Dustproof cover and hole opening tool including the same

Abstract

To achieve both of visibility of a machining position and suppression of scattering of powder dust during a hole opening work.SOLUTION: A dustproof cover 40 covers a tool body 10 while allowing a hole opening work. The dustproof cover 40 includes: a base section 42; a transparent cover section 46; and a bellows section 44. The base section 42 is supported by a support shaft of a hole opening tool. The transparent cover section 46 has a degree of transparency for enabling checking of a machining position in a state of a cover tip 46b abutting on a workpiece 2 by visual observation from the outside. The bellows section 44 is formed into a bellows shape which can contract in an axial direction so as to mutually connect the base section 42 and the transparent cover section 46 in an axial direction along the support shaft and allow relatively advancing of the base section 42 in the axial direction with respect to the transparent cover section 46.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a dustproof cover used for a drilling tool for drilling holes in walls, ceilings, and other workpieces, and to a drilling tool equipped with the dustproof cover. [Background technology]

[0002] Conventionally, a dust cover used for a drilling tool is known, as described in Patent Document 1. This dust cover has a bellows-shaped cover body and a base connected to the base end of the cover body, and the base is detachably attached to a tool holder of a rotary drive. The cylindrical body is capable of covering the tool body from start to finish while contracting as the drilling operation by the tool body of the drilling tool (a center drill and a cylindrical body in Patent Document 1) progresses, thereby preventing dust generated by the drilling operation from scattering to the outside. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2000-354935 A Summary of the Invention [Problem to be solved by the invention]

[0004] The dust cover covers the entire tool body during the drilling operation, so the operator cannot visually check the contact position between the tool body and the workpiece. This makes the drilling operation difficult and may hinder the improvement of the accuracy of the drilling position. In addition, the dust cover is in the shape of an expandable bellows to enable the tool body to be pushed into the workpiece, and the material of the dust cover is limited, so that it is practically difficult to make the dust cover transparent to enable the operator to see inside.

[0005] In order to solve such problems, the present invention aims to provide a dust cover that allows an operator to visually check the contact position between the tool body of the hole-drilling tool and the workpiece while preventing dust from scattering during hole-drilling operations with the hole-drilling tool, and a hole-drilling tool equipped with the dust cover. [Means for solving the problem]

[0006] What is provided is a dust cover for use in a hole drilling tool. The hole drilling tool includes a tool body, a spindle, and the dust cover. The tool body can be forced into the workpiece while being driven to rotate, thereby drilling a hole in the workpiece. The spindle has a base end connected to a rotary drive capable of outputting a rotational driving force, and a tip end at the opposite end thereof that holds the tool body, and transmits the rotational driving force to the tool body to rotate the tool body. The dust cover covers the tool body while allowing a hole drilling operation in which the tool body is forced into the workpiece, and includes a base, a transparent cover portion, and a bellows portion. The base is supported by the spindle at a position rearward of the tool body. The transparent cover part has a cylindrical shape capable of surrounding the tool body, includes a cover tip part capable of contacting the workpiece, and has a transparency that enables visual confirmation from the outside of a machining position of the workpiece by the tool body with the cover tip part in contact with the workpiece. The bellows part connects the base part and the transparent cover part to each other in an axial direction along the support shaft, and has a bellows shape that is contractible in the axial direction so as to allow the base part to advance relatively in the axial direction with respect to the transparent cover part.

[0007] In the dust cover, the combination of a cylindrical transparent cover part and a bellows-shaped expandable part allows the operator to both prevent dust from scattering during the drilling operation and to visually confirm the processing position. Specifically, the bellows part allows the tool body of the hole drilling tool to be pressed against the workpiece by moving the base forward relative to the transparent cover part while the bellows part contracts with the cover tip of the transparent cover part in contact with the workpiece, thereby allowing the tool body to perform the drilling operation while covering the tool body with the dust cover, that is, preventing dust generated by the drilling operation from scattering around. Meanwhile, the transparent cover part having the transparency allows the operator to visually confirm the contact position between the tool body and the workpiece through the transparent cover part, thereby allowing the hole drilling operation to be easily performed at the appropriate processing position.

