86 Part I: AutoCAD 101
Don’t assume that you can just create a new blank DWG file and start drawing things. Do read this chapter before you get too deep into the later chapters in this book. Many AutoCAD drawing commands and concepts depend on proper drawing setup, so you’ll have a much easier time drawing and editing things if you’ve done your setup homework. A few minutes invested in setting up a drawing well can save hours of thrashing around later on.
After you’ve digested the detailed drawing setup procedures described in this and the following chapter, use the AutoCAD Drawing Setup Roadmap on the Cheat Sheet (which you can find at this book’s companion website at www.dummies.com/cheatsheet/autocad2013) as a quick reference to guide you through the process.
A Setup Roadmap
You have to set up AutoCAD correctly, partly because AutoCAD is so flexible and partly because, well, you’re doing CAD — computer-aided drafting (or design). The computer can’t aid your drafting (or design) if you don’t clue it in on things like system of measure, drawing scale, paper size, and units. In this context, the following facts help explain why AutoCAD drawing setup is important:
Electronic paper: The most important thing you can do to make using AutoCAD fun is to work on a correctly set up drawing so that your screen acts like paper, only smarter. When drawing on real paper, you constantly have to translate between units on the paper and the reallife units of the object you’re drawing. But when drawing in AutoCAD’s smarter paper, you draw directly in real-life units — feet and inches, millimeters, or whatever you typically use on your projects. AutoCAD can then calculate distances and dimensions for you and add them to the drawing. You can make the mouse pointer jump directly to preset intervals onscreen, and a visible, resizable grid gives you a better sense of the scale of your drawing. However, this smart-paper function works well only if you first tell AutoCAD some crucial parameters for your specific drawing. AutoCAD can’t really do its job until you tell it how
to work.
Dead-trees paper: Creating a great drawing onscreen that doesn’t fit well on paper is all too easy. After you finish creating your drawing on the smart paper that AutoCAD provides onscreen, you usually have to plot it on the good old-fashioned, real-world paper that people have used for thousands of years. At that point, you must deal with the fact that people like to use certain standard paper sizes and drawing scales. (Most people also like everything to fit neatly on one sheet of paper.) If you set up AutoCAD correctly, good plotting is the automatic result; if not, plotting time can become one colossal hassle.
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It ain’t easy: Hey, if it were easy, then any dummy could do it, right? AutoCAD provides templates and Setup Wizards for you, but the templates don’t work well unless you understand them, and some of the wizards don’t work well even if you do understand them. This deficiency is one of the major weaknesses in AutoCAD. You must figure out on your own (with the help of this book, of course) how to make the program work right. If you just plunge in without carefully setting up, your drawing and printing efforts are likely to wind up a real mess.
Fortunately, setting up AutoCAD correctly is a bit like following a road map to a new destination. Although the directions for performing your setup are complex, you can master them with attention and practice. Even more fortunately, this chapter provides a detailed and field-tested route. And soon, you’ll know the route like the back of your hand.
While you’re working in AutoCAD, always keep in mind what your final output should look like on real paper. Even your first printed drawings should look just like hand-drawn ones — only without all those eraser smudges and coffeecup rings. They need to be added manually in AutoCAD.
Before you start the drawing-setup process, you need to make decisions about your new drawing. The following four questions are absolutely critical; if you don’t answer them or your answers are wrong, you’ll probably need to rework the drawing later:
What system of measure — metric or imperial — will you use?
What drawing units will you use?
At what scale — or scales — will you plot it?
On what size paper does it need to fit?
In some cases, you can defer answering one additional question, but it’s usually better to deal with it upfront:
What kind of border or title block does your drawing require?
If you’re in a hurry, it’s tempting to find an existing drawing that was set up for the drawing scale and paper size that you want to use, make a copy of that DWG file, erase the objects, and start drawing. Use this approach with care, though. When you start from another drawing, you inherit any setup mistakes that may lurk in that drawing. Also, drawings that were created in much older versions of AutoCAD may not take advantage of current program features and CAD practices. If you can find a suitable drawing that was set up in a recent version of AutoCAD by an experienced person who was conscientious about doing setup right, then consider using it. Otherwise, you’re better off setting up a new drawing from scratch.
