associated modifiers, separated by a dash, are entered in one compartment of the feature control frame. See para. 3.4.2 and Fig. 4-19. Since the features have equal importance, datum reference letters may be entered in any order within this compartment.
126.96.36.199 Simulation of a Single Datum Plane. Figure 4-20 is an example of a single datum plane simulated, as explained in para. 4.5.1, by simultaneously contacting the high points of two surfaces. Identification of two features to establish a single datum plane may be required where separation of the features is caused by an obstruction, such as in Fig. 4-20, or by a comparable opening (for example. a slot) of sufficient width. Where appropriate, an extension line may be used to indicate a continuation of one datum feature across slots or obstructions. For controlling coplanarity of these surfaces, see para. 6.5.6.
188.8.131.52 Single Axis of Two Coaxial Features. Figure 4-21 is an example of a single datum axis established by two coaxial diameters. The datum axis is simulated by simultaneously contacting the high points of both surfaces with two coaxial cylin-
Was this article helpful?