Grinding stones and grinding tools with shafts

Abstract

The grinding stone (1) with a shaft comprises: a grinding stone (2) and a shaft (3) extending from the grinding stone (2). The grinding stone (2) is a grinding stone in which a plurality of fiber bundles (22) of a plurality of inorganic long fibers (21) are bonded together with resin (23). The shaft (3) satisfies condition (A) when the rigidity is set to S. The rigidity of the shaft (3) is determined by the formula (B) described later. In this case, the shaft (3) is fixed with a 30mm area from the rear end as a handle (4), and the rear end of the outer peripheral end (2a) of the grinding stone (2) is pressed in from a direction orthogonal to the axis (L), with the pressing load set as F (N) and the displacement of the front end of the shaft (3) set as δ (mm).

Description

Technical Field

[0001] The present invention relates to: a grinding stone with an axle used after being held by a hand-held rotary tool, and a grinding tool in which the grinding stone with an axle is held by a hand-held rotary tool. Prior Technology

[0002] Patent Document 1 describes a grinding stone with an axle for use after being held by a handheld rotary tool such as a rotary pneumatic drill bit. The grinding stone with an axle in this document comprises: a grinding stone and an axle connected to the grinding stone. The grinding stone has a rotationally symmetrical shape relative to the axis of the axle. The grinding stone is an inorganic long-fiber reinforced resin body and comprises: a plurality of abrasive material bundles, each bundle containing a plurality of inorganic long fibers; and resin for binding the plurality of abrasive material bundles. The axle comprises: a support member connected to the grinding stone; and a rod-shaped handle connected to the support member. The handle is the part that is held (chucking) by the rotary tool. The axle can elastically deform in a direction orthogonal to the axis of the support member. During grinding, the outer peripheral surface of the grinding stone contacts the grinding target area of ​​the workpiece.

[0003] The grinding stone with a shaft described in this document can elastically press the grinding stone against the workpiece due to the shaft's flexibility. Therefore, when performing grinding by hand-holding a rotating tool, the positional accuracy of the grinding stone contacting the workpiece is low. Furthermore, due to the shaft's flexibility, if excessive force is applied to the grinding stone, the force can be absorbed by the shaft's elastic deformation. Therefore, there is no situation where the grinding stone "over-grinds the workpiece." Moreover, because the grinding stone can be elastically pressed against the workpiece, there is no grinding stone bouncing on the workpiece surface. As a result, because the grinding stone can consistently contact the workpiece surface, it can effectively perform deburring and grinding. [Previous Technical Documents] [Patent Literature]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2006-35414 Summary of the Invention

[0005] [The problem the invention aims to solve]

[0006] However, grinding stones with flexible shafts can experience uneven wear during grinding. Once uneven wear occurs, the contact between the grinding stone and the workpiece becomes inconsistent, sometimes hindering effective deburring and grinding. Furthermore, uneven wear prevents the grinding stone from returning to its original rotationally symmetrical shape during grinding, exacerbating deformation. This results in phenomena such as the grinding stone bouncing on the workpiece surface. This bouncing further disrupts the contact between the grinding stone and the workpiece, again hindering effective deburring and grinding.

[0007] In view of the above problems, the object of the present invention is to provide a grinding stone with a shaft that can suppress uneven wear of the grinding stone during grinding even in cases of shaft deflection. Furthermore, the object of the present invention is to provide a grinding tool equipped with a grinding stone having the shaft. [Solutions]

[0008] The inventors of this case, through repeated review, have reached the following insight: the uneven wear of the grinding stone is caused by "the vibration generated by the resonance of the grinding stone with an axis during the grinding process." More specifically, the insight obtained is as follows: once the grinding stone vibrates due to resonance, the grinding stone will repeatedly impact the surface of the workpiece, and the impact during the impact causes localized breakage of the grinding stone, resulting in uneven wear. This invention is developed based on the inventors' above-mentioned insights.

[0009] To solve the aforementioned problems, the present invention is a grinding stone with a shaft, comprising: a shaft having a handle at its rear end; and a grinding stone having a rotationally symmetrical shape about the axis of the aforementioned shaft, fixed to the front end of the aforementioned shaft, with its outer peripheral end located on a more peripheral side than the aforementioned shaft. The handle is held by a handheld rotating tool and the workpiece is ground using the aforementioned outer peripheral end of the aforementioned grinding stone. The grinding stone is characterized in that: the aforementioned grinding stone has a plurality of bundles of abrasive material "bundled together with a plurality of inorganic long fibers" and a resin for binding the plurality of abrasive material bundles. Its inherent vibration frequency, when the rigidity of the aforementioned shaft is set to S, becomes a value that will not resonate during the grinding process by satisfying the following conditional expression. 0.4≦S≦100 The rigidity of the aforementioned shaft, in the case described later, is obtained using the calculation formula described later. This case refers to the case where a 30mm area from the rear end of the aforementioned shaft is used as the aforementioned handle and fixed to the fixture, and the "rear end of the aforementioned grinding stone's outer peripheral end" is pressed in from a direction orthogonal to the aforementioned axis, with the pressing load set as F (N) and the displacement of the front end of the aforementioned shaft set as δ (mm). S=F / δ

[0010] In the shaft-equipped grinding stone of the present invention, the rigidity of the shaft is set to a value within a predetermined range determined by a conditional formula. This ensures that the natural vibration frequency of the shaft-equipped grinding stone is a value that will not resonate during grinding. Therefore, it suppresses the occurrence of uneven wear of the grinding stone caused by vibrations of the grinding stone resulting from resonance of the shaft-equipped grinding stone. Furthermore, by setting the rigidity of the shaft to a value within a predetermined range determined by the conditional formula, it prevents or suppresses the grinding stone from bouncing on the workpiece surface during grinding. As a result, since the contact between the grinding stone and the workpiece becomes uniform, it prevents or suppresses situations where deburring and grinding cannot be performed effectively.

