Circles and Drawing Aids

DIXMC02_0131713884.qxd 8/29/05 12:21 PM Page 44 2 Circles and Drawing Aids COMMANDS CIRCLE ERASE OOPS SNAP DDRMODES GRID PLOT UNITS DIST HELP RECTANGLE OVERVIEW This chapter is loaded with new material and techniques. Here you begin to gain control of your drawing environment by changing the spacing of the grid and snap and the units in which coordinates are displayed. You add to your repertoire of objects by drawing circles with the CIRCLE command and rectangles with the REC- TANGLE command. You explore the many methods of object selection as you continue to learn editing procedures with the ERASE command. You gain access to convenient Help features and begin to learn AutoCAD s extensive plotting and printing procedures. TASKS 2.1 Changing the Grid Setting 2.9 Using the DIST Command 2.2 Changing the Snap Setting 2.10 Plotting or Printing a Drawing 2.3 Changing Units 2.11 Review Material 2.4 Drawing Circles Giving Center 2.12 WWW Exercise 2 (Optional) Point and Radius 2.13 Drawing 2-1: Aperture Wheel 2.5 Drawing Circles Giving Center 2.14 Drawing 2-2: Roller Point and Diameter 2.15 Drawing 2-3: Fan Bezel 2.6 Accessing AutoCAD Help Features 2.16 Drawing 2-4: Switch Plate 2.7 Using the ERASE Command 2.17 Drawing 2-5: Gasket 2.8 Using the RECTANGLE Command 44

DIXMC02_0131713884.qxd 8/29/05 12:21 PM Page 45 Chapter 2 Circles and Drawing Aids 45 2.1 Changing the Grid Setting GENERAL PROCEDURE 1. Type grid. 2. Enter a new value. When you begin a new drawing using the acad template, the grid and snap are set with a spacing of 0.5000. In Chapter 1, all drawings were completed without altering the grid and snap spacings from the default value. Usually you want to change this to a value that reflects your application. You might want a 10-mile snap for a mapping project, or a 0.010-inch snap for a printed circuit diagram. The grid can match the snap setting or can be set independently. To begin, open a new drawing by typing new or selecting New from the File menu. Check to see that acad is in the File name box and press Enter. Once again, this ensures that you begin with the settings we have used in preparing this chapter. Using F7 and F9, or clicking on the status bar, be sure that Grid and Snap are both on. Using the status bar, turn other modes off. Type z and press Enter to enter the ZOOM command. Type a to zoom all. Type grid. We will no longer remind you to press Enter after typing a command or response to a prompt. Do not use the pull-down menu or toolbar yet. We will get to those procedures momentarily. The command area prompt appears like this, with options separated by slashes (/): Specify grid spacing(x) or [ON/OFF/Snap/Aspect]<0.5000>: If dynamic input is on, you also see part of this prompt next to the crosshairs. You can ignore the options for now. The number <0.5000> shows the current setting. AutoCAD uses this format <default> in many command sequences to show you a current value or default setting. It usually comes at the end of a series of options. Pressing the Enter key or spacebar at this point confirms the default setting. In answer to the prompt, type 1 and watch what happens. (Of course, you remembered to press Enter.) The screen changes to show a 1-unit grid. Move the cursor around to observe the effects of the new grid setting. The snap setting has not changed, so you still have access to all half-unit points, but the grid shows only single-unit increments. Try other grid settings. Try 2, 0.25, and 0.125. Remember that you can repeat the last command, GRID, by pressing Enter or the spacebar. What happens when you try 0.05?

DIXMC02_0131713884.qxd 8/29/05 12:21 PM Page 46 46 Part I Basic Two-Dimensional Entities When you get too small (smaller than 0.07 on our screen), the grid becomes too dense to display and you see this message in the command area: Grid too dense to display Before going on to Task 2.2, set the grid back to 0.5000. 2.2 Changing the Snap Setting GENERAL PROCEDURE 1. Select Drafting Settings from the Tools pull-down menu, or right-click the Grid or Snap button and select Settings. 2. Enter a new snap value. 3. Click OK to exit the dialog box. The process for changing the snap setting is really the same as changing the grid, but we use the Drafting Settings dialog box this time. Grid and snap are similar enough to cause confusion. The grid is only a visual reference. It has no effect on selection of points. Snap is invisible, but it dramatically affects point selection. Grid and snap might or might not have the same setting. Using the Drafting Settings Dialog Box Snap can be changed using the SNAP command at the prompt, as we did with the GRID command in the last section. Both can also be changed in the Drafting Settings dialog box, as we do in this task. Type ds or open the Tools pull-down menu and click Drafting Settings, as shown in Figure 2-1. This opens the Drafting Settings dialog box shown in Figure 2-2. DSETTINGS is the command that calls up this dialog box, and ds is the command alias. Look at the dialog box. It contains some common features, including tabs, check boxes, radio buttons, and edit boxes. Tabs At the top of the dialog box, there is an arrangement that resembles a wellordered set of four tabbed index cards with the words Snap and Grid, Polar Tracking, Object Snap, and Dynamic Input on the tabs. Tabbed dialog boxes are common in Windows applications. With this tabbed arrangement, a single dialog box can provide organized access to a variety of related features. By clicking a tab, you can bring the related file card to the top of the stack so that it is visible in front of the others. We do not need to access the Polar Tracking, Object Snap, or Dynamic Input tabs at this time. If the Snap and Grid card is not on top, click its tab to bring it up. Check Boxes Below the tabs you will see check boxes labeled Snap On (F9) and Grid On (F7). You can turn snap and grid on and off by moving the arrow inside the appropriate

DIXMC02_0131713884.qxd 9/3/05 3:21 AM Page 47 Chapter 2 Circles and Drawing Aids 47 Figure 2-1 check box and pressing the pick button. A checked box is on and an empty box is off. In your dialog box, check boxes should show that both snap and grid are on. Panels On the Snap and Grid tab there are four bordered and labeled areas. Most dialog boxes are divided into sections in this way. We refer to these labeled sections as panels. They are also sometimes referred to as panes. The four panels here are Snap, Grid, Snap type & style, and Polar spacing. In this task, we look at the Snap and Grid panels only.

