Rotary dresser

Abstract

A rotary dresser is provided with a base metal (103) having an outer peripheral surface, and an abrasive grain layer (101) provided on the outer peripheral surface of the base metal (103). The abrasive grain layer (101) has a bonding material (203) disposed on the base metal (103) and abrasive grains (204) fixed into one layer by the bonding material (203), and the diameter of the abrasive grain layer (101) of the rotary dresser differs depending on a first location and a second location of the abrasive grain layer. The larger the diameter of the abrasive grain layer (101) is, the smaller the area ratio of the active surface (205) of the surface of the abrasive grain layer (101) is.

Description

Technical Field

[0001] The present disclosure relates to a rotary dresser. This application claims priority based on Japanese Patent Application No. 2022-178078 filed on November 7, 2022, and Japanese Patent Application No. 2023-051173 filed on March 28, 2023. All the descriptions recorded in the Japanese patent application are incorporated herein by reference. Background Art

[0002] As an example of a rotary dresser for shaping the shape and grinding surface of a forming grinding stone, there is a rotary dresser described in Japanese Patent Application Laid-Open No. 2012-091292 (Patent Document 1).

[0003] The rotary dresser described in Patent Document 1.

[0004] Prior Art Documents

[0005] Patent Documents

[0006] Patent Document 1: Japanese Patent Application Laid-Open No. 2012-091292 Summary of the Invention

[0007] A rotary dresser includes a base metal having an outer peripheral surface and an abrasive grain layer provided on the outer peripheral surface of the base metal. The abrasive grain layer has a bonding material provided on the base metal and abrasive grains fixed in a layer by the bonding material. The diameter of the abrasive grain layer of the rotary dresser varies depending on the position, and the difference in diameter of the abrasive grain layer depending on the position is 5% or more. A flat working surface is provided for the abrasive grains appearing on the surface of the abrasive grain layer, and the area ratio of the working surface on the surface of the abrasive grain layer is smaller at the position where the diameter of the abrasive grain layer is larger. Brief Description of the Drawings

[0008] Figure 1 Figure 1 is a photograph of a rotary dresser 100 according to an embodiment of the present disclosure.

[0009] Figure 2 Figure 2 is a view showing a state in which the rotary dresser 100 contacts the grinding stone 200 and the rotary dresser 100 dresses the grinding stone 200.

[0010] Figure 3 Figure 3 is a view showing a state in which the grinding stone 200 contacts the workpiece 300 and the grinding stone 200 grinds the workpiece 300.

[0011] Figure 4 Figure 4 ​​​​​​​​It is a diagram showing a cross-sectional structure of the abrasive grain layer 101 along the direction from the center of the rotary dresser 100 toward the outer circumference.

[0012] Figure 5 Figure 5 It is a schematic diagram of the rotary dresser 100 shown for explaining a method of measuring the area ratio of the working surface.

[0013] Figure 6 Figure 6 It is a schematic diagram of the rotary dresser 100 shown for explaining a method of measuring the area ratio of the working surface.

[0014] Figure 7 Figure 7 It is a schematic diagram of the rotary dresser 100 shown for explaining a method of measuring the area ratio of the working surface.

[0015] Figure 8 Figure 8 It is a schematic diagram of the rotary dresser 100 before dressing in the embodiment.

[0016] Figure 9 Figure 9 It is a schematic diagram of the rotary dresser 100 after 100 dressings.

[0017] Figure 10 Figure 10 It is a schematic diagram of the rotary dresser 100 after 100 dressings and the grindstone 400 for machining the shape transfer material in contact with the rotary dresser 100.

[0018] Figure 11 Figure 11 It is a schematic diagram of the grindstone 400 for machining the shape transfer material and the shape transfer material 500 in contact with the grindstone 400 for machining the shape transfer material.

[0019] Figure 12 Figure 12 It is a schematic diagram of the shape transfer material 500 on which the shape of the rotary dresser 100 after 100 dressings is transferred.

