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Do You Really Know Tolerances and Fits for Prototype/Machined Parts?
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Do You Really Know Tolerances and Fits for Prototype/Machined Parts?

  • Categories:FAQ
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  • Time of issue:2020-08-24 11:06
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(Summary description)It is necessary that the dimensions, shape and mutual position of surfaces of individual parts of mechanical engineering products are kept within a certain accuracy to achieve their correct and

Do You Really Know Tolerances and Fits for Prototype/Machined Parts?

(Summary description)It is necessary that the dimensions, shape and mutual position of surfaces of individual parts of mechanical engineering products are kept within a certain accuracy to achieve their correct and

  • Categories:FAQ
  • Author:
  • Origin:
  • Time of issue:2020-08-24 11:06
  • Views:
Information
It is necessary that the dimensions, shape and mutual position of surfaces of individual parts of mechanical engineering products are kept within a certain accuracy to achieve their correct and reliable functioning. Routine production processes do not allow maintenance (or measurement) of the given geometrical properties with absolute accuracy. Actual surfaces of the produced parts therefore differ from ideal surfaces prescribed in drawings. Deviations of actual surfaces are divided into four groups to enable assessment, prescription and checking of the permitted inaccuracy during production:
 
Dimensional deviations
Shape deviations
Position deviations
Surface roughness deviations
This toll includes the first group and can therefore be used to determine dimensional tolerances and deviations of machine parts.
 
As mentioned above, it is principally impossible to produce machine parts with absolute dimensional accuracy. In fact, it is not necessary or useful. It is quite sufficient that the actual dimension of the part is found between two limit dimensions and a permissible deviation is kept with production to ensure correct functioning of engineering products. The required level of accuracy of production of the given part is then given by the dimensional tolerance which is prescribed in the drawing. The production accuracy is prescribed with regards to the functionality of the product and to the economy of production as well.
 
A coupling of two parts creates a fit whose functional character is determined by differences of their dimensions before their coupling.

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