DIXMC02_0131713884.qxd 8/29/05 12:21 PM Page 48 48 Part I Basic Two-Dimensional Entities Figure 2-2 Edit Boxes The snap and grid settings are shown in edit boxes, labeled Snap X spacing, Snap Y spacing, Grid X spacing, and Grid Y spacing. Edit boxes contain text or numerical information that can be edited as you would in a text editor. You can highlight the entire box to replace the text, or point anywhere inside to do partial editing. To change the snap setting, do the following: Move the arrow into the edit box labeled Snap X spacing. Note: The dialog box has places to set both x and y spacing. It is unlikely that you want to have a grid or snap matrix with different horizontal and vertical increments, but the capacity is there if you do. Also notice that you can change the snap angle. Setting the snap angle to 45, for example, would turn your snap and grid at a 45-degree angle. When you alter the grid or snap angle, you might also want to designate x and y base points around which to rotate. This is the function of the x and y base point settings. Double-click to highlight the entire number 0.5000 in the Snap X spacing edit box. Type 1 and press Enter.

DIXMC02_0131713884.qxd 8/29/05 12:21 PM Page 49 Chapter 2 Circles and Drawing Aids 49 2.3 Changing Units Pressing Enter at this point is like clicking on OK in the dialog box. It takes you out of the dialog box and back to the screen. Snap is now set at 1 and grid is still at 0.5. This makes the snap setting larger than the grid setting. Move the cursor around the screen and you will see that you can only access half of the grid points. This type of arrangement is not too useful. Try some other settings. Tip: Another way to open the Drafting Settings dialog box is to right-click while pointing at the Grid or Snap button on the status bar. This opens a shortcut menu with On, Off, and Settings options. Selecting Settings opens the Drafting Settings dialog box. Open the dialog box again by right-clicking the Snap button on the status bar and then choosing Settings from the shortcut menu. Change the Snap X spacing value to 0.25. Move the cursor slowly and observe the coordinate display. This is a more efficient arrangement. With grid set coarser than snap, you can still pick exact points easily, but the grid is not so dense as to be distracting. Note: Commands that call dialog boxes, like other commands, can be repeated by pressing the spacebar or Enter. Press Enter to open the Drafting Settings dialog box again and set the snap to 0.05. Remember what happened when you tried to set the grid to 0.05? Move the cursor and watch the coordinate display. Observe how the snap setting is reflected in the available coordinates. How small a snap will AutoCAD accept? Try 0.005. Move the cursor and observe the coordinate display. Try 0.0005. You could even try 0.0001, but this would be like turning snap off, because the coordinate display is registering four decimal places anyway. Unlike the grid, which is limited by the size and resolution of your screen, you can set snap to any value you like. Finally, before you leave this task, set the snap back to 0.25 and leave the grid at 0.5. Tip: If you wish to keep snap and grid the same, set the grid to 0 in the Drafting Settings dialog box, or enter the GRID command and then type s for the Snap option. The grid then changes to match the snap and continues to change anytime you reset the snap. To free the grid, just give it its own value again using the GRID command or the dialog box. GENERAL PROCEDURE 1. Type Units, or select Units from the Format menu. 2. Answer the prompts.

DIXMC02_0131713884.qxd 8/29/05 12:21 PM Page 50 50 Part I Basic Two-Dimensional Entities Drop-Down Lists and the Drawing Units Dialog Box The Drawing Units dialog box makes use of drop-down lists, another common dialog box feature. Lists give you quick access to settings, files, and other items that are organized as a list of options. Type Units or select Units from the Format menu. This opens the Drawing Units dialog box shown in Figure 2-3. This fourpanel dialog box has five drop-down lists for specifying various characteristics of linear and angular drawing units, and a Sample Output area at the bottom. Drop-down lists show a current setting next to an arrow that is used to open the list of other possibilities. Your dialog box should show that the current Length Type in your drawing is decimal units precise to 0.0000 places, and Angle Type is decimal degrees with 0 places. Click on the arrow to the right of the word Decimal, under Type in the Length panel of the dialog box. A list drops down with the following options: Architectural Decimal Engineering Fractional Scientific Architectural units display feet and fractional inches ( 1-3 1 2 ), engineering units display feet and decimal inches ( 1-3.50 ), fractional units display Figure 2-3

