Why is there the concept of tolerance and fit?
This has to start with interchangeability! What is interchangeability? In the machinery and instrument manufacturing industry, the interchangeability of parts and components means that in a batch of parts or components of the same specification, any one can be installed on the machine without any selection or additional repairs (such as fitter repairs). to meet the specified performance requirements.
In order to meet the interchangeability of parts in mechanical manufacturing, it is required that the size of the produced parts should be within the allowable tolerance range. This requires a unified standard for the form, size, precision, performance, etc. of a part. Similar products also need to be classified according to size to reduce the series of products, which is product standardization.
1) From the perspective of use, such as the parts of bicycles and watches that people often use, and the parts of various equipment used in production, etc., when they are damaged, the repair personnel can quickly replace them with parts of the same specification to restore the bicycle , watch and device features. In some cases, the role of interchangeability is difficult to measure in value. For example, on the battlefield, it is absolutely necessary to eliminate the faults of weapons and equipment immediately and continue to fight.
2) From the perspective of manufacturing, interchangeability is a powerful means to improve production levels and carry out civilized production. When assembling, there is no need for auxiliary processing and repairing, so it can reduce the labor intensity of the assembly workers, shorten the assembly cycle, and enable the assembly workers to work in an assembly line, so as to carry out automatic assembly, thereby greatly improving production efficiency. During processing, due to the specified tolerances, various zeros on the same machine can be processed at the same time. Standard parts with a large amount can also be produced separately by specialized factories. In this way, high-efficiency special equipment can be used, and even computer-aided processing can be used. In this way, the output and quality will inevitably be improved, and the cost will be significantly reduced.
3) From the design point of view, due to the design and production of standard parts and components based on the principle of interchange, it can simplify drawing, calculation and other work, shorten the design cycle, and facilitate the use of computer-aided design.