[0011] In other words, when the shaft stiffness value is below the lower limit of the conditional expression, the shaft stiffness decreases, and the natural vibration frequency of the grinding stone with the shaft decreases. As a result, resonance is easily generated during grinding, and the grinding stone is prone to uneven wear due to vibrations caused by resonance. Conversely, when the shaft stiffness value is above the upper limit of the conditional expression, the shaft stiffness becomes excessively high. That is, the higher the shaft stiffness, the higher the natural vibration frequency of the grinding stone with the shaft, thus preventing resonance in the grinding stone with the shaft during grinding. However, once the shaft stiffness becomes too high, the shaft cannot adequately absorb the vibrations transmitted from the workpiece side to the grinding stone with the shaft during grinding, and the grinding stone is prone to bouncing on the workpiece surface during grinding. Therefore, setting the shaft stiffness value below the upper limit of the conditional expression suppresses the bouncing of the grinding stone during grinding. This allows for easy and efficient removal of burrs and grinding of the target area.

[0012] Furthermore, the grinding stone comprises "a plurality of abrasive material bundles formed from a plurality of inorganic long fibers" and a resin for binding the aforementioned plurality of abrasive material bundles. Compared to grinding stones that "use resin to bind abrasive grains," grinding stones formed from this inorganic long fiber resin are less prone to localized chipping when subjected to impact. That is, grinding stones that use resin to fix abrasive grains are prone to uneven wear due to the chipping of individual abrasive grains when subjected to impact, while grinding stones that use resin to fix the plurality of abrasive material bundles do not experience this chipping of individual abrasive grains. Therefore, uneven wear of the grinding stone is more easily suppressed.

[0013] In this case, when a flexible abrasive stone is mounted on a handheld rotary tool for grinding, vibrations generated during deburring are absorbed by the shaft and sometimes not transmitted to the operator holding the tool. In such situations, it's impossible to perceive whether the grinding is being performed effectively. Therefore, when grinding areas that are difficult to visually inspect, such as the inner wall of a deep hole in a workpiece, using a flexible abrasive stone can lead to inefficient grinding and reduced workability. To address this issue, the inventors have demonstrated that when the shaft stiffness meets the specified condition, there is no problem of insufficient stiffness, preventing vibrations from being transmitted to the operator through the shaft and the rotating tool. Therefore, even when grinding areas that are difficult to visually inspect, the operator can intuitively judge whether the necessary grinding has been performed. This helps to suppress the decline in grinding workability.

[0014] Furthermore, traditionally, when grinding the inner wall of a hole in a workpiece, a longer shaft is required to allow the grinding stone to reach the deepest point of the object being ground. However, generally speaking, if the flexible shaft is lengthened, its rigidity decreases. Therefore, if the shaft is lengthened, resonance will occur during grinding, leading to the problem of uneven wear of the grinding stone. Moreover, if the shaft is lengthened, the operator may not be able to judge whether the required grinding has been performed by touch. Therefore, it is not easy to lengthen the shaft while suppressing the decline in workability of grinding. In contrast, according to the present invention, when the shaft rigidity value meets the conditional formula, uneven wear of the grinding stone can be suppressed regardless of the shaft length, and the operator can judge whether the required grinding has been performed by touch. Therefore, according to the present invention, the shaft can be lengthened while suppressing the decline in workability of grinding.

[0015] Here, conventionally, the shafted grinding stones that are flexible and have an axle, i.e., the shafted grinding stones circulating in the market, typically have a length from the rear end of the axle to the grinding stone that is less than 50 mm. In contrast, in this invention, the length from the rear end of the aforementioned axle to the aforementioned grinding stone can be 50 mm or more.

[0016] In this invention, the outer diameter of the aforementioned shaft can be less than 6 mm. This prevents the shaft from becoming too thick, thus preventing or suppressing the shaft's rigidity from exceeding the upper limit of the conditional expression. Furthermore, as long as the outer diameter of the shaft is less than 6 mm, when an operator holding the rotating tool wants to observe the area being ground, the situation where the area being ground becomes invisible due to the shaft's shadow can be easily avoided.

[0017] In this invention, the aforementioned grinding stone can be formed to a weight of 0.8g or less. In this way, in situations such as "applying force to the grinding stone with an axis from the workpiece side during grinding processing", the situation of "the grinding stone bouncing on the surface of the workpiece" can be easily suppressed.

[0018] In this invention, a fixing mechanism can be formed that "detachably fixes the aforementioned grinding stone to the aforementioned front end of the aforementioned shaft". With such a fixing mechanism, a new grinding stone can be replaced when the grinding stone wears out.

[0019] In this invention, the aforementioned grinding stone can be formed to be square or circular when viewed from a direction orthogonal to the aforementioned axis.

[0020] In this invention, the outer diameter of the aforementioned shaft is 3 mm or more, and the outer diameter of the aforementioned shank and the thickness of the aforementioned grinding stone in the axial direction are smaller than the outer diameter of the aforementioned grinding stone. As a result, the grinding stone has a shape that is "longer radially than axially," and the outer peripheral end of the grinding stone is located further outward than the shaft. This facilitates the formation of a shape where the outer peripheral end of the grinding stone contacts the burr-producing portion of the workpiece.

[0021] In this invention, the aforementioned grinding stone can be formed such that, when viewed from a direction orthogonal to the aforementioned axis, it has a shape that tapers towards the outer periphery. In this case, the shape of the grinding stone as seen from the direction intersecting the axis is an isosceles triangle, a rhombus, an ellipse, or the like.

[0022] In this invention, the aforementioned grinding stone can be formed to be rectangular when viewed from a direction orthogonal to the aforementioned axis. As long as the shape of the grinding stone is rectangular when viewed from a direction orthogonal to the axis, the grinding surface of the grinding stone, that is, the radial outer periphery, becomes: having a certain (constant) width in the axial direction.

[0023] In this invention, the length from the rear end of the aforementioned shaft to the aforementioned grinding stone can exceed 150 mm. In this way, the grinding stone can easily reach the "deepest grinding target area of ​​the hole provided in the workpiece".