DIXMC02_0131713884.qxd 8/29/05 12:21 PM Page 51 Chapter 2 Circles and Drawing Aids 51 15 1 2 units in a mixed number format ( ), and scientific units use exponential notation for the display of very large or very small numbers (1.55E 01). With the exception of engineering and architectural formats, these formats can be used with any basic unit of measurement. For example, decimal mode works for metric units as well as English units. Throughout most of this book, we stick to decimal units. Obviously, if you are designing a house you would use architectural units. If you are building a bridge, you might want engineering-style units. You might want to use scientific units if you are mapping subatomic particles. Whatever your application, once you know how to change units, you can do so at any time. However, as a drawing practice you should choose appropriate units when you first begin work on a new drawing. Click Decimal, or click anywhere outside the list box to close the list without changing the setting. Now we will change the precision setting to two-place decimals. Click the down arrow next to 0.0000 in the Precision list box in the Length panel. This opens a list with options ranging from 0 to 0.00000000, as shown in Figure 2-4. We use two-place decimals because they are practical and more common than any other choice. Run your cursor arrow down the list until 0.00 is highlighted, as shown in Figure 2-4. Figure 2-4

DIXMC02_0131713884.qxd 8/29/05 12:21 PM Page 52 52 Part I Basic Two-Dimensional Entities Click 0.00. The list closes and 0.00 replaces 0.0000 as the current precision for units of length. Notice that the Sample Output has also changed to reflect the new setting. The area to the right allows you to change the units in which angular measures, including polar coordinates, are displayed. If you open the Angle Type list, you see the following options: Decimal Degrees Deg/Min/Sec Grads Radians Surveyor s Unit The default system is standard decimal degrees with 0 decimal places, measured counterclockwise, with 0 being straight out to the right (3 o clock), 90 straight up (12 o clock), 180 to the left (9 o clock), and 270 straight down (6 o clock). Leave these settings alone. Check to see that you have two-place decimal units for length and zero-place decimal degree units for angles. Then click OK to close the dialog box. Tip: All dialog boxes can be moved on the screen by clicking the gray title area at the top of the dialog box, holding down the pick button, and dragging the box across the screen. 2.4 Drawing Circles Giving Center Point and Radius GENERAL PROCEDURE 1. Type c, select Circle from the Draw menu, or select the Circle tool from the Draw toolbar. 2. Pick a center point. 3. Enter or show a radius value. Circles can be drawn by giving AutoCAD a center point and a radius, a center point and a diameter, three points on the circle s circumference, two points that determine a diameter, or two tangent points on other objects and a radius. In this chapter, we use the first two options. We begin by drawing a circle with radius 3 and center at the point (6,5). Then we draw two smaller circles centered at the same point. Later we erase them using the ERASE command. Grid should be set to 0.5, snap to 0.25, and units to two-place decimal. Type c, select Circle from the Draw menu, or select the Circle tool from the Draw toolbar, illustrated in Figure 2-5.

DIXMC02_0131713884.qxd 8/29/05 12:21 PM Page 53 Chapter 2 Circles and Drawing Aids 53 Figure 2-5 The prompt that follows looks like this: Specify center point for circle or [3P/2P/Ttr (tan tan radius)]: Type coordinates or point to the center point of the circle you want to draw. In our case, it is the point (6,5). AutoCAD assumes that a radius or diameter will follow and shows the following prompt: Specify radius of circle or [Diameter]: If we type or point to a value now, AutoCAD takes it as a radius because that is the default. Move your cursor and observe the rubber band and dragged circle. If your dynamic input display is not on, turn it on by pressing F12 or by clicking the Dyn button. Dynamic input is a great feature for drawing circles. It will give you the radius or diameter of the circle you are drawing. Watch the dynamic input display and move the crosshairs 3.00 away from the center point. With snap on, you will find that you can only move exactly 3.00 if you are at 0, 90, 180, or 270 degrees.

DIXMC02_0131713884.qxd 8/29/05 12:21 PM Page 54 54 Part I Basic Two-Dimensional Entities Figure 2-6 If your coordinate display is not showing polar coordinates, click it once or twice or press F6 until you see something like 3.00 0,000 Move the crosshairs 3.00 away from the center point in any direction. Press the pick button to show the radius endpoint at a distance of 3.00 from the center. Your first circle should now be complete. Draw two more circles using the same center point, radius method. They should be centered at (6,5) and have radii of 2.50 and 2.00. The results are illustrated in Figure 2-6. 2.5 Drawing Circles Giving Center Point and Diameter GENERAL PROCEDURE 1. Type c, select Circle from the Draw menu, or select the Circle tool from the Draw toolbar. 2. Pick a center point. 3. Type d. 4. Enter or show a diameter value. We will draw three more circles centered on (6,5) having diameters of 1, 1.5, and 2. This method of drawing circles is almost the same as the radius method, except you do not use the default, and you will see that the rubber band and dynamic input display work differently. Press Enter or the spacebar to repeat the CIRCLE command. Indicate the center point (6,5) by typing coordinates or pointing. Answer the prompt by typing d for diameter. Move the crosshairs away from the center point.

DIXMC02_0131713884.qxd 8/29/05 12:21 PM Page 55 Chapter 2 Circles and Drawing Aids 55 Figure 2-7 Figure 2-8 Notice that the crosshairs are now outside the circle you are dragging on the screen (see Figure 2-7). This is because AutoCAD is looking for a diameter, but the last point you gave was a center point. So the diameter is being measured from the center point out, twice the radius. Also notice that the dynamic input display has responded to the diameter specification and is now measuring the distance across the circle. Move the cursor around, in and out from the center point, to get a feel for this. Point to a diameter of 1.00, or type 1. You should now have four circles. Draw two more circles with diameters of 1.50 and 2.00. When you are done, your screen should look like Figure 2-8. Studying Figure 2-9 and using the HELP command, as discussed in the next task, give you a good introduction to the remaining options in the CIRCLE command.

