Keep Control of Datum Features Simple.
Frequently, designers use one or
two features within a pattern as datum features. On the part
shown, it is desirable to use two of the holes in the
three-hole pattern as datum features. One approach would be to
apply individual controls to each of the holes in the pattern
as the first drawing illustrates. Another approach is to
control the holes as a pattern using position relative to the
primary datum, A. Then, label individual holes as datum
features as shown in the second plan view. Depending on the
tolerances and modifiers used, nearly the same control may be
achieved with two less geometric controls, which simplifies
the drawing and may simplify verification while meeting
functional requirements.
|