[0024] Secondly, the grinding tool of the present invention is characterized by having: the aforementioned grinding stone with a shaft, and a rotating tool that holds the aforementioned shank of the grinding stone with a shaft. [The effects of the invention]

[0025] According to the present invention, the grinding stone with a shaft suppresses uneven wear of the grinding stone even when the shaft is elastic during grinding. Simple Explanation of the Diagram

[0026] [Figure 1] is a three-dimensional view of a grinding stone with an axle. [Figure 2] is an exploded perspective view of a grinding stone with an axis. [Figure 3] is an explanatory diagram of a grinding tool formed by a "grinding stone with a shaft" and a rotating tool. [Figure 4] is an explanatory diagram of a grinding stone. [Figure 5] is an illustration of a measurement method for measuring the rigidity of the shaft of a "grindstone with a shaft". [Figure 6] A table summarizing the rigidity, total length, and number of revolutions during grinding of the handle of the "grinding stone with shaft" in the embodiments and comparative examples. [Figure 7] is an explanatory diagram of the workpiece used in the evaluation test. [Figure 8] is an explanatory diagram of the evaluation experiment. [Figure 9] is a table showing the evaluation results of evaluation test 1. [Figure 10] is a table showing the evaluation results of evaluation test 2. [Figure 11] is a table showing the evaluation results of evaluation test 3. [Figure 12] is an explanatory diagram of a modified grinding stone with a shaft. [] Implementation

[0027] The following describes an embodiment of the present invention, namely a grinding stone with an axis and a grinding tool, with reference to the figures.

[0028] Figure 1 is a side view of a grinding stone with an axle. Figure 2 is an exploded perspective view of a grinding stone with an axle. Figure 3 is an explanatory diagram of a grinding tool formed by a grinding stone with an axle and a rotating tool. Figure 3 shows the operator holding the grinding tool. Figure 4 is an explanatory diagram of the grinding stone. Figure 5 is an explanatory diagram of a measurement method for measuring the rigidity of the axle of a grinding stone with an axle. In the following description, the direction along the axis L of the axle 3 of the grinding stone 1 with an axle will be referred to as the axial direction X. Furthermore, in the axial direction X, the side where the grinding stone 2 is located is referred to as the front X1 of the grinding stone 1 with an axle, and the opposite side is referred to as the rear X2 of the grinding stone 1 with an axle.

[0029] The grinding stone 1 with an axle includes: a grinding stone 2, and an axle 3 extending rearward X2 from the grinding stone 2. The axle 3 has a handle 4 at its rear end. As shown in Figure 3, the handle 4 is the part of the axle 3 that is held (chucking) by the rotating tool 10. The grinding stone 2 has a shape that is rotationally symmetrical about the axis L of the axle 3. In this example, the grinding stone 2 is disc-shaped. With the grinding stone 2 fixed to the front end of the axle 3, the outer peripheral end 2a of the grinding stone 2 is located on the outer periphery side of the axle 3.

[0030] The grinding stone 2 is fixed to the shaft 3 via the fixing mechanism 6. The fixing mechanism 6 detachably fixes the grinding stone 2 to the shaft 3. As shown in Figure 2, the fixing mechanism 6 has: a headed screw 7, which has a head 7a and a threaded portion 7b protruding from the head 7a. In addition, the fixing mechanism 6 has: a fixing hole 8, which penetrates the center of the grinding stone 2 in the axial direction X; and a threaded hole 9, which is provided on the front end face of the shaft 3. The threaded portion 7b of the headed screw 7 is locked into the threaded hole 9 through the fixing hole 8, so that its head 7a abuts against the grinding stone 2. The grinding stone 2 can also be directly fixed to the shaft 3. In this case, the grinding stone 2 has a fixing hole at its center for the front end of the shaft 3 to be fitted. The fixing hole forms an opening X2 to the rear. In addition, with the front end of the shaft 3 inserted into the fixing hole, the grinding stone 2 is fixed to the shaft 3 by adhesive applied to the front end of the shaft 3 or the inner circumferential surface of the fixing hole.

[0031] As shown in Figure 3, the grinding stone 1 with a shaft is held by a rotating tool 10 and used as a grinding tool 15. In this example, the rotating tool 10 is a handheld electric grinder or a handheld rotating pneumatic drill bit, etc. That is, the grinding tool 15 in this example has a gripping part 11 for the operator to hold. The handle 4 of the grinding stone 1 with a shaft is held by the chuck mechanism 12 of the rotating tool 10. During grinding, the operator holds the rotating tool 10 in their hand and brings the grinding stone 2 into contact with the grinding target area of ​​the workpiece.

[0032] (millstone) The grinding stone 2 is a rotating body. As shown in Figure 1, the outer diameter D of the grinding stone 2 is 3 mm or more. The outer diameter D of the grinding stone 2 is larger than the outer diameter O of the shaft 3. Therefore, the outer peripheral end 2a of the grinding stone 2 is located on a more peripheral side than the shaft 3. Furthermore, the outer diameter D of the grinding stone 2 is larger than the thickness E of the grinding stone 2 in the axial direction X. Therefore, the radial direction of the grinding stone 2 is longer than that in the axial direction X. The weight of the grinding stone 2 is 0.8 g or less.

[0033] In this example, the shape of the grinding stone 2 when viewed from a direction orthogonal to axis L is a rectangle that is longer radially than axially in the direction X. Therefore, the machined surface of the grinding stone 2, i.e., the radially outer peripheral end 2a, has a certain (constant) width in the axial direction X. In this example, the outer diameter D of the grinding stone 2 is 15 mm, and the thickness of the grinding stone 2 is 2 mm. The weight of the grinding stone 2 is 0.8 g.