DIXMC02_0131713884.qxd 8/29/05 12:21 PM Page 56 56 Part I Basic Two-Dimensional Entities 2.6 Accessing AutoCAD Help Features Figure 2-9 Tip: Here are two ways to stay heads-up and avoid going to the keyboard to type d for the diameter option: (1) After entering the CIRCLE command and picking a center point, right-click to open a shortcut menu with the options Enter, Cancel, Diameter, Pan, and Zoom. Select Diameter. (2) If you enter the CIRCLE command from the Draw pull-down menu and select one of the options on the submenu, some of the command steps are automated. For example, if you select the Center, Diameter option, the command behaves as if Diameter is the default and you do not have to enter a d. GENERAL PROCEDURE 1. Press F1 or open the Help menu and select Help. 2. Click the Index tab. 3. Type the name of a command or topic. 4. Highlight the item you want. 5. Press Enter or click Display.

DIXMC02_0131713884.qxd 8/29/05 12:21 PM Page 57 Chapter 2 Circles and Drawing Aids 57 The AutoCAD HELP command gives you access to an extraordinary amount of information in a comprehensive library of AutoCAD references and information. The procedures for using HELP are standard Windows procedures and access the User s Guide, the Command Reference, the AutoCAD Driver and Peripheral Guide, the Installation and Licensing Guide, and the Customization Guide. In this task, we focus on the use of the Index feature, which pulls information from all the references, depending on the topic you select. For a demonstration, we look for further information on the CIRCLE command. To begin you should be at the command prompt. HELP is context sensitive; it goes directly to the AutoCAD Command Reference if you ask for help while in the middle of a command sequence. You should try this later. Press F1 or open the Help menu and select Help. This opens the AutoCAD Help dialog box shown in Figure 2-10. If the Contents tab is showing, you see the list of available references. You can browse through the contents of each reference but it is usually quicker to use the Index tab. You also see a Search tab and an Ask Me tab. Search is similar to index, but does not show you a list of topics until after you enter words as a search criterion. Ask Me is another way of searching for information. Instead of entering search words, you type questions or issues and Ask Me lists relevant pages. Figure 2-10

DIXMC02_0131713884.qxd 8/29/05 12:21 PM Page 58 58 Part I Basic Two-Dimensional Entities Figure 2-11 If necessary, click the Index tab. You should see the Index as shown in Figure 2-10. The list of topics is very long, so it is rare that you use the scroll bar on the right. Most often you type in a command or topic. The list updates as you type, so you might not need to type the complete word or command. Type Ci. Do this slowly, one letter at a time, and you can see how the index follows along. When you have typed ci, the list shows entries beginning with Circle. Adding the rest of the letters rcle has no further effect. Double-click CIRCLE command. This opens a second smaller dialog box with two options, as shown in Figure 2-11. We want the first option. Double-click CIRCLE again, press Enter, or click Display. AutoCAD displays the CIRCLE command page from the AutoCAD Command Reference, as shown in Figure 2-12. Links to additional information on items on this page are available for words underlined and shown in bold. Click Ttr (tan tan radius). This adds the information for the Tangent, Tangent, Radius option of the CIRCLE command, shown in Figure 2-13. Note: If you click the link that says Display all hidden text on this page, you open a complete discussion of the CIRCLE command and all of its options. Try it. Concepts, Procedures, and Commands Before leaving the Help dialog box, notice the three tabs at the top of the Command Reference page, labeled Concepts, Procedures, and Commands. These give you access to further discussion of the command or topic you have reached through the index. For example, consider the following: Click the Concept tab.

DIXMC02_0131713884.qxd 8/29/05 12:21 PM Page 59 Chapter 2 Circles and Drawing Aids 59 Figure 2-12 Figure 2-13

DIXMC02_0131713884.qxd 8/29/05 12:21 PM Page 60 60 Part I Basic Two-Dimensional Entities Figure 2-14 This calls up a page of discussion of concepts related to the topic you have chosen, in this case, drawing circles, as shown in Figure 2-14. The Procedures tab takes you to general procedures lists that are similar to the ones we use at the beginning of many of the sections in this book. Try it. The Commands tab shows you glossary-like entries for commands and system variables relating to the topic you have chosen. Try that, too. To exit Help, click on the Close button, the X in the upper right corner of the Help window. This terminates the HELP command and brings you back to the command prompt. 2.7 Using the ERASE Command GENERAL PROCEDURE 1. Type e or select the Erase tool from the Modify toolbar. 2. Select objects. 3. Press Enter to carry out the command. or 1. Select objects. 2. Type e or select the Erase tool from the Modify toolbar.

DIXMC02_0131713884.qxd 8/29/05 12:21 PM Page 61 Chapter 2 Circles and Drawing Aids 61 AutoCAD allows for many different methods of editing and even allows you to alter some of the basics of how edit commands work. Fundamentally, there are two different sequences for using most edit commands. These are called the noun/verb and the verb/noun methods. In earlier versions of AutoCAD, most editing was carried out in a verb/noun sequence. That is, you would enter a command, such as ERASE (the verb), then select objects (the nouns), and press Enter to carry out the command. This method is still effective, but AutoCAD also allows you to reverse the verb/noun sequence. You can use either method as long as noun/verb selection is enabled in your drawing. In this task, we explore the traditional verb/noun sequence and then introduce the noun/verb or pick first method along with some of the many methods for selecting objects. Verb/Noun Editing To begin this task you should have the six circles on your screen, as shown previously in Figure 2-8. We use verb/noun editing to erase the two outer circles. Type e or select the Erase tool from the Modify toolbar, as shown in Figure 2-15. Erase can also be found on the Modify menu, but the other methods are more efficient. The crosshairs disappear, but the pick box is still on the screen and it moves when you move your cursor. In the command area and the dynamic input display you see the prompt Select objects: This is a very common prompt. You will find it in all edit commands and many other commands as well. Move your cursor so that the outer circle crosses the pick box. The outer circle will darken. This is the rollover preview introduced in Chapter 1. Tip: In many situations, you might find it convenient or necessary to turn snap off (press F9) while selecting objects because this gives you more freedom of motion. Press the pick button. The circle will be highlighted (dotted). This is how AutoCAD indicates that an object has been selected for editing. It is not yet erased, however. You Figure 2-15

