JP2001038640A - Centerless grinding wheel and regenerating method and grinding method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To delay a speed of forming a step difference between a cemented carbide abrasive grain layer and a sticking grinding wheel layer by sticking a grinding wheel including microcrystalline sintered alumina abrasive grains to one or both side surfaces of a centerless grinding wheel body, and binding this by a vitrified binder. SOLUTION: A centerless grinding wheel body 10 is composed of a cemented carbide abrasive grain layer, a sticking grinding wheel 11 is a grinding wheel including microcrystalline sintered alumina abrasive grains, and the thickness is within a range of 1/2 to 2/1 of a grinding object 13. Here, capacity of the microcrystalline sintered alumina abrasive grains occupies 10 to 100 volume % of the whole abrasive grains, and the grain size (a F value) of the microcrystalline sintered alumina abrasive grains according to stipulations of JIS R 6001 is the grain size within a range of ± three stages by centering the grain size of of the average particle size closest to the average particle size of the grain size according to stipulations of JIS B 4130 of cemented carbide abrasive grains, and a binding degree according to stipulations of JIS R 6210 is within a range of J to P.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a centerless grindstone in which super-hard abrasive grains such as cubic boron nitride and danmond are bonded with a vitrified binder, a method of regenerating the same, and a method of grinding the same.

[0002]

2. Description of the Related Art In a centerless grinding wheel using super-hard abrasive grains, a grinding wheel using a laminated bake plate or a low-grade abrasive is attached to a side surface of a centerless grinding wheel using ultra-hard abrasive grains, or a finer grain than a diamond is polished. It is disclosed that a guide plate and a diamond grindstone mixed with a material are alternately arranged to prevent the super hard abrasive grain grindstone from being damaged and to perform preliminary grinding and finish grinding (Japanese Patent Publication No. 55-46868).
Reference).

[0003]

However, in the conventional method as described above, there is too much difference in the service life between the super hard abrasive grains and the laminated bake plate or the low-grade abrasives. A step is easily generated at the boundary between the grindstone and the attaching plate or the grindstone. When the step becomes large, a phenomenon occurs in which the corner of the super-hard abrasive grain grindstone is chipped. Since this adversely affects the surface roughness of the workpiece and the roundness of the workpiece, it is often necessary to grind the grinding surface of the grindstone in order to eliminate such a large step, and there is a problem that the processing work is troublesome. is there.

[0004] Further, the phenomenon that the side surface of the centerless grinding stone is chipped is caused not only by the grinding stone to be used, but also by the loading of the work material,
It may also occur when vibration and shoulder tapping occur during unloading. However, in the above prior art, measures are taken against chipping of the super-hard abrasive grains, but no measures are taken when corners of the attached grinding stone are chipped. In the case of conventional centerless whetstones, whetstones are replaced when large chippings occur and cannot be corrected.However, due to the manufacturing cost, waiting time for replacement, etc., there is also a problem that productivity is reduced. is there.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the prior art, and its gist is as follows. (1) In a centerless grinding wheel in which ultra-hard abrasive grains are bonded with a vitrified binder, one or both side surfaces of a centerless grinding wheel body is attached with a grinding stone containing microcrystalline sintered alumina-based abrasive grains, Is a grindstone in which a sintered alumina-containing abrasive grain containing abrasive grains is bonded with a vitrified binder, and the volume of the microcrystalline sintered alumina-based abrasive grains is 10 to 10% of the total abrasive grains.
Occupies 100% by volume, and the particle size (F value) of the microcrystalline sintered alumina-based abrasive according to JISR6001 is the average particle size closest to the average particle size according to JISB4130 of the ultra-hard abrasive. A centerless whetstone having a grain size within a range of ± 3 stages as a center and a degree of bonding in accordance with JISR6210 within a range of J to P.

(2) In a centerless grinding wheel in which super-hard abrasive grains are bonded with a vitrified binder, one or both side faces of a centerless grinding wheel body are attached with a grinding stone containing microcrystalline sintered alumina-based abrasive grains, The ultra-hard abrasive grains are cubic boron nitride abrasive grains, and the microcrystalline sintered alumina-based abrasive-containing grindstone is a grindstone combined with a resinoid binder,
The grain size (F value) of the microcrystalline sintered alumina-based abrasive grain according to JISR6001 is a grain size in a range from the grain size closest to the average grain size of the ultra-hard abrasive grain according to JISB4130 to three-step coarse. A centerless grinding wheel having a degree of bonding in accordance with JISR6212 within the range of L to T.