[0020] Figure 13 Figure 13 It is a schematic diagram for explaining a method of measuring the depth of the recess 519 as a wear mark formed on the shape transfer material 500. Detailed Description

[0021] [Problems to be Solved by the Present Disclosure]

[0022] In the existing rotary dresser, there is a problem of high dressing resistance.

[0023] ​​​​​​​​​​​​​​​​​​In the case of dressing a grinding stone with a profiling rotary dresser, the diameter of the grinding stone decreases at the portion of the rotary dresser with a larger diameter, and the diameter of the grinding stone increases at the portion of the rotary dresser with a smaller diameter. Further, in the dressing of a grinding stone for outer diameter grinding where dressing resistance is a problem, generally the diameter of the rotary dresser is almost smaller than the diameter of the grinding stone, and the rotational speed during dressing is also lower for the rotary dresser than for the grinding stone. The rotational directions of the rotary dresser and the grinding stone are usually opposite to each other (down-cut), and the same direction (up-cut) of the rotational directions of the rotary dresser and the grinding stone is not used except in special cases such as when the sharpness of the rotary dresser is poor and dressing cannot be performed.

[0024] When using a profiling rotary dresser in such a situation, the peripheral speed ratio between it and the grinding stone is different in the large-diameter portion and the small-diameter portion of the rotary dresser.

[0025] That is, the peripheral speed ratio V1 (VRD / Vgrinding stone) between the small-diameter portion of the rotary dresser and the large-diameter portion of the grinding stone becomes smaller, and the peripheral speed ratio V2 (VRD / Vgrinding stone) between the large-diameter portion of the rotary dresser and the small-diameter portion of the grinding stone becomes larger and approaches 1.

[0026] When the peripheral speed ratio approaches 1, the resistance becomes very large, and the sharpness of the rotary dresser also deteriorates.

[0027] Therefore, when the overall composition of the abrasive grain layer of the profiling rotary dresser is the same, the dressing resistance is significantly different between the large-diameter portion and the small-diameter portion of the rotary dresser, and there is a portion with a large dressing resistance, so chattering etc. are likely to occur and the accuracy of the dressed grinding stone deteriorates.

[0028] In addition, the wear of the rotary dresser becomes uneven, and the life of the rotary dresser becomes shorter.

[0029] The rotary dresser of the present disclosure solves the above problems.

[0030] Figure 1 is a photograph of a rotary dresser 100 according to an embodiment of the present disclosure. Figure 2 is a view showing a state where the rotary dresser 100 is in contact with a grinding stone 200 and the rotary dresser 100 dresses the grinding stone 200. Figure 3 is a view showing a state where the grinding stone 200 is in contact with a workpiece 300 and the grinding stone 200 grinds the workpiece 300.

[0031] As Figures 1 to 3 shown, the rotary dresser 100 as a diamond rotary dresser has a base metal 103 and an abrasive grain layer 101 as a superabrasive grain layer provided on the surface of the base metal 103.

[0032] The base metal 103 is made of, for example, stainless steel. The base metal 103 is cylindrical, and an abrasive grain layer 101 is provided on the outer peripheral surface of the base metal 103. Diamond as abrasive grains is fixed in the abrasive grain layer 101. It should be noted that CBN (cubic boron nitride) can also be used instead of diamond. In addition, diamond and cubic boron nitride can also coexist.

[0033] Grooves 102 extending in the circumferential direction are formed in the abrasive grain layer 101. The grooves 102 are formed along the shape of the workpiece. Such a rotary dresser 100 dresses a so-called form grinding wheel.

