Chapter 3

Setting Up and Using AutoCAD’s Drafting Tools

Chapters 1 and 2, “Exploring the AutoCAD Interface” and “Creating Your First Drawing,” covered the basic information you need to understand the workings of AutoCAD. Now you’ll put this knowledge to work. In this architectural tutorial, which begins now and continues through Chapter 14, “Advanced Editing and Organizing,” you’ll draw an apartment building composed of studios. The tutorial illustrates how to use AutoCAD commands and gives you a solid understanding of the basic AutoCAD package. With these fundamentals, you can use AutoCAD to its fullest potential regardless of the kinds of drawings you intend to create or the enhancement products you may use in the future.

In this chapter, you’ll start drawing an apartment’s bathroom fixtures. In the process, you’ll learn how to use AutoCAD’s basic tools. You’ll also be introduced to the concept of drawing scale and how the size of what you draw is translated into a paper sheet size.

In this chapter, you’ll learn to do the following:

• Set up a work area
• Explore the drawing process
• Plan and lay out a drawing
• Use the AutoCAD modes as drafting tools

Setting Up a Work Area

Before beginning most drawings, you should set up your work area. To do this, determine the measurement system, the drawing sheet size, and the scale you want to use. The default work area is roughly 16˝ ⇒ 9˝ at full scale, given a decimal measurement system in which 1 unit equals 1 inch. Metric users will find that the default area is roughly 550 mm ⇒ 300 mm, in which 1 unit equals 1 mm. If these are appropriate settings for your drawing, you don’t have to do any setting up. It’s more likely, however, that you’ll make drawings of various sizes and scales. For example, you might want to create a drawing in a measurement system in which you can specify feet, inches, and fractions of inches at 1˝ = 1´ scale and print the drawing on an 8½˝-⇒-11˝ sheet of paper.

In the following sections, you’ll learn how to set up a drawing exactly the way you want.

Specifying Units

You’ll start by creating a new file called Bath. Then you’ll set up the unit type.

Use these steps to create the file:

The next thing you want to tell AutoCAD is the unit type you intend to use. So far, you’ve been using the default, which is a generic decimal unit. This unit can be interpreted as inches, centimeters, feet, kilometers, or light years. When it comes time to print your drawing, you can tell AutoCAD how to convert these units into a meaningful scale.

If you are a U.S. user, decimal units typically represent inches. If you want to be able to enter distances in feet, you must change the unit type to one that accepts feet as input. You’ll do this through the Drawing Units dialog box shown in Figure 3-1.

If you’re a civil engineer, you should know that the Engineering unit type lets you enter feet and decimal feet for distances. For example, the equivalent of 12´-6˝ is 12.5´. If you use the Engineering unit type, you’ll ensure that your drawings conform to the scale of drawings created by your architectural colleagues.

Follow these steps to set a unit type:

If you use the Imperial system of measurement, you selected Architectural measurement units for this tutorial, but your work may require a different unit type. You saw the unit types available in the Drawing Units dialog box. Table 3-1 shows examples of how the distance 15.5 is entered in each of these styles.

Table 3-1: Measurement systems available in AutoCAD

Measurement System	AutoCAD’s Display of Measurement
Scientific	1.55E+01 (inches or metric)
Decimal	15.5000 (inches or metric)
Engineering	1´-3.5˝ (input as 1´3.5˝)
Architectural	1´-3½˝ (input as 1´3-½˝)
Fractional	15½˝ (input as 15-½˝)

In the previous exercise, you needed to change only two settings. Let’s look at the other Drawing Units settings in more detail. As you read, you may want to refer to Figure 3-1.

Fine-Tuning the Measurement System

Most of the time, you’ll be concerned only with the Length and Angle settings of the Drawing Units dialog box. But as you saw in the preceding exercise, you can control many other settings related to the input and display of units.

The Precision pop-up list in the Length group lets you specify the smallest unit value that you want AutoCAD to display in the status bar and in the prompts. If you choose a measurement system that uses fractions, the Precision pop-up list includes fractional units. You can also control this setting with the Luprec system variable. (You can find out more about system variables on the AutoCAD Mac Help website.)

