CN118215556A - Grindstone having shaft and grinding tool - Google Patents

Abstract

A grindstone (1) having a shaft includes a grindstone (2) and a shaft member (3) extending from the grindstone (2). The grindstone (2) is obtained by bonding a plurality of fiber bundles (22) formed by bundling a plurality of inorganic long fibers (21) with a resin (23). The shaft member (3) satisfies the conditional expression (A) with the rigidity being S. When the rear end of the outer peripheral end (2 a) of the grindstone (2) is pressed in from the direction perpendicular to the axis (L) with a region of 30mm from the rear end of the shaft member (3) as a shank (4) and fixed, the press-in load is F (N), and the displacement amount of the front end of the shaft member (3) is delta (mm), the rigidity of the shaft member (3) is obtained by the following formula (B). S is more than or equal to 0.4 and less than or equal to 100 (A), S=F/delta (B).

Description

Grindstone having shaft and grinding tool

Technical Field

The present invention relates to a grindstone having a shaft used by being held by a hand-held rotary tool, and a grinding tool having a shaft and held by a hand-held rotary tool.

Background

Patent document 1 describes a grindstone having a shaft, which is used by being clamped to a hand-held rotary tool such as a rotary air drill. The grindstone having a shaft of this document has a grindstone and a shaft member coupled to the grindstone. The grindstone has a rotationally symmetrical shape with respect to the axis of the shaft member. The grindstone is an inorganic long fiber reinforced resin body, and includes a plurality of abrasive bundles obtained by bundling a plurality of inorganic long fibers, and a resin for bonding the plurality of abrasive bundles. The shaft member includes a support member coupled to the grindstone and a rod-shaped shank coupled to the support member. The shank is the part that is clamped to the rotary tool. The support member of the shaft member is elastically deformable in a direction orthogonal to the axial direction. During polishing, the outer peripheral surface of the grindstone is brought into contact with a portion to be polished of the workpiece.

Since the shaft member of the grindstone having the shaft in this document is deflected, the grindstone can be elastically pressed against the workpiece. Therefore, when the grinding process is performed by holding the rotary tool by hand, the positional accuracy at the time of bringing the grindstone into contact with the workpiece can be low. Further, since the shaft member is deflected, when an excessive force is applied to the grindstone, such force is absorbed by elastic deformation of the shaft member. Therefore, the grindstone does not over-cut the workpiece. Further, since the grindstone can be elastically pressed against the workpiece, the grindstone does not bounce on the surface of the workpiece. Accordingly, the abrasive can be brought into uniform contact with the surface of the workpiece, and therefore, burr removal and polishing can be performed satisfactorily.

Prior art literature

Patent literature

Patent document 1: japanese patent laid-open No. 2006-35414

Disclosure of Invention

Technical problem to be solved by the invention

However, in the grindstone having the shaft in which the shaft member is deflected, the grindstone may be worn out unevenly during the grinding process. When uneven wear occurs in the grindstone, contact of the grindstone with the workpiece becomes uneven, and therefore, there are cases where burr removal and grinding cannot be performed well. In addition, when uneven wear occurs in the grindstone, the shape of the grindstone does not return to the original rotationally symmetrical shape during the grinding process, and deformation of the grindstone is intensified. Thus, during the polishing process, the phenomenon such as bouncing of the grindstone on the surface of the workpiece occurs. When the grindstone bounces, contact of the grindstone with the workpiece becomes uneven, and therefore, burr removal and grinding cannot be performed well.

In view of the above-described problems, an object of the present invention is to provide a grindstone having a shaft, which can suppress uneven wear of the grindstone during grinding even when a shaft member is deflected. Further, the present invention has an object to provide an abrasive tool including the above-described grindstone having a shaft.

Technical proposal adopted for solving the technical problems

The inventors of the present application have conducted intensive studies and as a result, have found that uneven wear of a grinding stone is caused by vibration generated by resonance of the grinding stone having a shaft during grinding. More specifically, it was found that when the grindstone vibrates due to resonance, the grindstone repeatedly collides against the surface of the workpiece, and therefore, the impact at the time of collision causes a part of the grindstone to fall off to form uneven wear. The present application has been made based on the above findings of the inventors.

In order to solve the above technical problems, the present invention provides a grindstone having a shaft, comprising: a shaft member having a shank at a rear end portion; and a grindstone having a shape rotationally symmetrical around an axis of the shaft member, the grindstone being fixed to a front end of the shaft member and an outer peripheral end thereof being located on an outer peripheral side of the shaft member, the shank being held by a hand-held rotary tool and grinding a workpiece with the outer peripheral end of the grindstone, characterized in that the grindstone includes a plurality of abrasive bundles in which a plurality of inorganic long fibers are bundled, and includes a resin that bonds the plurality of abrasive bundles, and a natural frequency of the grindstone having the shaft becomes a value at which resonance does not occur in grinding by satisfying the following conditional expression when a rigidity of the shaft member is set to S,

0.4≤S≤100

When a region of 30mm from the rear end of the shaft member is fixed to a jig as the shank, the rear end of the outer peripheral end of the grindstone is pressed in from a direction orthogonal to the axis, and the press-in load is F (N), and the displacement amount of the front end of the shaft member is δ (mm), the rigidity of the shaft member is obtained by the following equation,

S＝F/δ。

In the grindstone with a shaft of the present invention, the rigidity of the shaft member is set to a value within a prescribed range determined by a conditional expression. Thus, the natural frequency of the grindstone having the shaft is a value at which resonance does not occur during the grinding process. Therefore, uneven wear of the grindstone due to vibration of the grindstone caused by resonance of the grindstone having the shaft can be suppressed. Further, by setting the rigidity of the shaft member to a value within a predetermined range determined by the conditional expression, it is possible to prevent or suppress bouncing of the grindstone on the surface of the workpiece at the time of grinding processing. This makes contact between the grindstone and the workpiece uniform, and therefore prevents or suppresses failure in burr removal and grinding.