[0034] Figure 4 FIG. is a cross-sectional view of the abrasive grain layer 101 along the direction from the center of the rotary dresser 100 toward the outer periphery. As Figure 4 shown, the abrasive grain layer 101 is formed on the surface of the base metal 103 via a low melting point alloy layer 104. The abrasive grain layer 101 is produced by an inversion plating method and has a bonding material 203 as a plating layer and abrasive grains 204 fixed in a layer. The abrasive grain layer 101 is fixed to the base metal 103 by the low melting point alloy layer 104.

[0035] The total area ratio of the plurality of working surfaces 205 is represented by a ratio S with respect to the area of a virtual surface 206 that gently connects the working surfaces 205.

[0036] The working surface 205 of the abrasive grains 204 is formed by grinding or lapping the abrasive grains 204. By changing the time for grinding or lapping the abrasive grains 204, the area of the working surface 205 can be adjusted. As the abrasive grains 204, not only super abrasive grains such as diamond and CBN can be used, but also conventional abrasive grains such as alumina can be used.

[0037] The rotary dresser 100 includes: a base metal 103 having an outer peripheral surface 109, and an abrasive grain layer 101 provided on the outer peripheral surface 109 of the base metal 103. The abrasive grain layer 101 has a bonding material 203 provided on the base metal 103 and abrasive grains 204 fixed in a layer by the bonding material 203. The diameter of the abrasive grain layer 101 of the rotary dresser 100 is different according to the first part and the second part of the abrasive grain layer 101.

[0038] When the diameter of the abrasive grain layer 101 at the first part is set as D1 and the diameter of the abrasive grain layer 101 at the second part is set as D2, (D1 - D2) / D1 is 5% or more. A flat working surface 205 is provided for the abrasive grains appearing on the surface of the abrasive grain layer 101.

[0039] The larger the diameter of the part of the abrasive grain layer 101, the smaller the area ratio of the working surface 205 on the surface of the abrasive grain layer 101.

[0040] Preferably, the area ratio (ratio S) of the working surface 205 of the portion with the largest diameter in the abrasive grain layer 101 is 5% or more and 15% or less.

[0041] Preferably, the larger the diameter of the portion of the abrasive grain layer 101, the fewer the number of abrasive grains in one revolution of the rotary dresser 100.

[0042] Preferably, the larger the diameter of the portion of the abrasive grain layer 101, the wider the spacing between the abrasive grains 204.

[0043] The abrasive grains 204 are synthetic diamonds, and the crystal planes of the synthetic diamonds are oriented.

[0044] When synthetic diamonds are used as the abrasive grains 204, since the shape in which the crystal planes of the diamonds are clearly shown, they are joined in a state where the joining surface of the crystal planes and the base metal 103 is close to parallel. As a result, the abrasive grains 204 are tightly joined in a stable form. Even if the grinding amount for forming the working surface on the abrasive grains 204 is reduced, the working area ratio can be increased. As a result, it is easy to form the working surface, and since the thickness of the abrasive grain layer 101 becomes thicker, the lifespan is also increased.

[0045] Preferably, the abrasive grains 204 are linearly arranged on the surface of the abrasive grain layer 101. The arrangement direction can be any one of the axial direction, the circumferential direction of the rotary dresser 100, or a direction having an angle with respect to them, and can be linear or curved.

[0046] By linearly arranging the abrasive grains 204, it is easy to adjust the area ratio of the working surface 205 when manufacturing the rotary dresser 100.

[0047] Figures 5 to 7 It is a schematic diagram of the rotary dresser 100 shown to illustrate the method for measuring the area ratio of the working surface. In Figures 5 to 7 it, the rotary dresser 100 rotates around the rotation axis 108. In Figure 5 it, the outer peripheral surface 109 has a stepped shape.

[0048] Step (1)

[0049] Select an arbitrary position of the rotary dresser 100. A portion with a diameter of D1 is selected.

[0050] Step (2)

[0051] Select a position different from the position selected in 1) above and having a diameter 5% or more different. A portion with a diameter of D2 is selected. (D1 - D2) / D1 is set to 5% or more. Further, a portion with a diameter of D3 is selected, and (D2 - D3) / D2 is set to 5% or more.