[0008] The base of the dust cover may be immovably fixed to the spindle, but is preferably configured to be attached to the spindle so as to be movable in the axial direction relative to the spindle between an advanced position and a retracted position. The advanced position is a position where the transparent cover part covers at least a part of the tool body when the bellows part is not contracted, and the retracted position is a position closer to the base end of the spindle than the advanced position, i.e., a rear position. The axial movement of the base relative to the spindle, in combination with the contraction of the bellows part, makes it possible to further increase the distance that the tool body can advance beyond the tip end of the cover, i.e., the effective machining depth.

[0009] In this case, it is preferable that the dust cover further includes a biasing means for biasing the base portion toward the forward position, which enables the transparent cover portion to reliably cover at least a portion of the tool body at the start of processing.

[0010] Also provided is a hole-drilling tool comprising: a tool body capable of drilling a hole in a workpiece by being driven to rotate and being pushed into the workpiece; a spindle having a base end connected to a rotary drive machine capable of outputting a rotational driving force and an opposite end which is a tip end which holds the tool body, and which transmits the rotational driving force to the tool body to rotate the tool body; and the dust cover. Effect of the Invention

[0011] As described above, according to the present invention, it is possible to provide a dust cover and a drilling tool equipped with the dust cover, which can prevent dust from scattering during drilling operations with the drilling tool while allowing an operator to visually check the contact position between the tool body of the drilling tool and the workpiece. [Brief description of the drawings]

[0012] [Figure 1] 1 is a partial cross-sectional view of a hole drilling tool according to an embodiment of the present invention, showing a state at the start of processing. [Diagram 2] FIG. 4 is a partial cross-sectional view of the hole-making tool, showing a state at the end of processing. [Diagram 3] FIG. 13 is a cross-sectional view of only the dust cover of the hole-punching tool, showing the state at the start of processing. [Figure 4] FIG. 11 is a cross-sectional view of only the dust cover of the hole-punching tool, showing the state after machining is completed. [Diagram 5] 4 is a cross-sectional view showing a main portion of a rear connector in the hole punching tool. FIG. [Figure 6] 4 is a cross-sectional view showing a main portion of a front connector in the hole punching tool. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] A preferred embodiment of the present invention will now be described with reference to the drawings.

[0014] 1 to 4 show the hole drilling tool according to the embodiment. The hole drilling tool includes a tool body 10, an intermediate shaft 20, an adapter 30, and a dust cover 40.

[0015] The tool body 10 has a center drill 12 and a hole saw 14, which are combined to machine a circular hole in a workpiece, such as a wall or a ceiling. The hole saw 14 includes a cylindrical body 14a and a plurality of blades 14b, which are fixed at a plurality of positions aligned in the circumferential direction at the tip of the body 14a. The plurality of blades 14b are pressed against the workpiece 2 while the entire hole saw 14 is rotated around its central axis, so that a circular hole having a diameter corresponding to the diameter of the body 14a can be machined in the workpiece 2. The center drill 12 is positioned to protrude forward from the tip of the hole saw 14 so as to drill a center hole for centering prior to the hole saw 14.

[0016] The tool body according to the present invention is not limited to the combination of the center drill 12 and the hole saw 14. The tool body may be, for example, composed of only the center drill 12.

[0017] The intermediate shaft 20 and the adapter 30 are connected in series to each other in the axial direction to form a support shaft. The axial direction is a direction along the central axis of rotation of the tool body 10. The support shaft has a base end portion connected to a rotary driver (not shown) and a tip end portion on the opposite side, and the tip end portion holds the tool body 10 (in this embodiment, both the center drill 12 and the hole saw 14).

[0018] The intermediate shaft 20 is a member interposed between the adapter 30 and the output shaft of the rotary driver to adjust the overall length of the support shaft, and has a drive connection end 22 and an adapter holding end 24. The drive connection end 22 corresponds to the base end of the support shaft, and can be detachably connected to the output shaft of the rotary driver. The adapter holding end 24 is the end opposite to the drive connection end, and the adapter 30 is connected to the adapter holding end 24.

[0019] The adapter 30 holds the tool body 10 and transmits the rotational driving force of the rotary drive machine thereto, and has a held end 32 and a tool body holding end 34 on the opposite side. The held end 32 is detachably held by the adapter holding end 24 of the intermediate shaft 20. The tool body holding end 34 corresponds to the tip of the support shaft, and detachably holds the tool body 10.

[0020] The support shaft according to the present invention is not limited to the combination of the intermediate shaft 20 and the adapter 30. The support shaft may be composed of only a single shaft member extending in one direction.

