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UNIT 5
Multiview Drawings
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After completing this unit, you will be able to:
Explain the relationship between an orthographic
projection and a multiview drawing.
Identify and define the three dimensions of an object.
Define the three regular views.
Identify three principal planes of projection.
Explain three visualization principles for multiview
drawings.
Identify the three types of flat surfaces.
Explain characteristics of cylindrical surfaces.
Explain characteristics of fillets, rounds, and runouts.
Identify differences between third-angle and first-
angle projection.
The purpose of a drawing is to show the size
and shape of the object. A drawing can also provide
certain information on how an object is to be made.
Various methods of presentation are available to
the designer or drafter. However, the best way to
show every feature of an object in its true size and
shape is to use an arrangement of more than one
view known as a multiview drawing. Multiview
drawings are created using the principles of
orthographic projection. Many drafting and print
reading texts use the terms orthographic projection
and multiview drawing interchangeably.
Orthographic Projections of Views
Any view of an object drawn by a drafter can
be explained as the projection of an object’s features
onto a two-dimensional plane. For a drawing, the
plane is often a piece of paper or computer screen.
Simply defined, orthographic projection is a
system wherein parallel lines, called projectors, are
used to project the object onto a projection plane.
The projectors are perpendicular to the projection
plane, thus resulting in an exact and very precise
view. If more than one projection plane is used, the
result is a multiview projection. In general terms,
a multiview drawing is a drawing based on the
principles of orthographic projection.
The different views of a multiview drawing
are systematically arranged. This allows anyone
“reading” the drawing to “connect” the views
together, thus forming a mental picture, Figure 5-1.
Projection Explained
A skilled technician reading a print must be able
to visualize the object as a whole. This means they
must be able to look at the views in a drawing and
interpret those into a mental picture. Understanding
how views are projected and arranged will help
you later in the visualization process.
One way to help you understand the multiview
system is to observe how a cardboard box unfolds.
Each side of the box is oriented similar to
orthographic projection views. The sides are at right
angles to each other and have a definite relationship.
See Figure 5-2. If the front of the box remains in
position, the four adjoining sides unfold similar to
how the views of a multiview drawing are arranged.
Now think of the cardboard box as made out
of glass. Place an object inside of the glass box and
imagine that the points of the object are projected
onto the glass planes as views. See Figure 5-3.
Imaginary projection lines are used to bring the
separate views to each projection plane. If the glass
box is unfolded like the cardboard box, six views are
shown in an orthographic arrangement. Once you
have perfected mentally projecting orthographic
views using the glass box, you will be able to see
orthographic views looking at any object, Figure 5-4.