Machining tool and machining apparatus

Abstract

To provide an electroplated whetstone related to cutting work of a target material, enabling high-accuracy machining with excellent cutting dust discharge performance by arranging diamond abrasive grains at optimal intervals for each cutting site of the electroplated whetstone tool.SOLUTION: A machining tool of the present invention includes a columnar peripheral portion 12 and a tapered portion 15 having its diameter becoming smaller from the peripheral portion 12 to its tip. It is characterized in that distance between neighboring abrasive grains fixed to the peripheral portion 12 is 100 μm or over.SELECTED DRAWING: Figure 6

Description

[Technical field]

[0001] The present invention relates to a processing tool that is rotated by a processing device and grinds a workpiece, and to a processing device that rotates the processing tool. [Background technology]

[0002] In dental treatment or dental technology, tools that have abrasive grains fixed to the processing part with a plating layer are known as processing tools for grinding teeth and dental caps. In particular, electroplated grindstones using natural or artificial diamond grains as abrasive grains are used to grind not only teeth but also a wide range of dental materials such as resins, metals, and ceramics.

[0003] However, when grinding dentures or prosthetics made of resin with such electroplated grinding wheels, the grinding chips get caught between the abrasive grains, which then become embedded, reducing the grinding efficiency. This causes a problem of significantly increasing the processing time. In addition, it takes a lot of effort to remove the grinding chips wrapped around the abrasive grains.

[0004] In response to this, Patent Document 1 describes an electroplated grindstone in which abrasive grains are continuously fixed to the outer circumferential surface of a cylindrical base metal to form multiple rows of abrasive grains in the longitudinal direction. It also describes that clogging is less likely to occur by setting the interval between adjacent rows of abrasive grains to 1 to 10 times the circumferential width of the rows of abrasive grains.

[0005] [Patent Document 1] JP 2004-74356 A Summary of the Invention [Problem to be solved by the invention]

[0006] However, Patent Document 1 does not describe the arrangement of individual abrasive grains. It was thought that even if the abrasive grains were continuously fixed in rows on the outer periphery, the effect of preventing clogging would not be sufficient. [Means for solving the problem]

[0007] In order to solve the above problems, the machining tool of the present invention is characterized in that it comprises a cylindrical outer periphery and a tapered portion whose diameter decreases from the outer periphery toward the tip, and the spacing between adjacent abrasive grains fixed to the outer periphery is 100 μm or more. Effect of the Invention

[0008] According to the present invention, it is possible to provide a machining tool from which grinding chips can be easily removed from the outer periphery. [Brief description of the drawings]

[0009] [Figure 1] 1 is a schematic perspective view showing an electroplated grinding wheel according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a schematic cross-sectional view for explaining a surface structure of the electroplated grindstone according to the embodiment. [Diagram 3] 4 is a flowchart illustrating a method for manufacturing an electroplated grindstone according to an embodiment. [Figure 4] 4A to 4C are diagrams for explaining the state of transfer of abrasive grains in the method for producing an electroplated grindstone according to an embodiment. [Diagram 5] Particle size distribution of grinding debris from sintered zirconia when machined with randomly arranged abrasive grains. [Figure 6] (a) Schematic cross-sectional view of a tool tip including a hemispherical portion (b) Schematic cross-sectional view of a tool tip including a sloped portion (a). DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] The present invention can be applied to machining tools used as a part of power tools, such as indexable inserts for milling, indexable inserts for turning, and indexable inserts for high-speed cutting tools used in dental treatment equipment, etc. The present invention may also be used in drills, end mills, metal saws, diamond t-saws, high-speed cutting tools used in dental treatment equipment, etc., surgical instruments such as electric cutters for resecting bones, polishing tools for grinders, etc. In the following embodiments, an example will be described in which the present invention is used in a machining tool having a rod-shaped (cylindrical) processing part.

[0011] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. In addition, the same reference numerals are given to the same members throughout the drawings, and duplicated explanations will be omitted.

[0012] <Embodiment> Fig. 1 is a schematic perspective view showing an embodiment of the electroplated grindstone of the present invention. Fig. 2 is a schematic cross-sectional view for explaining the surface structure of the electroplated grindstone of the present embodiment. In these figures, the configuration of each part is exaggerated for easy understanding, and the relative size and scale of each part are different from the actual configuration. Fig. 2 also shows the outer peripheral surface of the processing part described later as a schematic plane.

