Constructions. C Using Offset to Draw Parallel Lines and Curves J

Geometric Constructions Learning Objectives After completing this chapter, yon will he able to do thefollowing: / Use the OFFSET command to draw parallel lines and curves. / Divide existing objects into equal lengths using the DIVIDE command. / Use the MEASURE command to set designated increments on an existing object. / Create orthographic multiview drawings. / Adjust UCS settings to construct auxiliary views. / Use construction lines to assist in drawing orthographic views and auxiliary views. This chapter explains how to create parallel offset copies, divide objects, and place point objects. These skills, and the other geometry-creating skills you have acquired, are applied in the creation of multiview drawings. C Using Offset to Draw Parallel Lines and Curves J The OFFSET command is used to draw concentric circles, concentric arcs, concen tric curves, parallel polylines, and parallel lines. This command is accessed by picking the Offset button in the Modify toolbar or the 2D Draw control panel of the Dashboard, picking Modify > Offset, or typing O or OFFSET. Specifying a Distance to Offset The simplest way to use the OFFSET command is to enter an offset value at the Specify offset distance or [Through/Erase/Layer] <current>: prompt. The last offset distance used is the default and is shown in brackets. Forexample, if you want to draw two parallel circles a distance of.1 unit apart, use the following command sequence. See Figure 8-1. Command: O or OFFSETJ Current settings: Erase source=cnrrent Layer=current OFFSETGAPTYPE=current Specify offset distance or [Through/Erase/Layer] <cnrrent>:.u Select object to offset or [Exit/Undo] <cnrrent>: (pick the object) Specify point on side to offset or [Exit/Multiple/Undo] <cnrrent>: (pick the side ofthe object on which the offset will be drawn) Select object to offset or [Exit/Undo] <current>: (select another object orpress [Enter]) Command: 2D Draw OFFSET > Offset Modify Offset BE Modify > Offset Through Layer Multiple H LJ C/) U_ 245

Figure 8-1. Drawing an offset using a designated distance. Pick box Pick side to offset / Select Object Side to Offset Offset If you do not know the offset value, but two reference points exist in the drawing area, you can pick a first point and then a second point instead of typing in an offset value. The distance between these two points is used as the offset value. When the Select object to offset or [Exit/Undo] <current>: prompt first appears, the cursor turns into a pick box. After the object is picked, the cursor turns back into crosshairs. No other selection option (such as window or crossing) works with the OFFSET command. The other option is to pick a point through which the offset is drawn. Type T, as follows, to produce the results shown in Figure 8-2: Command: O or OFFSETJ Current settings: Erase source=current Layer=current OFFSETGAPTYPE=a<rrenf Specify offset distance or [Through/Erase/Layer] <current>: TJ Select object to offset or [Exit/Undo] <current>: (pick the object) Specify through point or [Exit/Multiple/Undo] <current>: (pick the point through which the offset will be drawn) Select object to offset or [Exit/Undo] <current>: J Command: Object snap modes can be used to assist in specifying the offset distance. For example, suppose you have a circle and a line and want to draw a concentric circle tangent to the line. Refer to Figure 8-3 and the following command sequence: Command: O or OFFSETJ Current settings: Erase source=current Layer=current OFFSETGAPTYPE=n/rre/7f Specify offset distance or [Through/Erase/Layer] <current>: QUAJ of (pick the existing circle) Specify second point: PERJ to (pick the existing line) Select object to offset or [Exit/Undo] <current>: (pick the existing circle) Specify point on side to offset or [Exit/Multiple/Undo] <current>: (pick between the circle and line) Select object to offset or [Exit/Undo] <current>: J Command: Figure 8-2. Drawing an offset through a given point. Pick box Pick through V point Select Object Through Point 246 AutoCAD and Its Applications Basics