The Angle group lets you set the style for displaying angles. You have a choice of five angle styles: Decimal Degrees, Degrees/Minutes/Seconds, Grads, Radians, and Surveyor’s Units. In the Angle group’s Precision pop-up list, you can specify the degree of accuracy you want AutoCAD to display for angles. You can also control these settings with the Aunits and Auprec system variables. Go to the AutoCAD Mac Help website and select the Command Reference option in the left column of the page, and then select the first letter of a system variable name from the System Variable listing.

You can tell AutoCAD which direction is positive, either clockwise or counterclockwise. The default, which is counterclockwise, is used in this book. The Base Angle Directions group lets you set the direction of the 0 base angle. The default base angle (and the one used throughout this book) is a direction from left to right. However, at times you may want to designate another direction as the 0 base angle. You can also control these settings with the Angbase and Angdir system variables.

The Insertion scale units setting in the Drawing Units dialog box lets you control how blocks are scaled as they’re inserted into your current drawing. A block is a collection of drawing objects that form a single object. Blocks are frequently used to create standard symbols. You’ll learn more about blocks in Chapter 4, “Organizing Objects with Blocks and Groups.” The Insertion Scale setting lets you compensate for drawings of different scales by offering an automatic scale translation when importing blocks from an external file. The Insunits system variable also controls the Insertion Scale setting.

The Light intensity units setting relates to the 3D rendering feature discussed in Chapter 21, “Rendering 3D Drawings.”

If you’re new to AutoCAD, don’t worry about the Insertion Scale setting right now. Make a mental note of it. It may come in handy in your work in the future.

Setting Up the Drawing Limits

One of the big advantages of using AutoCAD is that you can draw at full scale; you aren’t limited to the edges of a piece of paper the way you are in manual drawing. But you may find it difficult to start drawing without knowing the drawing boundaries. You can set up some arbitrary boundaries using the Limits feature. You got a taste of the Limits feature in Chapter 2. You’ll use it again here to set up a work area for your next drawing.

You’ll be drawing a bathroom that is roughly 8´ ⇒ 5´ (230 cm ⇒ 150 cm for metric users). You’ll want to give yourself some extra room around the bathroom, so your drawing limits should be a bit larger than that actual bathroom size. You’ll use an area of 11´ ⇒ 8´-6˝ for the limits of your drawing. Metric users will use an area 297 cm ⇒ 210 cm. These sizes will accommodate your bathroom with some room to spare.

Now that you know the area you need, you can use the Limits command to set up the area:

In step 6, the coordinate readout shows you that your drawing area is larger than before. The background grid can help you visualize the area you’re working with. You can control the grid using the Grid Display tool in the status bar. Grid Display shows a background grid that helps you visualize distances and can also show you the limits of your drawing. It can also be a bit distracting for a new user, so I’ve asked you to turn it off for now.

Looking at an Alternative to Limits

As an alternative to setting up the drawing limits, you can draw a rectangle that outlines the same area used to define the drawing limits. For example, in the previous exercise, you could use the Rectangle tool to draw a rectangle that has its lower-left corner at coordinate 0,0 and its upper-right corner at 132,102 (297,210 for metric users). You can set up the rectangle to be visible without printing using the Layer feature. You’ll learn more about layers in Chapter 5, “Keeping Track of Layers and Blocks.”

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 factors 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 example, 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 drawing, 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 book, which means that if you enter a distance as 1, you can assume the distance to be 1 cm.

Table 3-2: Scale conversion factors

In older drawings, scale factors were used to determine text height and dimension settings. Chances are you will eventually have to work with drawings created by older AutoCAD releases, so understanding scale factors will pay off later. Printing to a particular scale is also easier with an understanding of scale factors.

Using Polar Tracking

In this section, you’ll draw the first item in the bathroom: the toilet. It’s composed of a rectangle representing the tank and a truncated ellipse representing the seat. To construct the toilet, you’ll use Polar Tracking, which is one of the most versatile drafting tools. Polar Tracking helps you align your cursor to exact horizontal and vertical angles, much like a T-square and triangle.

In this exercise, you’ll use Polar Tracking to draw a rectangular box:

As you can see from the exercise, you can use Polar Tracking to restrain your cursor to horizontal and vertical positions, just as you would use a T-square and triangle. Later, you’ll learn how you can set up Polar Tracking to set the angle to any value you want in a way similar to an adjustable triangle.

