Abrading – Rigid tool – Rotary cylinder
Reexamination Certificate
1998-10-19
2001-08-21
Eley, Timothy V. (Department: 3723)
Abrading
Rigid tool
Rotary cylinder
C451S532000, C451S542000, C451S547000, C408S144000
Reexamination Certificate
active
06277016
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a core drill for drilling a fine hole, which is used for drilling a fine hole having a diameter about some tens &mgr;m onto a work formed from a metal or a ceramics, or for grinding an inner diameter of the drilled fine hole to a predetermined shape, and a method of manufacturing the same.
For example, a core drill having no spiral groove for discharging chips and grinding powders is used as a tool for drilling a fine hole having a diameter about some tens &mgr;m onto the work or for grinding an inner diameter of the fine hole already drilled in accordance with an ultrasonic machining.
2. Description of Related Art
Conventionally, as this kind of core drill for drilling the fine hole, there has been known one structured such that an abrasive grain is fixed to a superfine core material in accordance with a plating treatment by a nickel or a copper after electro-coating a diamond abrasive grain or a ceramics abrasive grain on a surface of the core material such as a piano wire or a cemented carbide tungsten, and a diameter of the drill has been about 50 &mgr;m at the minimum.
However, since the diameter is fine, it is hard to uniformly electro-coat the abrasive grain on a periphery of the core material, so that there have been problems such as a plated film fixing the abrasive grain on the core material is easily broken away together with the abrasive grain when an external force is operated, in addition that the abrasive grains partly cohere so as to easily attach.
Further, since the diameter of the core drill is determined by a diameter of the core material and a thickness of the plated film, it is necessary to finely adjust the thickness of the plated film for finishing the diameter of the core drill at a predetermined accuracy, particularly in the case that the diameter of the drill is fine, the adjustment has been hard.
Still further, in the case that the core material is made of a metal material such as a piano wire, since there is a limitation for making the diameter of the core material fine, it is significantly hard to manufacture a core drill having a diameter finer than the current size in the manufacturing method which applying a plating treatment to the core material so as to fix the abrasive grain.
SUMMMARY OF THE INVENTION
The invention is made in view of the problems mentioned above, and an object thereof is to provide a core drill for drilling a fine hole which can securely fix an abrasive grain to a core material, can finish to a predetermined diameter in a relatively easy manner, and can manufacture one having a superfine diameter about some &mgr;m, and a method of manufacturing the same.
Accordingly, a core drill for drilling a fine hole in accordance with the invention is structured such as to drill a fine hole onto a work, or grind an inner diameter of the drilled fine hole to a predetermined shape, and characterized by bundling ceramics long fibers so as to make a core material, impregnating the core material with a molten synthetic resin so as to harden, and holding an abrasive grain by the hardened synthetic resin.
In accordance with this technical means, since the core material bundling the ceramics long fibers is impregnated with the synthetic resin so as to be hardened, the synthetic resin enters between the bundled ceramics long fibers, so that the core material and the synthetic resin are firmly united. Accordingly, a disadvantage such that the synthetic resin holding the abrasive grain is broken away from the core material during the use of the core drill can be avoided.
Further, since the synthetic resin fleshes out the periphery of the core material, it is possible to easily finish the diameter of the core drill to a predetermined diameter by plastically deforming the hardened synthetic resin by using a die and a pressure roller.
Further, since the diameter of the ceramics long fiber itself is some &mgr;m, the thickness of the core material can be freely adjusted by changing the number of the bundled ceramics long fibers, so that a core drill having a superfine diameter about some &mgr;m can be theoretically manufactured.
In this case, a certain degree of heat resistance and rigidity are required for the ceramics fiber forming the core material, a ceramics fiber of an alumina type or a zirconia type can be used. Further, even by a ceramic fiber having a rigidity lower than them, for example, a glass fiber can secure a rigidity necessary for the core drill since some ones are bundled so as to form the core material.
As the synthetic resin impregnated in the core material, either a thermosetting synthetic resin or a thermoplastic synthetic resin may be employed. As the thermosetting synthetic resin, an epoxy resin, a phenol resin or an unsaturated polyester can be used. Further, as the thermoplastic synthetic resin, taking into consideration that a temperature of the core drill is increased due to a friction heat at a time of processing the work, it is preferable that a temperature of thermal deformation is higher, so that, for example, a mixture of a polyphenylene sulfide (PPS) and a norbornen resin can be used.
On the contrary, the core drill for drilling the fine hole in accordance with the invention can be manufactured by the following two manufacturing methods.
At first, one of the manufacturing methods is characterized by comprising a first process for bundling ceramics long fibers so as to form a core material having a desired diameter, a second process for impregnating the core material with a molten synthetic resin, and thereafter, hardening it so as to form a drill material in which a synthetic resin fleshes out a periphery of the core material, and a third process for attaching an abrasive grain onto a surface of the drill material, and thereafter, inserting and fixing the abrasive grain to the synthetic resin at the same time when finishing the drill material to a predetermined diameter by a plastic formation.
Further, another of the manufacturing methods is characterized by comprising a first process for bundling ceramics long fibers so as to form a core material, a second process for impregnating the core material with a molten synthetic resin in which an abrasive grain is dispersed, and thereafter, hardening it so as to form a drill material in which a synthetic resin together with the abrasive grain flesh out a periphery of the core material, and a third process for finishing the drill material to a predetermined diameter by a plastic formation.
In the former manufacturing method, since the abrasive grain is later inserted on the surface of the drill material formed by the second process, that is, the surface of the synthetic resin covering the core material, the abrasive grain exists only on the surface of the core drill. On the contrary, in the latter manufacturing method, since the synthetic resin in which the abrasive grain is previously dispersed fleshes out the core material, the abrasive grain exists not only on the surface of the core drill but also near the core material.
Accordingly, the core drill manufactured by the former manufacturing method is suitable for a so-called lapping treatment for grinding an inner diameter of a prepared hole previously formed on the work, and on the contrary, the core drill manufactured by the latter manufacturing method is suitable for the case of drilling the fine hole on the work in accordance with an ultrasonic treatment.
Further, both of these manufacturing methods can manufacture the core drill having a predetermined length by forming the core material having a predetermined length in the first step and receiving the core material within an injection molding metal mold so as to flesh out the synthetic resin, however, a core drill having a significantly long size can be manufactured without being restricted by a size of the injection molding metal mold by continuously performing each of the first, second and third processes on the transfer path while continuously feeding a long core material. The lon
Arent Fox Kintner & Plotkin & Kahn, PLLC
Berry Jr. Willie
Eley Timothy V.
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