Abrasive tool making process – material – or composition – With synthetic resin
Reexamination Certificate
2000-06-13
2002-09-10
Marcheschi, Michael (Department: 1755)
Abrasive tool making process, material, or composition
With synthetic resin
C051S295000, C051S293000, C051S307000, C051S309000
Reexamination Certificate
active
06447562
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an abrasive such as a polishing grindstone and the like, and particularly, to an abrasive which is suitable for polishing a hard material such as a sintered hard alloy, a highly hard steel and a hardened steel, and particularly, which is capable of accurately polishing a very fine portion such as a rib and a boss made of such a hard material manually or using a vibrating tool or a rotating tool.
2. Description of the Related Art
In recent years, the demand for a mold made of a highly hard steel or a hardened steel having a Rockwell hardness C (HRC) equal to or larger than 50, or a sintered hard alloy having a further high hardness, has been increased.
The abrasive material capable of polishing such hard materials is mainly diamond. However, the conventional diamond grindstone is formed by binding diamond abrasive grains using a metal or a thermosetting resin as a binder, and is used broadly for grinding and cutting such a hard material, but little used for polishing such a hard material. It is true that there has been no diamond grindstone hitherto, which is suitable, particularly for an accurate polishing. The reason is as follows: In the accurate polishing, it is a conventional common practice to polish a material by a spatula made of wood or bamboo using a diamond powder or a diamond paste. This method suffers from a problem that a long time is taken and a skill is required for the polishing. Therefore, the development of a solid grindstone type has been desired strongly. However, if the grindstone is not of a small-sized and thin shape, the grindstone cannot accommodate a work, and at the same time, the grindstone itself requires a considerable strength and a resiliency. When the conventional diamond grindstone is formed into such a shape, it is brittle and is not suitable for a practical use.
On the other hand, there are broadly known methods for reinforcing a grindstone by incorporating any of various types of reinforcing fibers. For example, Japanese Patent Application Laid-open No. 63-52972 has proposed a method for reinforcing a grindstone with a short fiber such as a silicon carbide fiber, a carbon fiber, a silicon nitride fiber, a boron fiber and an alumina fiber. It is also disclosed in this Japanese Patent Application Laid-open No. 63-52972 that a method for reinforcing a material with a long fiber is also conventionally known. A grindstone, which comprises three components: a reinforcing fiber, abrasive grains and a matrix resin and which is capable of accurately polishing a hard material, has been not known hitherto. Both of an excellent polishing property and a high strength for polishing a hard material are required for grindstones, but conventionally known fiber-reinforced grindstones do not meet this requirement sufficiently.
The fiber-reinforced grindstone suffers from the following problem: If an attempt is made to increase the content of abrasive grains in the fiber-reinforced grindstone with a polishing property taken into a serious view, the strength of the grindstone is reduced. On the other hand, if an attempt is made to increase the content of the fiber in the grindstone with the strength taken into a serious view, a practical polishing property is not provided.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide an abrasive which has a sufficient practical strength, while having an excellent polishing property, wherein the problem associated with the prior art is solved.
To achieve the above object, according to a first aspect and feature of the present invention, there is provided an abrasive comprising an alumina-based long fiber bound by a matrix resin containing diamond abrasive grains therein, and a diamond abrasive grain layer formed on the surface of the bound fiber.
According to a second aspect and feature of the present invention, in addition to the first feature, the abrasive is formed into a flat plate-shape, and the diamond abrasive grain layer is provided at least on any one of opposite surfaces of the bound fiber.
According to a third aspect and feature of the present invention, in addition to the second feature, the abrasive is formed into a flat plate-shape, and the diamond abrasive grain layer is provided on opposite surfaces of the bound fiber.
According to a fourth aspect and feature of the present invention, in addition to the second feature, the alumina-based long fiber is wound helically at an intersection angle of 6 to 30° around a cylindrical member, and cut open in an axial direction of the cylindrical member into a sheet, the side perpendicular to the cutting-open direction being defined as a polishing end face.
According to a fifth aspect and feature of the present invention, in addition to the second feature, the abrasive is formed into a flat plate having a thickness in a range of 0.45 to 1.2 mm.
According to a sixth aspect and feature of the present invention, in addition to the first or second feature, abrasive grains forming the diamond abrasive grain layer are embedded in the matrix resin.
According to a seventh aspect and feature of the present invention, in addition to the first or second feature, the content of the diamond abrasive grains excluding the diamond abrasive grains in the abrasive grain layer is in a range of 3 to 15% by weight.
According to an eighth aspect and feature of the present invention, in addition to the first or second feature, filaments of the alumina-based long fiber are mainly filaments having a flat cross-sectional shape.
According to a ninth aspect and feature of the present invention, in addition to the eighth feature, the ratio of a long axis to a short axis of the cross-sectional shape is in a range of 1.3 to 1.8.
According to a tenth aspect and feature of the present invention, in addition to the first or second feature, the abrasive has a flexural strength of 500 Mpa or more and a flexural elastic modulus of 50 Gpa or more under application of a load in a direction perpendicular to the lengthwise direction of the alumina-based long fiber.
To produce the abrasive according to the present invention, the alumina-based fiber, the diamond abrasive grains and the matrix resin are used as necessary components, and the alumina-based fiber and the diamond abrasive grains are first arranged in a particular distributed state in the abrasive material, whereby the produced abrasive exhibits an excellent polishing property and has an enhanced strength. Such arrangements of the alumina-based fiber and the diamond abrasive grains ensures that an amount of abrasive grains necessary and sufficient for polishing a work can be incorporated without a reduction in strength of the abrasive. Further, a higher strength of the abrasive can be achieved by using the particular alumina-based long fiber as a reinforcing fiber.
Thus, the abrasive according to the present invention can be used commonly for a rough-polishing and a finish-polishing of even a hard material such as a highly hard steel having a Rockwell hardness (HRC) of 50 or more and a sintered hard alloy having a higher hardness, and further utilized for polishing a very fine portion or a small-area portion such as a groove and a corner of a mold for a rib and a boss. Further, the abrasive has an excellent accurate polishing property and such a polishing efficiency that a surface roughness Ra of a mold made of a sintered hard alloy, which is equal to 0.5 &mgr;m or less usually required, can be achieved easily in a short time.
DETAILED DESCRIPTION OF THE INVENTION
The fiber used in the abrasive according to the present invention is an alumina-based long fiber. A glass fiber, a carbon fiber, a silicon carbide fiber and the like are known conventionally as a reinforcing fiber. However, any of the known fibers is used in the abrasive, a problem of slipping of the abrasive on a surface to be polished is encountered, and the alumina-based fiber is most suitable for polishing a work, because it is considered that the leading end of
Miyazawa Takuma
Sumiyoshi Takehiko
Marcheschi Michael
Pillsbury Winthrop LLP Intellectual Property Group
XEBEC Technology Co. Ltd.
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