[0034] The grinding stone 2 is a so-called inorganic long fiber reinforced resin body. As shown in Figure 4, the grinding stone 2 has a plurality of fiber bundles 22 "wound with a plurality of inorganic long fibers 21". Furthermore, the grinding stone 2 has a resin 23 for bonding the aforementioned plurality of fiber bundles 22. The resin 23 is a binder used to fix the plurality of fiber bundles 22. In this example, the resin 23 is a thermosetting resin, impregnated in each of the plurality of fiber bundles 22 and hardened. The tips of the plurality of inorganic long fibers 21 reach the processing surface of the grinding stone 2, i.e., the outer peripheral end 2a.

[0035] More specifically, the grinding stone 2 comprises: a plurality of first fiber bundles 22A, oriented at predetermined intervals in a first direction; and a plurality of second fiber bundles 22B, oriented at predetermined intervals in a second direction "orthogonal to the first fiber bundles 22A". The first fiber bundles 22A and 22B exhibit a state where one fiber bundle 22A, 22B partially enters between the other fiber bundles 22A, 22B. Resin 23 is impregnated between the fiber bundles 22A, 22B and hardens. The resin 23 promotes the bonding of the plurality of fiber bundles 22. Epoxy resin, unsaturated polyester resin, vinyl ester resin, bismaleimide resin, phenol resin, etc., can be used as the resin 23.

[0036] The inorganic long fiber 21 can be made of glass long fiber, alumina long fiber, boron long fiber, or silicon carbide long fiber. In this example, alumina long fiber is used as the inorganic long fiber 21. The inorganic long fiber 21 can be a fiber with an average fiber diameter of 3μm to 40μm. The fiber bundle 22 is made of 500 to 3000 Tex. In this example, after impregnating the resin 23 with a fine fiber bundle of about 500 Tex, a plurality of abrasive material bundles are aligned and arranged as shown in Figures 4(a) and 4(b). Then, the resin 23 is impregnated again and the bundle is hardened to serve as the substrate of the grinding stone 2.

[0037] (axis) Shaft 3 is rod-shaped and has the flexibility to flex in a direction orthogonal to axis L. Shaft 3 is a rotating body with a shape that is rotationally symmetrical about axis L. As shown in Figure 1, shaft 3 has a handle 4 and a neck 5 sequentially from rear X2 to front X1. The handle 4 is a region extending 30mm from the rear end of shaft 3. The neck 5 is a region located between the handle 4 and the grinding stone 2 in the axial direction X. The neck 5 has a large-diameter portion 5a on its front end side, the outer diameter of which is larger than that of the rear end of shaft 3. A threaded hole 9 for fixing the grinding stone 2 to shaft 3 is formed on the front end face of the large-diameter portion 5. In this example, shaft 3 is made of stainless steel.

[0038] Shaft 3, when its rigidity is set to S, satisfies the following condition (A).

[0039] When measuring the rigidity of shaft 3, as shown in Figure 5, a 30mm area from the rear end of shaft 3 is used as the handle 4 and fixed to fixture 30. After that, a predetermined indenting load is applied from a direction orthogonal to axis L to the load application position P at the rear end of the outer peripheral end 2a of grinding stone 2. The rigidity of shaft 3 is obtained using the following formula (B) when the indenting load is set to F (N) and the displacement at the front end of shaft (3) is set to δ (mm).

[0040] Here, the material, total length M, and outer diameter O of the shaft 3 are not restricted, as long as its rigidity meets condition (A). However, the total length M of the shaft 3 is preferably 50 mm or more. The total length M of the shaft 3 refers to the length from the rear end of the shaft 3 to the grinding stone 2. Therefore, when the front end of the shaft 3 is inserted into the fixing hole of the grinding stone 2 and the grinding stone 2 is fixed in the grinding stone 1 with the shaft of the shaft 3, the total length M of the shaft 3 is the length from the rear end of the shaft 3 to the opening edge of the fixing hole of the grinding stone 2.

[0041] Furthermore, the outer diameter O of shaft 3 is preferably less than 6 mm. This prevents shaft 3 from becoming too thick, thus preventing or suppressing its rigidity from exceeding the upper limit of condition (A). Here, the outer diameter O of shaft 3 refers to the outer diameter of the thickest part of shaft 3. Therefore, in this example, the outer diameter O of shaft 3 is the outer diameter of the large diameter portion 5a.

[0042] (Examples and Comparative Examples) The following describes seven grinding stones 1(1) to 1(7) with shafts, each having the same grinding stone 2 and fixing mechanism 6, but with variations in the rigidity of the shaft 3 and the total length M. Figure 6 is a table summarizing the rigidity of the handle, the total length, and the number of revolutions during grinding for the grinding stones of the embodiments and comparative examples. Among the grinding stones 1(1) to 1(7) with shafts, grinding stones 1(2) to 1(5) with shafts are embodiments of the present invention, where the rigidity of the shaft 3 is within the range of conditional expression (A). Grinding stones 1(1), (6), and (7) with shafts are comparative examples, where the rigidity of the shaft 3 deviates from the range of conditional expression (A).

[0043] In the grinding stones 1(1) to 1(7) with shafts, grinding stone 2 is formed of inorganic long fiber reinforced resin. The outer diameter D of grinding stone 2 is 15 mm. The thickness E of grinding stone 2 in the axial direction X is 2 mm. The shaft 3 is made of stainless steel (SUS303). In addition, the rigidity of the shaft 3 and the total length M of the shaft 3 are different for each of the grinding stones 1(1) to 1(7). Furthermore, when grinding is performed, the rotating tool 10 causes each grinding stone 1 with shaft to rotate at different speeds.

[0044] The grinding stone 1(1) has a shaft 3 with a rigidity of 0.2 N / mm. The rigidity of the shaft 3 is lower than the lower limit of condition (A). The total length M of the shaft 3 is 261 mm. After deducting the shank 4 held by the rotating tool 10, the length N of the neck 5 is 231 mm. The grinding speed is 2000 rpm.