That is, when the value of the rigidity of the shaft member is lower than the lower limit value of the conditional expression, the rigidity of the shaft member becomes low, and the natural frequency of the grindstone having the shaft is reduced. As a result, resonance is likely to occur during polishing, and hence uneven wear of the grindstone is likely to occur due to vibration caused by resonance. On the other hand, in the case where the value of the rigidity of the shaft member is higher than the upper limit value of the conditional expression, the rigidity of the shaft member becomes excessively high. That is, if the rigidity of the shaft member is increased, the natural frequency of the grindstone having the shaft is increased, and therefore, the grindstone having the shaft can be prevented from resonating during the grinding process. However, when the rigidity of the shaft member becomes excessively high, the shaft member cannot sufficiently absorb the vibration transmitted from the workpiece side to the grindstone having the shaft at the time of the grinding process, so that the grindstone easily bounces on the surface of the workpiece at the time of the grinding process. Therefore, the value of the rigidity of the shaft member is set to be equal to or less than the upper limit value of the condition, so that the bouncing of the grindstone during the grinding process is suppressed. This facilitates the removal and polishing of burrs at the target site.

In addition, the grindstone includes a plurality of abrasive bundles composed of a plurality of inorganic long fibers, and includes a resin that bonds the plurality of abrasive bundles. In comparison with a grindstone obtained by bonding abrasive grains with a resin, a part of the grindstone made of the inorganic long fiber-reinforced resin body is less likely to collapse when an impact is applied. That is, in the grindstone in which the abrasive grains are fixed by the resin, uneven wear is likely to occur due to chipping of the abrasive grains when an impact is applied, but such chipping of the abrasive grains is not likely to occur in the grindstone in which the abrasive grains are fixed by the resin. Therefore, uneven wear of the grindstone is easily suppressed.

Here, if the grindstone having the shaft, in which the shaft member is deflected, is attached to the hand-held rotary tool and subjected to polishing, vibrations generated during deburring or the like may be absorbed by the shaft member and may not be transmitted to a worker who holds the rotary tool. In this case, the operator cannot obtain the feeling of whether the polishing process is performed well. Therefore, when the grindstone having the shaft, in which the shaft member is deflected, is used for processing a portion to be polished, which is difficult to visually observe, such as polishing processing of an inner wall surface of a deep hole provided in a workpiece, a worker cannot efficiently perform polishing processing, and there is a problem that workability is lowered. In view of the above-described problems, according to the study of the inventors of the present application, in the case where the value of the rigidity of the shaft member satisfies the conditional expression, the rigidity of the shaft member does not become excessively low, so that vibrations generated at the time of deburring or the like are transmitted to the operator via the shaft member and the rotary tool. Therefore, even when the operator performs the processing of the polishing target portion that is difficult to visually observe, the operator can determine whether or not the required polishing processing is performed by the touch feeling. Therefore, the workability of the polishing process can be suppressed from being lowered.

In addition, conventionally, when polishing an inner wall surface of a hole provided in a workpiece, it has been necessary to lengthen a shaft member in order to make a grindstone reach a polishing target portion deep in the hole. However, in general, if the shaft member having elasticity is made longer, the rigidity of the shaft member is lowered. Therefore, if the shaft member is lengthened, resonance occurs during polishing, and uneven wear of the grindstone is likely to occur. Further, if the shaft member is made longer, the operator may not be able to determine whether or not the required polishing process is being performed by the touch feeling. Therefore, it is not easy to lengthen the shaft member while suppressing a decrease in workability of the polishing process. In contrast, according to the present invention, when the value of the rigidity of the shaft member satisfies the conditional expression, uneven wear of the grindstone can be suppressed regardless of the length of the shaft member, and the operator can determine whether or not the required grinding process is being performed based on the touch feeling. Therefore, according to the present invention, the shaft member can be lengthened while suppressing a decrease in workability of the polishing process.

Here, conventionally, in a grinding stone having a shaft, which is flexible and is circulated in the market, a length dimension from a rear end of the shaft member to the grinding stone is generally less than 50mm. In contrast, in the present invention, the length from the rear end of the shaft member to the grindstone may be 50mm or more.

In the present invention, the shaft member may have an outer diameter dimension of less than 6mm. In this way, the shaft member can be prevented or suppressed from becoming too thick, and the rigidity of the shaft member can be set to a value exceeding the upper limit value of the condition. Further, if the outer diameter of the shaft member is smaller than 6mm, it is easy to avoid that the polishing target portion becomes a shadow of the shaft member and becomes invisible when an operator holding the rotary tool wants to observe the polishing target portion.

In the present invention, the grindstone may be 0.8g or less. In this way, when a force is applied to a grindstone having a shaft or the like from the workpiece side during grinding, bouncing of the grindstone on the surface of the workpiece is easily suppressed.

In the present invention, the grindstone having the shaft may have a fixing mechanism that detachably fixes the grindstone to the tip of the shaft member. With such a fixing mechanism, the grinding stone can be replaced with a new one when worn.

In the present invention, the grindstone may have a square shape or a circular shape when viewed from a direction orthogonal to the axis.

In the present invention, the outer diameter size of the grindstone is 3mm or more, and the outer diameter size of the shank and the thickness of the grindstone in the axial direction may be smaller than the outer diameter size of the grindstone. In this way, the grindstone is formed in a shape longer in the radial direction than in the axial direction, and the outer peripheral end of the grindstone is located on the outer peripheral side of the shaft member. This makes it easy to bring the outer peripheral end of the grindstone into contact with the burr-generating portion of the workpiece.

In the present invention, the grindstone may have a shape tapered toward the outer peripheral side and the tip thereof when viewed from a direction orthogonal to the axis. In this case, the shape of the grindstone as viewed from the direction orthogonal to the axis is an isosceles triangle, a diamond, an ellipse, or the like.

In the present invention, the grindstone may have a rectangular shape when viewed from a direction orthogonal to the axis. The outer peripheral end in the radial direction of the grinding surface as the grindstone has a constant width in the axial direction, as long as the shape of the grindstone is rectangular when viewed from the direction orthogonal to the axis.

