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Common difference
When makes the components, to enable the components to have the interchangeability, the request components' size in a reasonable scope, has stipulated from the extreme dimension. After making the actual size, should in the stipulation biggest extreme dimension and in the least limit size range. The permission size's amount of variation is called the size common difference, the abbreviation common difference.
Standard common difference: The standard common difference IT value by basic is uses to confirm the tolerance zone size which the standard arranges in order any common difference. The standard common difference divides into 20 ranks, namely: IT01, IT02, IT1 to IT18. IT expresses the standard common difference, the digital presentation grade of tolerance. The IT01 common difference value is smallest, the precision is highest; The IT18 common difference value is biggest, the precision is lowest.
Basic size: The design assigns size.
Extreme dimension: The permission size change's two limit values, it is determines take the basic size as the cardinal number.
Difference: Some actual size reduces its basic size obtained algebraic difference.
Limit deviation: Namely refers to the upper deviation and the lower deviation. The biggest extreme dimension reduces its basic size obtained algebraic difference is an upper deviation; The least limit size reduces its basic size obtained algebraic difference is a lower deviation.
Size common difference: Permission size amount of variation. Namely biggest extreme dimension and difference of the least limit size; Is also equal to the upper deviation and the lower deviation algebraic difference absolute value.
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