[0013] In this embodiment, the substrate 10 of the processing tool 1 is formed in a rod shape (cylindrical shape). As shown in Fig. 1, the substrate 10 has a shank portion 11 in the longitudinal direction thereof, and a processing portion (outer peripheral portion) 12 provided integrally at one end of the shank portion 11. The shank portion 11 is attached to a processing device, and rotated in the direction of arrow D or the opposite direction around the rotation axis R of the main shaft. The substrate 10 can be formed from metals such as stainless steels such as SUS (Stainless Used Steel), alloys such as aluminum alloys, carbon fibers, etc.

[0014] <Arrangement of abrasive grains> 1, abrasive grains 20 are regularly arranged and fixed on the outer peripheral surface, which is the circumferential surface of the substrate 10 in the processing portion 12, in a direction parallel to the rotation axis R and in the circumferential direction of the outer peripheral surface in a plane perpendicular to the rotation axis R. In other words, the abrasive grains are regularly arranged on the outer peripheral surface of the substrate 10 no matter where in the direction parallel to the rotation axis R the substrate 10 is viewed in a cross section perpendicular to the rotation axis R.

[0015] In the manufacturing method of a general electroplated grinding wheel, the spacing between the abrasive grains varies, and the spacing between the abrasive grains is randomly arranged in sparse and dense areas. When grinding is performed with such an electroplated grinding wheel, the grinding chips are locally clogged, especially in the dense areas, which reduces the finish of the machined surface of the workpiece and increases the processing time as described above. On the other hand, if the spacing between the abrasive grains is made too wide so that the cutting chips do not clog the gaps, the cutting ability decreases. Thus, the placement of the abrasive grains is an important factor that determines the cutting ability. In this embodiment, the abrasive grains are regularly placed in two directions, the direction of the rotation axis and the circumferential direction of the outer circumferential surface, to control the locations where the workpiece is ground and the locations where the cutting chips are released. This makes it possible to obtain a processing tool in which the grinding chips are less likely to get stuck, and even if they do get stuck, the grinding chips can be easily removed.

[0016] <Abrasive grain> The type of abrasive grains 20 is not particularly limited as long as it is harder than the workpiece, and is appropriately selected depending on the material of the workpiece. For example, it can be selected from superabrasive grains such as diamond or CBN (Cubic Boron Nitride), or commonly used abrasive grains such as silicon carbide, chromium oxide, iron oxide, cerium oxide, zirconia, silica, and alumina. When the processing tool is used for cutting bones or teeth inside the body, diamond or CBN is preferable.

[0017] In addition, the larger the grain size of the abrasive grains 20, the smoother the surface to be machined will be and the longer the life of the abrasive grains, but the lower the cutting ability. Conversely, the smaller the grain size, the higher the cutting ability will be, but the rougher the surface to be machined will be and the shorter the life will be. Therefore, the grain size is appropriately selected according to the type of workpiece, cutting efficiency, and work content. For example, diamond abrasive grains with a grain size of #40 to 800 (average grain size 0.02 to 0.4 mm, the larger the grain size, the smaller the average grain size) are known. In this embodiment, diamond abrasive grains with a grain size of #100 to 120 (average grain size 0.13 to 0.16 mm) are used.

[0018] <Adhesive layer> In this embodiment, the abrasive grains 20 are fixed to the substrate 10 by an adhesion layer. Such an adhesion layer is often made mainly of metal. Known methods for forming an adhesion layer include electrodeposition and brazing. The electrodeposition method is a method for fixing the abrasive grains by forming a plating layer on the substrate by electrolytic plating or electroless plating. The brazing method is a method for fixing the abrasive grains by attaching the abrasive grains to the surface to be fixed with a paste-like brazing material containing a metal, and then melting the brazing material by heating to fix the abrasive grains. The present invention is applicable to either method, but the present embodiment uses the electrodeposition method.

[0019] 2, in this embodiment, the abrasive grains 20 are fixed onto the substrate 10 by an adhesive layer 40 formed on the substrate 10 and a plating layer 30 formed on the adhesive layer 40. As described below, the adhesive layer 40 is for temporarily fixing the abrasive grains 20. With the abrasive grains 20 temporarily fixed by the adhesive layer 40, the plating layer 30 is formed on the substrate 10, whereby the abrasive grains 20 are firmly bonded to the substrate 10.

