expressed fractionally as 1/2, or it could be given
as 1 in. = 2 in., or as 6 in. = 1 ft.
In this case, you made a drawing on a smaller
scale than the scale of the original object, the scale
of an original object being always 1/1, or unity.
The relative size of a scale is indicated by the
fractional representation of the scale. A scale
whose fractional representation equals less than
unity is a less-than-full scale. One whose fractional
representation is greater than unity (such as a scale
of 200/1) is a larger-than-full scale. A scale of
1/10,000 is, of course, smaller than a scale of
1/100.
A scale expressed as an equation can always
be expressed as a fraction. For example, the scale
of 1 in. = 100 ft, expressed fractionally, comes
to 1 over (100 x 12), or 1/1,200.
It is obvious that any object that is larger than
the drawing paper on which it is to be represented
must be “scaled down” (that is, reduced to less-
than-full scale) for graphic representation.
Conversely, it is often desirable to represent a
very small object on a scale larger than full
scale for the purpose of clarity and to show
small details. Because the drawings prepared
by an EA frequently require scaling down,
the following discussion refers mostly to that
procedure. However, scaling up rather than
down simply means selecting a larger-than-full
scale rather than a smaller-than-full scale for your
drawing.
You could, if necessary, determine the
dimensions of your drawing by arithmetical
calculation; for example, on a half-scale drawing,
you divide each of the actual dimensions of the
object by 2. However, this might be a time-
consuming process if you were drawing a map of
a certain area to a scale of 1 in. = 1,000 mi, or
1/6,335,000 ft.
Consequently, you will usually scale a
drawing up or down by the use of one or another
of a variety of scales. This sense of the term scales
refers to a graduated, rulerlike instrument on
which scale dimensions for a drawing can be
determined by inspection.
Scales vary in types of material, shapes, style
of division, and scale graduations. Good quality
scales are made of high-grade boxwood or plastic,
while inexpensive scales are sometimes made of
45.831
Figure 2-23.-Types of scales in cross section.
yellow hardwood. The boxwood scales have white
plastic scale faces that are permanently bonded
to the boxwood. The graduation lines on the
boxwood scales are cut by a highly accurate
machine. Plastic scales, while less expensive than
boxwood scales, have clear graduations and are
reasonably accurate.
Scales are generally available in four different
shapes, as shown in figure 2-23. The numbers in
the figure indicate the location of the scale face.
The triangular scale provides six scale faces on
one rule. The two-bevel flat scale provides two
scale faces on one side of the rule only. The
opposite-bevel flat scale provides two scale faces,
one on each side of the rule. And the four-bevel
flat scale provides four scale faces, two on each
side of the rule. The most common types of scales
are the architect’s, the engineer’s, the mechanical
engineer’s, and the metric. All of these scales
are found in the EA’s draftsman kit with the
exception of the mechanical engineer’s scale,
which is primarily used by machine draftsmen.
To gain a better understanding of the
architect’s and engineer’s scale, which will be
described in the following sections, it may be
helpful to have the actual scales at hand as you
study.
Architect’s Scale
ARCHITECT’S SCALES are usually tri-
angular in shape and are used wherever
dimensions are measured in feet and inches.
Major divisions on the scale represent feet which,
in turn, are subdivided into 12ths or 16ths,
depending on the individual scale.
2-17
