Lens barrel

This application claims benefit of Japanese Patent Application No. 2001-145302 filed on May 15, 2001, the contents of which are incorporated by this reference. For a camera lens barrel with helicoid threads, at the portion where the helicoid female thread of a fixed frame is threaded with the helicoid male thread of a rotary frame, six separation preventing pins are implanted in the portion of the helicoid male thread around the same circumference at the equal intervals. These separation presenting pins are implanted between convex thread portions of the helicoid male thread, respectively. Protruding portions of the separation preventing pins fit in and slidingly contact concave thread portions of the helicoid female thread that is threaded with the helicoid male thread in which the separation preventing pins are disposed. A contacting edge fits in and comes into sliding contact with the concave thread portion of the helicoid female thread by narrowing the circumferential surface thereof. An edge is formed around the shaft portion of each separation preventing pin, which is implanted in the rotary frame, at a position near to the end thereof by narrowing the circumferential surface of the shaft portion.