Figure 8-3. Using OFFSET to draw a concentric circle tangent to a line. Origins circle \L PER Side to offset QUA Select the object to offset A Erasing the Original Object When an object is being offset, you may want to remove the original object. Instead of offsetting the object and then erasing the source object, you can erase the source objectwhen it is offset.after initiating the OFFSET command, select Erase and Yes from the shortcut menu to erase the source object. TheYes option remains as the default until it is changed to No. Be sure to change this option back to No if you do not want the source offset object to be erased the next time the OFFSET command is used. Changing the Layer of the Offset Object The Layer option allows you to have the offset object placed on the current layer. For example, if the offset source object resides on the Electrical layer and the offset object needs to be placedon the Lighting layer, this can be done during the command if Lighting is the current layer by following this command sequence: Command: O or OFFSETJ Current settings: Erase source=current Layer=current OFFSETGAPTYPE=cnrrent Specify offset distance or [Through/Erase/Layer] <current>: I i Enter layer option for offset objects [Current/Source] <current>: CJ Specify offset distance or [Through/Erase/Layer] <current>: When Current is specified, the offset object is placed on the current layer. To have the offset object remain on the same layer as the offset source object, use the Source option. Offsetting Multiple Times After the object to offset has been selected, the Multiple option can be used to offset an object more than once with the same distance between the objects without having to reselect the objectto offset. Initiate the OFFSET command, specify the offset distance, and pick the source object. You can then select Multiple and begin picking to specify the offset direction. See Figure 8-4. Whenever the Undo option is available, it can be used to undo the last offset without exiting the command. Using the Exitoption by typing Eor Exit, pressing [Enter], or right-clicking exits the OFFSET command. Exercise 8-1 Complete the exercise on the Student CD. Chapter 8 Geometric Constructions 247

Figure 8-4. The Multiple option can be use to create multiple offsets with the same distance, without picking the source object again.,4,,4,,j, 1 c Drawing Points i- z o 0. POINT PO 2D Draw > Point Draw > Point Point DDPTYPE Format > Point Style. Points are useful for identifying specific locations on a drawing and, as you will see in the next section,for marking positions on objects. You can draw points anywhere on the screen using the POINT command. To access this command, pick the Point button from the Draw toolbar or from the 2D Draw control panel in the Dashboard, type PO or POINT, or select Draw > Point and one of the options. You can pick or type coordinates to place the points. If you need to place only a single point object, use the keyboard command or select the Single Point option from the Point cascading menu. If you need to draw multiple points, use the Point button on the Draw toolbar or the Multiple Point option from the Point cascading menu. Press [Esc] to exit the command. Setting Point Style The style and size of points are set using the Point Style dialog box. See Figure 8-5. This dialog box is accessed by selecting Format > Point Style... or by typing DDPTYPE. The Point Style dialog box contains twenty different point styles. The current point style is highlighted. To change the style, simply pick the graphic image of the desired style. Figure 8-5. The Point Style dialog box. This is a quick way to select the point style and change the point size. Pick to - change style IPointStyle DDfflK o] 1^ LS IS Lc[ ffl m m ffl h ra _ Current point style highlighted Point size options ~ Point Size: 5.0000 Set SizeRelativeto Screen O Set SizeinAbsoluteUnits 1*- _ Adjust point size Help 248 AutoCAD and Its Applications Basics

c The point style is stored in the PDMODE system variable. This vari able can be changed at the Command: prompt. The PDMODE values ofthe pointstyles shownin the top row ofthe Point Style dialog box are 0 through 4, from left to right. These are the basic point styles. Add a circle (second row in dialog box) by adding 32 to the basic PDMODE value. Add 64 to draw a square (third row), and add 96 to draw a circle andsquare (bottom row). For example, a point display of an X inside a circle has a PDMODE value of 35. This is the sum of the X value of 3 and the circle value of 32. Set the point size by entering a value in the Point Size: text box of the Point Style dialog box. Pick the Set Size Relative to Screen option button if you want the point size to change in relation to different screen magnifications. Picking the Set Size in Absolute Units option button makes the points appear the same size no matter what screen magnification is used. The effects of these options are shown in Figure 8-6. C Thepoint size and relative/absolute settings can also be modified by changing the PDSIZE (point display size) system variable. Positive PDSIZE values change size in relation to different display options (relative to screen). Negative PDSIZE values make the points appear the same size no matter how much you zoom the drawing (absolute units). Exercise 8-2 Complete the exercise on the Student CD. Figure 8-6. Points sized with the Set Size Relative to Screen setting change size as the drawing is zoomed. Points sized with the Set Size in Absolute Units setting remain a constant size. V Size Setting Original Point Size 2X Zoom 0.5 Zoom Relative to Screen K / Absolute Units 8 K X / H J Chapter 8 Geometric Constructions 249