[0020] As the plating layer 30, a metal plating layer, particularly a nickel plating layer, can be suitably used. When a nickel plating layer is used, it is preferable that the layer contains 0.1 to 15% by weight, more preferably 0.1 to 10% by weight, of phosphorus alone or a phosphorus compound. When a phosphorus compound is contained, nickel and phosphorus are combined, and the hardness of the plating layer can be improved. If the content of the phosphorus compound is too small, it is difficult to obtain the effect of improving the hardness of the plating layer, and if it is too large, the pH value of the plating bath decreases, making it difficult to adjust the plating conditions. Examples of phosphorus compounds added to the plating solution include, but are not limited to, phosphorous acid, ethyl phosphite, diethyl phosphite, dibutyl phosphite, triethyl phosphite, tributyl phosphite, trimethyl phosphite, disodium phosphite pentahydrate, hypophosphorous acid, and sodium hypophosphite hydrate.

[0021] If the thickness of the plating layer 30 is 1 / 3 to 1 / 2 of the average grain size of the abrasive grains 20, the abrasive grains 20 are embedded and can be fixed with sufficient strength. In this embodiment, since the average grain size of the abrasive grains is 0.13 to 0.16 mm, the thickness of the plating layer 30 is set to 0.04 to 0.08 mm (40 to 80 μm).

[0022] <Manufacturing Method of the Embodiment> The manufacturing method of the electroplated grindstone of this embodiment will be described with reference to the flow chart of Fig. 3. First, in step S80, the substrate 10 is processed. The substrate 10 is made of a metal such as SUS and is formed into a rod-like (cylindrical) shape having a shank portion 11 and a processing portion 12 by a method such as cutting, as shown in Fig. 1.

[0023] Next, in step S81, an adhesive is applied to the outer peripheral surface of the processed portion 12 to form an adhesive layer 40. In this embodiment, a conductive adhesive is used as the adhesive because the plating layer 30 will be formed later by electrolytic plating. In addition, because nickel plating will be used in a later process, the lower the volume resistivity, the better. - The viscosity is preferably 5 Ω·m or less. Furthermore, in order to temporarily fix the abrasive grains as described below, the viscosity is preferably in the range of 1 Pa·s to 30 Pa·s. The adhesive can be applied by any common application method such as spray application, flow coating, or dipping.

[0024] Next, in step S82, the abrasive grains 20 are temporarily fixed to the outer periphery of the substrate 10 of the processing section 12 to which the adhesive has been applied. In this embodiment, in order to arrange the abrasive grains 20 regularly, a method is used in which the abrasive grains 20 are arranged in a pattern in advance and then transferred to the outer periphery of the substrate 10. Figure 4 is a diagram for explaining the manner in which the abrasive grains 20 are transferred in this manner. Here, Figure 4(a) shows a schematic cross-sectional view, and Figure 4(b) shows a plan view.

[0025] In this step, a mesh sheet 60 is laid on the plane of the jig 50 shown in FIG. 4(a), and the mesh of this mesh sheet 60 accommodates the abrasive grains 20 in a staggered checkered pattern, with one grain skipped in two directions parallel to the fibers. This allows the abrasive grains 20 to be regularly arranged in two directions perpendicular to each other in the sheet plane. As a method of putting the abrasive grains 20 into the mesh, for example, a method of using another mesh sheet with a different mesh size from the mesh sheet 60 can be considered. The other mesh sheet is superimposed on the mesh sheet 60 so that the fiber direction forms an angle of 45 degrees, and the abrasive grains 20 are scattered on it, and then the excess abrasive grains 20 are brushed off. Here, the mesh size of the mesh sheet is such that only one abrasive grain 20 is accommodated in the mesh. As described above, in this embodiment, diamond abrasive grains with an average grain size of 0.13 to 0.16 mm are used, so a mesh sheet that matches the average grain size of these abrasive grains is used.

