TERMIUM Plus^®

Fiche 1,  Justifications,  Anglais

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The manufacturing tolerance and allowance permitted distinguishes one class of thread from another under the unified thread system. Because allowance is an intentional difference between correlated size dimensions of mating threads, and tolerance is the difference between limits of size, a thread class may be considered to control the looseness or tightness between mating threaded parts. The American National standard for unified and National screw threads provides classes 1A, 2A and 3A for external threads, classes 1B, 2B and 3B for internal threads, and classes 2 and 3 for both internal and external threads. Classes 1A and 2B are for ordnance and other special uses. Classes 2A and 2B are the recognized standards for the bulk of screw-thread work and for the normal production of threads on screws, bolts, and nuts. Classes 3A and 3B are for applications where smaller tolerances than those afforded by 2A and 2B are justified ....  2, fiche 1, Anglais, - thread%20class

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1/2-13UNC-2ALH. [The thread class here is 2A].  2, fiche 1, Anglais, - thread%20class

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Threads are designated by standardized notes. 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 (1A, 2A, and 3A or 1B, 2B and 3B). Threads are considered to be right-hand and single unless otherwise noted; therefore the specification for a left-hand thread must have the letters LH included.  2, fiche 1, Anglais, - thread%20class

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[Example of a thread identification by standardized symbol]: 1/2-13UNC-2ALH.  2, fiche 1, Anglais, - thread%20class

Fiche 1,  Justifications,  Français

Record number: 1, Textual support number: 1 CONT

Degrés de précision des filets. On entend par ajustement des pièces de visserie, le jeu au montage entre la tige filetée et le taraudage. Les types d'ajustement pour les divers degrés de précision requis pour les filets normalisés "Unified" se divisent en trois catégories : 1A, 2A et 3A pour les filets extérieurs, et 1B, 2B et 3B pour les filets intérieurs. Ces catégories différent entre elles par l'importance du jeu et la tolérance.  1, fiche 1, Français, - cat%C3%A9gorie%20de%20degr%C3%A9%20de%20pr%C3%A9cision%20des%20filets

Fiche 1,  Justifications,  Espagnol