(3) A centerless grindstone in which a grindstone containing microcrystalline sintered alumina-based abrasive grains is attached to one or both side surfaces of a centerless grindstone body in which ultra-hard abrasive grains are bonded with a vitrified binder. When the grindstone containing the crystalline sintered alumina-based abrasive grains is broken, the grindstone containing the microcrystalline sintered alumina-based abrasive grains is removed from the centerless grindstone, and a new microcrystalline sintered alumina-based grain is added to the centerless grindstone body. A method for regenerating a centerless whetstone, comprising attaching a whetstone containing steel.

(4) A method of centerless grinding a work material using a centerless grindstone, wherein the centerless grindstone is provided on one or both side surfaces of a centerless grindstone main body in which super-hard abrasive grains are bonded with a vitrified binder. A whetstone containing microcrystalline sintered alumina-based abrasive grains is applied, and the thickness of the microcrystalline sintered alumina-based abrasive-containing whetstone is within a range of 1/2 to 2/1 of the length of the work material. A centerless grinding method characterized by using a centerless grinding wheel.

(5) The ultra-hard abrasive grains are cubic boron nitride,
It can be abrasive grains such as dangmond. (6) The sticking grindstone may include a mixture of at least one of other alumina-based abrasive grains (particularly, fused white alumina-based abrasive grains) and silicon carbide-based abrasive grains together with microcrystalline sintered alumina-based abrasive grains. .

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A centerless grinding method is used when it is extremely difficult to support both ends of a workpiece at a center or when grinding a workpiece that may deform the workpiece. As a general method of supporting a workpiece, three methods of a grinding wheel a, a work rest b, and an adjusting wheel c are used as shown in FIG. As the adjusting wheel, a grinding wheel using rubber as a binder is generally used. When the peripheral speed of the grindstone is given an appropriate rotation, the workpiece is braked by the friction of the adjusted grindstone and rotates at substantially the same peripheral speed as the adjusted grindstone. Actually, due to the influence of the grinding force, the speed becomes about 2% higher than that of the adjusting grindstone.

In the case of centerless grinding, the rotational motion of the workpiece is rotated downward in the direction opposite to the direction of the grinding wheel, resulting in downward grinding, which is different from upward grinding which is the general case of cylindrical grinding. The adjusting wheel is normally inclined as shown in FIG. 1, and the workpiece is rotated by the inclination and fed in the axial direction. Thus, in the case of the next through grinding, an operation of pressing against the positioning stopper is performed.

In recent years, as a grinding wheel used for centerless grinding, a grinding wheel combined with an ultra-hard abrasive such as cubic boron nitride and a vitrified binder has been increasingly used. This grinding wheel has extremely high grinding performance, and the grinding wheel is less worn since the grinding wheel is less worn as compared with a grinding wheel using alumina-based abrasive grains and silicon carbide. Since abrasive grains are less likely to fall off and wear, compared to alumina-based abrasive grains and silicon carbide-based grindstones, the number of cycles of dressing work (dressing work) can be reduced, while maintaining stable quality and grinding performance. Can be maintained. Since the life of one whetstone is long, the number of replacements is very small. From the above advantages, a grindstone combined with a super hard abrasive such as cubic boron nitride and a vitrified binder is suitable for automation that requires little manual work,
This is a whetstone that can greatly reduce total cost.

[0013] In order to solve the disadvantages described in the section of the prior art in the centerless grinding wheel using such super-hard abrasive grains, the present invention provides a micro-crystalline sintered wheel on one or both of the side surfaces of the ultra-hard abrasive grain. It is characterized in that a grindstone containing sintered alumina-based abrasive grains is attached. The specification of a centerless grindstone using super hard abrasive grains generally used is described. Ultra-hard abrasive grains include cubic boron nitride (CBN) and diamond. The frequently used particle size is in the range of 120/140 to 270/325 as indicated by JIS B4130. The concentration of super hard abrasive grains is 200 (ultra hard abrasive grain volume ratio 5
0%). The degree of bonding is generally adjusted by the amount of the binder, but in the case of a centerless grinding wheel, the binder volume ratio is 15%.
From 35% to 35%. A commonly used binder is a grindstone bonded with a vitrified binder.

By attaching a microcrystalline sintered alumina abrasive grain-containing grindstone to a centerless grindstone body using such superhard abrasive grains, the ultrahard abrasive centerless grindstone is chipped by collision with the work material. Not only can be prevented, but also the speed at which a step can be formed between the super-hard abrasive wheel and the bonded wheel can be greatly suppressed, and the number of dressings can be reduced, so that the time and effort of dressing can be reduced. Not only that, super-hard abrasive wheels also reduce wasteful dressing and greatly improve the useful life.