In the present invention, a length dimension from the rear end of the shaft member to the grindstone may exceed 150mm. In this way, the grindstone can easily reach the target portion to be ground provided on the rear side of the hole of the workpiece.

Next, the polishing tool of the present invention is characterized by comprising: the above-mentioned grindstone with shaft; a rotary tool that grips the shank of the grindstone with a shaft.

Effects of the invention

According to the grindstone having the shaft of the present invention, even in the case where the shaft member has elasticity, the grindstone can be suppressed from being worn out unevenly during the grinding process.

Drawings

Fig. 1 is a perspective view of a grindstone having a shaft.

Fig. 2 is an exploded perspective view of a grindstone having a shaft.

Fig. 3 is an explanatory view of an abrasive tool composed of a grindstone having a shaft and a rotary tool.

Fig. 4 is an explanatory view of the grindstone.

Fig. 5 is an explanatory diagram of a measurement method for measuring the rigidity of a shaft member having a grindstone of a shaft.

Fig. 6 is a table showing the rigidity, the total length, and the rotational speed at the time of polishing of the handle of the grinding stone having the shaft of the example and the comparative example.

Fig. 7 is an explanatory view of a work piece for evaluation test.

Fig. 8 is an explanatory diagram of the evaluation test.

Fig. 9 is a table showing the evaluation results of the evaluation test 1.

Fig. 10 is a table showing the evaluation results of the evaluation test 2.

Fig. 11 is a table showing the evaluation results of the evaluation test 3.

Fig. 12 is an explanatory view of a grinding stone having a shaft according to a modification.

Detailed Description

Hereinafter, a grindstone and a grinding tool having a shaft according to an embodiment of the present invention will be described with reference to the drawings.

Fig. 1 is a side view of a grindstone having a shaft. Fig. 2 is an exploded perspective view of a grindstone having a shaft. Fig. 3 is an explanatory view of an abrasive tool composed of a grindstone having a shaft and a rotary tool. Fig. 3 shows a state in which the operator holds the polishing tool. Fig. 4 is an explanatory view of the grindstone. Fig. 5 is an explanatory diagram of a measurement method for measuring the rigidity of a shaft member having a grindstone of a shaft. In the following description, a direction along the axis L of the shaft member 3 of the grindstone 1 having a shaft is referred to as an axis direction X. In the axial direction X, the side on which the grindstone 2 is located is referred to as the front side X1 of the grindstone 11 having the shaft, and the opposite side is referred to as the rear side X2 of the grindstone 1 having the shaft.

The grinding stone 1 having a shaft has a grinding stone 2 and a shaft member 3 extending rearward X2 from the grinding stone 2. The shaft member 3 has a shank portion 4 at a rear end portion. As shown in fig. 3, the shank 4 is a portion of the shaft member 3 clamped to the rotary tool 10. The grindstone 2 has a rotationally symmetrical shape about the axis L of the shaft member 3. In this example, the grindstone 2 has a disc shape. In a state where the grindstone 2 is fixed to the front end of the shaft member 3, the outer peripheral end 2a of the grindstone 2 is located at the outer peripheral side from the shaft member 3.

The grindstone 2 is fixed to the shaft member 3 via a fixing mechanism 6. The fixing mechanism 6 detachably fixes the grindstone 2 to the shaft member 3. As shown in fig. 2, the fixing mechanism 6 includes a cap screw 7, and the cap screw 7 includes a head portion 7a and a threaded portion 7b protruding from the head portion 7 a. The fixing mechanism 6 includes a fixing hole 8 penetrating the center of the grindstone 2 in the axial direction X, and a screw hole 9 provided in the front end surface of the shaft member 3. The threaded portion 7b of the cap screw 7 is screwed into the screw hole 9 through the fixing hole 8, and the head portion 7a of the cap screw 7 abuts against the grindstone 2. The grindstone 2 may be directly fixed to the shaft member 3. In this case, the grindstone 2 has a fixing hole in its center, into which the tip end portion of the shaft member 3 can be fitted. The fixing hole opens to the rear X2. The grindstone 2 is fixed to the shaft member 3 by an adhesive applied to the distal end portion of the shaft member 3 or the inner peripheral surface of the fixing hole in a state where the distal end portion of the shaft member 3 is inserted into the fixing hole.

As shown in fig. 3, the grindstone 1 having a shaft is held to the rotary tool 10, thereby functioning as the grinding tool 15. In this example, the rotary tool 10 is a hand-held electric grinder, a hand-held rotary air drill, or the like. That is, the rotary tool 10 of the polishing tool 15 of this example has a grip portion 11 for the operator to grip. The shank 4 of the grindstone 1 having the shaft is held by the holding mechanism 12 of the rotary tool 10. In the polishing process, the worker brings the grindstone 2 into contact with the portion of the workpiece to be polished while holding the rotary tool 10 by hand.

(Grindstone)

The grindstone 2 is a rotating body. As shown in fig. 1, the outer diameter D of the grindstone 2 is 3mm or more. The outer diameter D of the grindstone 2 is larger than the outer diameter O of the shaft member 3. Therefore, the outer peripheral end 2a of the grindstone 2 is located at the outer peripheral side than the shaft member 3. Further, the outer diameter D of the grindstone 2 is larger than the thickness E of the grindstone 2 in the axial direction X. Therefore, the radial direction of the grindstone 2 is longer than the axial direction X. The weight of the grindstone 2 is 0.8g or less.

In this example, the shape of the grindstone 2 as viewed from a direction orthogonal to the axis L is a rectangle having a longer radial direction than the axis direction X. Therefore, the radial outer peripheral end 2a, which is the working surface of the grindstone 2, has a constant width in the axial direction X. In this example, the outer diameter dimension D of the grindstone 2 is 15mm, and the thickness of the grindstone 2 is 2mm. The weight of the grindstone 2 was 0.8g.

