| 摘要 |
PROBLEM TO BE SOLVED: To provide a specified axial direction pressure corresponding to a tightening torque of a union nut, and improve strength of threads in a tube fitting made of resin. SOLUTION: Male threads 9 of a tube fitting main body 1 and female threads 20 of the union nut 3 are respectively formed as asymmetric trapezoid-shaped screw. An angleα1 of threads of one side surface 9 and 20a of the asymmetric trapezoid-shaped screws to get in contact with each other as the union nut 3 is tightened is set at 70-90 deg., and an angleα2 of threads of the other side surface 9b and 20b on the opposite side to them is set at 40-80 deg., where it is smaller than the angleα1 of the threads.
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