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Unusually, it takes three, although three rights make a left and two Wrights made an airplane.

      DRAWING SCALE VERSUS DRAWING SCALE FACTOR

      CAD users employ two different ways of talking about a drawing’s intended plot scale: drawing scale and drawing scale factor.

      Drawing scale is the traditional way of describing a scale: “traditional” because it existed long before CAD came to be. Drawing scales are expressed with an equal sign or colon: for example, 1/8″ = 1′0″, 1:20, or 2:1. You can translate the equal sign or colon as “corresponds to.” In all cases, the measurement to the left of the equal sign or colon indicates a paper measurement, and the number to the right indicates a real-world measurement. A metric drawing scale is usually expressed without units, as a simple ratio. Thus, a scale of 1:20 means 1 unit on the plotted drawing corresponds to 20 units in the real world.

      Drawing scale factor is a single number that represents a multiplier, such as 96, 20, or 0.5. The drawing scale factor for a drawing is the conversion factor between a measurement on the plot and a measurement in the real world.

The “Drawing scale versus drawing scale factor” sidebar explains how you arrive at the scale factor, but this isn’t an issue until it comes time to annotate your drawing. I cover noncontinuous linetype scaling in Chapter 9, text sizing in Chapter 13, dimensions in Chapter 14, and crosshatching in Chapter 15. The good news is that AutoCAD can now take care of all this automatically, but a well-placed rumor has it that there may still be a few drawings out there that did it the old way, so I cover both methods in the appropriate chapters.

      

You shouldn’t just invent some arbitrary scale based on what looks okay on whatever size paper you happen to have handy. Most industries work with a small set of approved drawing scales that are related to one another by factors of 2 or 5 or 10. If you use other scales, you’ll be branded a clueless newbie, at best. At worst, you’ll have to redo all your drawings at an accepted scale.

      

The SCale command covered in Chapter 11 has nothing to do with ladders, fish, or setting drawing scales or scale factors!

Table 4-1 lists some common architectural drawing scales, using both imperial and metric systems of measure. The table also lists the drawing scale factor corresponding to each drawing scale and the common uses for each scale. If you work in industries other than those listed here, ask drafters or coworkers what the common drawing scales are and for what kinds of drawings they’re used.

TABLE 4-1 Common Architectural Drawing Scales

Drawing Scale	Drawing Scale Factor	Common Uses
1/16″ = 1′-0″	192	Large-building plans
1/8″ = 1′-0″	96	Medium-sized building plans
1/4″ = 1′-0″	48	House plans
1/2″ = 1′-0″	24	Small-building plans
1″ = 1′-0″	12	Details
1:200	200	Large-building plans
1:100	100	Medium-sized building plans
1:50	50	House plans
1:20	20	Small building plans
1:10	10	Details

After you choose a drawing scale, engrave the corresponding drawing scale factor on your desk, write it on your hand (don’t reverse those two, okay?), and put it on a sticky note on your monitor. You eventually need to know the drawing scale factor for many drawing tasks, as well as for some plotting. You should be able to recite the drawing scale factor of any drawing you’re working on in AutoCAD without even thinking about it.

      

Even if you’re going to use the Plot dialog box’s Fit to Paper option (rather than a specific scale factor) to plot the drawing, you still need to choose a scale to make the nonreal things (such as text, dash-dot linetypes, hatch patterns, and so on) appear at a useful size. I cover plotting in Chapter 16.

      Thinking about paper

      You don’t normally need to worry about the size of the paper that you want to use for plotting your drawing until much later in the drawing process. And that’s the beauty of CAD: You can easily move views around to suit after you get the basic object drawn, and you don’t need to worry about scale factors until you’re ready to add annotations. I cover this in excruciatingly more (just kidding, it’s actually quite simple) detail in Chapters 12–16. Here again, most industries use a small range of standard sheet sizes.

      Here are the two ways of laying out a drawing so it’s ready to be plotted:

       In model space: In this process, everything is drawn in model space, which at one time was the only known universe in AutoCAD. The drawing is created full size, while text and dimension component sizes, hatch pattern scaling, title blocks, and borders are all created at the inverse of the final plotting scale. This was the only way for many years, so you’ll encounter many drawings that were made this way.

       In paper space: Finally, Autodesk programmers figured out how to tunnel through into a parallel universe called paper space, which revolutionized drawing production. Current preferred practice is to draw the object full size in model space, cut a viewport in paper space so you can look through to the model space, and then apply documentation such as dimensions and text in paper space.

      I cover model space versus paper space in Chapter 16.

      Defending your border

      The next decision to make is what kind of border your drawing needs. The options include a full-blown title block,

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