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Dimensional tolerance

  • Author:Memory
  • Source:Www.xy-global.com
  • Release on :2018-05-09
Dimensional Tolerances Short-term tolerances mean the absolute value of the difference between the maximum limit size minus the minimum limit size, or the allowable upper deviation minus the difference in the deviation. The dimensional tolerance is an absolute value with no sign. Limit deviation = limit size - basic size, upper deviation = maximum limit size - basic size, lower deviation = minimum limit size - basic size. The dimensional tolerance is the allowable variation in the size of the part during the cutting process. With the same basic dimensions, the smaller the dimensional tolerance, the higher the dimensional accuracy.
During the manufacturing process of a part, due to factors such as processing or measurement, there is always a certain error in the actual size of the finished part.

In order to ensure the interchangeability of parts, the actual size of the parts must be controlled within the allowable range of variation. This allowable size variation is called dimensional tolerance.


1, basic size Design given size: 30mm

2, limit size Two limit values ​​for allowable dimensional changes:

Maximum limit size=30+0.01=30.01mm

Minimum limit size = 30-0.01 = 29.99mm

3, the limit deviation limit value minus the basic size of the algebraic value. That is, the algebraic differences obtained by subtracting the basic size from the maximum limit size and the minimum limit size are the upper deviation and the lower deviation, respectively, and collectively referred to as the limit deviation. The upper and lower deviations of the holes are indicated by the capital letters ES and EI, respectively:

Upper deviation ES=30.01-30=+0.01

Lower deviation EI=29.99-30=-0.01

4, Dimensional tolerances Allowable size variation, that is, the maximum limit size minus the minimum limit size, is also equal to the algebraic difference in the upper deviation minus the deviation.

The dimensional tolerance is an absolute value with no sign.

Tolerance: 30.01-29.99=0.02

Or I0.01-(-0.01)=0.02