| 摘要 |
PURPOSE:To shorten operating time by carrying out a process wherein the end of a cylindrical material obtained by removing the bottom of a bottomed material formed by cold working is heated in high frequency wave over a definite length, deformed to the internal direction and then finished by cutting or polishing. CONSTITUTION:Plural grooves 6 are processed on the bottomed material 2 by a punch 5 provided with plural protrusions 4 on the external circumference surface. One end (a) of the cylindrical material obtained by shearing the bottom part is heated in high frequency wave and processed by a die to finish the internal circumference part. The working process is shortened and simultaneously the product quality is improved in this way.
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