[0052] As Figure 6As shown, in the case of a shape with a continuously varying diameter, positions that are 5% different from the diameter of the position selected in 1) above, such as 5%, 10%, and 15% respectively, are selected. Specifically, an arbitrary position (the position of line A) is selected. The position of line B that is 5% different in diameter from the position of line A is selected. The position of line C that is 5% different in diameter from the position of line B is selected. The position of line D that is 5% different in diameter from the position of line C is selected.

[0053] As Figure 7 shown, in the case where a groove 102 is formed, the position of line A outside the groove 102 is selected. Let the diameter of the position of line A outside the groove be D1 and the diameter of the position of line B inside the groove 102 be D2. If (D1 - D2) / D1 is 5% or more, measurement is also performed on line B.

[0054] Step (3)

[0055] In the circumferential direction of the positions selected in the above steps (1) and (2), within a range of an axial length of 2 mm and a circumferential length of 10 mm, 10 arbitrary positions are selected in the circumferential direction. Thus, the measurement positions 121 to 124 are determined. There are 10 measurement positions 121 on line A. There are 10 measurement positions 122 on line B. There are 10 measurement positions 123 on line C. There are 10 measurement positions 124 on line D.

[0056] Step (4)

[0057] For each of the selected positions, using a measuring device VR5000 manufactured by KEYENCE, according to the steps of surface correction, cut-off correction, threshold setting, and area measurement, the area ratio of the working surface of the abrasive grains is measured.

[0058] Specifically, the measuring instrument is VR5000 manufactured by KEYENCE. The measurement principle is the "optical section method". The analysis steps are: (1) Three-dimensional measurement. (2) Flatten the shape with either or both of the following A and B. A: Fluctuation removal (cut-off processing). Flatten the fluctuations above a certain wavelength. B: Quadratic curve correction. Flatten the circular arc obtained by fitting the entire shape with a quadratic curve. (3) Set the threshold and calculate the working area. For each of line A, line B, line C, and line D, the average value of the 10 measured working areas is taken as the working area of that line.

[0059] The smaller the circumferential speed difference between the rotary dresser 100 and the grinding stone in contact with the rotary dresser 100 (the circumferential speed ratio is close to 1), the greater the dressing resistance. In form dressing, the circumferential speed difference varies according to the outer diameter of the rotary dresser 100. The circumferential speed of the form dresser cannot be changed according to the location. Therefore, the dressing resistance can be reduced by decreasing the ratio of the working surface 205 of the abrasive grains 204 in the portion with a large outer diameter in the rotary dresser 100.

[0060] The dressing resistance of the entire rotary dresser can be reduced by decreasing the dressing resistance of the large-diameter portion of the form rotary dresser. In addition, since the difference in dressing resistance between the large-diameter portion and the small-diameter portion of the rotary dresser becomes smaller, the accuracy of the grinding stone after dressing is improved. Furthermore, the wear of the large-diameter portion and the small-diameter portion of the abrasive grain layer can be made to approach evenly, and the life of the rotary dresser can be increased.

[0061] When the rotary dresser performs dressing, a working surface is provided at the head of the abrasive grains acting on the grinding stone, and the area ratio of this working surface has a great influence on the dressing resistance. In the form rotary dresser, the larger the diameter portion, the more it acts on the smaller-diameter portion of the grinding stone, and the circumferential speed ratio of this portion is closer to 1. Therefore, the dressing resistance becomes larger. If the area ratio of the working surface of the abrasive grains in the large-diameter portion of the rotary dresser where the resistance becomes larger is decreased, the dressing resistance of the large-diameter portion of the rotary dresser is reduced, and the dressing resistance of the entire rotary dresser is also reduced.

