 is connected to the water injection unit 23, and the recovery hose 52 is connected to a bush holder placed on the work surface of the concrete W. The bit 10 and shank 1 of the drill bit tool 20 are rotatably mounted in the bush holder. In this state, the lubricating water circulation device 50 is operated to supply lubricating water while starting the drilling operation, and the sludge is collected and filtered, and the operation proceeds while the lubricating water is circulated. Specifically, the drilling operation is performed by aligning the tip of the bit 10 with the drilling position and operating the switch of the drill bit tool 20 to rotate the bit 10, and supplying lubricating water to the cutting position via the lubricating water flow path 8 and the bit flow path 17.

[0027] Furthermore, as the bit 10 cuts the concrete, sludge, a mixture of cuttings and lubricating water, is produced and collected in a filter in the lubricating water circulation device 50 by a collection hose 52 connected to the bush holder via a drainage flow path on the outer periphery of the shank 1 and the inner periphery of the drilled hole. During drilling work, the bit 10 drills a small hole with a diameter of 5 mm or less, so the drilled hole is the length of the shank 1.

[0028] Furthermore, when performing drilling operations using the drill bit tool 20, if the grinding wheel 16 has a diameter of 5 mm, it is possible to drill more than 500 holes, and when the grinding wheel 16 of the bit 10 wears out, the bit 10 can be replaced with a new bit 10 using the screw mechanism attached to the shank 1, making it possible to reuse the bit. In the rotary tool 30 of the present application, the shank 1 and bit 10 can drill 500 to 600 holes before the bit connection portion 2 side of the shank 1 is damaged and needs to be replaced, which is approximately twice the service life of the conventional configuration, which can drill around 300 holes.

[0029] Incidentally, there are the following differences between a rotary tool 300 without an inclined surface, as shown in Figure 5A, and a rotary tool 30 with a base inclined surface 14 and a shank inclined surface 4, as shown in Figure 5B, which affect the service life. 5A, when the shank 4 wears from the position indicated by the imaginary line to the position indicated by the solid line, the spigot portion A1 on the base end side of the bit 14 is exposed from the end of the shank 4. When the spigot portion A1 is exposed in this way, the bit 14 becomes detached. 5B, even if the shank 4 wears from the position indicated by the imaginary line to the position indicated by the solid line, the spigot portion B1 is still covered by the shank inclined surface 4 and the base inclined surface 14. Therefore, the connection between the bit 14 and the shank 4 is maintained, extending the service life.

[0030] As shown in FIG. 6, a first modified example of the rotary tool according to the present invention may have a configuration in which a first screw on the bit side is female-threaded and a second screw on the shank side is male-threaded. That is, in a rotary tool 30C, a bit 10C has a female-threaded first screw 15c adjacent to a base metal 12, a first inclined surface 14c on the side opposite the base metal 12, and an end-face abutment portion 13c at the end of the first inclined surface 14c. A shank 1C has a second inclined surface 4c at one end of the shank body and a male-threaded second screw 5c adjacent to the second inclined surface 4c. Finally, a step portion 3c is provided at one end of the shank body.

[0031] 2, the rotary tool 30C shown in Fig. 6 has a configuration in which the shank 1C has a male thread (second thread 5c) and the bit 10C has a female thread (first thread 15c). The shank 1C has a stepped portion 3c, and the bit 10C has an end face abutment portion 13c that abuts against the stepped portion 3c. In this way, even if the positions of the male and female threads are reversed between the shank 1C and the bit 10C, the rotary tool is configured so that the first inclined surface 14c and the second inclined surface 4c abut against each other, thereby enabling the rotary tool to have an extended service life, similar to the configuration described above.

[0032] 7(a) to 7(c), as a second modified example of the rotary tool, rotary tools 30D1, 30D2, and 30D3 may be configured to include either or both of a first circumferential surface 19 formed between the first screw and the first inclined surface and a second circumferential surface 9 formed between the second screw and the second inclined surface. When both are included, the first circumferential surface 19 and the second circumferential surface 9 have the same length. By including the first circumferential surface 19 and / or the second circumferential surface 9, a "relief" space is formed at a position facing the first circumferential surface 19 and / or the second circumferential surface 9 when the bit 10D and the shank 1, the bit 10 and the shank 1D, or the bit 10D and the shank 1D are connected, respectively. By including the first circumferential surface 19 and / or the second circumferential surface 9 in the rotary tools 30D1, 30D2, and 30D3, the first circumferential surface 19 and / or the second circumferential surface 9 facilitates the positional adjustment of the first inclined surface 14 and the first screw 15 during manufacturing. Furthermore, the shank 1D is provided with the second peripheral surface 9, which makes it easy to adjust the position of the second inclined surface 4 and the second screw 5 during manufacturing.

