Also, reference dimensions do not apply and are not used. When adding feature tolerances, tolerance accumulation only exists between two mating features. With datum references on the gage and tolerances applied DFS, then datum features on the part and their irregular features on the part need not contact the gage. Basic dimensions of size and true position are found on the measuring instruments and never on the actual parts. Basic dimensions can be found on rulers, scales, CMMs, milling machine lead screws, optical comparators, and optical comparator charts and templates.
Actual dimensions are on the parts themselves.
Measure the size and locations on the part and compare these dimensions to the basic dimensions of size and position on the gages. The three kinds of tolerances are size, position and form. No size or position tolerance can be specified without considering how the tolerances affect interchangeability. The Basic Method uses the Taylor Principle, which was published in the early 1900s and is mentioned in Y14.5. Profile tolerance all around that shows the MMC and LMC limits between the arrowheads, For example, see the feature control symbol with the 0.02 tolerance all around.