Method for manufacturing cylindrical body having different diameters by cold forging
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United States of America Patent
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-
Nov 10, 2020
Grant Date -
Dec 6, 2018
app pub date -
Oct 12, 2016
filing date -
Nov 24, 2015
priority date (Note) -
In Force
status (Latency Note)
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Abstract
A multi-diameter tubular body is cold-forged by forming a large-diameter hole portion in a formed body having a preliminary hole through subjection of the preliminary hole to deep hole forming and by punching out the bottom surface of the large-diameter hole portion to thereby form a small-diameter hole portion. Since a punch having a central protrusion on its forward end surface is used, an internal flaw is generated by dead metal in the inner circumferential surface of a depression, formed by the protrusion, in the bottom surface of the large-diameter hole portion. An outside diameter of a protrusion of a deep hole forming punch is rendered smaller than an inside diameter of the small-diameter hole portion to be formed later by punching out the bottom surface of the large-diameter hole portion. As a result, the internal flaw is removed when the small-diameter hole portion is formed.
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