COIL SPRING AND ITS MANUFACTURING METHOD

摘要

PROBLEM TO BE SOLVED: To provide a coil spring and a coil spring manufacturing method different from a conventional method. SOLUTION: This coil spring manufacturing method comprises the steps of: forming an outside spiral groove on an outer peripheral surface of a base metal; forming to the base metal an inner diameter hole extending in a longitudinal direction; forming, in an inner peripheral surface of the inner diameter hole, an inside spiral groove having a depth which reaches the outside spiral groove to form strands, in a position arrayed with respect to the outside spiral groove; and pulling the coil spring in the longitudinal direction to be plastically deformed, whereby the adjacent strands are separated from each other.