[0033] As described above, when drilling is performed while lubricating water is circulating, the drill bit 20 using a rotary tool can be used with an extended service life by preventing the tiles of the building being drilled from peeling off. The rotary tool drills holes with a diameter of 4 to 5 mm in the tiles and joints, and tile adhesive is injected through the drilled holes to prevent the tiles from peeling off. The rotary tool and drill bit can be used with a longer service life than conventional tools.

[0034] The lengths of the first and second inclined surfaces are set to 30 to 40% of the 4 to 5 mm diameter of the grinding wheel 16, but are preferably 33 to 38%. The inclination angle has been described as 10 to 45 degrees, but is preferably 15 to 40 degrees, and more preferably 20 to 35 degrees. In a configuration in which the bit is provided with a female thread 15c and the shank is provided with a male thread 5c, the first circumferential surface 19 and / or the second circumferential surface 9 may also be provided. The rotary tool and the drill bit tool according to the embodiments of the present invention have been described in detail above. However, the above-described and illustrated embodiments are merely examples of specific embodiments for carrying out the present invention, and the technical scope of the present invention should not be interpreted in a limited manner based on these embodiments. [Explanation of symbols]

[0035] 1 shank 2 Bit Connection 3 End surface contact part 4 Shank inclined surface (second inclined surface) 5 Female thread (second screw) 6 Main unit connection part 8 Lubricating water flow path 10-bit 11 base money 12 Connection 13 Step 14 Base metal slope (first slope) 15 Male thread (first screw) 16 Grindstone 17-bit channel 20 Drilling bit tool 21 Electric drive motor 22 Output shaft 23 Water injection section 30 Rotary Tools 40 Power supply 50 Lubricating water circulation device 51 Supply hose 52 Recovery hose 100 Lubricated Water Circulation Drilling System

Claims

1. A rotary tool in which a bit having a grinding wheel with a diameter of 5 mm or less attached to the tip of a base metal having a flow path for lubricating water is detachably connected to a cylindrical shank, The bit includes the base metal having a joining portion at one end thereof for joining the grinding wheel, a first screw at the other end thereof, and a first inclined surface formed adjacent to the first screw, The shank is a rotary tool having a second screw at one end that engages with the first screw, and a second inclined surface that is formed adjacent to the second screw and abuts the first inclined surface.

2. the first thread of the bit is a male thread; the first inclined surface is disposed between the base metal and the male screw, the second thread of the shank is an internal thread; The rotary tool according to claim 1 , wherein the second inclined surface is disposed from the opening at one end of the shank toward the female screw.

3. the first thread of the bit is a female thread; The first inclined surface is disposed adjacent to the female screw on the side opposite to the base metal, the second thread of the shank is a male thread; The rotary tool according to claim 1 , wherein the second inclined surface is disposed between the shank body and the male thread.

4. The rotary tool according to claim 2 , wherein the first inclined surface disposed on the male thread side is inclined in a direction in which the diameter decreases toward the male thread.

5. 2. The rotary tool according to claim 1, wherein the first inclined surface has a length of 30 to 40% of the diameter of the grinding wheel and an inclination angle of 10 to 45°.

6. the first inclined surface is formed adjacent to the joint portion via a step portion, and is integral with the joint portion; The rotary tool according to claim 1 , wherein an end of the second inclined surface has an end surface abutting portion that abuts against the step portion.

7. the first screw is formed continuously on the first inclined surface, The rotary tool according to claim 1 , wherein the second screw is formed continuously with the second inclined surface.

8. the first screw is disposed via a first peripheral surface interposed on the first inclined surface, The rotary tool according to claim 1 , wherein the second screw is disposed via a second peripheral surface that is interposed in the second inclined surface.

9. The rotary tool according to claim 1 , wherein the shank has a main body connecting portion at the other end thereof that is detachably connected to an output shaft of a drive mechanism.

10. A rotary tool according to any one of claims 1 to 9 is provided, A boring bit tool comprising: an output shaft to which the shank is detachably connected; and an electric drive motor for rotating the output shaft.

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