Chapter 3 Communicating Design Ideas
81
Alphabet of Lines
A number of different types of lines are used to produce orthographic
drawings. Each line is used for a particular purpose and should not be
used for anything else. Look at the casting in Figure 3-31A. The alphabet
of lines can be used to produce the orthographic drawing of this casting
shown in Figure 3-31B. The alphabet of lines consists of the standard line
types and widths used on technical drawings.
gure 3-31. A—An isometric view of a metal casting. B—The orthographic views of the casting shown
in A. Note the types of lines and their uses.
A
B
Object or visible line
Thick line used to show
the outline of the object
Extension line
Thin line that connects a dimension
line to the object being dimensioned
Dimension line
Thin line that shows the
size or location of an
object or its features
Centerline
Alternating long and short thin dashes
used to show the center of holes
Hidden line
Short, evenly spaced thin dashes
used to show hidden features