block: a previously shape Symb ' r c Dividing an Object A line, circle, arc, or polyline can be divided into an equal number of segments using the DIVIDE command. To start the DIVIDE command, select Draw > Point > Divide or type DIV or DIVIDE. The DIVIDE command does not break an object into multiple parts. Itplaces point objects or blocks at the locations where the breaks would occur if the objectwere actually divided into multiple segments. Suppose you have drawn a line and want to divide it into seven equal parts. Enter the DIVIDE command, select the object to divide, and then enter the number of segments. See Figure 8-7. The Block option of the DIVIDE command allows you to place a block at each division point. To initiate the Blockoption, type Bat the Enter the number of segments or[block]: prompt. AutoCAD asks if the blockis to be aligned with the object. A block isa previously drawn symbol orshape. Blocks are discussed indetail inchapter 23 of this text. After the number of segments is given, the object is divided with points. By default, however, points are displayed as dots, which may not show very well. Change the point style to make the points more visible. Figure 8-7. Using the DIVIDE command. Note that the default marks (points) have been changed to Xs. Points divide the object into equal-sized parts ^< X X X X > c Marking an Object at Specified Distances Unlike the DIVIDE command, in which an object is divided into a specified number of parts, the MEASURE command places marks a specified distance apart. To activate the MEASURE command, pick Draw > Point > Measure from the pull-down menu or type ME or MEASURE. Pick the object and type in the distance. The line shown in Figure 8-8 is measured with.75 unit segments. Measuring begins at the end closest to where the object is picked. All increments are equal to the specified segment length, except the last segment, which may be shorter. The point style determines the type of marks placed on the object, just as it does with the DIVIDE command. Blocks can be inserted at the given distances using the Block option of the MEASURE command. Exercise 8-3 Complete the exercise on the Student CD. 250 AutoCAD and Its Applications Basics

Figure 8-8. Using the MEASURE command. Notice that the last segment may be shorter than the others,depending on the total length of the object..75.75.75.75.75 < >.75.75.75 -x X X X X X X * Last segment is short unless / equal to specified segment length < > C Orthographic Multiview Drawings ) Each field of drafting has its own method to present views of a product. Architectural drafting uses plan views, exterior elevations, and sections. In electronics drafting, symbols are placed in a schematic diagram to show a circuit layout. In civil drafting, contour lines are used to show the topography of land. Mechanical drafting uses multiview drawings. Multiview drawings are based on the standard ASME Y14.3M, Multiview and Sectional View Drawings. The views of a multiview drawing are created through ortho graphic projection. Orthographic projection involves projecting object features onto an imaginary planecalleda projection plane. Theimaginaryprojection plane is placed parallelto the object. Thus, the line of sight is perpendicular to the object. This results in views that appear two-dimensional. See Figure 8-9. Sixtwo-dimensional views show all sides of an object. The six views are the front, right side, leftside, top, bottom, and rear. The views are placed in a standard arrange ment so others can read the drawing. The front view is the central, or most important, view. Other views are placed around the front view. See Figure 8-10. Notice in this figure that the horizontal and vertical edges illustrated in the front view are aligned with the corresponding edges in the other views. You will create the other views from the front view by using the object snapping and tracking features covered in Chapter 7. Very few products require all six views. The number of views needed depends on the complexity of the object. Use only enough views to completely describe the object. Drawing too many views is time-consuming and can clutter the drawing. In some cases, a single view may be enough to describe the object. The object shown in Figure 8-11 needs only two views. These two views completely describe the width, height, depth, and features of the object. multiview drawings: Presentation of views of drawings created through orthographic projection. orthographic projection: Projecting object features onto an imaginary plane. projection plane: The imaginary projection plane that is parallel to the object. Figure 8-9. Obtaining a front view with orthographic projection. Two-dimensional drawing N. Projection plane Three-dimensional object Chapter 8 Geometric Constructions 251

