| 摘要 |
PROBLEM TO BE SOLVED: To efficiently erasure hardens for an extremely short time, without causing scratches to products. SOLUTION: The device for selecting metal blocks in a bearing manufacturing process is provided with a pair of electric power source terminals 2 which come into contact with the surface of a metal block 1 for passing electricity through the metal block 1, an electric power source 3 connected to the electric power source terminals 2, and a detecting electrode 4 to come into contact with the surface of the metal block 1 to detect the surface potential. The selecting device selects metal blocks having out of specifications by detecting a voltage induced in the detecting electrode 4.
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