Basic dimensions are used to locate True Positions. There is no tolerance or deviation in the basic dimensions themselves, as they are theoretically perfect. The tolerance zone for the feature comes through the
Are BASIC dimensions measured?
BASIC dimensions can be thought of as the movement of a processing or measuring tool, the shift is always in absolute values (without plus or minus). ... The BASIC dimensions of the location and position of the tolerance zone remain unchanged, so there is no value in noting them in the measurement report.
What is basic dimension tolerance?
All a basic dimension does is tell you where the geometric tolerance zone or datum target is located. Look for a geometric tolerance in a feature control frame related to the features being dimensioned. Basic dimensions are used to establish the "true profile" which a profile tolerance will then control.