[0062] (Example)

[0063] (Description of the rotary dresser 100, grinding stone 200, and workpiece 300)

[0064] Figure 8 It is a schematic diagram of the rotary dresser 100 before dressing produced in the example. The details are shown in Tables 1 and 2.

[0065] [Table 1]

[0066]

[0067] [Table 2]

[0068]

[0069] The "average abrasive grain interval of 2 mm width" refers to the distance obtained by "circumferential length of the central portion within a 2 mm width / number of abrasive grains within a 2 mm width" for each part. It should be noted that for the abrasive grains located at the outer peripheral portion of the 2 mm wide area and for the case where a part of the abrasive grains falls within this area, the number of abrasive grains is counted as 0.5.

[0070] The abrasive grains 204 of the rotary dresser 100 are made of diamond, and the base metal 103 ( Figure 3)Made of stainless steel, combined with material 203( Figure 3 )Made of nickel plating. The diameter of the abrasive grains 204 is #20 / 25 (average particle size is 700 μm to 850 μm). The abrasive grains 204 are fixed at intervals in the circumferential direction and arranged linearly.

[0071] The rotary dresser 100 dresses the grinding stone 200 as Figure 2 shown.

[0072] The grinding stone 200 to be dressed( Figure 2 )is a grinding stone with a mesh #60 (average particle size 250 μm) and a bond strength K, manufactured by Kure-Norton Co., Ltd. The material of the grinding stone 200 is WA.

[0073] The workpiece 300( Figure 3 )is a round bar with a diameter of 100 mm and a thickness (length in the axis direction) of 130 mm, made of S45C.

[0074] The rotary dresser 100 and the grinding stone 200 rotate in opposite directions (down-cut). Thus, the grinding fluid is sucked between the rotary dresser 100 and the grinding stone 200. The grinding stone 200 and the workpiece 300 also rotate in opposite directions.

[0075] The average outer diameter of the rotary dresser 100 is 93 mm, the rotational speed is 1200 rpm, and the circumferential speed is 5.8 m / s. The average outer diameter of the grinding stone 200 is 248 mm, the rotational speed is 1490 (rpm), and the circumferential speed is 19.4 m / s. The circumferential speed ratio represented by the average circumferential speed of the rotary dresser 100 / the average circumferential speed of the grinding stone 200 is 0.3.

[0076] (Description of the dressing process)

[0077] First, the grinding stone 200 is dressed using the rotary dresser 100. Then, the grinding of the workpiece 300 is repeated using this grinding stone. When the accuracy of the workpiece 300 after processing deviates from the specified value, the grinding stone 200 is dressed again using the rotary dresser 100. The results after repeating this operation 100 times are shown in Tables 3 and 4.

[0078] [Table 3]

[0079]

[0080] [Table 4]

[0081]

[0082] The "dressing resistance" in Tables 3 and 4 is the resistance for rotating the rotary dresser, which is obtained by measuring the load in the cutting-in direction using the piezoelectric sensor "Multi-Component Dynamometer 9257B" manufactured by Kistler.

[0083] The "workpiece roughness" is the surface roughness of the workpiece 300 machined by the grindstone 200 immediately after each of the 100 dressings, which is measured using a tactile surface roughness meter and set as the average value of the 100 measured values.

[0084] The "wear amount of the RD radius after 100 dressings" is the wear amount of the rotary dresser after 100 dressings as described in the above (description of the dressing process). Figure 9 It is a schematic diagram of the rotary dresser 100 after 100 dressings. As Figure 9 shown, at the end of 100 dressings, a recess 119 is formed on the outer peripheral surface 109. The area where the recess 119 is formed is the dressing area 118. The recess 119 is formed because the part of the recess 119 mainly contacts the grindstone 200.

