| 摘要 |
A method of and apparatus for forming spirally-shaped indentations in tubular products. An internal shaft is formed with a spirally-shaped female die and an outside die consists of a single metal ball magnetically suspended from the outside die holder in registry with the spiral formation on the internal female die. The tube to be formed extends between the two dies and is clamped to prevent rotation but permitted to move in either axial direction. A threaded insert in the external die is advanced axially and then locked to predetermine the maximum indentation to be impressed into the tubular product. Thereafter, a reversible motor drives a holder for the external die and the internal shaft in unison to form a spiral indentation in the tubular product.
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