DIXMC02_0131713884.qxd 8/29/05 12:21 PM Page 62 62 Part I Basic Two-Dimensional Entities can go on and add more objects to the selection set and they, too, will become dotted. Use the box to pick the second circle moving in toward the center. It too should now be dotted. Press Enter, the spacebar, or the right button on your pointing device to carry out the command. This is typical of the verb/noun sequence in most edit commands. Once a command has been entered and a selection set defined, a press of the Enter key is required to complete the command. At this point the two outer circles should be erased. Tip: In verb/noun edit command procedures where the last step is to press Enter to complete the command, it is good heads-up practice to use the right button on your mouse in place of the spacebar or Enter key. Noun/Verb Editing Now let s try the noun/verb sequence. Type u to undo the ERASE command and bring back the circles. Use the pick box to select the outer circle. The circle is highlighted, and your screen should now resemble Figure 2-16. Those little blue boxes are called grips. They are part of AutoCAD s autoediting system, which we begin exploring in Chapter 3. For now, you can ignore them. Pick the second circle in the same fashion. The second circle also becomes dotted, and more grips appear. Type e or select the Erase tool from the Modify toolbar. Your two outer circles disappear as soon as you press Enter or pick the tool. Note that in this sequence the right mouse button calls a shortcut menu, so you should avoid it unless you have use for the options on the menu. Also note that you can use the Delete key on your keyboard in place of typing e. Figure 2-16

DIXMC02_0131713884.qxd 8/29/05 12:21 PM Page 63 Chapter 2 Circles and Drawing Aids 63 The two outer circles should now be gone. As you can see, there is not a lot of difference between the two sequences. One difference that is not immediately apparent is that there are numerous selection methods available in the verb/noun system that cannot be activated when you pick objects first. We cover other object selection methods momentarily, but first try the OOPS command. OOPS Type oops and watch the screen. If you have made a mistake in your erasure, you can get your selection set back by typing oops. OOPS is to ERASE as REDO is to UNDO. You can use OOPS to undo an ERASE command, as long as you have not performed another ERASE in the meantime. In other words, AutoCAD only saves your most recent ERASE selection set. You can also use U to undo an ERASE, but notice the difference: U simply undoes the last command, whatever it might be; OOPS works specifically with ERASE to recall the last set of erased objects. If you have drawn other objects in the meantime, you can still use OOPS to recall a previously erased set. However, if you tried to use U, you would have to backtrack, undoing any newly drawn objects along the way. Other Object Selection Methods You can select individual entities on the screen by pointing to them one by one, as we have done previously, but in complex drawings this is often inefficient. Auto- CAD offers a variety of other methods, all of which have applications in specific drawing circumstances. In this exercise, we select circles by the windowing and crossing methods, by indicating last or L, meaning the last entity drawn, and by indicating previous or P for the previously defined set. There are also options to add or remove objects from the selection set and other variations on windowing and crossing. We suggest that you study Figure 2-17 to learn about other methods. The number of selection options available might seem a bit overwhelming at first, but time learning them is well spent. These same options appear in many AutoCAD editing commands (MOVE, COPY, ARRAY, ROTATE, MIRROR) and should become part of your CAD vocabulary. Selection by Window The object selection window was demonstrated in Chapter 1. Now we put it to use. Window and crossing selections, like individual object selection, can be initiated without entering a command. In other words, they are available for noun/verb selection. Whether you select objects first or enter a command first, you can force a window or crossing selection simply by picking points on the screen that are not on objects. AutoCAD assumes you want to select by windowing or crossing and asks for a second point. Let s try it. We will show AutoCAD that we want to erase all of the inner circles by throwing a temporary selection window around them. The window is defined by two points moving left to right that serve as opposite corners of a

DIXMC02_0131713884.qxd 8/29/05 12:21 PM Page 64 64 Part I Basic Two-Dimensional Entities Figure 2-17 rectangular window. Only entities that lie completely within the window are selected (see Figure 2-18). Pick point 1 at the lower left of the screen, as shown. Any point in the neighborhood of (3.5,1) will do. AutoCAD prompts for another corner: Specify opposite corner: Pick point 2 at the upper right of the screen, as shown. Any point in the neighborhood of (9.5,8.5) will do. To see the effect of the window, be sure that it crosses the outside circle, as shown in Figure 2-18.