However, in order to realize the above-described desired effects, the specification of the grindstone to be bonded must be determined within a range that is in relation to the specification of the centerless grindstone using super-hard abrasive grains. Broadly speaking, the type of binder of the grinding wheel to be applied is preferably used when the vitrified binder is particularly required to have high precision of the work material and when the resinoid binder is prioritized for efficiency. Accordingly, in the present invention, a vitrified grindstone is generally used, but a resinoid grindstone may be used depending on the application. When using a vitrified binder, the grain size of the microcrystalline sintered alumina abrasive used for the bonding wheel is the particle size range of the super hard abrasive and the particle size of the microcrystalline sintered alumina abrasive. Considering the range, it is preferable that the number of the average particle diameter closest to the average particle diameter of the super-hard abrasive grains is the same, and the number is used in the range of three-stage fine particle size to three-stage coarse particle size. If the grain size is finer than three steps, a problem of welding occurs, and if the grain size is coarser than three levels, a problem occurs in which the surface roughness of the work material is excessive.

However, regarding the particle size, the method of displaying the particle size is different between the ultra-hard abrasive grains and the microcrystalline sintered alumina-based abrasive grains of the present invention. The particle size of the alumina abrasive grains of the present invention
Use the rules of R6001. As the average particle size of these particle sizes, the dimension value of the third sieve of the particle size distribution specified in JIS R6001 is applied. The particle size number (F value) and the average particle size are shown below.

[0017]

[Table 1]

On the other hand, the super hard abrasive grains conform to the provisions of JIS B4130, and the relationship between the particle size display and the average particle size is as follows. The degree of coupling is used in the range of J to P in the degree of coupling specified in JIS R6210. If it is softer than J, a problem of a wear step occurs, and if it is harder than P, a problem of burning of the work material occurs.

When a resinoid binder is used,
The grain size of the microcrystalline sintered alumina abrasive grains used in the pasting whetstone should be taken into consideration with the grain size range of ultra-hard abrasive grains and the grain size range of microcrystalline sintered alumina grains. The number of the average particle diameter closest to the average particle diameter of the abrasive grains is set to the same particle size, and is used in the range from the same particle size to three coarse steps. If it is smaller than the same particle size, a problem of welding will occur, and if it is coarser than three stages, a problem will occur in which the surface roughness of the work material is excessive. The particle size display and the average particle size are the same as those described above for the vitrified grinding wheel.

The degree of coupling is used in the range of L to T in the degree of coupling specified in JIS R6212. If it is softer than L, a problem of a wear step occurs, and if it is harder than T, a problem of burning of the work material occurs. The used surface thickness of the pasting whetstone is the same as that when the vitrified binder is used. If the content of the microcrystalline sintered alumina-based abrasive grains used in the bonding whetstone is within the range of 10 to 100% by volume, a certain effect can be obtained. In order to reduce the speed at which a step can be made with the bonded abrasive wheel using alumina abrasive grains, it is necessary to make the grinding force as close as possible, and the content of microcrystalline sintered alumina abrasive grains in the bonded abrasive stone should be as low as possible. The better, the better
50 to 100% by volume is desirable, 70 to 100% by volume is more desirable, and 100% by volume is most desirable. As the abrasive used together with the microcrystalline sintered alumina-based abrasive, fused alumina-based abrasive such as fused white alumina-based abrasive, silicon carbide-based abrasive, and the like can be used.

By satisfying these conditions, the life can be greatly extended as compared with the conventional centerless grinding wheel, and the labor for replacing the grinding wheel can be greatly reduced. According to the present invention, by attaching a grindstone containing microcrystalline sintered alumina-based abrasive grains, it is possible to greatly reduce the wear and chipping of the attached grindstone, and therefore, the step with the ultra-hard abrasive grain grindstone is also reduced. Although it is unlikely to occur, if the bonded whetstone is still chipped or severely worn, only the bonded whetstone is removed from the main body of the ultra-hard abrasive grain, and the new bonded whetstone containing microcrystalline sintered alumina-based abrasive grains is removed using a super hard abrasive. It was also found that if the centerless whetstone was regenerated by attaching it to the main body of the whetstone, the cost could be significantly reduced.