In some situations, you may find that you don’t want Polar Tracking on. You can turn it off by clicking the Polar Tracking tool in the status bar.

Although this exercise tells you to use the Line tool to draw the tank, you can also use the Rectangle tool. The Rectangle tool creates what is known as a polyline, which is a set of line or arc segments that act like a single object. You’ll learn more about polylines in Chapter 17, “Drawing Curves.”

By using the Snap modes in conjunction with the coordinate readout and Polar Tracking, you can locate coordinates and measure distances as you draw lines. This is similar to the way you draw when using a scale. The smallest distance registered by the coordinate readout and Polar Tracking readout depends on the area you’ve displayed on your screen. For example, if you’re displaying an area the size of a football field, the smallest distance you can indicate with your cursor may be 6˝, or 15 cm. On the other hand, if your view is enlarged to show an area of only one square inch or centimeter, you can indicate distances as small as 1⁄1000 of an inch or centimeter by using your cursor.

Setting the Polar Tracking Angle

You’ve seen how Polar Tracking lets you draw exact vertical and horizontal lines. You can also set Polar Tracking to draw lines at other angles, such as 30° or 45°. To change the angle Polar Tracking uses, you use the Polar Tracking tab in the Drafting Settings dialog box (see Figure 3-3).

Right-click the Polar Tracking tool in the status bar, and then choose Settings from the shortcut menu to open the Drafting Settings dialog box. As an alternative, you can type DS↵ and then click the Polar Tracking tab.

To change the Polar Tracking angle, enter an angle in the Increment Angle text box or select a predefined angle from the pop-up list. You can do this while drawing a series of line segments, for example, so that you can set angles on the fly.

Numerous other settings are available in the Polar Tracking tab. Here is a listing of their functions for your reference:

Additional Angles This setting lets you enter a specific angle for Polar Tracking. For example, if you want Polar Tracking to snap to 12°, click the New button next to the Additional Angles list box and enter 12. The value you enter appears in the list box, and when the Additional Angles check box is selected, Polar Tracking snaps to 12°. To delete a value from the list box, highlight it and click the Delete button.

The Additional Angles option differs from the Increment Angle setting in that the latter causes Polar Tracking to snap to every increment of its setting, whereas Additional Angles snaps only to the angle specified. You can enter as many angles as you want in the Additional Angles list box. As a shortcut, you can use the Polarang system variable (Polarang↵) to set the incremental angle without using the dialog box.

Object Snap Tracking Settings These settings let you control whether Object Snap Tracking uses strictly orthogonal directions (0°, 90°, 180°, and 270°) or the angles set in the Polar Angle Settings group in this dialog box. (See the section “Aligning Objects by Using Object Snap Tracking” later in this chapter.)

Polar Angle Measurement These radio buttons let you determine the zero angle on which Polar Tracking bases its incremental angles. The Absolute option uses the current AutoCAD setting for the 0° angle. The Relative To Last Segment option uses the last drawn object as the 0° angle. For example, if you draw a line at a 10° angle and the Relative To Last Segment option is selected with Increment Angle set to 90°, Polar Tracking snaps to 10°, 100°, 190°, and 280°, relative to the actual 0° direction.

Exploring the Drawing Process

The following sections present some of the most common AutoCAD commands and show you how to use them to complete a simple drawing. As you draw, watch the prompts and notice how your responses affect them. Also notice how you use existing drawing elements as reference points.

While drawing with AutoCAD, you create simple geometric forms to determine the basic shapes of objects, and you can then modify the shapes to fill in detail.

AutoCAD offers a number of basic 2D drawing object types; lines, arcs, circles, text, dimensions, traces, polylines, points, ellipses, elliptical arcs, spline curves, regions, hatches, and multiline text are the most common. All drawings are built on at least some of these objects. In addition, there are several 3D solids and meshes, which are three-dimensional shapes. You’re familiar with lines and arcs; these, along with circles, are the most commonly used objects. As you progress through the book, you’ll learn about the other objects and how they’re used. You’ll also learn about 3D objects in Part 4, “Modeling and Imaging.”