[0021] The dustproof cover 40 is configured to cover the tool body 10 while allowing a hole-making operation in which the tool body 10 is pressed into the workpiece 2. Specifically, the dustproof cover 40 has a base 42, a bellows portion 44, a transparent cover portion 46, a rear connector 47, a front connector 48, and a biasing means 50.

[0022] The base 42 supports the bellows portion 44 and the transparent cover portion 46 at a position in front of the base 42 while being supported by the support shaft (the intermediate shaft 20 in this embodiment) at a position rearward of the tool body.

[0023] Specifically, the base 42 has a rear end wall 42a, a rear peripheral wall 42b, a front end wall 42c, and a front peripheral wall 42d. The rear end wall 42a is in the shape of a doughnut plate extending radially outward from the intermediate shaft 20, and is supported by the intermediate shaft 20 so as to be movable in the axial direction along the peripheral surface of the intermediate shaft 20. The rear peripheral wall 42b is in the shape of a cylinder extending forward (in the direction toward the tip of the tool body 10; leftward in Figs. 1 to 4) from the radially outer edge of the rear end wall 42a. The front end wall 42c is connected to the front end (left end in Figs. 1 to 4) of the rear peripheral wall 42b, and is in the shape of a doughnut plate extending radially outward from the intermediate shaft 20. The front peripheral wall 42d extends forward from the outer circumferential edge of the front end wall 42c, and is connected to the bellows portion 44.

[0024] Bearings 43 are interposed between radially inner ends of the rear end wall 42a and the front end wall 42c and the outer circumferential surface of the intermediate shaft 20, allowing the two end walls 42a, 42c to rotate relative to the intermediate shaft 20 and to slide along the axial direction, i.e., to move relatively in the axial direction. The rear peripheral wall 42b can also function as a grip that can be held by an operator.

[0025] The transparent cover part 46 extends along the central axis of the tool body 10 and has a cylindrical shape surrounding the tool body 10 at a radially outer position thereof. The transparent cover part 46 is preferably cylindrical with its center on the central axis of the tool body 10. However, the specific cross-sectional shape of the transparent cover part 46 is not limited.

[0026] The transparent cover portion 46 has a rear end portion (right end portion in Figs. 1 to 4) 46a and an opposite front end portion (left end portion in Figs. 1 to 4) 46b, and the front end portion 46b constitutes a cover tip portion that can come into contact with the workpiece 2. The front end portion 46b (cover tip portion) in this embodiment forms an annular shape that surrounds the tool body 10 and can come into contact with the surface of the workpiece 2 over the entire circumference.

[0027] The transparent cover portion 46 is formed of a transparent material, and the material has a degree of transparency that allows the processing position of the workpiece 2 by the tool body 10 to be visually recognized from the outside when the front end portion 46b is in contact with the workpiece 2. The transparent material is preferably a resin, such as polycarbonate, that is relatively hard and has high rigidity and has the above-mentioned transparency. The transparency of the transparent cover portion 46 may be 100% (completely transparent), or may be a value less than 100% within a range that satisfies the condition of enabling the visibility. In addition, the transparent cover portion 46 is not necessarily limited to being entirely transparent, and may include an opaque portion within a range that satisfies the condition of enabling the visibility of the processing position. In the transparent cover portion 46 according to this embodiment, the front end portion (cover tip portion) 46b is made of a ring-shaped seal material such as rubber that easily adheres to the workpiece, and the front end portion 46b is opaque, but the other cylindrical body portion has the above-mentioned transparency, allowing the operator operating the hole drilling tool to visually recognize the processing position.

[0028] 1 to 4 has a total length slightly smaller than the total length of the hole saw 14 of the tool body 10, and within that range, the tool body 10 can be viewed from the outside through the transparent cover part 46. The axial length of the transparent cover part 46, particularly the length of the transparent part, can be appropriately set within a range that allows viewing of the processing position.

[0029] The bellows portion 44 connects the base portion 42 and the transparent cover portion 46 to each other in the axial direction and has a bellows shape that can be contracted in the axial direction. The contraction allows the base portion 42 to advance relatively in the axial direction with respect to the transparent cover portion 46 as shown in Figures 2 and 4.

[0030] The bellows portion 44 is integrally formed from a material (e.g., synthetic resin such as low-density polyethylene) that is relatively soft and easily elastically deformable. The bellows portion 44 has a rear end portion 44a and a front end portion 44b opposite thereto, and the rear end portion 44a is detachably connected to the front peripheral wall 42d of the base portion 42 via the rear connector 47, while the front end portion 44b is detachably connected to the rear end portion 46a of the transparent cover portion 46 via the front connector 48.

