GD&T Orientation (Angularity, Perpendicularity, Parallelism)

Orientation controls include angularity, perpendicularity, and parallelism. The orientation of features must be given in relation to datums. A table that is flat isn’t useful if you failed to control the angle of the tabletop in relation to the ground. When we ask if a table is level, we are asking if it is level in relationship to the floor, which we assume is level. The floor is acting as a datum feature simulator in this instance, allowing us to tell if the table is level, or parallel, to the floor. Without the datum, a table floating weightless in directionless space can’t be defined as level. Orientation controls refer to either a surface, median plane, or axis called out with a basic angle in relation to a datum. The three controls that do this are angularity, perpendicularity, and parallelism. Angularity is used to callout every angle except 90 and 180/0. When a surface or median plane is controlled with angularity, the tolerance zone is between two parallel planes that are nominally at the stat