Locating an Object in Reference to Others

To define the toilet seat, you’ll use an ellipse. Follow these steps:

Getting a Closer Look

During the drawing process, you’ll often want to enlarge areas of a drawing to edit its objects. In Chapter 1, you saw how to use the Zoom capability for this purpose. Follow these steps to enlarge the view of the toilet:

If you have a mouse with a scroll wheel, you can avoid using the Zoom command altogether. Just place the cursor on the toilet and turn the wheel to zoom into the image. For Magic Mouse users, use a one-finger vertical gesture on the Multi-Touch area of the mouse. Trackpad users can hold down and use a two-finger vertical gesture.

Modifying an Object

Now let’s see how editing commands are used to construct an object. To define the back edge of the seat, let’s put a copy of the line defining the front of the toilet tank 3˝ (7 cm for metric users) toward the center of the ellipse:

Notice that the Copy command acts exactly like the Move command you used in Chapter 2 except that Copy doesn’t alter the position of the objects you select and you must press ↵ to exit Copy.

Trimming an Object

Now you must delete the part of the ellipse that isn’t needed. You’ll use the Trim command to trim off part of the ellipse:

In step 1 of the preceding exercise, the Trim command produces two messages in the prompt. The first message, Select cutting edges..., tells you that you must first select objects to define the edge to which you want to trim an object. In step 3, you’re again prompted to select objects, this time to select the object to trim. Trim is one of a handful of AutoCAD commands that asks you to select two sets of objects: The first set defines a boundary, and the second is the set of objects you want to edit. The two sets of objects aren’t mutually exclusive. You can, for example, select the cutting-edge objects as objects to trim. The next exercise shows how this works.

First, you’ll undo the trim you just did. Then, you’ll use the Trim command again in a slightly different way to finish the toilet:

Here you saw how the ellipse and the line are both used as trim objects as well as the objects to be trimmed. The Trim options you’ve seen so far—Fence, Crossing, Project, Edge, eRase, and Undo—are described in the next section in this chapter. Also note that by holding down in step 4, you can change from trimming an object to extending an object.

Exploring the Trim Options

AutoCAD offers six options for the Trim command: Fence, Crossing, Project, Edge, eRase, and Undo. As described in the following list, these options give you a higher degree of control over how objects are trimmed:

Fence/Crossing [F or C] Lets you use a fence or crossing window to select objects.

Project [P] Useful when you’re working on 3D drawings. It controls how AutoCAD trims objects that aren’t coplanar. Project offers three options: None, UCS, and View. The None option causes Trim to ignore objects that are on different planes so that only coplanar objects are trimmed. If you choose UCS, the Trim command trims objects based on a plan view of the current UCS and then disregards whether the objects are coplanar. (See the middle of Figure 3-7.) View is similar to UCS but uses the current view’s “line of sight” to determine how non-coplanar objects are trimmed. (See the bottom of Figure 3-7.)

Edge [E] Lets you trim an object to an apparent intersection, even if the cutting-edge object doesn’t intersect the object to be trimmed (see the top of Figure 3-7). Edge offers two options: Extend and No Extend. You can also set these options by using the Edgemode system variable.

eRase [R] Allows you to erase an object while remaining in the Trim command.

Undo [U] Causes the last trimmed object to revert to its original length.

You’ve just seen one way to construct the toilet. However, you can construct objects in many ways. For example, you can trim only the top of the ellipse, as you did in the first trim exercise, and then use the Grips feature to move the endpoints of the line to meet the endpoints of the ellipse. As you become familiar with AutoCAD, you’ll start to develop your own ways of working, using the tools best suited to your style.

If you’d like to take a break, now is a good time. You can exit AutoCAD and then come back to the Bath drawing file when you’re ready to proceed.

Planning and Laying Out a Drawing

For the next object, the bathtub, you’ll use some new commands to lay out parts of the drawing. This will help you get a feel for the kind of planning you must do to use AutoCAD effectively. You’ll begin the bathtub by using the Line command to draw a rectangle 2´-8˝ ⇒ 5´-0˝ (81 cm ⇒ 152 cm for metric users) on the left side of the drawing area. For a change this time, you’ll use a couple of shortcut methods built into AutoCAD: the Line command’s keyboard shortcut and the Direct Distance method for specifying distance and direction.