[0045] Grinding stone 1(2) with shaft 3 has a rigidity of 0.4 N / mm. The rigidity of shaft 3 meets condition (A). The total length M of shaft 3 is 213 mm. The length N of neck 5 is 183 mm. The grinding speed is 3000 rpm. Grinding stone 1(3) with shaft 3 has a rigidity of 5 N / mm. The rigidity of shaft 3 meets condition (A). The total length M of shaft 3 is 109 mm. The length N of neck 5 is 79 mm. The grinding speed is 5000 rpm. Grinding stone 1(4) with shaft 3 has a rigidity of 10 N / mm. The rigidity of shaft 3 meets condition (A). The total length M of shaft 3 is 93 mm. The length N of neck 5 is 63 mm. The grinding speed is 8000 rpm. Grinding stone 1(5) with shaft 3 has a rigidity of 100 N / mm. The rigidity of shaft 3 meets condition (A). The overall length M of shaft 3 is 59 mm. The length N of neck 5 is 29 mm. The grinding speed is 10,000 rpm.

[0046] Grinding stone 1 (6) with shaft 3 has a rigidity of 110 N / mm. The rigidity of shaft 3 is higher than the upper limit of condition (A). The total length M of shaft 3 is 58 mm. The length N of neck 5 is 28 mm. The grinding speed is 10000 rpm. Grinding stone 1 (7) with shaft 3 has a rigidity of 120 N / mm. The rigidity of shaft 3 is higher than the upper limit of condition (A). The total length M of shaft 3 is 57 mm. The length N of neck 5 is 27 mm. The grinding speed is 10000 rpm.

[0047] (Evaluation Trial) Evaluation tests 1 to 3 were performed on the abrasive stones 1(1) to 1(7) with shafts. In evaluation tests 1 to 3, the abrasive stones 1(1) to 1(7) with shafts were clamped in the rotating tool 10 and rotated at the aforementioned number of revolutions to remove burrs from the grinding target area of ​​the workpiece 50. In evaluation test 1, the following was evaluated: whether the sensation of the abrasive stone 2 grinding the workpiece during the grinding process could be transmitted to the operator through the abrasive stone 2, the shaft 3, and the rotating tool 10. In evaluation test 2, the bounce of the abrasive stone 2 during the grinding process was evaluated. In evaluation test 3, the uneven wear of the abrasive stone 2 during the grinding process was evaluated. Figure 7 is a perspective view of the workpiece used in evaluation tests 1 to 3. Figure 8 is an explanatory diagram of evaluation tests 1 to 3. In Figure 8, the workpiece is shown in cross-section. In addition, in Figure 8, the rotating tool 10 is omitted, and the workpiece and the abrasive stone 1 with shaft are shown.

[0048] Workpiece 50 is made of carbon steel for mechanical construction. As shown in Figure 7, workpiece 50 is cylindrical. The outer diameter R of workpiece 50 is 30 mm, and the inner diameter T is 20 mm. As shown in Figure 8, an annular groove 51 is provided on the inner circumferential surface 50a of workpiece 50 at a position 20 mm from the end of workpiece 50. The width U of the annular groove 51 is 5 mm, and the depth V is 2.5 mm. Furthermore, when viewed radially, workpiece 50 has a through hole 52 with a diameter W of 3 mm at the position overlapping with the annular groove 51. The through hole 52 is provided in such a way that a drill bit can penetrate from the radial outside to the inner side of workpiece 50. The opening edge of the through hole 52 at the annular bottom surface 51a of the annular groove 51 is the grinding target area. Burrs are generated at the grinding target area. This grinding target area can be said to be located at the deepest side of the deep hole provided in workpiece 50.

[0049] In evaluation test 1, the "opening edge of the through hole 52 on the inner circumferential surface 50a of workpiece 50" was used as the object, and the rotating grinding stone 2 was brought into contact with workpiece 50 to remove burrs. In evaluation test 1, three evaluators judged whether the burr removal could be performed based on the "feeling transmitted to the hand through the grinding stone 2, shaft 3, and rotating tool 10".

[0050] The evaluation results of evaluation test 1 are shown in Figure 9. In Figure 9, "×" indicates that the evaluator cannot judge whether the burr removal is being performed based on the tactile sensation transmitted to the hand, and "○" indicates that the evaluator can judge whether the burr removal is being performed based on the tactile sensation transmitted to the hand. As shown in Figure 9, in the case where the grinding stone 1 (1) with a shaft is clamped in the rotating tool 10 and the grinding process is performed, none of the three evaluators can judge whether the burr removal has been performed based on the tactile sensation "transmitted to the hand through the grinding stone 2, shaft 3, and rotating tool 10". That is, the grinding stone 1 (1) with a shaft has low rigidity and is easy to bend, so the vibration generated during the burr removal is absorbed by the shaft 3 and cannot be transmitted to the evaluator. In the case where the grinding stones 1 (2) to (7) with shafts are clamped in the rotating tool 10 and the grinding process is performed, all three evaluators obtained the tactile sensation that the burr removal can be performed at the grinding drop area.

[0051] Evaluation Test 1 was conducted to confirm whether grinding stones with shafts 1(1)~1(7) could be used in grinding processes where the grinding target cannot be directly observed visually. According to the test results, grinding stones with shafts 1(2)~1(7) can be used in grinding processes where the grinding target cannot be directly observed visually.

[0052] In evaluation test 2, the opening edge of the through hole 52 on the inner circumferential surface 50a of the workpiece 50 was used as the object, and the rotating grinding stone 2 was brought into contact with the workpiece 50 to remove burrs. In addition, in evaluation test 2, three evaluators judged whether the grinding stone 2 bounced during the grinding process based on the "feel transmitted to the hand through the shaft 3 and the rotating tool 10".

[0053] The evaluation results of evaluation experiment 2 are shown in Figure 10. In Figure 10, "×" indicates that the evaluator felt the bounce of the grinding stone 2, and "○" indicates that the evaluator did not feel the bounce of the grinding stone 2. As shown in Figure 10, when the grinding stones 1 (1) to 1 (5) with shafts were clamped in the rotating tool 10 and grinding was performed, none of the three evaluators felt the bounce of the grinding stone 2 during grinding. When the grinding stone 1 (6) with shafts was clamped in the rotating tool 10 and grinding was performed, one of the three evaluators felt the bounce of the grinding stone 2 during grinding. When the grinding stone 1 (7) with shafts was clamped in the rotating tool 10 and grinding was performed, all three evaluators felt the bounce of the grinding stone 2 during grinding. The three evaluators gained the following impression: when the grinding stone 2 bounces during grinding, the grinding tool 15 becomes difficult to use. In addition, the three evaluators gained the following impression: when the grinding stone 2 bounces, the vibration transmitted to the operator's hand causes fatigue to accumulate in the operator (the operator feels fatigued).

