At the beginning of the XX century, almost all machine-building factories had their own branch of fasteners, but it was costly and inefficient production. Standards are not adhered to, respectively, and the quality of products was low. During the First World War in the United States and then in Europe have been set up factories for the production of fasteners. American experts in the field of industrial development were convinced that the key to success will be the specialization of enterprises.
Fasteners are the most common machine parts and structures. Only threaded fasteners account for about 60% of the range of machine parts. A variety of designs of fasteners and their properties, creating a variety of different requirements, starting with the functional capacity of fasteners and connections, durability, reliability, ease of installation and operation and ending Reusable their use, interchangeability, etc. Are diverse and range of fasteners, making relevant optimization of their the choice for the design of compounds and largely determines the level of technical and economical machines.
No special publications and reference data did not allow designers and engineers to have an appropriate understanding of the application possibilities of standardized fasteners and components. This made it impossible to assembly operations receive the same quality parts connections without the need for additional adjustment, which led to higher prices for the assembly, made it difficult to use the spare parts.
In turn, it is restrained and international industrial cooperation, hampering economic development in general. By the 20 th years of XX century have set the stage for the development and adoption of the basic principles of the production of interchangeable parts:
1. Enterprises producing fasteners should adopt a unified system of tolerances;
Enterprises should take some normal-sized system to limit the number used in the construction of diameters to reduce the set of the measuring and cutting tools. In some cases, adopted special ranks to meet the needs of specific industries, enterprises must adopt a uniform system limit gauges.
The solution of these problems it possible to start work on the development and implementation of normalization — in the modern sense — standardization. In 1928 it began drafting an international system of tolerances, and by the end of 1930 there was already a final draft of the international system ISA (International Federation of the National Standardizing Association) — an international association for normalization, in which the tolerances involved in the committee №3. The committee worked with the active participation of representatives of Germany, France, Czechoslovakia, Sweden and Switzerland.
In the USSR, the first draft of tolerances for metric threads (OST 32 and OST 193) was published in November 1930, approved in November 1931, as standards began to be applied from February 1932 (OST 1251 OST 1252 OST 1253 and then slightly later, in 1254, and OST OST 1255). In October 1932 it published with the timing of the introduction to the January 1, 1933 Standard tolerances for inch thread (OCT 1260). For fasteners taken the 2nd and 3rd class of accuracy, as well as more accurate class 2a. In 1932 the All-Union Institute of Metrology, Standardization and drafted a tolerance of 1 th and 2nd small thread (OST OST 21 and 272).