Figure 8-10. Arrangement of the six orthographic views. Three-dimensional view Projection lines Bottom Figure 8-11. The views you choose to describe the object should show all height, width, and depth dimensions. Selecting the Front View The front view is usually the most descriptive view. The following attributes should be considered when selecting the front view: / Most descriptive / Most natural position / Most stable position / Provides the longest dimension / Contains the least number of hidden features Additional views are selected relative to the front view. Remember to choose only the views needed to completely describe the object's features. Showing Hidden Features Hidden features are parts of the object not visible in the view at which you are looking. Avisible edgeappearsasa solid line. A hiddenedgeisshownwith a hidden line. Hidden lines were discussed in Chapter 5. Notice in Figure 8-12 how hidden features are shown as hidden lines. Hidden lines are thin to provide contrast to object lines. Exercise 8-4 Complete the exercise on the Student CD. 252 AutoCAD and Its Applications Basics

Figure 8-12. Hidden features are shown with hidden lines. Visibleedge Jf^ X "\ \ ^ Front view Hidden edges ' / Figure 8-13. A one-view drawing of a gasket. The thickness is given in a note. NOTE: THICKNESS 1.5mm One-View Drawings In some instances, an object can be fully described using one view. A thin part, such as a gasket, can be drawn with one view. SeeFigure 8-13. The thickness is given as a note in the drawing or in the title block. Showing Symmetry and Circle Centers The centerlines of symmetrical objects and the centers of circles are shown with centerlines. For example, in one view of a cylinder, the axis is drawn as a centerline. In the otherview, centerlines cross to show the center in the circularview. See Figure 8-14. The only place the small centerline dashes should cross is at the center of a circle. Figure 8-14. Drawing centerlines. Small dashes cross Centerline axis Centerline of hole Centerlines of a Cylinder Axis of hole ' J- Centerlines of a Hole C Drawing Auxiliary Views ) In most cases, an object can be completely described using a combination of one or more of the six standard views. Sometimes, however, the multiview layout is not enough to properlyidentify some object surfaces. It may then be necessary to draw an auxiliary view. An auxiliary vieiv is typically needed when a surface on the object is at an angle to the line of sight in all of the standard views. This slanted surface isforeshortened in a standard view, meaning it is shorter than the true size and shape of the surface. To show this surface in true size, an auxiliary view is needed. Foreshortened dimensions are not recommended. Chapter 8 Geometric Constructions auxiliary view: View needed when a surface on an object is at an angle to the three principal projection planes. foreshortened: Shorter than the true size and shape of the surface. 253

