| 摘要 |
PROBLEM TO BE SOLVED: To provide a highly accurate chuck for always gripping a round material by specific tensional force without using a preparatory plan an a tool when fixing the round material to the chuck. SOLUTION: This chuck is provided with a diametrally contractible collet for gripping the round material, collet positioning members for centering and positioning the collet by sandwiching the collet by a chuck body and a tensioner and a magnet structure composed of an N type yoke and an S type yoke in the collet positioning members. The mutual collect positioning members are approached by magnetic force by carrying an electric current to an exciting coil of the magnet structure. A collet diameter contracting member is arranged for diametrally contracting the collet so that the round material is always fixed by the specific tensional force.
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