Watch the Placement of Datum Identification
Symbols and the Feature Control Frames for Straightness,
Perpendicularity, Parallelism and Angularity!
When applying the above to features of size, the placement of the symbol or callout can greatly change the meaning. If the symbol or control is associated with the size dimension, the feature's axis or center plane is being identified or controlled. If the symbol or control is associated with the surface of the feature of size, it is identifying or controlling the surface - not the axis or center plane. In this example both the datum feature symbol and the perpendicularity apply to the feature's center plane. Notice that there are two center planes.
|
|
|
|
|
In the second example, both the datum feature symbol and the perpendicularity apply to the left surface of the slot. |
 |
|
|
|