DIXMC02_0131713884.qxd 8/29/05 12:21 PM Page 65 Chapter 2 Circles and Drawing Aids 65 Figure 2-18 Type e or select the Erase tool. The inner circles should now be erased. Type oops to retrieve the circles once more. Because ERASE was the last command, typing u or selecting the Undo tool also works. Selection by Crossing Window Crossing is an alternative to windowing that is useful in many cases where a standard window selection could not be performed. The selection procedure is the same, but a crossing box opens to the left instead of to the right and all objects that cross the box are chosen, not just those that lie completely inside the box. We use a crossing box to select the inside circles. Pick point 1 close to (8.0,3.0), as in Figure 2-19. Figure 2-19

DIXMC02_0131713884.qxd 8/29/05 12:21 PM Page 66 66 Part I Basic Two-Dimensional Entities AutoCAD then prompts Specify opposite corner: Pick a point near (4.0,7.0). This point selection must be done carefully to demonstrate a crossing selection. Notice that the crossing box is shown with dashed lines and a green color, whereas the window box was shown with solid lines and a lavender color. Also, notice how the circles are selected: those that cross and those that are completely contained within the crossing box, but not those that lie outside. At this point we could enter the ERASE command to erase the circles, but instead we demonstrate how to use the Esc key to cancel a selection set. Press the Esc key on your keyboard. This cancels the selection set. The circles are no longer highlighted and the grips disappear. Selecting the Last Entity AutoCAD remembers the order in which new objects have been drawn during the course of a single drawing session. As long as you do not close the drawing, you can select the last drawn entity using the last option. Type e or select the Erase tool. Notice that there is no way to specify last before you enter a command. This option is only available as part of a command procedure. In other words, it only works in a verb/noun sequence. Type L. One of the smaller circles should be highlighted. Press Enter to carry out the command. The circle should be erased. Selecting the Previous Selection Set The P or previous option works with the same procedure, but it selects the previous selection set rather than the last drawn entity. If the difference is not obvious to you now, don t worry; it will become clear as you work more with edit commands and selection sets. Remove and Add Together, the remove and add options form a switch in the object selection process. Under ordinary circumstances, whatever you select using any of the aforementioned options is added to your selection set. By typing r at the Select objects: prompt you can switch to a mode in which everything you pick is deselected or removed from the selection set. Then by typing a you can return to the usual mode of adding objects to the set. Undoing a Selection The ERASE command and other edit commands have an internal undo feature, similar to that found in the LINE command. By typing u at the Select objects:

DIXMC02_0131713884.qxd 8/29/05 12:22 PM Page 67 Chapter 2 Circles and Drawing Aids 67 prompt you can undo your last selection without leaving the edit command you are in and without undoing previous selections. You can also type u several times to undo your most recent selections one by one. This allows you to back up one step at a time without canceling the command and starting all over again. Other Options If you press any key other than the ones AutoCAD recognizes, at the Select objects: prompt, you see the following: Expects a point or Window/Last/Crossing/Box/All/Fence/WPolygon/CPolygon/Group/Class /Add/Remove/Multiple/Previous/Undo/AUto/SIngle Select objects: Along with the options already discussed, All, Fence, WPolygon, and CPolygon are shown in Figure 2-17. Box, Multiple, AUto, and SIngle are used primarily in programming customized applications. Look up the SELECT command in the AutoCAD Help index for additional information. 2.8 Using the RECTANGLE Command GENERAL PROCEDURE 1. Select the Rectangle tool from the Draw toolbar. 2. Pick the first corner point. 3. Pick another corner point. Now that you have created object selection windows, the RECTANGLE command comes naturally. Creating a rectangle in this way is just like creating an object selection window. To prepare for this exercise, erase all objects from your screen. Select the Rectangle tool from the Draw toolbar, as shown in Figure 2-20. AutoCAD prompts for a corner point: Specify first corner point or [Chamfer/Elevation/Fillet/Thickness/Width]: You can ignore the options for now and proceed with the defaults. Figure 2-20

DIXMC02_0131713884.qxd 8/29/05 12:22 PM Page 68 68 Part I Basic Two-Dimensional Entities Figure 2-21 Pick (3.00,3.00) for the first corner point, as shown in Figure 2-21. AutoCAD prompts for another point: Specify other corner point: Notice how the coordinate display and dynamic display work differently after you have entered the command. The coordinate display continues to show absolute coordinates relative to the screen grid. Dynamic input shows values relative to the first corner point of the rectangle so that you can see the dimensions of the rectangle you are drawing. Pick a second point to create a 6 3 rectangle. The dynamic input display will show 6.00 and 3.00, while the coordinate display will show that the second corner point is at (9.00,6.00), as shown in Figure 2-21. Pick (9.00,6.00) for a second corner point, as shown in Figure 2-21. As soon as you enter the second corner, AutoCAD draws a rectangle between the two corner points and returns you to the command prompt. This is a faster way to draw a rectangle than drawing it line by line. There are also some other advantages that we examine in Chapter 3. Leave the rectangle on your screen for the plotting demonstration in Task 2.10. 2.9 Using the DIST Command GENERAL PROCEDURE 1. Open the Tools menu, highlight Inquiry, and select Distance. 2. Pick a first point. 3. Pick a second point. 4. Read the information in the command area.

