Chapter 9 Multiview Drawings 213
When a surface is drawn as a true face in
a given view, the surface is seen as true height
and true width (in the front or back view),
true height and true depth (in the right or left
view), or true width and true depth (in the
top or bottom view). See Figure 9-11. True
faces do not have to be measured actual size.
They may be drawn to scale. In other words,
they may be drawn to a larger scale for easier
viewing or to a smaller scale to fi t on the
drawing media.
An object surface that is not parallel to the
projection plane is not drawn as a true face
in the resulting view. This type of surface is
drawn smaller than true size and shape. This
is known as foreshortening and is common g
for objects with inclined surfaces. See
Figure 9-12. Objects with inclined surfaces
have at least one view where a face is at an
angle to the projection plane. For this reason,
the surface does not appear in its true shape
when drawn on a two-dimensional surface.
For example, hole features on angled surfaces
are not drawn in their true shape as circles
when projected. They are drawn as ellipses
because they are not perpendicular to the line
of sight. The resulting features are said to be
foreshortened.
Edges, Intersections, and
Limiting Edges
When creating multiview drawings, the
visualization of objects can be simplifi by fied
identifying what the lines in the different views
should represent. In orthographic projection,
all lines on multiview drawings represent one
of three features of the object. Each line repre-
sents the edge view of a surface, an intersection
between two surfaces, or the limiting edge
of a round or elliptical feature. See Figure 9-
13. Notice that most of the object features are
described in the primary view. The secondary
views use straight lines to show intersections
Figure 9-10 Primary and secondary projection
planes. The primary view of a feature is projected
in its true size and shape to the primary projection
plane. Secondary views are projected to secondary
projection planes.
True
faces
True
faces
True
face
Figure 9-11 A surface that is parallel to the
projection plane is drawn as a true face (in its true
shape and size).