[0031] The rear connector 47 is detachably connected to the front peripheral wall 42d of the base 42 and to the rear end 44a of the bellows portion 44, thereby connecting the base 42 and the bellows portion 44 to each other. Specifically, the rear connector 47 is made of an elastically deformable material such as rubber and has an annular shape corresponding to the front peripheral wall 42d and the rear end 44a, and has a circumferential groove 47a and a bellows-corresponding inner circumferential surface 47b shown in Fig. 5. The circumferential groove 47a has an annular shape corresponding to the front end (the left end in Figs. 1 to 5) of the front peripheral wall 42d and opens rearward (to the right in Fig. 5), and the front peripheral wall 42d is press-fitted from the rear into the circumferential groove 47a, thereby connecting the rear connector 47 to the front peripheral wall 42d. The bellows-corresponding inner peripheral surface 47b has an inwardly facing mountain-shaped shape (a shape in which both sides are gradually tapered toward the axial center) corresponding to the valley-shaped shape (a shape in which both sides are gradually tapered toward the axial center) of the rear end 44a of the bellows portion 44, and the bellows-corresponding inner peripheral surface 47b is press-fitted into the valley-shaped portion of the rear end 44a, thereby connecting the rear connector 47 to the rear end 44a. Also, the rear connector 47 is formed with a notched groove 47c for facilitating press-fitting into the rear end 44a. The notched groove 47c is formed so as to extend from the apex (the portion with the smallest inner diameter) of the bellows-corresponding inner peripheral surface 47b toward the radially outward side (upward in FIG. 5), thereby facilitating the deformation of the rear connector 47 for the press-fitting.

[0032] The front connector 48 is detachably connected to the rear end 46a of the transparent cover portion 46 and to the front end 44b of the bellows portion 44 by a configuration similar to that of the rear connector 47, thereby connecting the transparent cover portion 46 and the bellows portion 44 to each other. Specifically, the front connector 48 is made of an elastically deformable material such as rubber and has a ring shape corresponding to the rear end 46a and the front end 44b, and has a circumferential groove 48a and a bellows-corresponding inner peripheral surface 48b shown in FIG. 6. The circumferential groove 48a is annular and opens forward (leftward in FIG. 6) corresponding to the rear end 46a of the transparent cover portion 46, and the rear end 46a is press-fitted into the circumferential groove 48a from the front side, thereby connecting the front connector 48 to the rear end 46a. The bellows-corresponding inner peripheral surface 48b has an inwardly facing mountain-shaped shape (a shape in which both sides are gradually tapered toward the axial center) corresponding to the valley-shaped shape (a shape in which both sides are gradually tapered toward the axial center) of the front end 44b of the bellows portion 44, and the bellows-corresponding inner peripheral surface 48b is press-fitted into the valley-shaped portion of the front end 44b, thereby connecting the front connector 48 to the front end 44b. The front connector 48 also has a notched groove 48c formed therein to facilitate press-fitting into the front end 44b. The notched groove 48c is formed so as to extend from the top (smallest inner diameter portion) of the bellows-corresponding inner peripheral surface 48b toward the radially outward side (upward in FIG. 6), thereby facilitating deformation of the front connector 48 for the press-fitting.

[0033] The biasing means 50 defines a relative axial movement range of the dust cover 40 with respect to the support shaft (the intermediate shaft 20 and the adapter 30 in this embodiment) and the tool body 10 between a forward position shown in Fig. 1 and a retracted position shown in Fig. 2, and biases the dust cover 40 forward (i.e., toward the forward position). The forward position is a position where the transparent cover part 46 covers at least a part of the tool body 10 when the bellows part 44 is not contracted (i.e., a natural state where no external force is applied in the axial direction), and is preferably a position where the front end part 46b (cover tip part) of the transparent cover part 46 is located near the tip of the tool body 10 (the tip of the center drill 12 in this embodiment), that is, a position where the transparent cover part 46 covers substantially the entire tool body 10. The retracted position is a position closer to the base end of the support shaft than the forward position, i.e., a rearward position, and in this embodiment, is a position where, when the bellows portion 44 is contracted, the front end 46b (tip of cover) of the transparent cover portion 46 is located equal to or further rearward (to the right in Figure 1) than the rear end of the tool main body 10 (in this embodiment, the rear end of the body 14a of the hole saw 14), i.e., a position where the entire dust cover 40 protrudes forward of the transparent cover portion 46.