DIXMC02_0131713884.qxd 8/29/05 12:22 PM Page 69 Chapter 2 Circles and Drawing Aids 69 The DIST command is one of AutoCAD s most useful inquiry commands. Inquiry commands give you information about your drawing or objects within it. DIST works like a simple LINE command procedure, but it gives you distances instead of actually drawing a line. Let us say that you need to know the distance from corner point 1 to corner point 2, the diagonal in the rectangle you just drew. Try the following: Select Inquiry and then Distance from the Tools menu, as shown in Figure 2-22. AutoCAD prompts you to pick a point: Specify first point: Pick (3,3) again. Notice that AutoCAD gives you a rubber band, just as if you were drawing a line. You are also prompted for a second point: Specify second point: Figure 2-22

DIXMC02_0131713884.qxd 8/29/05 12:22 PM Page 70 70 Part I Basic Two-Dimensional Entities Figure 2-23 Pick (9,6) again. You are returned to the command prompt and no line is drawn between the two points. However, you should see something like this in the command prompt area: Distance 6.71 Angle in XY Plane 27, Angle from XY Plane 0 Delta X 6.00, Delta Y 3.00, Delta Z 0.00 All this information can be useful, depending on the situation. Distance gives the straight-line distance between the two selected points. Angle in XY Plane gives the angle that a line between the two points would make within the coordinate system in which 0 degrees represents a horizontal line out to the right. Angle from XY Plane is a 3-D feature and is always 0 in 2-D drawings. Delta X is the horizontal displacement, which can be either positive or negative. Similarly, Delta Y is the vertical displacement. Delta Z is the displacement in the z direction. It is always 0 until we begin to explore AutoCAD s 3-D drawing capabilities in Chapter 12. Compare what is in your command prompt area with Figure 2-23. 2.10 Plotting or Printing a Drawing GENERAL PROCEDURE 1. Type Ctrl P, select the Plot tool from the Standard toolbar, or select Plot from the File menu. 2. Click Window. 3. Pick two points to define a window. 4. See that Fit to paper is showing in the Scale list box. 5. Prepare printer or plotter. 6. Click OK.

DIXMC02_0131713884.qxd 8/29/05 12:22 PM Page 71 Chapter 2 Circles and Drawing Aids 71 Figure 2-24 AutoCAD s printing and plotting capabilities are extensive and complex. In this book, we introduce you to them a little at a time. We try to keep you moving and get your drawing on paper as efficiently as possible. You will find discussions of plotting and printing in Chapters 2 through 8, before the review material and drawings in each chapter. Plotting and printing in AutoCAD requires that you understand the relationships among model space, paper space, plot styles, page setups, and layouts. All these concepts are introduced as you need them. In this chapter, we perform the simplest type of plot, going directly from your current model space objects to a sheet of drawing paper, changing only one or two plot settings. Different types of plotters and printers work somewhat differently, but the procedure we use here should achieve reasonably uniform results. It assumes that you do not have to change devices or fundamental configuration details. It should work for all plotters and printers and the drawings in this chapter. We use a window selection to define a plot area and scale this to fit on whatever size paper is in your plotter or printer. Type Ctrl P, or select Plot from the File menu or the Plot tool from the Standard toolbar, as shown in Figure 2-24. Any of these methods opens the Plot dialog box illustrated in Figure 2-25. You will become very familiar with it as you work through this book. It is one of the most important working spaces in AutoCAD. It contains many options and can be expanded to allow even more options by clicking the button at the bottom right. (If your dialog box is already expanded, you can reduce it by clicking the button.) In this exercise we will need only two settings. But first, you need to specify a plotter or printer. The second panel from the top is the Printer/plotter selection area. Look to see if the name of a plotting device is showing in the Name list box. If None is displayed in the list box, click the arrow on the right and select a plotter or printer. Now look at the panel labeled Plot area at the lower left. The drop-down list labeled What to plot gives you the choice of plotting based on what is on the Display, the Extents or Limits of the drawing, or a Window you define. For our purposes, defining a window gives more consistent results than relying on the Display area, which might differ more from one system to another. Windowing allows you to plot any portion of a drawing by defining a window in the usual way. AutoCAD bases the size and placement of the plot on the window you define. Before creating the plot area window, look at the Plot scale panel in the center of the dialog box. In the Scale list box, locate the Fit to paper check box. If your plot scale is configured to plot to fit your paper, as it should be by default, then AutoCAD plots your drawing at maximum size based on the paper size and the window you specify.

DIXMC02_0131713884.qxd 9/3/05 2:56 AM Page 72 72 Part I Basic Two-Dimensional Entities Figure 2-25 If for any reason Fit to paper is not checked, click in the box to check it. On the Custom line below Plot scale, you should see edit boxes with numbers like 1 4.768. Right now the plot area is based on the shape of your display area and these numbers are inaccessible. When you use a window to create a plot area that is somewhat smaller, these scale numbers change automatically. When you use Scales rather than Fit to paper, these numbers will be accessible and you can set them manually or select from a list. Select Window in the What to plot list. The Plot dialog box disappears temporarily, giving you access to the drawing. You will see the crosshairs, but the pick box is absent. AutoCAD prompts for point selection: Specify window for printing Specify first corner:

DIXMC02_0131713884.qxd 8/29/05 12:22 PM Page 73 Chapter 2 Circles and Drawing Aids 73 Figure 2-26 Select the point (1.00,1.00), as shown in Figure 2-26. AutoCAD prompts Specify opposite corner: Select the point (11.00,8.00), as shown in Figure 2-26. As soon as you have picked the second point, AutoCAD displays the Plot dialog box again with two changes. First, the Window radio button is now accessible and selected. Second, the Plot scale ratio changes to something like 1 0.9533. We use the phrase something like because there might be minor variations depending on your plotter. You are now ready to plot. If you want to plot or print the rectangle, prepare your plotter and then click OK. Otherwise, click Cancel. Clicking OK sends the drawing information to be printed. You can sit back and watch the plotter at work. If you need to cancel for any reason, click Cancel. For now, that s all there is to it. If your plot does not look perfect if it is not centered on your drawing sheet, for example don t worry; you will learn all you need to know about plotting in later chapters. 2.11 Review Material Questions 1. Which is likely to have the smaller setting, Grid or Snap? Why? What happens if the settings are reversed? 2. Name three ways to open the Drafting Settings dialog box. 3. How do you switch from decimal units to architectural units? 4. Where is 0 degrees located in AutoCAD s default units setup? Where is 270 degrees? Where is 45 degrees? 5. How do you enter the CIRCLE command? 6. Why does the rubber band touch the circumference of the circle when you are using the radius option, but not when you are using the diameter option?