The grindstone 2 is a so-called inorganic long fiber reinforced resin body. As shown in fig. 4, the grindstone 2 includes a plurality of fiber bundles 22 in which a plurality of inorganic long fibers 21 are gathered. The grindstone 2 includes a resin 23 for bonding the plurality of fiber bundles 22. The resin 23 is an adhesive for fixing the plurality of fiber bundles 22. In this example, the resin 23 is a thermosetting resin, which is impregnated into each of the plurality of fiber bundles 22 and cured. The tips of the plurality of inorganic long fibers 21 reach the outer peripheral end 2a as the working surface of the grindstone 2.

More specifically, the grindstone 2 has a plurality of first fiber bundles 22A oriented in a first direction at a predetermined interval and a plurality of second fiber bundles 22B arranged in a second direction intersecting the first fiber bundles 22A at a predetermined interval. The first fiber bundle 22A and the second fiber bundle 22B are located between the first fiber bundles 22A and 22B, and the second fiber bundles 22A and 22B are partially inserted. The resin 23 is impregnated into the fiber bundles 22A, 22B and cured. The resin 23 bonds the plurality of fiber bundles 22. As the resin 23, an epoxy resin, an unsaturated polyester resin, a vinyl ester resin, a bismaleimide resin, a phenol resin, or the like is used.

As the inorganic long fibers 21, glass long fibers, alumina long fibers, boron long fibers, or silicon carbide long fibers are used. In this example, alumina long fibers are used as the inorganic long fibers 21. As the inorganic long fibers 21, inorganic long fibers having an average fiber diameter of 3 μm to 40 μm are used. As the fiber bundle 22, a fiber bundle of 500 to 3000Tex is used. In this example, after the resin 23 is impregnated with the finer fiber bundles 22 of about 500Tex, a plurality of abrasive bundles are aligned and arranged in the state shown in fig. 4 (a) and 4 (b), and then the resin 23 is impregnated again and cured to serve as a base material for the grindstone 2.

(Shaft Member)

The shaft member 3 has a rod shape and has elasticity to flex in a direction orthogonal to the axis L. The shaft member 3 is a rotating body having a rotationally symmetrical shape about the axis L. As shown in fig. 1, the shaft member 3 includes a shank 4 and a neck 5 in this order from a rear side X2 toward a front side X1. The shank 4 is a region 30mm from the rear end of the shaft member 3. The neck 5 is a region located between the shank 4 and the grindstone 2 in the axial direction X. The neck portion 5 has a large diameter portion 5a on the front end side, and the outer diameter dimension of the large diameter portion 5a is larger than the outer diameter dimension of the shaft member 3 at the rear side thereof. A screw hole 9 for fixing the grindstone 2 to the shaft member 3 is formed in the front end face of the large diameter portion 5 a. In this example, the shaft member 3 is made of stainless steel.

The shaft member 3 satisfies the following conditional expression (a) assuming that the rigidity thereof is S.

0.4≤S≤100··(A)

As shown in fig. 5, in measuring the rigidity of the shaft member 3, a region of 30mm from the rear end of the shaft member 3 is fixed as the shank 4 to the jig 30. Then, a predetermined pressing load is applied to the load application position P of the rear end of the outer peripheral end 2a of the grindstone 2 from the direction orthogonal to the axis L. When the press-in load is F (N) and the displacement amount of the distal end of the shaft member 3 is δ (mm), the rigidity of the shaft member 3 is obtained by the following equation (B).

S＝F/δ··(B)

Here, the material, the entire length M, and the outer diameter dimension O of the shaft member 3 are not limited as long as the rigidity thereof satisfies the conditional expression (a). However, the total length M of the shaft member 3 is preferably 50mm or more. The entire length M of the shaft member 3 is a length dimension from the rear end of the shaft member 3 to the grindstone 2. Therefore, in the grindstone 1 having the shaft of the shaft member 3 in a state in which the front end portion of the shaft member 3 is inserted into the fixing hole of the grindstone 2, the entire length M of the shaft member 3 is a length dimension from the rear end of the shaft member 3 to the opening edge of the fixing hole of the grindstone 2.

Further, it is desirable that the outer diameter dimension O of the shaft member 3 is less than 6mm. In this way, the shaft member 3 can be prevented or suppressed from becoming too thick, so that the rigidity of the shaft member 3 can be a value exceeding the upper limit value of the conditional expression (a). Here, the outer diameter dimension O of the shaft member 3 is the outer diameter dimension of the thickest part in the shaft member 3. Therefore, in this example, the outer diameter dimension O of the shaft member 3 is the outer diameter dimension of the large diameter portion 5 a.

Examples and comparative examples

The seven grindstones 1 (1) to 1 (7) having shafts, each of which has the rigidity and the total length M of the shaft member 3, are changed by making the grindstone 2 identical to the fixing mechanism 6, will be described below. Fig. 6 is a table showing the rigidity of the shaft member of the grindstone having the shaft, the total length of the shaft member, and the rotational speed at the time of polishing in the examples and the comparative examples. The grindstone with shaft 1 (2) to 1 (5) among the grindstones with shaft 1 (1) to 1 (7) are embodiments of the present invention, and the rigidity of the shaft member 3 thereof is within the range of the conditional expression (a). The grindstones 1 (1), (6) and (7) having the shaft are comparative examples, and the rigidity of the shaft member 3 thereof deviates from the range of the conditional expression (a).

In the grindstone 1 (1) to 1 (7) having the shaft, the grindstone 2 is made of an inorganic long fiber reinforced resin body. The outer diameter dimension D of the grindstone 2 is 15mm. The thickness E of the grindstone 2 in the axial direction X is 2mm. The material of the shaft member 3 is stainless steel (SUS 303). On the other hand, in the grindstones 1 (1) to 1 (7) having the shaft, the rigidity of the shaft member 3 and the total length M of the shaft member 3 are different from each other. In addition, when the grinding stones 1 (1) to 1 (7) having the shaft are subjected to the grinding process, the rotation tool 10 rotates the grinding stone 1 having the shaft at different rotation speeds.

