filetage unifié

CONT: Depuis 1949, le Royaume-Uni, le Canada et les Etats-Unis se sont mis d'accord sur ces filetages et leur désignation : «UNC» pour ""Unified coarse thread [...] «UNF» pour «Unified fine thread» [...] «UNEF» pour «Unified extra-fine» [...] «UN» pour «Unified constant pitch» [...] Ces filetages figurent [...] dans la norme américaine ASA B1.1-1960 qui concerne les filetages unifiés.
CONT: Le filetage «Unified National» comprend les séries à filets gros et les séries à filets fins.
OBS: filetage en inches à profil UNJ : terme normalisé par l'ISO.

CONT: The unified thread form accompanied by the unified thread standards has in the past fulfilled the necessary requirements for interchangeability of threaded products between the United States, Great Britain, and Canada. This modified thread form represented two compromises between British Whitworth and United Stated National thread forms. The British accepted the 60° thread angle of the American thread, and the Americans accepted a rounded root and crest similar to the Whitworth form. The United States National unified form for external threads has a rounded root and may have either a rounded or flat crest. The unified thread contours provide advantages over both the earlier forms .... The unified thread is a general-purpose thread that is particularly suited for fasteners.
CONT: Unified and American National screw thread standards ... 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).
OBS: Under the unified system, threads are specified by giving in order the nominal diameter, number of threads per inch, the initial letters such as UNC or UNF that identify the series, and class of thread (IA, 2A, and 3A or 1B, 2B and 3B). ... the specification for a left-hand thread must have the letters LH included.