内螺纹车刀
internal threding tool
female screw cutting tool
机夹外螺纹车刀
mechanically-clamped turning tool for external threading
内螺纹外翅片铸铁管
Casting tube with female screw and side fins
内螺纹外肋片铸铁换热管
Cast iron heat exchange tube with inner corrugation and outer fins