The rigidity of the shaft member 3 of the grindstone 1 (1) having a shaft is 0.2N/mm. The rigidity of the shaft member 3 is lower than the lower limit value of the conditional expression (a). The overall length M of the shaft member 3 was 261mm. The length dimension N of the neck 5 after removal of the shank 4 clamped to the rotary tool 10 is 231mm. The rotational speed during the polishing process was 2000 rpm.

The rigidity of the shaft member 3 of the grindstone 1 (2) having a shaft is 0.4N/mm. The rigidity of the shaft member 3 satisfies the conditional expression (a). The overall length M of the shaft member 3 was 213mm. The length dimension N of the neck 5 is 183mm. The rotational speed during the polishing process was 3000 rpm. The rigidity of the shaft member 3 of the grindstone 1 (3) having a shaft is 5N/mm. The rigidity of the shaft member 3 satisfies the conditional expression (a). The overall length M of the shaft member 3 was 109mm. The length dimension N of the neck 5 is 79mm. The rotational speed during the grinding process was 5000 rpm. The rigidity of the shaft member 3 of the grindstone 1 (4) having a shaft is 10N/mm. The rigidity of the shaft member 3 satisfies the conditional expression (a). The overall length M of the shaft member 3 was 93mm. The length dimension N of the neck 5 is 63mm. The rotational speed during the polishing process was 8000 rpm. The rigidity of the shaft member 3 of the grindstone 1 (5) having a shaft is 10N/mm. The rigidity of the shaft member 3 satisfies the conditional expression (a). The overall length M of the shaft member 3 was 59mm. The length dimension N of the neck 5 is 29mm. The rotational speed during the grinding process was 10000 revolutions per minute.

The rigidity of the shaft member 3 of the grindstone 1 (6) having a shaft was 110N/mm. The rigidity of the shaft member 3 is higher than the upper limit value of the conditional expression (a). The overall length M of the shaft member 3 was 58mm. The length dimension N of the neck 5 is 28mm. The rotational speed during the grinding process was 10000 revolutions per minute. The rigidity of the shaft member 3 of the grindstone 1 (7) having a shaft is 120N/mm. The rigidity of the shaft member 3 is higher than the upper limit value of the conditional expression (a). The overall length M of the shaft member 3 was 57mm. The length dimension N of the neck 5 is 27mm. The rotational speed during the grinding process was 10000 revolutions per minute.

(Evaluation test)

Evaluation tests 1 to 3 were performed on grindstones 1 (1) to 1 (7) having a shaft. In the evaluation tests 1 to 3, burrs at the portions to be polished of the workpiece 50 were removed by holding the grindstones 1 (1) to 1 (7) each having a shaft on the rotary tool 10 and rotating the grindstones at the above-described rotation speeds. In the evaluation test 1, it was evaluated whether or not the feeling of polishing the work by the grindstone 2 during the polishing process was transmitted to the operator via the grindstone 2, the shaft member 3, and the rotary tool 10. In the evaluation test 2, the bouncing of the grindstone 2 during the grinding process was evaluated. In evaluation test 3, uneven wear of the grinding stone 2 during the grinding process was evaluated. Fig. 7 is a perspective view of the workpiece used in the evaluation tests 1 to 3. Fig. 8 is an explanatory diagram of evaluation tests 1 to 3. In fig. 8, the workpiece is shown in cross section. In fig. 8, the rotary tool 10 is omitted, and the workpiece and the grindstone 1 having the shaft are shown.

The workpiece 50 is made of carbon steel for mechanical structure. As shown in fig. 7, the workpiece 50 has a cylindrical shape. The workpiece 50 has an outer diameter dimension R of 30mm and an inner diameter dimension T of 20mm. As shown in fig. 8, in the inner peripheral surface 50a of the work 50, an annular groove 51 is provided at a position 20mm from one end of the work 50. The annular groove 51 has a width dimension U of 5mm and a depth dimension V of 2.5mm. Further, the work 50 has a through hole 52 having a diameter W of 3mm at a position overlapping the annular groove 51 when viewed from the radial direction. The through hole 52 is provided by penetrating a drill from the radially outer side to the inner side of the workpiece 50. The opening edge of the through hole 52 at the annular bottom surface 51a of the annular groove 51 is a polishing target portion. Burrs are generated at the polishing target portion. The polishing target portion is a portion located on the rear side of the deep hole of the work 50.

In the evaluation test 1, the burr removal was performed by bringing the rotating grindstone 2 into contact with the work 50 with the opening edge of the through hole 52 of the inner peripheral surface 50a of the work 50 as an object. Further, in the evaluation test 1, three evaluators judge whether or not burr removal is being performed based on the touch feeling transmitted to the hand through the grindstone 2, the shaft member 3 and the rotary tool 10, respectively.

The test results of evaluation test 1 are shown in fig. 9. In fig. 9, x indicates that the evaluator cannot determine whether or not the burr removal is being performed based on the touch feeling transmitted to the hand, and o indicates that the evaluator can determine whether or not the burr removal is being performed based on the touch feeling transmitted to the hand. As shown in fig. 9, when grinding is performed by sandwiching the grinding stone 1 (1) having the shaft between the rotary tools 10, three evaluators consider that it is impossible to determine whether or not burr removal is being performed based on the touch feeling transmitted to the hand through the grinding stone 2, the shaft member 3, and the rotary tools 10, respectively. That is, since the shaft member 3 of the grindstone 1 (1) having the shaft has low rigidity and is easily deflected, vibration or the like generated at the time of deburring is absorbed by the shaft member 3 and cannot be transmitted to the evaluator. When grinding is performed by sandwiching the grindstones 1 (2) to (7) having the shaft between the rotary tool 10, three evaluators each obtain a touch feeling that enables burr removal at the grinding target portion.

Further, the evaluation test 1 is a test for confirming whether or not the grindstone 1 (1) to 1 (7) having the shaft can be used in the polishing process in which the target portion to be polished cannot be confirmed directly by visual observation. From the test results, the grindstones 1 (2) to 1 (7) having the shaft can be used for polishing processing in which the target portion to be polished cannot be confirmed directly by visual observation.