[0054] In evaluation test 3, the opening edge of the through hole 52 on the inner circumferential surface 50a of workpiece 50 was used as the object. A rotating grinding stone 2 was brought into contact with workpiece 50 to begin deburring. Deburring was then stopped when the outermost diameter of the grinding stone 2 reached 10 mm. Furthermore, during the period from the start to the end of deburring, the deburring operation was interrupted every 15 seconds, and the grinding stone 2 and workpiece 50 were observed. This observation was performed by three evaluators on multiple workpieces 50 without updating the grinding stones 1, which each had a shaft.

[0055] Then, during the period before the "deburring removal" is completed, if the evaluator has confirmed three conditions: "the outline of the abrasive material is not circular", "the wear of the grinding stone 2 is faster when compared with the previous observation point", and "the bouncing of the grinding stone 2 is felt", and if the evaluator has observed the workpiece 50 after the "deburring removal" is completed and judged that "the surface treatment of the edge of the opening edge of the through hole 52 of the annular bottom surface 51a is inconsistent", then the evaluation result of the grinding stone 2 being worn unevenly is made.

[0056] The evaluation results of evaluation test 3 are shown in Figure 11. In Figure 11, "×" indicates that the grinding stone 2 has uneven wear, and "○" indicates that the grinding stone 2 has no uneven wear. As shown in Figure 11, when the grinding stone 1 (1) with a shaft is clamped in the rotating tool 10 and grinding is performed, all three evaluators gave the evaluation that "the grinding stone 2 has uneven wear". When the grinding stones 1 (2) to 1 (7) with shafts are clamped in the rotating tool 10 and grinding is performed, all three evaluators gave the evaluation that "the grinding stone 2 has no uneven wear".

[0057] Based on evaluation tests 1-3, it is clear that as long as the grinding stones 1(2)-1(5) with shafts that meet the rigidity condition (A) of shaft 3 are clamped in the rotating tool 10 and grinding is performed, the uneven wear of the grinding material during grinding can be prevented or suppressed, and the bouncing of the grinding material during grinding can be prevented or suppressed. Furthermore, it has been confirmed that as long as the grinding stones 1(2)-1(5) with shafts that meet the rigidity condition (A) of shaft 3 are clamped in the rotating tool 10 and grinding is performed, the operator can judge the execution of the grinding process by the feeling transmitted to the hand, and the accumulation of fatigue in the operator can be suppressed.

[0058] (Effects) In the grinding stones 1(2) to 1(5) with shafts in this example, the rigidity of shaft 3 is set to a value within a predetermined range determined by conditional expression (A). In this way, the natural vibration frequency of the grinding stone 1 with shaft becomes a value that will not resonate during the grinding process. Therefore, the situation where the grinding stone 2 experiences uneven wear due to the vibration of the grinding stone 2 caused by the resonance of the grinding stone 1 with shaft can be suppressed. Furthermore, in the grinding stones 1(2) to 1(5) with shafts in this example, since the rigidity of shaft 3 is set to a value within a predetermined range determined by conditional expression (A), the bouncing of the grinding stone 2 on the surface of the workpiece 50 can be prevented or suppressed during the grinding process.

[0059] That is, as with the grinding stone 1 (1) having a shaft, when the rigidity value of the shaft 3 is lower than the lower limit of condition (A), the rigidity of the shaft 3 decreases, and the natural vibration frequency of the grinding stone 1 with the shaft decreases. As a result, since resonance is easily generated during the grinding process, the grinding stone 2 is prone to uneven wear due to "vibration caused by resonance". Here, once uneven wear occurs in the grinding stone 2, the contact between the grinding stone 2 and the workpiece 50 becomes inconsistent, so sometimes it is not possible to perform deburring and grinding well. In addition, once uneven wear occurs in the grinding stone 2, the shape of the grinding stone 2 cannot be restored to its original rotationally symmetrical shape during the grinding process, and the deformation of the grinding stone 2 is aggravated. As a result, phenomena such as the grinding stone 2 bouncing on the surface of the workpiece 50 occur during the grinding process. Once the grinding stone 2 bounces, the contact between the grinding stone 2 and the workpiece 50 becomes inconsistent, so it is not possible to perform deburring and grinding well. Therefore, in the grinding stones 1(2) to 1(5) with shafts in this example, by setting the rigidity value of shaft 3 to be above the lower limit of conditional expression (A), the uneven wear of grinding stone 2 can be prevented or suppressed. Accordingly, the above-mentioned problems can be avoided.

[0060] Furthermore, as with the shaft-mounted grinding stone 1 (6) and the shaft-mounted grinding stone 1 (7), when the stiffness value of the shaft 3 exceeds the upper limit of conditional expression (A), the stiffness of the shaft 3 becomes excessively high. That is, the higher the stiffness of the shaft 3, the higher the natural vibration frequency of the shaft-mounted grinding stone 1, thus preventing resonance in the shaft-mounted grinding stone 1 during grinding. However, once the stiffness of the shaft 3 becomes excessively high, the shaft 3 will not be able to adequately absorb the vibration transmitted from the workpiece 50 side to the shaft-mounted grinding stone 1 during grinding, and the grinding stone 2 is prone to bouncing on the surface of the workpiece 50 during grinding. Here, once the grinding stone 2 bounces, the contact between the grinding stone 2 and the workpiece 50 will become inconsistent, thus failing to perform burr removal and grinding effectively. In addition, once the grinding stone 2 bounces, the grinding stone 2 will contact a part that is different from the grinding target part of the workpiece 50, sometimes damaging the workpiece 50. Furthermore, once the grinding stone 2 bounces, the vibration transmitted to the operator's hand will cause fatigue to accumulate in the operator (the operator will feel fatigued). Therefore, in this example, the rigidity value of the shaft 3 of the grinding stones 1(2)~1(5) with shafts is set below the upper limit of conditional expression (A) to suppress the bouncing of the grinding stone 2 during grinding. Accordingly, the above-mentioned problems can be avoided.