[0026] Next, as shown in FIG. 4(a), the substrate 10 with the adhesive layer 40 formed on the outer periphery is laid on the mesh sheet 60, and while rotating in the circumferential direction as shown by the arrow E, it is rolled in the direction of the arrow F. As a result, the abrasive grains 20 are attached to the adhesive layer 40 and transferred to the outer periphery of the substrate 10. Here, it is preferable to limit the gap G between the jig 50 and the substrate 10 by the thickness of the mesh sheet. Thereafter, when a thermosetting adhesive is used for the adhesive layer 40, the substrate 10 is heat-treated to harden the adhesive and temporarily fix the abrasive grains 20.

[0027] Next, in step S83, a plating layer 30 is formed on the base material 10 to which the abrasive grains 20 are temporarily fixed, thereby firmly fixing the abrasive grains (see FIG. 2). In this embodiment, nickel plating by electrolytic plating is used. In this case, an electrolytic solution containing nickel sulfamate, nickel sulfate, nickel nitrate, etc. is used as the plating solution. In addition to the phosphorus compound described above, a gloss agent such as saccharin or butynediol, or a surfactant may be added to this plating solution as necessary. Examples of the surfactant include water-soluble cationic, nonionic, and amphoteric surfactants that show cationicity at the pH value of the plating solution. In particular, a fluorosurfactant having a C-F bond in the molecule can be preferably used.

[0028] In this embodiment, the conditions for forming the plating layer 30 may be appropriately determined depending on the type of plating solution used, and the same solution temperature, pH value, current value, etc. as in the case of a general plating method can be applied. The method for stirring the plating solution is not particularly limited, and a method using a normal mechanical stirring means, such as screw stirring or stirring with a magnetic stirrer, can be used. After the plating layer 30 is formed, the surface hardness of the plating layer 30 can be further improved by performing a heat treatment at a temperature of 70 to 300°C.

[0029] In this manner, the electroplated grinding wheel 1 shown in FIG. 1 is manufactured by steps S80 to S83. In this embodiment, in order to improve the removability of grinding debris, the plating layer 30 may contain compound particles having a water-repellent function. After the plating layer 30 is formed, a resin film containing a compound having a water-repellent function may be formed on the plating layer 30. A fluorine compound can be suitably used as the compound having a water-repellent function. Examples of fluorine compounds include, but are not limited to, tetrafluoroethylene polymers, tetrafluoroethylene polymers, perfluoroalkoxy polymers, hexafluoropropylene / ethylene copolymers, tetrafluoroethylene / ethylene copolymers, perfluoromethylvinyl ether polymers, perfluoroalkylethyl (meth)acrylate polymers, perfluoroalkylethyl (meth)acrylate polymers, perfluorosulfonic acid polymers, fluoroacetylene polymers, fluoromaleic acid polymers, graphite fluoride, chlorotrifluoroethylene polymers, vinyl fluoride polymers, vinylidene fluoride polymers, chlorotrifluoroethylene polymers, and 1,4-cyclohexylenedimethylene terephthalate polymers.

[0030] <Cutting process according to the embodiment> When using the electroplated grindstone of this embodiment to process a workpiece with high hardness, for example, a sintered zirconia block (Vickers hardness 1300HV), the conditions for clogging of cutting chips include the average particle size of diamond abrasive grains, the interval between diamond abrasive grains, the embedding amount of diamond abrasive grains, etc., for electroplated grindstone. In addition, the processing conditions include spindle rotation speed, feed rate, processing amount, etc. Furthermore, it also depends on the size of the cutting chips discharged under the above processing conditions.

[0031] In this embodiment, the relationship between the size of cutting chips discharged by cutting and the spacing between diamond abrasive grains will be described.

[0032] First, the size of the cutting chips generated during cutting is not uniform, but rather there are several different sizes of cutting chips mixed together. Since the size of these cutting chips varies depending on the type of workpiece, it is necessary to select the tool.

[0033] Next, regarding the spacing between diamond abrasive grains, the wider the spacing between the diamond abrasive grains, the less clogging occurs, but the lower the cutting ability. This can be improved by adjusting the spindle speed and feed speed, but there are also disadvantages such as limitations on the equipment and increased processing time. Therefore, the arrangement of the abrasive grains is an important factor that determines cutting ability.

[0034] In order to reduce clogging of the workpiece, the interval between diamond abrasive grains should be set wider than the size of the main cutting chips produced by machining the workpiece. If the interval between diamond abrasive grains is set to 1 to 1.5 times the outer diameter of the largest peak in the particle size distribution of the cutting chips of the workpiece, the time during which cutting can be performed with one electroplated grinding wheel will be extended by 1.5 to 5 times.