partial auxiliary view: An auxiliary view that shows only a single surface of an object, rather than the entire object. viewing-plane line: Line identifying the viewing direction of a related view. An auxiliary view is drawn by projecting lines perpendicular (90 ) to a slanted surface. Usually, one projection line remains on the drawing. It connects the auxiliary view to the view where the slantedsurface appears as a line. The resulting auxiliaryview shows the surface in true size and shape. For most applications, the auxiliary view needs only to show the slanted surface, not the entire object. This is called a partial auxiliary vieiv and is shown in Figure 8-15. In some situations, there may not be enough room on the drawing to project directly from the slanted surface. The auxiliary view is then placed elsewhere. See Figure 8-16. A viewing-plane line is drawn next to the view where the slanted surface appears as a line. The viewing-plane line is drawn with a thick dashed or phantom line in accordance with ASME Y14.2M. It is terminated with bold arrowheads that point toward the slanted surface. Each end of the viewing-plane line is labeled with a letter. The letters relate the viewing-plane line with the proper auxiliary view. A title such as "VIEW A-A" is placed under the auxiliary view. When more than one auxiliary view is drawn, labels continue with B-B through Z-Z (if necessary). The letters I, O, and Q are not used because they may be confused with numbers. An auxiliary view drawn away from the standard view retains the same angle as if it is projected directly. world coordinate system (WCS): X, Y, and Z coordinate values measured from the origin (0,0,0). user coordinate system (UCS): A coordinate system with a user-defined origin location and axes rotation. Using the User Coordinate System for Auxiliary Views All the features on your drawing originate from the world coordinate system (WCS). This system includes the X, Y, and Z coordinate values measured from the origin (0,0,0). The WCS is fixed. A user coordinate system (UCS), on the other hand, can be moved to any orientation. User coordinate systems are discussed in detail in AutoCAD and Its Applications Advanced. In general, a UCS allows you to set your own coordinate origin. The WCS 0,0,0 origin has been in the lower-left corner of the screen for the drawings you have done so far. In many cases, this is fine, but when drawing an auxiliary view, it is best to have the measurements originate from a corner of the view. This, in turn, makes all auxiliary view features and the coordinate display true, as measured from the corner of the view. This method makes it easier to locate and later dimension the auxiliary view features. Figure 8-17shows an example of aligning the UCS to the auxiliary view. Draw the principal views, such as the front, top, and right side. Move the UCS origin to a location that coincides with a corner of the auxiliary view. Figure 8-15. Auxiliary views show the true size and shape of an inclined surface. This surface not shown on the auxiliary view Foreshortened surface Auxiliary view is true size and shape Projection line Foreshortened surface / / / o Circle appears as an ellipse / V. 254 AutoCAD and Its Applications Basics

Figure 8-16. Identifying anauxiliary view with a viewing-plane line. If there isnot enough room, the view can be moved to a different location. View is moved if needed Viewing-pl line Figure 8-17. Relocating the origin and rotating the Z axis of the UCS system. A Rotating the UCS to align with the auxiliary view angle. B The UCS icon is displayed at the current UCS origin at the corner of the auxiliary view. Select as origin of UCS UCS icon displayed at new origin UCS icon o o -&-X A B Tomove the UCS origin, type UCS, select the 3 Pointbutton on the UCS toolbar, or selecttools > New UCS > 3 Point. The command sequence is as follows: Chapter 8 Command: UCSJ Current ucs name: ^current* Enter an option [New/Move/orthoGraphic/Prev/Restore/Save/Del/Apply/?Mor1d] <World>: Nj Specify origin of new UCS or [ZAxis/3point/OBject/Face/View/X/Y/Z] <0,0,0>: 3J Specify new origin point <0,0,0>: (select Point A, as shown in Figure8-17) Specify point on positive portion of X-axis <current>: (select Point B) Specify point on positive-y portion of the UCS XY plane <current>: (select Point C) Command: Geometric Constructions UCS UCS k3 3 Point lflld«lm Tool New UCS > 3 Point 255 o D

The icon is rotated and moved, as shown in Figure 8-17B. If you want the UCS displayed in the lower-left corner of the drawing area, select Tools > Named UCS... from the pull-down menu. This displays the UCS dialog box. In the Settings tab, uncheck the Display at UCS origin point check box. Before you begin drawing the auxiliary view, use the Save option of the UCS command to name and save the new UCS: Command: UCSJ Current ucs name: ^current* Enter an option [New/Move/orthoGraphic/Prev/Restore/Save/Del/Apply/?/World] <World>: SJ Enter name to save current UCS or [?]: AUXJ Command: Now, proceed by drawingthe auxiliary view. Whenyou have finished, select the World UCS button from the UCS toolbar or enter the UCS command and use the default World option to reset the UCSback to the WCS origin: Command: UCSJ Current ucs name: AUX Enter an option [New/Move/orthoGraphic/Prev/Restore/Save/Del/Apply/?/World] <World>: J Command: Polar tracking is another method that can be used to draw auxiliary views. It can be used in place of or in addition to the UCS method described in this section. Polar tracking was covered in Chapter 7. J Exercise 8-5 Complete the exercise on the Student CD. C Construction Lines and Rays The tracking vectors and alignment paths you used in the previous sections are efficient methods of creating geometry because these types of lines appear only when they are needed. Sometimes, you may want the lines to stay visible while you continue to create geometry. This is when you want to use construction lines (XLINE) and rays (RAY). Both commands can be used for similar purposes. However, the XLINE command has more options and flexibility than the RAY command. construction line (xline): A line in AutoCAD that is infinite in both directions. Using the Xline Command A construction line, or xline, is a line of infinite length used to help build accurate geometry. Although these lines are infinite, they do not change the drawing extents. This means they have no effect on zooming operations. Construction lines can be modified by moving, copying, trimming, and other editing operations. Editing commands such as TRIM or FILLET change the object type. 256 AutoCAD and Its Applications Basics

