METHOD OF PRODUCING BENT TUBE AND MANDREL

摘要

PROBLEM TO BE SOLVED: To provide a method of producing a bent tube by using a mandrel capable of achieving good productivity while improving durability of a bent tube to be formed.SOLUTION: A large-diameter mandrel (40) includes a coil spring (41) capable of being inserted into the outer peripheral side of a small-diameter mandrel (30) and a plurality of segments (42) which have an axial-direction width larger than the wire diameter of the coil spring (41) and are formed annularly and arranged continuously along the central axis of the coil spring (41) on the outer peripheral side of the coil spring (41) and are separable from each other. A production method includes a step (S1) of inserting a blank tube (10) on the outer peripheral side of the bendable large-diameter mandrel (40) and a step (S3) of inserting the large-diameter mandrel (40) attached with the blank tube (10) on the outer peripheral side of the small-diameter mandrel (30) having a bent part (33b) to form a bent tube (20).