filetage à pas fin NF

OBS: Série à filets fins. Pour pièces et équipement où l'emploi des filets fins est plus avantageux. Ce filetage offre une plus grande résistance à la traction et à la torsion, tout en étant moins sujet au déboulonnage sous l'effet des vibrations.
OBS: ""UNF""=""Unified fine thread"" (pas fin).

CONT: Unified and American National screw thread standards for screws, bolts, nuts, and other threaded parts consist of six series of threads and a selection of special threads that cover nonstandard combinations of diameter and pitch. In general the unified screw threads are limited to three series: coarse (UNC), fine (UNF), and extrafine (UNEF). A 1/4-inch-diameter thread in the UNC series has 20 threads/in., while in the UNF series it has 28 ... The fine thread series (UNF and NF) is recommended for general use in the automotive and air craft fields for threads subject to strong vibration. In general, a fine thread should be used only where close adjustment, extra strength, or increased resistance to loosening is a factor.