Further, when grinding a work material using a centerless grindstone in which a microcrystalline sintered alumina abrasive grain-containing grindstone is adhered to the side surface of the super-hard abrasive grain grindstone main body of the present invention, the thickness of the adhered grindstone is increased. It is effective to use a centerless whetstone whose length is within the range of 1/2 to 2/1 of the length of the work material. 1/2
When the thickness is thinner, the effect of the application is small, and when the thickness is more than 2/1, the contribution of the application portion is increased, and the quality of the surface of the work material processed with the super-hard abrasive grains is changed. Was also found to disappear.

[0023]

The present invention is not limited to the following examples, and the present invention will be described by way of examples. (Example 1 and Comparative Example 1) A comparison is made in the case where the bonded grinding stone is a vitrified binder. Super hard abrasive layer layer layer grinding wheel dimensions 410 × 180 × 203.2 × 3 abrasive particles cubic boron nitride abrasive # 140/170 Microstructure Vg = 50 Vb = 20 Vp = 30 Concentration 200 Binder V Paste Wheel The abrasive grains used in the layer- attached grinding stone are microcrystalline sintered alumina abrasive grains (trade name: SG abrasive grains) developed by Norton as examples and fused white alumina abrasive grains (commercially available) as comparative examples. (Trade name: WA abrasive).

Attached whetstone dimensions 410 × 15 × 203.2 Example 1 Comparative Example 1 Abrasive grains used SG (100% by volume) WA (100% by volume) Abrasive particle size F150 F150 Coupling degree M M Structure 9 9 Binder V V. The sticking grindstones of the above Examples and Comparative Examples are applied to both sides of the superhard abrasive grains using an epoxy resin adhesive, and the sticking grindstones are respectively attached to the grindstones using the superhard abrasive grains.
The composition was cured at 60 ° C. for 48 hours to produce a test whetstone. Grinding conditions Work material: bearing steel Dimensions: 15 mmΦ × 10 mm Grinding wheel peripheral speed: 2000 m / min Test is determined by dress interval. In the dress, the step between the cubic boron nitride abrasive layer and the bonded abrasive layer was 0.
If a step of not less than 04 mm is formed, there is a possibility that the debris of the cubic boron nitride abrasive grain layer may be chipped off. Result Comparative Example 1 100 Example 1 500 As described above, the Example has a five-fold dress-to-dress amount with respect to the Comparative Example, and the superiority of the product of the present invention is clear.

(Comparative Examples 2 to 4) The same as Example 1, except that the amount of SG abrasive grains in the affixing whetstone was less than 10% by volume (Comparative Example 2). Samples of Comparative Example 3) and F300 (Comparative Example 4)
(Comparative Example 5) and Q (Comparative Example 6) were prepared,
Example 1 and the performance were compared by performing the same grinding test as in Example 1. The results are shown in the table below.

[0026] Grinding performance example 1 100 Comparative example 2 28 Comparative example 3 Surface roughness standard over work material Comparative example 4 Defects of welding occurred on the grindstone and burning occurred on the work material Comparative example 5 40 Comparative example 6 Work material Burning occurs. It has also been found that by attaching it to the main body of an abrasive grain, an expensive super-hard abrasive grain can be used effectively, thereby reducing the total cost.

The thickness of the microcrystalline sintered alumina abrasive-containing grindstone to be affixed to the main body of the ultra-hard abrasive grain in this manner is within the range of 1/2 to 2/1 of the length of the work material to be machined. We found that it was best to paste it. If it is thinner than 1/2, the effect of the bonding is small, and if it is thicker than 2/1, the contribution of the stuck portion is large, and the surface quality of the work material processed with ultra-hard abrasive grains changes, and ultra-hard abrasive grains are used. There are no benefits.

FIG. 2 shows a centerless grinding wheel of the present invention and a state of centerless grinding using the same. The centerless grindstone main body 10 is made of a super-hard abrasive grain layer, and the sticking grindstone 11 is a grindstone containing microcrystalline sintered alumina-based abrasive grains. Reference numeral 12 denotes an adjusting wheel, reference numeral 13 denotes a work material, and the thickness of the applied grinding wheel 11 is in the range of 1/2 to 2/1 on the table of the work material 13. (Example 2 and Comparative Example 7) Comparison is made in the case where the bonded grinding stone is a resinoid binder. Super hard abrasive layer layer layer grinding wheel dimensions 410 × 180 × 203.2 × 3 abrasive particles cubic boron nitride abrasive # 140/170 Microstructure Vg = 50 Vb = 20 Vp = 30 Concentration 200 Binder V Paste Wheel The abrasive grains used in the layer- attached grinding stone are microcrystalline sintered alumina abrasive grains (trade name: SG abrasive grains) developed by Norton as examples and fused white alumina abrasive grains (commercially available) as comparative examples. (Trade name: WA abrasive).

