How to read a feature control frame
A feature control frame is read from left to right. It reads “Type of control” of “Tolerance” to Datum. It should be noted that if a diameter symbol is present before “Tolerance” then it indicates the shape of the tolerance zone is cylindrical.
True position of 0.2 to datums A and B
Perpendicularity of 0.001 to datum A
Cylindricity of 0.001
Circular runout of 0.010 to datum A
Composite feature control frame
Basic dimensions are identified by a rectangular frame around the dimension. They are dimensions that are theoretically exact. They do not have a tolerance themselves (general blueprint tolerances do not apply). Instead they are controlled by another characteristic. This is often seen with positional tolerances such as the true position of a hole. The hole location will be specified as basic dimensions. A true position tolerance will then be assigned to the hole which will control how far off the nominal location the hole can be.