First, though, you’ll go back to the previous view of your drawing and arrange some more room to work. Follow these steps:

Instead of pressing ↵ during the Direct Distance method, you can press the spacebar, or you can right-click and choose Enter from the shortcut menu.

Now you have the outline of the tub. Notice that you don’t have to enter the at sign (@) or angle specification. Instead, you use the Direct Distance method to specify direction and distance. You can use this method for drawing lines or moving and copying objects at right angles. The Direct Distance method is less effective if you want to specify exact angles other than right angles.

The keyboard aliases for some of the tools or commands you’ve used in this chapter are CO (Copy), E (Erase), EL (Ellipse), F (Fillet), M (Move), O (Offset), and TR (Trim). Remember that you can enter keyboard aliases only when the Command prompt is visible in the Command Line palette.

Making a Preliminary Sketch

In this section, you’ll see how planning ahead will make your use of AutoCAD more efficient. When drawing a complex object, you’ll often have to do some layout before you do the actual drawing. This is similar to drawing an accurate pencil sketch using construction lines that you later trace over to produce a finished drawing. The advantage of doing this in AutoCAD is that your drawing doesn’t lose any accuracy between the sketch and the final product. Also, AutoCAD enables you to use the geometry of your sketch to aid in drawing. While you’re planning your drawing, think about what you want to draw, and then decide which drawing elements will help you create that object.

You’ll use the Offset command to establish reference lines to help you draw the inside of the tub. This is where the Osnap overrides are useful. (See the sidebar “The Osnap Options” later in this chapter.)

You can use the Offset tool on the Tool Sets palette to make parallel copies of a set of objects, such as the lines forming the outside of your tub. Offset is different from the Copy command; while Offset allows only one object to be copied at a time, it can remember the distance you specify. The Offset option doesn’t work with all types of objects. Only lines, arcs, circles, ellipses, splines, and 2D polylines can be offset.

Standard lines are best suited to the layout of the bathtub in this situation. In Chapter 6, “Editing and Reusing Data To Work Efficiently,” you’ll learn about two other objects, construction lines and rays, that are specifically designed to help you lay out a drawing. In this exercise, you’ll use standard lines:

Using the Layout

Now you’ll begin to draw the inside of the tub, starting with the narrow end. You’ll use your offset lines as references to construct the arcs that make up the tub. Also in this exercise, you’ll set up some of the osnap options to be available automatically whenever AutoCAD expects a point selection. Here are the steps:

You’ve just set up the Endpoint, Midpoint, and Intersection osnaps to be on by default. This is called a Running Osnap; AutoCAD automatically selects the nearest osnap point without your intervention. Now let’s see how a Running Osnap works:

The top image in Figure 3-12 shows the sequence I just described.

Figure 3-11:The Draw ⇒ Arc submenu on the menu bar offers several ways to draw an arc.

If you have several Running Osnap modes on (Endpoint, Midpoint, and Intersection, for example), pressing the Tab key cycles through those osnap points on the object. This feature can be especially useful in a crowded area of a drawing.

Next, you’ll draw an arc for the left side of the tub:

Now, you’ll draw the bottom of the tub:

Next, create the right side of the tub by mirroring the left side:

In this exercise, you were able to use osnaps in a Running Osnap mode. You’ll find that you’ll use osnaps constantly as you create your drawings. For this reason, you may want Running Osnaps on all the time. Even so, at times Running Osnaps can get in the way. For example, they may be a nuisance in a crowded drawing when you want to use a zoom window. The osnaps can cause you to select an inappropriate window area by automatically selecting osnap points.

Fortunately, you can toggle Running Osnaps on and off easily by clicking the Object Snap tool in the status bar. If you don’t have any Running Osnaps set, clicking the Object Snap tool opens the Object Snap settings in the Drafting Settings dialog box, enabling you to select your osnaps. Or you can right-click the Object Snap tool and select Settings from the shortcut menu that appears.

Erasing the Layout Lines

Next, you’ll erase the layout lines you created using the Offset command. But this time, you’ll try selecting the lines before issuing the Erase command.