Attached whetstone dimensions 410 × 15 × 203.2 Example 2 Comparative Example 7 Abrasive particles used SG (100% by volume) WA (100% by volume) Abrasive particle size F80 F80 Coupling degree N N structure 8 8 Binder B B. The sticking grindstones of the above Examples and Comparative Examples are applied to both sides of the superhard abrasive grains using an epoxy resin adhesive, and the sticking grindstones are respectively attached to the grindstones using the superhard abrasive grains.
The composition was cured at 60 ° C. for 48 hours to produce a test whetstone. Grinding conditions Work material: bearing steel Dimensions: 15 mmΦ × 10 mm Grinding wheel peripheral speed: 2000 m / min Test is determined by dress interval. In the dress, the step between the cubic boron nitride abrasive layer and the bonded abrasive layer was 0.
If a step of not less than 04 mm is formed, there is a possibility that the debris of the cubic boron nitride abrasive grain layer may be chipped off. Result Comparative Example 7 100 Example 2 500 As described above, the example has a five-fold dress-to-dress volume as compared with the comparative example, and the superiority of the product of the present invention is apparent.

(Comparative Examples 8 to 12) The same as Example 2, except that the amount of SG abrasive grains in the affixing whetstone was less than 10% by volume (Comparative Example 8). Samples having Comparative Example 9) and F150 (Comparative Example 10), and samples having binding degrees of K (Comparative Example 11) and U (Comparative Example 12) were prepared, and the performance was the same as that of Example 1 and Example 2. A grinding test was performed and compared. The results are shown in the table below.

[0031] Grinding performance Example 2 100 Comparative example 8 29 Comparative example 9 Surface roughness standard over work material Comparative example 10 Defects of welding occurred on the grindstone and burning occurred on the work material Comparative example 11 42 Comparative example 12 Work material Example 3 Burning occurred (Example 3) Comparison of replacement of only the attached grindstone and remanufacture of a grindstone containing a cubic boron nitride abrasive grain layer were compared with respect to the number of working days and cost. Example Replacement work procedure of pasted whetstone 1) A grindstone requiring pasting exchange is carried in.

2) On the one side or both sides of the damaged bonding whetstone, a surface grinder is used to scrape off all of the bonded parts that have been damaged by plane processing. 3) Apply a replacement grindstone to a thickness of 0.5 mm thicker than the target thickness using a surface grinder. 4) Thoroughly dry the super-hard grindstone layer from which the damaged portion has been removed and the bonded grindstone.

5) Using a resin adhesive, the replacement bonding whetstone is bonded to the superhard abrasive whetstone and cured. 6) Work the thickness, hole diameter, and outer diameter of the bonded grindstone so that it will have the prescribed dimensions. 7) Perform truing and dressing on the outer peripheral surface. 8) Wash and clean the whole.

9) Dry sufficiently. Comparative Example Reproduction of Grinding Stone Containing Cubic Boron Nitride Abrasive Layer The production of a cubic boron nitride abrasive layer grindstone is generally performed by mixing, molding, drying, firing and final finishing. In addition, a bonding whetstone is stuck on both sides or one side. Comparison result of replacement days and replacement costs Comparison of days and costs is represented by multiples with 100 being the case of replacing one sheet only on one side of the embodiment.

[0035]

[Table 2]

As described above, in comparison of the number of replacement days and the cost, the number of replacement days is 1/3 or less, and the cost is 1/46 for exchange of one card on one side and 1/23 for exchange of 2 cards on both sides, clearly showing the superiority of the present invention. It is. (Example 4) A grinding test was performed on the relationship between the thickness of the attached grinding wheel and the length of the work material to be processed. The sample was such that the thickness of the attached grinding wheel used in Example 1 was in the range of 1/2 to 2/1 with respect to the length of the work material of 10 mm. As a comparative example 13, when the thickness of the applied grinding wheel is less than 1/2 with respect to the length of the workpiece, as Comparative Example 14, the thickness of the applied grinding wheel is greater than 2/1 with respect to the length of the workpiece, In the same manner as in Example 1, the height of the work material was set such that the step between the cubic boron nitride abrasive grain layer and the attached grindstone layer was 0.03 mm, and the example was set to 100 and compared with the comparative example.

