The theoretically exact dimensions are written in rectangular frames while the tolerances concerning that position are written in feature control frames. True position theory is the concept of indicating geometrical characteristics ( true position, profile, and angularity) using theoretically exact dimensions (TED). List of geometric tolerance symbols (Relevant standard: ISO 5459) True Position Theory (Size Value in Rectangular Frame) Feature levelĪssociated feature (Requires datum feature)

An associated feature is a feature related to a datum, and specifies the orientation tolerance, location tolerance, and/or run-out tolerance. A datum is a theoretical, ideal feature established to determine the orientation, location, and/or run-out. that do not require reference datum indication).

“Single feature” under “Feature level” means features that are independent of datums (i.e. The following is a list of symbols used for geometric tolerancing.

True Position Theory (Size Value in Rectangular Frame)Ĭlassification and Symbols of Geometric Tolerance Characteristics.

Classification and Symbols of Geometric Tolerance Characteristics.

Currently, we have 16 symbols for geometric tolerances, which are categorized according to the tolerance they specify. Geometric tolerances are specified using symbols on a drawing.

Flatness symbol gd&t