Follow these steps:

If you right-clicked to use the shortcut menu in step 2, you’ll notice that you have several options besides Erase. You can move, copy, scale, and rotate the objects you selected. These options are similar to the tools on the Tool Sets palette in the way they act. But be aware that they act somewhat differently from the hot-grip options described in Chapter 2.

If you need more control over the selection of objects, you’ll find the Add/Remove Selection Mode setting useful. This setting lets you deselect a set of objects within a set of objects you’ve already selected. While in Object Selection mode, enter R↵, then proceed to use a window or other selection method to remove objects from the selection set. Enter A↵ to continue to add options to the selection set. Or, if you need to deselect only a single object, -click it.

Putting On the Finishing Touches

The inside of the tub still has some sharp corners. To round out these corners, you can use the versatile Fillet tool on the Tool Sets palette. Fillet enables you to join lines and arcs end to end, and it can add a radius where they join so there is a smooth transition from arc to arc or line to line. Fillet can join two lines that don’t intersect, and it can trim two crossing lines back to their point of intersection.

Another tool, called Chamfer, performs a similar function, but instead of joining lines with an arc, Chamfer joins lines with another line segment. Since they perform similar functions, Fillet and Chamfer are next to each other on the Tool Sets palette.

Continue with your tutorial by following these steps:

Aligning Objects by Using Object Snap Tracking

You saw how to use lines to construct an object such as the bathtub. In many situations, using these construction lines is the most efficient way to draw, but they can also be a bit cumbersome. AutoCAD offers another tool that helps you align locations in your drawing to existing objects without having to draw intermediate construction lines. The tool is called Object Snap Tracking, or Osnap Tracking.

Osnap Tracking is like an extension of object snaps that enables you to align a point to the geometry of an object instead of just selecting a point on an object. For example, with Osnap Tracking, you can select a point that is exactly at the center of a rectangle.

In the following exercises, you’ll draw a plan view of a bathroom sink as an introduction to the Osnap Tracking feature. This drawing will be used as a symbol in later chapters.

Getting Set Up

First, as a review, you’ll create a new file. Because this drawing will be used as a symbol for insertion in other CAD drawings, don’t worry about setting it up to conform to a sheet size. Chances are you won’t be printing individual symbols. Here are the steps:

If you find that you use the same drawing setup over and over, you can create template files that are already set up to your own, customized way of working. Templates are discussed in Chapter 6.

Drawing the Sink

You’re ready to draw the sink. First, you’ll draw the sink countertop. Then, you’ll make sure Running Osnaps and Osnap Tracking are turned on. Finally, you’ll draw the bowl of the sink.

Here are the steps for drawing the outline of the sink countertop:

When you draw the bowl of the sink, the bowl will be represented by an ellipse. You want to place the center of the ellipse at the center of the rectangle you’ve just drawn. To do this, you’ll use the midpoint of two adjoining sides of the rectangle as alignment locations. This is where the Osnap Tracking tool will be useful.

You need to make sure that both the Object Snap tool and the Midpoint Object Snap option are turned on. Then you’ll make sure Osnap Tracking is turned on. Use these steps:

Finally, you’re ready to draw the ellipse:

In this exercise, you saw how Object Snap Tracking enables you to align two locations to select a point in space. Although you used only the Midpoint osnap setting in this exercise, you aren’t limited to one osnap setting. You can use as many as you need to select the appropriate geometry. You can also use as many alignment points as you need, although in this exercise you used only two. If you like, erase the ellipse and repeat this exercise until you get the hang of using the Object Snap Tracking feature.

As with all the other tools in the status bar, you can turn Object Snap Tracking on or off by clicking the Object Snap Tracking tool.

Using the AutoCAD Modes as Drafting Tools

Before you finish this chapter, you’ll want to know about a few of the other drafting tools that are common to drawing programs. These tools may be compared to a background grid (Grid mode) and the ability to “snap” to grid points (Snap modes). These drawing modes can be indispensable tools under certain conditions. Their use is fairly straightforward. You can experiment with them on your own using the information in the following sections.

