| 摘要 |
PROBLEM TO BE SOLVED: To provide a clamping ring, which has so smooth surface that no burr is developed. SOLUTION: The lead holding part 2B of a chuck 2 is divided into a plurality. A protruded head part 2C is formed on the outer surface of the lead holding part 2B. In order to open and close the chuck 2, the clamping ring 5 is externally fitted to the head part 2C of the chuck 2. The clamping ring 5 is formed in nearly the same shape in front and in rear.
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