Dimensional tolerance

Dimensional tolerance is referred to as tolerance, which refers to the size of the absolute value of the difference between the maximum limit size minus the minimum limit size, or the allowable upper deviation minus the deviation difference. The dimensional tolerance is an absolute value without a sign. Limit deviation = limit size-basic size, upper deviation = maximum limit size-basic size, lower deviation = minimum limit size-basic size. The dimensional tolerance refers to the allowable variation of the part size during cutting. In the case of the same basic size, the smaller the dimensional tolerance, the higher the dimensional accuracy.

During the manufacturing process, due to the influence of factors such as processing or measurement, there is always a certain error in the actual size after completion.

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 amount of dimensional variation is called dimensional tolerance.

example:

1. Basic size Designed size: 30mm

2. Limit size Two limit values that allow size changes:

Maximum limit size=30+0.01=30.01mm

Minimum limit size=30-0.01=29.99mm

3. Limit deviation The algebraic value of the limit size minus the basic size. That is, the algebraic difference between the maximum limit size and the minimum limit size minus the basic size is the upper deviation and the lower deviation, respectively, collectively called the limit deviation. The upper and lower deviations of the holes are indicated by capital letters ES and EI, respectively:

Upper deviation ES=30.01-30=+0.01

Lower deviation EI=29.99-30=-0.01

4. Dimension tolerance The allowable amount of dimensional variation, that is, the maximum limit size minus the minimum limit size, is also equal to the algebraic difference obtained by subtracting the deviation from the upper deviation.

The dimensional tolerance is an absolute value without a sign.

Tolerance: 30.01-29.99=0.02

Or I0.01-(-0.01)=0.02