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
a
Geometrical characteristic symbol
Write the type of geometric tolerance.
b
Diameter symbol (when needed)
The geometric characteristics that need to be specified are as follows:
Area inside a circle on a two-dimensional plane: position, concentricity
Area inside a cylinder in three-dimensional space: straightness, parallelism, perpendicularity, angularity, position, coaxiality
Area inside a sphere in three-dimensional space: position
c
Geometric tolerance value
Tolerance value. The unit is the millimeter (mm).
d
Material requirement, common tolerance zone, etc.
Typical indications include (maximum material requirement), (least material requirement), and CZ (common [tolerance] zone). Others include and .
e
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.

Home