For a work material of 10 mm Adhesive wheel thickness Thickness of multiple times of adhesive wheel thickness Grinding performance Example 4 15 mm 1.5 times 100 Comparative example 13 4 mm 0.4 times 70 Comparative example 14 22 mm 2.2 times 90 Thickness of the adhered grindstone with respect to the length of the work material If it is less than 1/2, the abrasion of the affixing whetstone will be faster and the dress interval will be shorter.
On the other hand, if the thickness of the bonded whetstone is greater than 2/1 with respect to the length of the work material, the width of the grinding surface is limited due to the design of the grinder to be attached. It was necessary to reduce the width of the abrasive layer, and as the width of the ultra-hard abrasive layer was reduced, the grinding performance of the ultra-hard abrasive layer was reduced and the dress interval was shortened. If the thickness of the applied grinding wheel becomes larger than this, the quality of the work material is displaced. As described above, the thickness of the applied grinding wheel is preferably in the range of 1/2 to 2/1 with respect to the length of the work material.

[0038]

As described above, by using the product of the present invention, the speed at which the step between the super-hard abrasive layer and the bonded abrasive layer can be reduced can be reduced, and the repair work for preventing the chipping of the super-hard abrasive layer can be reduced. The number of times can be reduced. In addition, according to the method of the present invention, the bonded grindstone layer is large, and even when it is necessary to replace the grindstone, only the bonded grindstone is replaced, the correction can be performed in a small number of days, and the cost can be reduced. . Further, it is possible to perform grinding under optimum conditions using the grindstone of the present invention.

[Brief description of the drawings]

FIG. 1 shows a state of centerless grinding.

FIG. 2 shows a centerless grinding wheel of the present invention and a state of grinding thereof.

[Explanation of symbols]

 a: Grinding whetstone b: Work rest c: Adjustment wheel d: Work material 10: Centerless whetstone super-hard abrasive layer 11 ... Sticking whetstone layer 12: Adjustment wheel 13 ... Work material

Claims (4)

[Claims] 1. A centerless grindstone in which ultra-hard abrasive grains are bonded with a vitrified binder, wherein one or both side faces of a centerless grindstone body are bonded with a grindstone containing microcrystalline sintered alumina-based abrasive grains, A grindstone in which a microcrystalline sintered alumina-based abrasive grain is bonded with a vitrified binder, wherein the volume of the microcrystalline sintered alumina-based abrasive grain occupies 10 to 100% by volume of all the abrasive grains, and is defined by JISR6001. Particle size (F value) of the microcrystalline sintered alumina-based abrasive grains according to
Is a particle size in the range of ± 3 steps around the average particle size closest to the average particle size according to JISB4130 of the super hard abrasive grains, and the bonding degree according to JISR6210 is in the range of J to P. A centerless whetstone characterized by being inside. 2. A centerless grindstone in which ultra-hard abrasive grains are bonded with a vitrified binder, wherein one or both side faces of the centerless grindstone main body are bonded with a grindstone containing microcrystalline sintered alumina-based abrasive grains, A grindstone in which a microcrystalline sintered alumina-based abrasive grain is bonded with a resinoid binder, and the grain size (F value) of the microcrystalline sintered alumina-based abrasive grain according to JISR6001 is ultra-hard abrasive grain JISB413.
A centerless grindstone having a particle size in a range from a particle size closest to an average particle size according to the definition of 0 to a three-step coarseness, and having a degree of bonding in a range of L to T according to the specification of JIS R6212. 3. A centerless grindstone in which a grindstone containing microcrystalline sintered alumina-based abrasive grains is attached to one or both side surfaces of a centerless grindstone body in which ultra-hard abrasive grains are bonded with a vitrified binder. When the sintered alumina-based abrasive grain-containing grindstone is damaged, the microcrystalline sintered alumina-based abrasive grain-containing grindstone is removed from the centerless grindstone, and the centerless grindstone body contains a new microcrystalline sintered alumina-based abrasive grain. A method for regenerating a centerless whetstone, comprising applying a whetstone. 4. A method of centerless grinding a work material using a centerless grindstone, wherein said centerless grindstone is finely ground on one or both side surfaces of a centerless grindstone main body in which super-hard abrasive grains are bonded with a vitrified binder. A grindstone containing crystalline sintered alumina-based abrasive grains is adhered, and the thickness of the microcrystalline sintered alumina-based abrasive grain-containing grindstone is one of the length of the work material.
A centerless grinding method characterized by using a centerless grindstone in the range of / 2 to 2/1.