[0035] In addition, the diamond abrasive grains can be arranged in a staggered checkerboard pattern, with one grain spaced apart in both the direction of the rotation axis and the circumferential direction of the outer circumferential surface, thereby further improving the discharge of cutting chips.

[0036] For example, a substrate 10 can be created using a material made of SUS304, with the tip machined into a cylindrical shape with a diameter of 6 mm as shown in Figure 1. After this, plasma treatment can be performed to modify the surface of the substrate 10. Next, a conductive adhesive is applied to the machined portion 12 of the substrate 10 to a thickness of 10 μm to form an adhesive layer 40, which makes it easier to fix the abrasive grains at the targeted position (see Figure 2). As the adhesive, TB3331D (manufactured by ThreeBond Co., Ltd.), which has an epoxy binder and a silver conductive filler, can be used.

[0037] Next, as shown in FIG. 4, a polyethylene mesh sheet 60 having a mesh of equal pitch is laid on the plane of the jig 50, and the abrasive grains 20 are scattered on the mesh sheet 60, so that the grains are arranged in a staggered (zigzag) checkered pattern as shown in FIG. 4, with one grain skipped in each of two directions along the fibers. Diamond abrasive grains having an average grain size of 150 μm are preferably used as the abrasive grains 20. At this time, the interval between the diamond abrasive grains and the adjacent diamond abrasive grains is preferably 120 μm. The substrate 10 on which the adhesive layer 40 is formed is held horizontally on the mesh sheet at a position where the gap G is 150 μm. Then, the substrate 10 is rolled while maintaining the gap G, and the abrasive grains 20 are transferred to the outer peripheral surface of the substrate 10. Thereafter, the substrate 10 is heated at 80° C. for 60 minutes to harden the adhesive layer 40 and temporarily fix the abrasive grains 20.

[0038] Next, the substrate 10 with the abrasive grains 20 temporarily fixed thereto is immersed in a plating bath, and electrolytic plating is performed with a current density of 5 A / dm2 to form a plating layer 30 with a thickness of 65 μm, thereby fixing the abrasive grains 20. The plating solution used has the following composition, and is finally adjusted to a pH of 2.5. For 1L of distilled water, Nickel sulfate: 125g Boric acid: 30g Sodium chloride: 25g Sodium hypophosphite: 0.08g Sodium saccharin: 0.024g Sodium dodecyl sulfate: 0.005g

[0039] At this time, the plating is performed while rotating the substrate in order to make the film thickness of the plating layer 30 uniform. After plating, the substrate 10 is heat-treated at 260° C., whereby the Vickers hardness becomes 617 HV, improving the hardness.

[0040] By varying the spacing between diamond abrasive grains and carrying out a grinding test under the conditions described below, the degree of clogging can be evaluated. The time during which clogging did not occur can also be evaluated.

[0041] <Grinding test> Outer periphery Outer periphery A sintered zirconia block (Vickers hardness 1300HV) is used as the workpiece. A grinding test is carried out on this workpiece using an electroplated grinding wheel with diamond abrasive grains spaced 120μm apart on the outer periphery. One surface of the zirconia block is ground back and forth for 20 minutes at a spindle speed of 60000RPM, a feed rate of 600mm / min, and a processing amount of 0.025mm, and this is repeated until clogging occurs.

[0042] Figure 5 shows the distribution of chip sizes when a sintered zirconia block is cut with a tool formed by randomly arranging diamond abrasive grains with an average grain size of 150 μm. The measurements were performed using a Mastersizer 3000 (Malvern). It can be seen that the chip sizes of the sintered zirconia block cut with a tool formed by randomly arranging diamond abrasive grains with an average grain size of 150 μm are mixed, with four types of chip sizes: 110 μm, 20 μm, 5 μm, and 1 μm. In Figure 5, the maximum peak of 110 μm is represented by P1, 20 μm by P2, 5 μm by P3, and 1 μm by P4.

[0043] (Other Examples) Fig. 6(a) shows a shape in which the tip side of the cylindrical outer periphery 12 is made semispherical, and Fig. 6(b) shows a shape in which the tip side of the outer periphery 12 is made flat (trapezoidal) after being inclined. Both the hemispherical portion 13 and the inclined portion 14 form a tapered portion 15 whose diameter decreases toward the tip.

