Importance

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Abstract

A method of increasing the thickness of a tube which increases a thickness of an end part of a tube without a burr being formed, comprising placing a tube 21 between a die 25 and mandrel 22 in the state with a space for increasing the thickness between a small diameter part 22a of the mandrel 22 and a first end part 21a of a tube 21 and between a large diameter hole part 25C of the die 25 and a second end part 21b of the tube 21, using a first upsetting punch 23 and a second upsetting punch 24 to respectively process the first end part 21a and the second end part 21b of the tube 21, pulling out the mandrel 22 from the tube 31 in the state with the second upsetting punch 24 constraining the second end part 31b of the tube 31, and using the first upsetting punch 23 to push up the first end part 31a of the tube 31 to take out the tube 31 from the die 25.

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First Claim