[0061] Here, by setting the rigidity value of shaft 3 within the range of conditional expression (A), the natural vibration number of the grinding stone 1 with shaft can be increased to a level that prevents resonance, regardless of the material, total length M, and outer diameter O of shaft 3. Furthermore, the natural vibration number of the grinding stone 1 with shaft is higher than the excitation frequency, which depends on the rotational speed of the grinding stone 1 with shaft during grinding. Therefore, by setting the rigidity value of shaft 3 within the range of conditional expression (A), resonance of the grinding stone 1 with shaft can be prevented or suppressed, regardless of the rotational speed of the grinding stone 1 with shaft during grinding.

[0062] Furthermore, the grinding stone 2 of the "grinding stone 1 with an axis" is made of inorganic long fiber reinforced resin, and has a plurality of "fiber bundles 22 formed by a plurality of inorganic long fibers 21", and a resin 23 for bonding the aforementioned plurality of fiber bundles 22. Compared with grinding stones that "use resin to bond abrasive grains", this grinding stone 2 is less prone to localized chipping when subjected to impact. That is, grinding stones that use resin to fix abrasive grains are prone to uneven wear due to the chipping of individual abrasive grains when subjected to impact, while grinding stone 2 that uses resin 23 to fix a plurality of fiber bundles 22 does not experience the aforementioned chipping of individual abrasive grains. Therefore, uneven wear of the grinding stone 2 during grinding is easily suppressed.

[0063] In this example, the total length M of shaft 3 is 50 mm or more. Traditionally, when grinding the inner wall of a deep hole in a workpiece, there is a requirement to "increase the total length M of shaft 3" in order for the grinding stone 2 to reach the deepest part of the hole. However, generally speaking, if the total length M of the elastic shaft 3 is increased, the rigidity of shaft 3 will decrease. Therefore, if the total length M of shaft 3 is increased, resonance will occur during grinding, resulting in the problem of "the grinding stone easily forming uneven wear". In addition, if the total length M of shaft 3 is increased, sometimes the operator will not be able to judge whether the "required grinding" has been performed by touch. Therefore, it is not easy to "increase the shaft 3 while suppressing the decline in the workability of grinding". In contrast, in the grinding stones 1(2) to 1(5) with shafts in this example, since the rigidity value of shaft 3 meets the condition (A), uneven wear of grinding stone 2 can be prevented regardless of the total length M of shaft 3. Furthermore, the operator can judge whether the "required grinding process" has been performed based on their sense of touch. Therefore, in the grinding stones 1(2) to 1(5) with shafts in this example, the decline in the workability of the grinding process can be suppressed, and the total length of the shaft 3 can be increased.

[0064] Here, the traditionally flexible shaft-type grinding stones, that is, the shaft-type grinding stones circulating in the market, usually have a length dimension from the rear end of the shaft 3 to the grinding stone that is less than 50 mm. In contrast, in the shaft-type grinding stones 1(2) to 1(5) in this example, the length dimension from the rear end of the shaft 3 to the aforementioned grinding stone is more than 50 mm.

[0065] Furthermore, in the current situation, it is not possible to provide an object with a "shaft 3 having a total length exceeding 150mm" as a "grinding stone 1 with a shaft that can be flexible". The reason is as follows: In the grinding of the inner circumferential surface of a deep hole that requires a "grinding stone 1 with a shaft having a total length exceeding 150mm", it is difficult for the operator to visually confirm the grinding target area of ​​the workpiece during the grinding process. If the total length of the shaft is too long, it is difficult for the operator to feel whether the desired processing is in progress by holding the rotating tool 10 during the grinding process. In contrast to this problem, in the grinding stone 1 (2) with a shaft in this example where the total length of the shaft 3 exceeds 150mm, since the rigidity value of the shaft 3 meets the condition (A), even when the operator cannot visually confirm the grinding target area of ​​the workpiece, the operator can obtain the feeling that "the desired processing is in progress" during the grinding process. Furthermore, by setting the rigidity of the shaft 3 to a value within the range of conditional formula (A), it is possible to prevent or suppress uneven wear of the grinding stone 2 and to prevent or suppress bouncing of the grinding stone 2 during the grinding process. Therefore, by using a grinding stone 1 (2) with a shaft that has a total length of "shaft 3 exceeding 150 mm", burr removal and grinding can be performed well.

[0066] In this example, the outer diameter O of shaft 3 is less than 6 mm. Therefore, shaft 3 will not become too thick, making it easy to prevent or suppress the rigidity of shaft 3 from becoming "above the upper limit of condition (A)". In addition, as long as the outer diameter O of shaft 3 is less than 6 mm, when the operator holding the rotating tool 10 wants to observe the grinding object, the situation where "the grinding object becomes invisible due to the shadow of shaft 3" can be easily avoided.

[0067] In this example, the grinding stone 2 weighs less than 0.8g. Therefore, in situations such as "applying force to the grinding stone 1 with a shaft from the workpiece 50 side during grinding processing", the situation of "the grinding stone 2 bouncing on the surface of the workpiece 50" can be easily suppressed.

[0068] Furthermore, this example includes a fixing mechanism 6, which detachably fixes the grinding stone 2 to the front end of the shaft 3. Therefore, when the grinding stone 2 becomes worn, the worn grinding stone 2 can be replaced with a new grinding stone 2.

