Graphics Programs Reference
In-Depth Information
COORDINATING WITH PAPER SIZES
At this point, you may have questions about how your f full-scale draw ing w ill fit onto standard paper
sizes. AutoCAD offers several features that give you precise control over the scale of your drawing.
These features offer industry-standard scales to match your drawing with any paper size you need.
You'll learn more about these features as you work through the chapters of this topic. However, if
you're anxious to find out about them, look at the sections on layouts in Chapters 8 and 15 and also
check out the Annotation Scale feature in Chapter 9.
Understanding Scale Factors
When you draft manually, you work on the final drawing directly with pen and ink or pencil.
With a CAD program, you're a few steps removed from the finished product. Because of this,
you need a deeper understanding of your drawing scale and how it's derived. In particular,
you need to understand
scale factors
. For example, one of the most common uses of scale fac-
tors is translating the size of a graphic symbol, such as a section symbol in an architectural
drawing, to the final printed text size. When you draw manually, you draw your symbol at the
size you want. In a CAD drawing, you need to translate the desired final symbol size to the
drawing scale.
When you start adding graphic symbols to your drawing (see Chapter 4), you have to specify a
symbol height. The scale factor helps you determine the appropriate symbol height for a particular
drawing scale. For example, you may want your symbol to appear ½˝ high in your final print. But
if you draw your symbol to ½˝ in your drawing, it appears as a dot when printed. The symbol has
to be scaled up to a size that, when scaled back down at print time, appears ½˝ high. For a ¼˝-scale
drawing, you multiply the ½˝ text height by a scale factor of 48 to get 24˝. Your symbol should be
24˝ high in the CAD drawing in order to appear ½˝ high in the final print.
Where did the number 48 come from? The scale factor for fractional inch scales is derived by
multiplying the denominator of the scale by 12 and then dividing by the numerator. For exam-
ple, the scale factor for ¼˝ = 1´-0˝ is (4
×
12) / 1, or 48/1. For
3
⁄
16
˝ = 1´-0˝ scale, the operation is (16
×
12) / 3, or 64. For whole-foot scales such as 1˝ = 10´, multiply the feet side of the equation by 12.
Metric scales require simple decimal conversions.
You can also use scale factors to determine your drawing limits. For example, if you have a
sheet size of 11˝
×
17˝ and you want to know the equivalent full-scale size for a ¼˝ scale draw-
ing, you multiply the sheet measurements by 48. In this way, 11˝ becomes 528˝ (48
×
11˝), and 17˝
becomes 816˝ (48
×
17˝). Your work area must be 528˝
×
816˝ if you intend to have a final output
of 11˝
×
17˝ at ¼˝ = 1´. You can divide these inch measurements by 12˝ to get 44´
×
68´.
Table 3.2 shows scale factors as they relate to standard drawing scales. These scale factors
are the values by which you multiply the desired final printout size to get the equivalent full-
scale size. If you're using the metric system, you can use the drawing scale directly as the scale
factor. For example, a drawing scale of 1:10 has a scale factor of 10, a drawing scale of 1:50 has
a scale factor of 50, and so on. Metric users need to take special care regarding the base unit.
Centimeters are used as a base unit in the examples in this topic, which means that if you enter
a distance as 1, you can assume the distance to be 1 cm.