[0044] The spacing between adjacent grains in the reduced diameter section may be the same as or denser than that in the outer periphery, but in this embodiment, the spacing between adjacent grains is set to 20 μm or more and less than 100 μm. Since the particle size distribution peak of sintered zirconia is also at 20 μm, the spacing between adjacent grains is set to be larger than the second largest peak, making it difficult for the grains to become clogged.

[0045] A cutting test is carried out using a sintered zirconia block (Vickers hardness 1300Hv) as the workpiece, and the electroplated grinding tool of this embodiment. The machining conditions are the same for both the outer periphery for cutting the flat surface of the workpiece and the reduced diameter part for cutting the curved surface, with a spindle speed of 60,000 RPM, a feed rate of 600 mm / min, and a machining amount (cutting depth): 0.025 mm. As shown in FIG. 6, the machining procedure is as follows: first, the outer periphery of the electroplated grinding tool is used to cut the flat surface of the side of the sintered zirconia block to a depth of 0.025 mm at a time, until the cutting depth reaches 0.1 mm. Next, the reduced diameter part of the electroplated grinding tool is used to cut the upper and lower surfaces of the sintered zirconia block into curved surfaces by tilting the block and cutting the block to a depth of 0.025 mm at a time, until the cutting depth reaches 0.1 mm.

[0046] As a result of the cutting process, no clogging of cutting chips between the diamond abrasive grains was observed on either the outer periphery or the inclined portion (hemispherical portion) of the electroplated grinding tool.

[0047] In this embodiment, the high density abrasive grains have a lower load on each grain during machining, so the grains last longer than the low density grains, and so the tool life can be optimized by concentrating the grains on the inclined portion that has a higher frequency of contact with the workpiece. In addition, by increasing the grain density on the inclined portion, the effect of the reduction in the number of teeth per revolution can be reduced, and the effect of the reduction in peripheral speed can also be partially offset.

[0048] A machining tool formed by randomly arranging diamond abrasive grains with an average grain size of 150 μm becomes clogged when used to grind a sintered zirconia block (a sintered ceramic) continuously for about 30 minutes under the above-mentioned conditions.

[0049] <Other embodiments> The present invention is not limited to the above-described embodiment, and various applications and modifications are possible. For example, in the above-described embodiment, the electroplated grindstone is formed in a rod shape (cylindrical shape), but the present invention can be applied to any shape of electroplated grindstone as long as it is rotated by a processing device and has an outer circumferential surface for grinding a workpiece. In addition, the present invention may be used for an electroplated grindstone in which a groove is formed on the outer circumferential surface of the substrate in order to more efficiently remove grinding debris. Furthermore, the arrangement of the abrasive grains is not limited to the above-described embodiment, and for example, an electroplated grindstone in which abrasive grains are fixed in a spiral shape on the outer circumferential surface is also within the technical scope of the present invention. The present invention includes all such application examples and modifications as long as they do not deviate from the scope of the claims. [Explanation of symbols]

[0050] 10 Base material 12 Outer periphery 13 Hemisphere 14 Slope 15 Reduced diameter part 20 grit 30 Plating layer 40 Adhesive layer 50 Jig 60 mesh sheet

Claims

1. A cylindrical outer periphery; A tapered portion having a diameter that decreases from the outer periphery toward the tip, A machining tool characterized in that the spacing between adjacent abrasive grains fixed to the outer periphery is 100 μm or more.

2. The machining tool according to claim 1 , wherein the abrasive grains are partly embedded in an adhesive layer and a plating layer formed on the machining tool.

3. 2. The machining tool according to claim 1, wherein the abrasive grains are fixed to the surface of the cylindrical base metal in only one layer.

4. 2. The machining tool according to claim 1, wherein the abrasive grains are made of diamond or CBN.

5. The machining tool according to claim 2 , wherein the adhesive layer is a conductive adhesive.

6. 2. The machining tool according to claim 1, wherein the interval between adjacent abrasive grains fixed to the reduced diameter portion is 20 μm or more and less than 100 μm.

7. A processing device comprising a spindle for rotating the processing tool according to any one of claims 1 to 6.

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