| Use Profile to Control Size and Form
Often features are not simple
planes, holes and bosses. The next few tips will deal with
various means of controlling irregular and complex features.
These features should be dimensioned using BASIC dimensions
and toleranced for size and form using profile of a surface.
Virtually any shape may be defined and controlled in this
manner. On the part shown below, a hex shaped hole uses this
approach. Two profile of a surface controls are shown. The
lower of these two feature control frames is a profile of a
surface control without a datum reference. Without any datum
reference, the size of the hex is being controlled. As
illustrated in the lower figure, the form of the hex, angles
of the hex shape and flatness of individual surfaces that make
up the hex must be held within the tolerance of