In the evaluation test 2, the burr removal was performed by bringing the rotating grindstone 2 into contact with the work 50 with the opening edge of the through hole 52 of the inner peripheral surface 50a of the work 50 as an object. In the evaluation test 2, three evaluators each judge whether or not the grindstone 2 bounces during the grinding process, based on the touch feeling transmitted to the hand through the grindstone 2, the shaft member 3, and the rotary tool 10.

The test results of evaluation test 2 are shown in fig. 10. In fig. 10, x indicates that the evaluator felt the bounces of the grindstone 2, and o indicates that the evaluator did not feel the bounces of the grindstone 2. As shown in fig. 10, when grinding is performed by sandwiching the grinding stones 1 (1) to (5) having the shaft between the rotary tool 10, none of the three evaluators has perceived bouncing of the grinding stone 2 during the grinding. When grinding is performed by sandwiching the grinding stone 1 (6) having the shaft between the rotary tools 10, one of three evaluators receives the bouncing of the grinding stone 2 during the grinding. When grinding is performed by sandwiching the grinding stone 1 (7) having the shaft between the rotary tools 10, three evaluators all feel bouncing of the grinding stone 2 during the grinding. In addition, three evaluators gave the following impressions: in the case where the grindstone 2 bounces during the grinding process, the grinding tool 15 becomes difficult to use. Furthermore, three evaluators gave the following impressions: when the grindstone 2 bounces, fatigue is accumulated in the worker due to vibration transmitted to the worker's hand.

In the evaluation test 3, the burr removal was started by bringing the rotating grindstone 2 into contact with the work 50 with the opening edge of the through hole 52 of the inner peripheral surface 50a of the work 50 as an object. Thereafter, burr removal is ended at the point in time when the outermost diameter of the grindstone 2 becomes 10 mm. Further, the burr removal operation was interrupted every 15 seconds during the period from the start to the end of the burr removal, and the grindstone 2 and the workpiece 50 were observed. The three evaluators observe the plurality of workpieces 50 without replacing each of the grindstones 1 having the shaft with a new one.

Here, when the evaluator confirms that three elements of "the contour of the abrasive is not circular", "the abrasion of the grindstone 2 becomes faster when compared with the previous observation time point", and "the bouncing of the grindstone 2 is felt", and when the evaluator observes the work 50 after the burr removal is completed, it is determined that "the processing of the edge of the opening edge of the through hole 52 at the annular bottom surface 51a is uneven", it is evaluated that the grindstone 2 is unevenly worn.

The test results of evaluation test 3 are shown in fig. 11. In fig. 11, x indicates that uneven wear has occurred in the grinding stone 2, and o indicates that uneven wear has not occurred in the grinding stone 2. As shown in fig. 11, when grinding is performed by sandwiching a grinding stone 1 (1) having a shaft between rotary tools 10, three evaluators all evaluate that uneven wear has occurred in the grinding stone 2. When grinding is performed by sandwiching the grindstone 1 (2) to 1 (7) having the shaft between the rotary tool 10, all three evaluators evaluate that uneven wear does not occur in the grindstone 2.

As is clear from the evaluation tests 1 to 3, if the grinding process is performed by sandwiching the grindstones 1 (2) to 1 (5) having the shaft with the rigidity of the shaft member 3 satisfying the condition (a) between the rotary tool 10, uneven wear of the abrasive during the grinding process can be prevented or suppressed, and bouncing of the abrasive during the grinding process can be prevented or suppressed. Further, it was confirmed that if the grinding process is performed by sandwiching the grindstones 1 (2) to 1 (5) having the shaft with the rigidity of the shaft member 3 satisfying the condition (a) between the rotary tools 10, the operator can determine that the grinding process is performed based on the touch feeling transmitted to the hand, and suppress the accumulation of fatigue to the operator.

(Effects of action)

In the grindstones 1 (2) to 1 (5) having the shaft of this example, the rigidity of the shaft member 3 is set to a value within a predetermined range determined by the conditional expression (a). Thus, the natural frequency of the grindstone 1 having the shaft is a value at which resonance does not occur during grinding. Therefore, uneven wear of the grinding stone 2 due to vibration of the grinding stone 2 caused by resonance of the grinding stone 1 having the shaft can be suppressed. In the grindstone 1 (2) to 1 (5) having the shaft of this example, since the rigidity of the shaft member 3 is set to a value within a predetermined range determined by the conditional expression (a), the surface bouncing of the grindstone 2 on the workpiece 50 during the grinding process can be prevented or suppressed.

That is, when the value of the rigidity of the shaft member 3 is lower than the lower limit value of the condition (a) like the grindstone 1 (1) having the shaft, the rigidity of the shaft member 3 becomes low, and the natural frequency of the grindstone 1 having the shaft decreases. As a result, resonance is likely to occur during polishing, and hence uneven wear of the grindstone 2 is likely to occur due to vibration caused by resonance. Here, when uneven wear occurs in the grindstone 2, contact of the grindstone 2 with the workpiece 50 becomes uneven, and therefore, burr removal and grinding may not be performed well. In addition, when uneven wear occurs in the grinding stone 2, the shape of the grinding stone 2 does not return to the original rotationally symmetrical shape during the grinding process, and the deformation of the grinding stone 2 is further increased. As a result, the grinding stone 2 bounces on the surface of the workpiece 50 during the grinding process. When the grindstone 2 bounces, the contact of the grindstone 2 with the workpiece 50 becomes uneven, and therefore, burr removal and grinding cannot be performed well. Therefore, in the grindstones 1 (2) to 1 (5) having the shaft of this example, the value of the rigidity of the shaft member 3 is set to be equal to or higher than the lower limit value of the conditional expression (a), so that uneven wear of the grindstone 2 is prevented or suppressed. Therefore, the occurrence of the above-described problem can be avoided.

