212 Exploring Drafting
view. In such cases, the feature is drawn partly
with object lines and partly with hidden lines.
Nevertheless, all features are represented in
every view.
The view in which the feature appears in its
true shape and size is the primary view of the
feature. All other views then become secondary
views of the feature, Figure 9-9. The primary
view of a feature usually represents the feature
with object lines, except in more complex situ-
ations. The secondary views usually represent
the feature with hidden lines. In dimensioning
multiview drawings, you will learn that, with
few exceptions, the primary view is the view
in which the drafter will both locate and give
the size of any given feature. Dimensioning is
discussed in Chapter 10.
The primary projection plane is the face
of the glass box to which the primary view of
a given feature is projected. The other faces
then become the secondary projection planes
for that feature, Figure 9-10.
True Faces and
Foreshortening
When an object surface is drawn in its
true shape and size within a view, it is said
to be a true face. An object surface or feature
is drawn true size when it is parallel to the
projection plane. Multiview drawings of
planar objects are normally made up of views
representing true faces.
Orthographic drawings use different
views to show the width, height, and depth
of objects. These are the three most basic
dimensions of any object. Width is defi as fined
the horizontal distance measured across an
object from side to side. Height is the vertical t
distance measured from the bottom to the top
of an object. Depth is the horizontal distance
measured from the front to the back of an
object.
Top view
Front view
Object feature
Primary centerlines
Side view
Secondary view
(Not true shape)
Secondary
centerlines
Secondary view
(Not true shape)
Primary view
(True shape and size)
Figure 9-9 Primary and secondary views. Object lines are used to represent
an object feature in its true size and shape in the primary view. Hidden lines are
used to represent the feature in the secondary view.