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88 Part I: AutoCAD 101
Enter the metric system
. . . or, “Let’s forget everything we learned about measuring stuff and start over again!” All (well, nearly all) the world is metric. Instead of a system of linear measure based on twelves, of volume measure based on sixteens, and of temperature measure based on who knows what (legend has it that Fahrenheit set his first thermometer outside on a cold day to establish zero, and in his mouth one day when he must have been running a slight fever to define 100), metric bases all types of measure on tens and to repeatable physical standards. (Of course, For Dummies books are in the metric vanguard because every single For Dummies title includes a Part of Tens. Check out Part VI.)
The metric system first gained a toehold (ten toes, of course) in France during the Revolution.
Over time, it became apparent that some standardization was called for, and a mere century and a half later, SI Metric became that standard. SI is short for Systeme International d’Unites. (That’s International System of Units in English. Isn’t it great to speak more than one language?)
The United States may be late coming to the party, but the U.S. federal government has made a commitment to adopt SI Metric. For more information, point your browser to the National Institute of Standards and Technology’s Special Publication 814 (http://ts.nist.
gov/weightsandmeasures/metric/ pub814.cfm).
Choosing your units
AutoCAD is extremely flexible about drawing units; it lets you have them your way. Usually, you choose the type of units that you normally use to talk about whatever you’re drawing: feet and inches for a building in the United States, millimeters for a metric screw, and so on.
Speaking of millimeters, there’s another choice you have to make even before you choose your units of measure, and that’s your system of measure.
Most of the world abandoned local systems of measure generations ago. Even widely adopted ones like the imperial system have mostly fallen by the wayside, just like their driving force, the British Empire. Except, of course, in the United States, where feet, inches, pounds, gallons, and degrees Fahrenheit still rule.
During drawing setup, you choose settings for length units (for measuring linear objects and distances) and angle units (for measuring angles between nonparallel objects or points on arcs or circles) in the Drawing Units dialog box, as shown in Figure 4-1. (We show you how to specify these settings in the section “Setting your units,” later in this chapter.) AutoCAD’s length unit types are as follows:
Architectural units are based in feet and inches and use fractions to represent partial inches.
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Decimal units are unitless — that is, they’re not based on any particular real-world unit. With decimal units, each unit in the drawing could represent an inch, a millimeter, a cubit (if you’re into building arks in case that rainy day should come), or any other unit of measure you deem suitable.
Engineering units are based in feet and inches and use decimals to represent partial inches.
Fractional units, like decimal units, are unitless and show values as fractions rather than decimal numbers.
Scientific units are also unitless and show values as exponents, used for drawing really tiny or really large things. If you design molecules or galaxies, this is the unit type for you.
AutoCAD’s angle unit types are as follows:
Decimal Degrees show angles as decimal numbers and are by far the easiest to work with — if your type of work allows it!
Deg/Min/Sec is based on the old style of dividing a degree into minutes and minutes into seconds. But seconds aren’t fine enough to display AutoCAD’s precision capabilities, so seconds can be further divided into decimals. One nautical mile (6,076 feet) is approximately one minute
of arc of longitude on the equator. David Letterman once said that the equator is so long that it would reach once around the world.
Grads and Radians are mathematically beautiful (so I’m told) but are not widely used in drafting. Apparently the French artillery uses grads, but as long as we’re friends with them, we shouldn’t have to worry.
Surveyor’s Units type is similar to Deg/Min/Sec, but uses quadrants (quarter circles), rather than a whole circle, where an angle in Deg/Min/ Sec might measure 300°0'0.00", the same angle in Surveyor’s Units would be represented as S 30°0'0.00" E.
For the great majority of AutoCAD users, the unit types to know and use are
Decimal, Architectural, and Decimal Degree. You’ll know or be told if you need to use one of the other types!
After you specify a type of unit, you draw things onscreen at full size in those units just as though you were laying them out on the construction site or in the machine shop. You draw an 8-foot-high line, for example, to indicate the height of a wall and an 8-inch-high line to indicate the cutout for a doggie door (for a dachshund, naturally). The onscreen line may actually be only
2 inches long at a particular zoom magnification, but AutoCAD stores the length as 8 feet. This way of working is easy and natural for most people for whom CAD is their first drafting experience, but it seems weird to people who’ve done a lot of manual drafting. If you’re in the latter category, don’t worry; you’ll soon get the hang of it.
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