On the other hand, when the value of the rigidity of the shaft member 3 is higher than the upper limit value of the condition (a) like the grindstone 1 (6) having the shaft and the grindstone 1 (7) having the shaft, the rigidity of the shaft member 3 becomes excessively high. That is, if the rigidity of the shaft member 3 increases, the natural frequency of the grindstone 1 having the shaft increases, and therefore, resonance of the grindstone 1 having the shaft during grinding can be prevented. However, when the rigidity of the shaft member 3 becomes excessively high, the shaft member 3 cannot sufficiently absorb the vibration transmitted from the work 50 side to the grindstone 1 having the shaft at the time of the grinding, so that the grindstone 2 easily bounces on the surface of the work 50 during the grinding. Here, when the grindstone 2 bounces, the contact of the grindstone 2 with the workpiece 50 becomes uneven, and therefore, burr removal and grinding cannot be performed well. When the grindstone 2 bounces, the grindstone 2 may contact a portion different from the portion to be polished of the workpiece 50, and damage the workpiece 50. In addition, when the grindstone 2 bounces, fatigue is accumulated in the worker due to vibration transmitted to the worker's hand. Therefore, in the grindstone 1 (2) to 1 (5) having the shaft of this example, the value of the rigidity of the shaft member 3 is set to the upper limit value of the conditional expression (a) or less, so that the bouncing of the grindstone 2 during the grinding process is suppressed. Therefore, the occurrence of the above-described problem can be avoided.

Here, if the value of the rigidity of the shaft member 3 is set within the range of the conditional expression (a), the natural frequency of the grindstone 1 having the shaft can be increased to a level that can prevent resonance, regardless of the material of the shaft member 3, the entire length M, and the outer diameter dimension O. Further, the natural frequency of the grindstone 1 with the shaft is higher than the excitation frequency depending on the rotation speed of the grindstone 1 with the shaft at the time of grinding processing. Accordingly, if the value of the rigidity of the shaft member 3 is set within the range of the conditional expression (a), resonance of the grindstone 1 with the shaft can be prevented or suppressed irrespective of the rotation speed of the grindstone 1 with the shaft during the grinding process.

The grindstone 2 of the grindstone 1 having the shaft is an inorganic long fiber reinforced resin body, and includes a plurality of fiber bundles 22 composed of a plurality of inorganic long fibers 21, and includes a resin 23 that bonds the plurality of fiber bundles 22. In comparison with a grinding stone obtained by bonding abrasive grains with a resin, the above-mentioned grinding stone 2 is less likely to collapse in a part of the grinding stone 2 when an impact is applied thereto. That is, in the grindstone obtained by fixing the abrasive grains with the resin, uneven wear is likely to occur due to chipping of the abrasive grains by the individual abrasive grains when an impact is applied, but such chipping of the abrasive grains by the individual abrasive grains does not occur in the grindstone 2 obtained by fixing the plurality of fiber bundles 22 with the resin 23. Therefore, uneven wear of the grinding stone 2 during the grinding process is easily suppressed.

In this example, the total length M of the shaft member 3 is 50mm or more. In addition, conventionally, when polishing an inner wall surface of a deep hole provided in a workpiece, it has been necessary to increase the total length M of the shaft member 3 so that the grindstone 2 reaches a polishing target portion on the rear side of the hole. However, in general, if the total length M of the shaft member 3 having elasticity is made longer, the rigidity of the shaft member 3 is lowered. Therefore, if the entire length M of the shaft member 3 is made longer, resonance occurs during polishing, and uneven wear of the grindstone is likely to occur. Further, if the total length M of the shaft member 3 is made longer, the operator may not be able to determine whether or not the required polishing process is being performed by the touch feeling. Therefore, it is not easy to lengthen the shaft member 3 while suppressing a decrease in workability of the polishing process. In contrast, in the grindstones 1 (2) to 1 (5) having the shaft of this example, the value of the rigidity of the shaft member 3 satisfies the conditional expression (a), and therefore, uneven wear of the grindstone 2 can be prevented regardless of the entire length M of the shaft member 3. Further, the operator can determine whether or not the required polishing process is being performed based on the touch feeling. Therefore, in the grindstones 1 (2) to 1 (5) having the shaft of this example, the entire length of the shaft member 3 can be increased while suppressing a decrease in workability of the polishing process.

Here, conventionally, in a grinding stone having a shaft, which is flexible and is circulated in the market, a length dimension from a rear end of the shaft member 3 to the grinding stone is generally less than 50mm. In contrast, in the grindstones 1 (2) to 1 (5) having the shaft in this example, the length dimension from the rear end of the shaft member 3 to the grindstone is 50mm or more.

Further, it is now the case that the flexible grindstone 1 with a shaft of the shaft member 3 having the total length of the shaft member 3 exceeding 150mm cannot be provided. The reason for this is that the following problems exist: in the polishing process requiring the use of the inner peripheral surface of the deep hole of the grindstone 1 having the shaft with the total length of the shaft member 3 exceeding 150mm, it is difficult for the operator to visually confirm the portion to be polished of the workpiece during the polishing process, and for this reason, it is difficult for the operator to obtain the touch feeling during the desired process via the rotary tool 10 held during the polishing process. In order to solve the above-described problem, in the grinding stone 1 (2) with a shaft of this example in which the total length of the shaft member 3 exceeds 150mm, the value of the rigidity of the shaft member 3 satisfies the conditional expression (a), so that even when the operator cannot visually confirm the grinding target portion of the workpiece, the operator can obtain the touch feeling during the grinding process to perform the required process. Further, if the rigidity of the shaft member 3 is set to a value that satisfies the range of the conditional expression (a), uneven wear of the grinding stone 2 can be prevented or suppressed, and bouncing of the grinding stone 2 during the grinding process can be prevented or suppressed. Therefore, burr removal and grinding can be performed well by the grindstone 1 (2) with a shaft having the entire length of the shaft member 3 exceeding 150 mm.