[0034] Specifically, the biasing means 50 according to this embodiment includes a spring seat 51 and a compression coil spring 52 shown in Fig. 1 and Fig. 2. The spring seat 51 is attached to an appropriate portion of the support shaft (in this embodiment, the intermediate portion of the intermediate shaft 20) via a bearing 43 and protrudes radially outward from the outer circumferential surface of the support shaft (in this embodiment, the outer circumferential surface of the intermediate shaft 20). The bearing 43 allows the spring seat 51 to rotate relative to the intermediate shaft 20, but a retaining ring prevents the spring seat 51 from moving axially relative to the intermediate shaft 20. In other words, the spring seat 51 is attached to the support shaft in a state in which its axial movement relative to the support shaft is restricted. It does not matter whether the spring seat 51 is allowed to rotate relative to the support shaft. The compression coil spring 52 is interposed between the spring seat 51 and an appropriate portion of the base 42 (in this embodiment, the radially inner edge of the front end wall 42c), thereby holding the entire transparent cover portion 46 including the base 42 in the forward position, while allowing relative axial displacement of the base 42 toward the retracted position (i.e., rearward) with respect to the support shaft by the compressive elastic deformation of the compression coil spring 52, and urging the base 42 toward the forward position (i.e., forward) by the elastic force of the compression coil spring 52.

[0035] Next, the operation of the above-described dust cover 40 and the hole drilling tool equipped with the same will be described.

[0036] In a state before the hole drilling process by the hole drilling tool, i.e., in a state in which no axial load is applied to either the dust cover 40 or the tool body 10, the bellows portion 44 of the dust cover 40 is not contracted, and the base portion 42 of the dust cover 40 is held at the front end position shown in Fig. 1 by the compression coil spring 52 of the biasing means 50. Therefore, the front end portion 46b of the transparent cover portion 46, which is the cover tip portion of the dust cover 40, is held at a position near the tip of the tool body 10 (the tip of the center drill 12 in this embodiment). This makes it possible for the transparent cover portion 46 to reliably cover at least a part of the tool body 10 at the start of the hole drilling process, and for the front end portion 46b (cover tip portion) to reliably come into contact with or be close to the workpiece 2 in this embodiment.

[0037] When a rotational driving force is input from a rotary drive machine (not shown) to the drive connection end 22 of the intermediate shaft 20 in the stage before the machining, the intermediate shaft 20 and the support shaft formed by the adapter 30, and further the tool body 10 held by the adapter 30, are rotationally driven. A bearing 43 is interposed between the intermediate shaft 20 and the base 42 of the dust cover 40, and the dust cover 40 may rotate somewhat together with the support shaft due to the resistance of the bearing 43.

[0038] In this manner, with the tool body 10 being rotationally driven, the hole drilling tool is pressed against the workpiece 2. At this time, the cover tip portion (the front end portion 46b) of the dustproof cover 40 comes into contact with the workpiece 2 prior to the tool body 10, or the operator grips the rear peripheral wall 42b of the base portion 42, whereby the rotation of the dustproof cover 40 (the co-rotation) stops, and only the tool body 10 and the spindle inside the dustproof cover 40 rotate.

[0039] When the hole-drilling tool is further pressed against the workpiece 2 in this state, the position of the transparent cover portion 46 remains the same, and the tool body 10 is pressed into the workpiece 2 by the relative displacement of the base portion 42 with respect to the transparent cover portion 46 accompanied by the contraction of the bellows portion 44 and the relative displacement of the intermediate shaft 20 with respect to the base portion 42 accompanied by the contraction of the compression coil spring 52, thereby performing hole-drilling in the workpiece 2. During this hole-drilling process, the tool body 10 is always covered by the dust cover 40, and therefore, scattering of dust generated by the hole-drilling process to the surroundings is effectively suppressed.

[0040] In the hole drilling process according to this embodiment, first the center drill 12 starts drilling to position the hole drilling tool relative to the workpiece 2, and then the multiple blades 14b of the hole saw 14 cut around it to drill a hole of approximately the same diameter as the diameter of the body 14a of the hole saw 14, but when the center drill 12 comes into contact with the workpiece 2, the position of contact, i.e., the processing position, can be visually confirmed by the operator from outside the dust cover 40 through the transparent cover portion 46. This makes the positioning process easier and enables the accuracy of the processing position to be improved.