[0085] Figure 10 It is a schematic diagram of the rotary dresser 100 after 100 dressings and the grindstone 400 for machining the shape transfer material in contact with the rotary dresser 100. As Figure 10 shown, using the rotary dresser 100 after 100 dressings, the rotary dresser 100 is rotated around the rotary axis 108, and the grindstone 400 for machining the shape transfer material is rotated around the rotary axis 408. The grindstone 400 for machining the shape transfer material is dressed. Thereby, the shape of the outer peripheral surface of the abrasive grain layer 101 of the rotary dresser 100 is transferred onto the grindstone 400 for machining the shape transfer material. The grindstone 400 for machining the shape transfer material uses a grindstone with a grit size of #60 (average particle size 250 μm), an abrasive grain type of WA, and a width of the grindstone 400 for machining the shape transfer material that is equal to or greater than the width of the rotary dresser 100.

[0086] Figure 11 It is a schematic diagram of the grindstone 400 for machining the shape transfer material and the shape transfer material 500 in contact with the grindstone 400 for machining the shape transfer material. As Figure 11 shown, the grindstone 400 for machining the shape transfer material is rotated around the rotary axis 408, and the shape transfer material 500 is rotated around the rotary axis 508. Thereby, using the grindstone 400 for machining the shape transfer material, a round bar-shaped shape transfer material 500 made of material S45C is machined.

[0087] Figure 12 It is a schematic diagram of the shape transfer material 500 on which the shape of the rotary dresser 100 after 100 dressings is transferred. As Figure 12As shown, in the measurement area 518, the shape transferred to the shape transfer material 500 is measured by a shape measurement device. Any general shape measurement device can be used for the measurement.

[0088] Figure 13 It is a schematic diagram for explaining a method of measuring the depth of the concave portion 519 as a wear mark formed on the shape transfer material 500. In Figure 13 the minute unevenness of the surface observed in the measurement area 518 is described. When performing shape measurement, any one of the reference portion 521, the reference portion 522, and the portion (the bottom of the concave portion 519) where the rotary dresser 100 acts during dressing has minute unevenness. The intermediate points (average positions) of the reference portion 521 and the reference portion 522 of the rotary dresser RD transferred to the shape transfer material 500 are calculated by the shape measurement device. The intermediate point 523 is the intermediate point of the reference portion 521. The intermediate point 524 is the intermediate point of the reference portion 522. Similarly, the intermediate point 526 of the portion where the rotary dresser 100 acts during dressing is calculated by the shape measurement device. The distance L between the straight line 525 connecting the intermediate point 523 of the reference portion 521 and the intermediate point 524 of the reference portion 522 and the intermediate point 526 of the portion where the rotary dresser 100 acts during dressing is the "wear amount of the RD radius when dressing 100 times". This distance is the distance in the direction perpendicular to the straight line 525.

[0089] In the "dressing resistance determination" column, if the "dressing resistance" is less than 33, it is set as "A", if it is 33 or more and less than 35, it is set as "B", and if it is 35 or more, it is set as "C".

[0090] From these results, it can be seen that in sample numbers 8 and 10 where the action area ratio is equal in each part, the evaluation in the dressing resistance determination is "C".

[0091] It can be seen that in sample number 7 where the action area ratio in the small-diameter part is small, the evaluation in the dressing resistance determination is "C".

[0092] In contrast, it can be seen that in sample numbers 1 to 6 and 9 where the action area ratio in the small-diameter part is large, the evaluations of "A" or "B" are obtained in the dressing resistance determination. In particular, in sample number 9, since the dressing resistance is extremely small, it can be considered that excellent results are shown.

[0093] In sample numbers 1 to 6 and 9, the wider the diameter of the abrasive grain layer, the wider the interval of the abrasive grains represented by the "average abrasive grain interval in 2 mm width". It can be seen that in this case, as shown in sample numbers 1 to 6 and 9, preferable results are obtained.