DIXMC02_0131713884.qxd 8/29/05 12:22 PM Page 74 74 Part I Basic Two-Dimensional Entities 7. What does the dynamic input display show when you are drawing a circle using a diameter dimension? 8. What does the dynamic input display show when you are selecting the second point of a rectangle in the RECTANGLE command? 9. How does AutoCAD know when you want a crossing selection instead of a window selection? 10. What is the difference between a Last selection and a Previous selection? 11. What is the difference between noun/verb and verb/noun editing? 12. How do you access the AutoCAD Help index? Drawing Problems 1. Leave the grid at 0.50 and set snap to 0.25. 2. Use the 3P option to draw a circle that passes through the points (2.25,4.25), (3.25,5.25), and (4.25,4.25). 3. Using the 2P option, draw a second circle with a diameter from (3.25,4.25) to (4.25,4.25). 4. Draw a third circle centered at (5.25,4.25) with a radius of 1.00. 5. Draw a fourth circle centered at (4.75,4.25) with a diameter of 1.00. 2.12 WWW Exercise 2 (Optional) In this second voyage to the World Wide Web, we show you how to change the default Uniform Resource Locator (URL) so that you don t have to type a long, ugly address every time you go out to the Web. We show you how to change the default Web location to the companion website for this book. Of course the general procedure works just as well with any other legitimate Web address or file on your computer. Whether or not you actually want to retain our website as the default, we encourage you to go there now, take the self-scoring review test, and try the Web project. Type inetlocation at the command prompt. INETLOCATION is a system variable that stores the name of the default URL. AutoCAD prompts Enter new value for inetlocation <http:www.autodesk.com>: Remember that the address within the arrows is the current default. This value is replaced by the address you enter. Type www.prenhall.com/dixriley. The new value is stored, and AutoCAD returns you to the command prompt. Now all you need to do is enter the BROWSER command and press Enter at the prompt. Type browser. The AutoCAD prompt shows the new default URL: Enter web location (URL) <prenhall.com/dixriley>: Press Enter to accept the default location. Away you go. Good luck on the test.

DIXMC02_0131713884.qxd 8/29/05 12:22 PM Page 75 Chapter 2 Circles and Drawing Aids 75 2.13 Drawing 2-1: Aperture Wheel This drawing gives you practice creating circles using the center point, radius method. Refer to the table following the drawing for radius sizes. With snap set at 0.25, some of the circles can be drawn by pointing and dragging. Other circles have radii that are not on a snap point. These circles can be drawn by typing in the radius. Drawing Suggestions GRID 0.50 SNAP 0.25 A good sequence for doing this drawing would be to draw the outer circle first, followed by the two inner circles (h and c) in Drawing 2-1. These are all centered on the point (6.00,4.50). Then begin at circle a and work around clockwise, being sure to center each circle correctly. Notice that there are two circles c and two h. The two circles having the same letter are the same size. Remember, you can type any value you like, and AutoCAD gives you a precise graphic image. However, you cannot always show the exact point you want by pointing. Often it is more efficient to type a few values than to turn Snap off or change its setting for a small number of objects.

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DIXMC02_0131713884.qxd 8/29/05 12:22 PM Page 77 Chapter 2 Circles and Drawing Aids 77 2.14 Drawing 2-2: Roller This drawing gives you a chance to combine lines and circles and to use the center point, diameter method. It also gives you some experience with smaller objects, a denser grid, and a tighter snap spacing. Tip: Even though units are set to show only two decimal places, it is important to set the snap using three places (0.125) so that the grid is on a multiple of the snap (0.25 2 0.125). AutoCAD shows you rounded coordinate values, like 0.13, but keeps the graphics on target. Try setting snap to either 0.13 or 0.12 instead of 0.125, and you will see the problem for yourself. Drawing Suggestions GRID 0.25 SNAP 0.125 The two views of the roller appear fairly small on your screen, making the snap setting essential. Watch the coordinate display as you work and get used to the smaller range of motion. Choosing an efficient sequence makes this drawing much easier to complete. Because the two views must line up properly, we suggest that you draw the front view first, with circles of diameter 0.25 and 1.00, and then use these circles to position the lines in the right side view. The circles in the front view should be centered in the neighborhood of (2.00,6.00). This puts the upper left-hand corner of the 1 1 square at around (5.50,6.50).

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DIXMC02_0131713884.qxd 8/29/05 12:22 PM Page 79 Chapter 2 Circles and Drawing Aids 79 2.15 Drawing 2-3: Fan Bezel This drawing should be easy for you at this point. Set grid to 0.50 and snap to 0.125 as suggested, and everything falls into place nicely. Drawing Suggestions GRID 0.50 SNAP 0.125 Notice that the outer figure in Drawing 2-3 is a 6 6 square and that you are given diameters for the circles. You should start with the lower left-hand corner of the square somewhere near the point (3.00,2.00) if you want to keep the drawing centered on your screen. Be careful to center the large inner circle within the square.