[0041] On the other hand, the combination of the relative displacement of the base 42 with respect to the transparent cover part 46 due to the contraction of the bellows part 44 and the relative displacement of the intermediate shaft 20 with respect to the base 42 increases the amount of relative displacement of the tool body 10 in the axial direction with respect to the transparent cover part 46, thereby making it possible to ensure a large effective machining depth by the tool body 10. For example, the relative displacement of the tool body 10 with respect to the transparent cover part 46 can be realized only by the elastic deformation of the compression coil spring 52 (without the bellows part 44), but in this case, in order to ensure a large effective machining depth, it is necessary to significantly increase the axial length of the compression coil spring 52 and even the axial length of the entire hole drilling tool. In contrast, the combination of the contraction of the bellows part 44 and the relative displacement of the base 42 with respect to the support shaft makes it possible to ensure a large effective machining depth with a compact structure.

[0042] In the present invention, the relative displacement of the base 42 with respect to the support shaft is not essential. For example, the base 42 may be fixed to the intermediate shaft 20 in the retreated position shown in Fig. 2. However, in this case, in order to position the front end 46b of the transparent cover part 46, i.e., the cover tip end part, forward of the tip end of the tool body 10 as shown in Fig. 1, the axial length of the bellows part 44 must be increased, and the shape stability of the entire dust cover 40 decreases accordingly. However, the combination of the bellows part 44 and the relative displacement of the base 42 with respect to the support shaft makes it possible to secure a large effective machining depth while securing good shape retention by appropriately suppressing the axial length of the bellows part 44.

[0043] The base and the bellows part according to the present invention may be integrally (i.e., inseparably) connected to each other, and similarly, the bellows part and the transparent cover part may be integrally connected to each other. On the other hand, the provision of a rear connector 47 that detachably connects the base 42 and the rear end 44a of the bellows part 44 and a front connector 48 that detachably connects the front end 44b of the bellows part 44 and the transparent cover part 46 makes it possible to replace the bellows part 44 according to the axial length of the tool body 10, for example, and also makes it easy to perform maintenance work on each part. [Explanation of symbols]

[0044] 2 Workpiece 10 Tool body 12 Center drill 14 Hole saw 20 Intermediate shaft (support shaft) 22 Drive connection end (base end of support shaft) 30 Adapter (support shaft) 34 Tool body holding end (tip of spindle) 40 Dust cover 42 Base 44 Bellows 46 Transparent cover part 46b Front end (tip of cover) 50 Actuation means

Claims

1. a tool body that can be driven to rotate and be forced into a workpiece to drill a hole in the workpiece; and a spindle that has a base end connected to a rotary drive device capable of outputting a rotational driving force and a tip end opposite the base end for holding the tool body, and that transmits the rotational driving force to the tool body to rotate the tool body, the dustproof cover being used for a hole drilling tool that includes the tool body and that covers the tool body while allowing a hole drilling operation in which the tool body is forced into the workpiece, a base portion supported by the spindle at a position rearward of the tool body; a transparent cover part having a cylindrical shape capable of surrounding the tool body, including a cover tip part capable of contacting the workpiece, and having a transparency that allows a position where the workpiece is machined by the tool body to be visually confirmed from the outside when the cover tip part is in contact with the workpiece; A dust cover comprising: a bellows-shaped bellows portion that connects the base and the transparent cover portion to each other in the axial direction along the support shaft, and that is contractible in the axial direction to allow the base to move forward in the axial direction relative to the transparent cover portion.

2. 2. A dust cover as described in claim 1, wherein the base of the dust cover is attached to the spindle so as to be movable relative to the spindle in the axial direction between an advanced position and a retracted position, the advanced position being a position in which the transparent cover portion covers at least a portion of the tool body when the bellows portion is not contracted, and the retracted position being a position closer to the base end of the spindle than the advanced position.

3. 3. The dust cover of claim 2, further comprising biasing means for biasing said base toward said forward position.

4. a tool body that is driven to rotate and pushed into the workpiece to drill a hole in the workpiece; a spindle having a base end connected to a rotary drive device capable of outputting a rotary drive force and a tip end opposite to the base end and holding the tool body, the spindle transmitting the rotary drive force to the tool body to rotate the tool body; A hole drilling tool comprising: a dust cover according to any one of claims 1 to 3.

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