[0094] (Supplementary Note 1)

[0095] A rotary dresser, comprising:

[0096] A base metal having an outer peripheral surface, and

[0097] An abrasive grain layer provided on the outer peripheral surface of the base metal,

[0098] The abrasive grain layer has a bonding material provided on the base metal and abrasive grains fixed in a layer by the bonding material,

[0099] The diameter of the abrasive grain layer of the rotary dresser varies according to the position,

[0100] The difference in diameter of the abrasive grain layer according to the position is 5% or more,

[0101] A working surface formed flat is provided for the abrasive grains appearing on the surface of the abrasive grain layer,

[0102] The larger the diameter of the part of the abrasive grain layer, the smaller the area ratio of the working surface on the surface of the abrasive grain layer.

[0103] (Supplementary Note 2)

[0104] According to the rotary dresser described in Supplementary Note 1, wherein the proportion of the working area of the part with the largest diameter in the abrasive grain layer is 5% or more and 15% or less.

[0105] (Supplementary Note 3)

[0106] According to the rotary dresser described in Supplementary Note 1 or 2, wherein the larger the diameter of the part of the abrasive grain layer, the fewer the number of abrasive grains per one rotation of the rotary dresser.

[0107] (Supplementary Note 4)

[0108] According to the rotary dresser described in any one of Supplementary Notes 1 to 3, wherein the larger the diameter of the part of the abrasive grain layer, the wider the spacing between the abrasive grains.

[0109] (Supplementary Note 5)

[0110] According to the rotary dresser described in any one of Supplementary Notes 1 to 4, wherein the abrasive grains are synthetic diamonds and the crystal planes of the synthetic diamonds are oriented.

[0111] (Supplementary Note 6)

[0112] According to the rotary dresser described in any one of Supplementary Notes 1 to 5, wherein the abrasive grains are arranged linearly on the surface of the abrasive grain layer.

[0113] It should be understood that the embodiments disclosed herein are exemplary in all aspects and not restrictive. The scope of the present invention is represented by the claims rather than the above description, and is intended to include all modifications within the meaning and scope equivalent to the claims.

[0114] Description of Symbols

[0115] 100 Rotary dresser, 101 Abrasive layer, 102 Groove, 103 Base metal, 104 Low melting point alloy, 108, 408, 508 Rotary shaft, 109 Outer peripheral surface, 118 Dressing area, 203 Bonding material, 204 Super abrasive grain, 205 Top surface, 206 Imaginary surface, 300 Workpiece, 400 Grinding stone for machining shape transfer material, 500 Shape transfer material, 518 Measurement area, 521, 522 Reference part, 523, 524, 526 Intermediate point, 525 Straight line.

Claims

1. A rotary dresser, comprising: a base metal having an outer peripheral surface, and an abrasive grain layer provided on the outer peripheral surface of the base metal, the abrasive grain layer having a bonding material provided on the base metal and abrasive grains fixed in a layer by the bonding material, the diameter of the abrasive grain layer of the rotary dresser varying according to the position, the difference in diameter according to the position of the abrasive grain layer being 5% or more, a working surface formed flat is provided for the abrasive grains appearing on the surface of the abrasive grain layer, the larger the diameter of the part of the abrasive grain layer, the smaller the area ratio of the working surface on the surface of the abrasive grain layer.

2. The rotary dresser according to claim 1, wherein the area ratio of the working surface of the part having the largest diameter in the abrasive grain layer is 5% or more and 15% or less.

3. The rotary dresser according to claim 1 or 2, wherein the larger the diameter of the part of the abrasive grain layer, the fewer the number of abrasive grains per revolution of the rotary dresser.

4. The rotary dresser according to claim 1 or 2, wherein the larger the diameter of the part of the abrasive grain layer, the wider the spacing between the abrasive grains.

5. The rotary dresser according to claim 1 or 2, wherein the abrasive grains are synthetic diamonds, and the crystal planes of the synthetic diamonds are oriented.

6. The rotary dresser according to claim 1 or 2, wherein the abrasive grains are arranged linearly on the surface of the abrasive grain layer.

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