Using Grid Mode as a Background Grid

Using Grid mode is like having a grid under your drawing to help you with layout, as shown in Figure 3-24. In this figure, the grids are set to a 1´ spacing with major grid lines at 5´. The grid also shows, in darker lines, the X and Y axes that start at the origin of the drawing.

Grids will not print in your final output. They are a visual aid to help you gauge distances. In AutoCAD, Grid mode can also let you see the limits of your drawing because the grid can be set to display only within the limits setting of your drawing. Grid mode can help you visually determine the distances with which you’re working in any given view. In this section, you’ll learn how to control the grid’s appearance. You can also click the Grid Display tool in the status bar.

To set up the grid spacing, follow these steps:

If you prefer, you can use the Gridunit system variable to set the grid spacing. Enter Gridunit↵, and at the Enter new value for GRIDUNIT <0´-0 ½˝,0´-0 ½˝>: prompt, enter a grid spacing in X,Y coordinates. You must enter the Gridunit value as an X,Y coordinate.

There are several other grid options in the Drafting Settings dialog box. The Grid Style group lets you display the grid as a series of dots instead of the graph-paper-style lines. Place a check by the view name where you want to display dots instead of grid lines.

In the Grid Spacing group, the Major Line Every option lets you control how frequently the major grid lines (lines that appear darker than the others) appear.

In the Grid Behavior group, the Adaptive Grid option adjusts the grid spacing depending on how much of the view is displayed. If you zoom out to a point where the grid becomes too dense to view the drawing, the grid automatically increases its interval. The Display Grid Beyond Limits check box lets you determine whether the grid displays outside the limits of the drawing.

Once you’ve set up your grid, you can press F-G to turn the grid on and off.

Using the Snap Modes

The Snap modes force the cursor to move in steps of a specific distance. Snap modes are useful when you want to select points on the screen at a fixed interval. Two snap modes are available in AutoCAD: Grid Snap and Polar Snap. You can click the Snap tool in the status bar to turn the Snap mode on and off. Follow these steps to access the Snap modes:

With Snap mode on, the cursor seems to move in steps rather than in a smooth motion. The Snap Mode tool in the status bar appears blue, indicating that Snap mode is on. Click the Snap Mode tool in the status bar to turn Snap mode on or off.

Note that you can use the Snapunit system variable to set the snap spacing. Enter Snapunit↵. Then, at the Enter new value for SNAPUNIT <0´0˝,0´0˝>: prompt, enter a snap distance value as an X,Y coordinate.

Take a moment to look at the Drafting Settings dialog box in Figure 3-25. The other option in the Snap Spacing group enables you to force the X and Y spacing to be equal (Equal X and Y Spacing).

In the Snap Type group, you can change the snap and grid configuration to aid in creating 2D isometric drawings by clicking the Isometric Snap radio button. The Polar Snap option enables you to set a snap distance for the Polar Snap feature. When you click the Polar Snap radio button, the Polar Distance option at the middle left of the dialog box changes from gray to black and white to allow you to enter a Polar Snap distance.

You can also set up the grid to follow the snap spacing automatically. To do this, set Grid X Spacing and Grid Y Spacing to 0 in the Snap Spacing group.

The Bottom Line

Set up a work area. A blank AutoCAD drawing offers few clues about the size of the area you’re working with, but you can get a rough idea of the area shown in the drawing window.

Master It Name two ways to set up the area of your work.

Explore the drawing process. To use AutoCAD effectively, you’ll want to know how the different tools work together to achieve an effect. The drawing process often involves many cycles of adding objects and then editing them.

Master It Name the tool that causes the cursor to point in an exact horizontal or vertical direction.

Plan and lay out a drawing. If you’ve ever had to draw a precise sketch with just a pencil and pad, you’ve probably used a set of lightly drawn guidelines to lay out your drawing first. You do the same thing in AutoCAD, but instead of lightly drawn guidelines, you can use any object you want. In AutoCAD, objects are easily modified or deleted, so you don’t have to be as careful when adding guidelines.

Master It What is the name of the feature that lets you select exact locations on objects?

Use the AutoCAD modes as drafting tools. The main reason for using AutoCAD is to produce precise technical drawings. AutoCAD offers many tools to help you produce a drawing with the precision you need.

Master It What dialog box lets you set both the grid and snap spacing?