[0069] (Modified Example) Figures 12(a) to (f) are explanatory diagrams of the grinding stones with shafts in variations 1 to 6. In the grinding stones 1A to 1F with shafts shown in Figures 12(a) to (f), the rigidity of shaft 3 in all variations 1 to 6 satisfies condition (A). Figure 12 shows the load application position P when measuring the rigidity of shaft 3 in each of the grinding stones 1A to 1F with shafts in variations 1 to 6.

[0070] The grinding stone 1A with an axis shown in Figure 12(a) is square when viewed from a direction orthogonal to the axis L. Therefore, the grinding stone 2 is cylindrical. The grinding stone 1B with an axis shown in Figure 12(b) is circular when viewed from a direction orthogonal to the axis L. Therefore, the grinding stone 2 is spherical.

[0071] Next, when viewed from a direction orthogonal to axis L, the grinding stone 2 can also have a shape that tapers towards the outer periphery. In this case, as shown in the axial grinding stone 1C of variant 3 in Figure 12(c) and the axial grinding stone 1D of variant 4 in Figure 12(d), the shape of the grinding stone 2 when viewed from a direction orthogonal to axis L can form an isosceles triangle. In the axial grinding stone 1C of variant 3, the grinding stone 2 presents a cone shape with its apex facing forward X1. In the axial grinding stone 1D of variant 4, the grinding stone 2 presents a cone shape with its apex facing backward X2. Furthermore, in this case, as shown in the axial grinding stone 1E of variant 5, the shape of the grinding stone 2 when viewed from a direction orthogonal to axis L can form a rhombus. Furthermore, in this case, as shown in the axial grinding stone 1F of variant 6, the shape of the grinding stone 2 when viewed from a direction orthogonal to axis L can form an ellipse.

[0072] In the shaft-equipped grinding stones 1A-1F of these variations 1-6, the grinding stone 2 has a fitting hole 25 at its center for fitting the front end of the shaft 3. The fitting hole 25 forms an opening X2 to the rear. Furthermore, with the front end of the shaft 3 inserted into the fitting hole 25, the grinding stone 2 is fixed to the shaft 3 by an adhesive applied to the front end of the shaft 3 or the inner circumferential surface of the fitting hole 25. Even in the shaft-equipped grinding stones 1A-1F of variations 1-6, uneven wear and bounce of the grinding stone 2 during grinding can be suppressed.

[0073] D: Outer diameter E: Thickness E F: Pressurized load L: Axis M: Total length N: Length dimension O: Outer diameter P: Location of load application Q: Distance R: Outer diameter T: Inner diameter U: Width dimension V: Depth dimension W: Diameter X: Axis direction X1: Ahead X2: Rear δ: Displacement 1: Grinding stone with shaft 1(1)~1(7): Grinding stone with shaft 1A~1F: (Modified examples) Grinding stones with shafts 2: Grinding stone 2a: Peripheral end 3: Axis 4: Handle 5: Neck 5a: Large diameter part 6: Fixed mechanism 7: Headed screws 7a: Head 7b: Threaded section 8: Fixing hole 9: Threaded hole 10: Rotating tools 11: Grip section 12: Chuck mechanism 15: Grinding tools 21: Inorganic long fibers 22: Fiber bundle 22A: First fiber bundle 22B: Second fiber bundle 23: Resin 25: Fitting hole 30:Jig 50: Workpiece 50a: Inner circumferential surface 51: Circular Ditch 51a: Annular bottom surface 52: Through hole

Claims

1. A grinding stone with a shaft, comprising: a shaft having a handle at its rear end; a grinding stone having a rotationally symmetrical shape about the axis of the shaft and fixed to the front end of the shaft, with its outer peripheral end located further outward than the shaft, the handle being held by a handheld rotating tool and the workpiece being ground using the outer peripheral end of the grinding stone, characterized in that: the grinding stone comprises a plurality of bundles of abrasive material having bundled a plurality of inorganic long fibers, and a resin for binding the plurality of abrasive material bundles; the rigidity S of the shaft satisfies the following condition: 0.4≦S≦100; the rigidity of the shaft is determined by the following formula (B) when the handle is fixed to a fixture in a region 30 mm from the rear end of the shaft, and the rear end of the outer peripheral end of the grinding stone is pressed in from a direction orthogonal to the axis, the pressing load is set as F (N), and the displacement at the front end of the shaft is set as δ (mm). S = F / δ.

2. A millstone with an axle as described in claim 1, wherein, The length from the rear end of the aforementioned shaft to the aforementioned grinding stone is 50 mm or more.

3. A millstone with an axle as described in claim 1 or claim 2, wherein, The outer diameter of the aforementioned shaft is less than 6 mm.

4. A millstone with an axle as described in claim 1 or claim 2, wherein, The aforementioned grinding stone weighs less than 0.8g.

5. A millstone with an axle as described in claim 1 or claim 2, wherein, It has a fixing mechanism for detachably fixing the aforementioned grinding stone to the aforementioned front end of the aforementioned shaft.

6. A millstone with an axle as described in claim 1 or claim 2, wherein, The aforementioned millstone appears square or circular when viewed from a direction orthogonal to the aforementioned axis.

7. A millstone with an axle as described in claim 1 or claim 2, wherein, The outer diameter of the aforementioned whetstone is 3mm or more, and the outer diameter of the aforementioned handle and the thickness of the aforementioned whetstone in the aforementioned axial direction are smaller than the outer diameter of the aforementioned whetstone.

8. A millstone with an axle as described in claim 7, wherein, The aforementioned grinding stone, when viewed from a direction orthogonal to the aforementioned axis, has a shape that becomes tapered towards the outer periphery.

9. A millstone with an axle as described in claim 7, wherein, The aforementioned millstone appears rectangular when viewed from a direction orthogonal to the aforementioned axis.

10. A millstone with an axle as described in claim 1 or claim 2, wherein, The length from the rear end of the aforementioned shaft to the aforementioned grinding stone exceeds 150mm.

11. A grinding tool comprising: a grinding stone with an axle as described in any one of claims 1 to 10; and a rotating tool that holds the aforementioned shank of the grinding stone with an axle.

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