Chapter 9 Profile Tolerances 331 True profile ∅40.2 ∅39.8 30° 0.04 wide profile tolerance zone The Drawing The Meaning Example 9-17. Specifying the profi le of a conical feature. half of the feature control frame is called the locating tolerance zone. This is the profile tolerance that locates the feature from datums. The related datum reference is given in the order of precedence in the feature control frame and the feature to be controlled is located from datums with basic dimensions. The bottom half of the feature control frame is called the profile form and orientation tolerance zone. Datum referencing in the lower area establishes the limits of size, form, and orientation of the profile related to the locating tolerance zone. The actual feature surface must be within both tolerance zones, as shown in Example 9-18. In Example 9-18, Datum B is in the lower segment of the feature control frame. This means that the profile tolerance of 0.2 must remain oriented (parallel) to Datum Feature B. In Example 9-19, Datum B is removed from the lower segment of the Example 9-19 , Datum B is removed from the lower segment of the Example 9-19 feature control frame. This allows the profile tolerance to float anywhere inside the profile locating tolerance zone, and profile tolerance no longer has an orientation to Datum Feature B.