Method of making a double wall twist tube

摘要

A double wall twist tube is formed from at least two tubular blanks with a smaller tubular blank forming the inner wall and a larger tubular blank forming the outer wall. The smaller tubular blank is located within the larger tubular blank and the tubular blanks are each impressed with at least one indentation near one end. Sleeves are inserted into ends of the smaller tubular blank and a mandrel is inserted through the sleeves. Clamping chuck jaws or other clamping devices are provided on a longitudinally movably non-rotatable tail stock squeeze the indented end of the larger tubular blank, securing it to the indented end of the smaller tubular blank and simultaneously securing the tubular blanks to the tail stock. Clamping chuck jaws or other clamping devices are provided on a rotatable head stock squeeze the opposite end of the larger tubular blank, securing it to the opposite end of the smaller tubular blank and simultaneously securing the tubular blanks to the head stock. Rotation of the head stock causes the tubular blanks to undergo torsional stress which creates spiral corrugations to be formed beginning at and extending from the indentation to the head stock. The tail stock moves toward the head stock and the mandrel moves through the sleeves in response to shortening of the twist tube caused by spiral corrugations being formed therein.