Feature Control Frame

A geometric tolerance is specified in the feature control frame. The following elements are written in the feature control frame.

Feature control frame
Geometrical characteristic symbol
Write the type of geometric tolerance.
Diameter symbol (when needed)
The geometric characteristics that need to be specified are as follows:
Area inside a circle on a two-dimensional plane: true position, concentricity
Area inside a cylinder in three-dimensional space: straightness, parallelism, perpendicularity, angularity, true position, coaxiality
Area inside a sphere in three-dimensional space: true position
Geometric tolerance value
Tolerance value. The unit is the millimeter (mm).
Material requirement, common tolerance zone, etc.
Typical indications include (maximum material requirement), (least material requirement), and CZ (common [tolerance] zone). Others include and .
Priority datum
The designer can specify as a datum the part that they want to prioritize as a reference. To specify multiple datums, write them in the order of priority (left to right).
Generally, designers determine the letter assigned to a datum in the order of priority—therefore, priority is generally described by alphabetical order.