In this example, the outer diameter dimension O of the shaft member 3 is less than 6mm. Therefore, it is easy to prevent or suppress the shaft member 3 from becoming too thick so that the rigidity of the shaft member 3 becomes a value exceeding the upper limit value of the conditional expression (a). When the outer diameter O of the shaft member 3 is smaller than 6mm, it is easy to avoid that the polishing target portion becomes a shadow of the shaft member 3 and cannot be visually observed when an operator holding the rotary tool 10 wants to observe the polishing target portion.

In this example, the amount of the grindstone 2 is 0.8g or less. Therefore, in the case where a force is applied to the grindstone 1 or the like having the shaft from the work 50 side in the grinding process, the surface bounce of the grindstone 2 on the work 50 is easily suppressed.

In this example, the grinding stone 2 is detachably fixed to the front end of the shaft member 3 by a fixing mechanism 6. Therefore, when the grindstone 2 wears, the worn grindstone 2 can be replaced with a new grindstone 2.

(Modification)

Fig. 12 (a) to (f) are explanatory diagrams of grinding stones having shafts according to modification examples one to six. In the grindstones 1A to 1F with shafts of the first to sixth modification examples shown in fig. 12 (a) to (F), the rigidity of the shaft member 3 satisfies the conditional expression (a). Fig. 12 shows load application positions P when the rigidity of the shaft members 3 of the grindstones 1A to 1F having shafts according to the first to sixth modifications is measured.

The grinding stone 1A having the shaft of the first modification shown in fig. 12 (a) has a square shape when viewed from a direction orthogonal to the axis L. Thus, the grindstone 2 has a cylindrical shape. The shape of the grindstone 2 of the second modification example shown in fig. 12 (B) when the grindstone 1B having the shaft is viewed from a direction orthogonal to the axis L is a circle. Thus, the grindstone 2 is spherical.

Next, the grindstone 2 may have a shape tapered toward the outer peripheral side and the tip thereof when viewed from the direction orthogonal to the axis L. In this case, like the grinding stone 1C with shaft of the third modification shown in fig. 12 (C) and the grinding stone 1D with shaft of the fourth modification shown in fig. 12 (D), the shape of the grinding stone 2 when viewed from the direction orthogonal to the axis L may be an isosceles triangle. In a grinding stone 1C having an axis according to a third modification, a grinding stone 2 has a conical shape with its apex directed toward the front direction X1. In the grinding stone 1D with the shaft of the fourth modification, the grinding stone 2 has a conical shape with the apex facing the rear direction X2 as a whole. In this case, like the grindstone 1E having the shaft of the fifth modification, the shape of the grindstone 2 as viewed from the direction orthogonal to the axis L may be a diamond shape. In this case, like the grindstone 1F having the shaft of modification six, the shape of the grindstone 2 as viewed from the direction orthogonal to the axis L may be an ellipse.

In each of the grindstones 1A to 1F having the shafts of the above-described modification examples one to six, the grindstone 2 includes, at its center, an engagement hole 25 into which the tip end portion of the shaft member 3 can be engaged. The fitting hole 25 opens rearward X2. The grindstone 2 is fixed to the shaft member 3 by an adhesive applied to the distal end portion of the shaft member 3 and the inner peripheral surface of the fitting hole 25 in a state where the distal end portion of the shaft member 3 is inserted into the fitting hole 25. In the grinding stones 1A to 1F each having the shaft according to the first to sixth modifications, uneven wear of the grinding stone 2 and bouncing of the grinding stone 2 during the grinding process can be suppressed.

Claims (11)

1. A grindstone having a shaft, comprising: a shaft member including a shank at a rear end portion; and a grindstone having a shape rotationally symmetrical about an axis of the shaft member, fixed to a front end of the shaft member and having an outer peripheral end located at an outer peripheral side of the shaft member, the shank being held by a hand-held rotary tool and grinding a workpiece through the outer peripheral end of the grindstone, the grindstone having a shaft,

The grindstone includes a plurality of abrasive bundles in which a plurality of inorganic long fibers are bound, and a resin binding the plurality of abrasive bundles,

When the rigidity of the shaft member is S, the natural frequency of the grindstone having the shaft is a value at which resonance does not occur during grinding by satisfying the following conditional expression,

0.4≤S≤100

When a region of 30mm from the rear end of the shaft member is fixed to a jig as the shank, the rear end of the outer peripheral end of the grindstone is pressed in from a direction orthogonal to the axis, and the press-in load is F (N), and the displacement amount of the front end of the shaft member is δ (mm), the rigidity of the shaft member is obtained by the following equation,

S＝F/δ。

2. The grindstone with the shaft as claimed in claim 1, characterized in that,

The length from the rear end of the shaft member to the grindstone is 50mm or more.

3. The grindstone with the shaft according to claim 1 or 2, characterized in that,

The shaft member has an outer diameter dimension of less than 6mm.

4. A grindstone with a shaft according to any one of claims 1 to 3, characterized in that,

The grinding stone is below 0.8 g.

5. The grindstone with the shaft according to any one of claims 1 to 4, characterized in that,

The grindstone having a shaft has a fixing mechanism that detachably fixes the grindstone to the tip of the shaft member.

6. The grindstone with the shaft according to any one of claims 1 to 5, characterized in that,

The grindstone is square or circular in shape when viewed from a direction orthogonal to the axis.

7. The grindstone with the shaft according to any one of claims 1 to 5, characterized in that,

The outer diameter size of the grinding stone is more than 3mm,

The outer diameter dimension of the shank and the axial thickness of the grindstone are smaller than the outer diameter dimension of the grindstone.

8. The grindstone with the shaft according to claim 7, characterized in that,

The grindstone has a shape tapered toward an outer peripheral side and a front end when viewed from a direction orthogonal to the axis.

9. The grindstone with the shaft according to claim 7, characterized in that,

The grindstone has a rectangular shape when viewed from a direction orthogonal to the axis.

10. The grindstone with the shaft according to any one of claims 1 to 9, characterized in that,

The length dimension from the rear end of the shaft member to the grindstone exceeds 150mm.

11. An abrasive tool, comprising:

The grindstone having a shaft according to any one of claims 1 to 10; and

A rotary tool that grips the shank of the grindstone with a shaft.