| 摘要 |
PROBLEM TO BE SOLVED: To obtain a gap having a high productivity and a high dimensional precision by making the abutting surfaces of legs form a continuous arc, and forming flat surfaces at the outside parts of the abutting surfaces of both legs. SOLUTION: A U-shaped ferrite core 1 has two legs 2, and the abutting surfaces of the legs are formed so as to have the shape of arcs 3. These surfaces 3 in the shape of arcs are formed on one virtual line. Flat parts 4 are formed at the outside parts of the abutting surfaces of both legs 2. And a gap is formed by the difference between each flat part 4 and the lowest part, and this gap is made so as to be equal to or longer than 1μm. For this working method, a cup diamond forming a diamond grinding stone is used, and its rotation axis is tilted against a perpendicular to the reference surface of a surface to be ground of the U-shaped ferrite core 1 by an angleθ. The cup diamond rotates, causes the U-shaped ferrite core 1 to pass in the direction of C or D, and works the whole abutting surfaces. By doing this way, gap formation by only one continuous grinding becomes feasible, and it becomes possible to obtain a U-shaped ferrite core having high-precision gaps.
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