Entries from August 2010 ↓

Composite Tolerances

A composite tolerance specifies two tolerances for the same geometric characteristic of a feature or features that have different datum requirements. One tolerance relates to a pattern of features and the other tolerance to each feature within the pattern. The individual feature tolerance is more restrictive than the pattern tolerance. In the illustration, where datums […]

Projected Tolerance Zones

Projected tolerances are specified in addition to positional tolerances to make the tolerance more specific. For example, projected tolerances specify the perpendicularity tolerance zone of an embedded part. The symbol for projected tolerance (p) is preceded by a height value, which specifies the minimum projected tolerance zone. The projected tolerance zone height and symbol appear […]

Datum Reference Frames

The tolerance values in the feature control frame are followed by up to three optional datum reference letters and their modifying symbols. A datum is a theoretically exact point, axis, or plane from which you make measurements and verify dimensions. Usually, two or three mutually perpendicular planes perform this task best. These are jointly called […]

Material Conditions

Material conditions apply to features that can vary in size. At maximum material condition (, also known as MMC), a feature contains the maximum amount of material stated in the limits. At MMC, a hole has a minimum diameter, whereas a shaft has a maximum diameter. At least material condition (, also known as LMC), […]