For example, ifone end of aconstruction line is trimmed off, itbecomes a ray. Aray is considered semi-infinite because it is infinite in one direction only. If the infinite end ofa ray is trimmed off, it becomes a line object. Construction lines and rays are drawn on the current layer and plot the same as other objects. This may cause conflict with other lines on that layer. Agood way to handle this problem is to set up a special layer justfor construction lines. The XLINE command can be accessed by picking the Construction Line button on the Draw toolbar or from the 2D Draw control panel of the Dashboard, picking Draw > Construction Line in the pull-down menu, ortyping XL orxline. You can specify two points through which the construction line passes. The first point of a construction line is called the root point. After you pick the first point, you can select as many points as you would like. Xlines are created between every point and the root point. Figure 8-18 shows how construction lines can be used to help project features between views. After picking the first point, right-click the drawing area to see the following XLINE options in the shortcut menu: Hor. Draws a horizontal construction line through a single specified point. Ver. Draws a vertical constructionline through a specified point. Ang. Draws a construction line at a specified angle through a selected point. The default lets you specify an angle and thenpick a point through which the construction line is to be drawn. This works well if you know the angle. You can alsopick two points in the drawing to describe the angle. The Reference option allows you to usetheangle ofan existing line object as a reference angle for construction lines. This option is useful when you do not know the angle of the construction line, but you know the angle between an existing object and the construction line. Figure 8-19 shows the Ang option used to draw construc tion lines establishing the location of an auxiliary view. Bisect. This option draws a construction line that bisects a specified angle. This isa convenient tool for usein some geometric constructions, as shownin Figure 8-20. Offset. This XLINE option draws a construction line a specified distance from a selected line object. You have the option ofspecifying an offset distance or using the Through option to pick a point through which to draw the construction line. ray: Line that is infinite in one direction only. XLINE XL 2D Draw > Construction Line / Draw / Construction Line B g Draw > Construction Line Ver Ang Bisect Offset root point: The first point of a construction line. LU Figure ngure 8-18. o-io. Creating horizontal construction lines using two points and the Hor option. Construction lines Enter the XLINE command and pick two points for the construction line to pass through. Object snap modes are used here to help pick points accurately. Front View At- ^\Enter the XLINE command again and pick two points for another construction line. Use the construction line to establish a visible edge in the side view. Usethe object snap modes to your advantage. c=^ Use the construction lines to establish the location for hidden lines in the side view. Step 2 Chapter 8 Geometric Constructions 257

Figure 8-19. Using the XLINE command Ang option. Enter an angle from 0 or from a selected object Figure 8-20. Using the XLINE command Bisect option. Angle start point Angle vertex Xline bisects angle Angle endpoint Exercise 8-6 Complete the exercise on the Student CD. j Using the Ray Command The RAY command is limited, compared to the XLINE command. The RAY command allows you to specify the point of origin and a point through which the ray passes. In this manner, the RAY command works much like the default option of the XLINE command. The ray, however, extends beyond only thesecond pick point. The XLINE command results in a construction line that extends both directions from the pick points. The RAY command can be accessed by picking Draw > Ray or by typing RAY. The RAY command sequence is as follows: Command: RAYJ Specify start point: (pick a point) Specifythrough point: (pick a second point) Specify through point: (draw more construction lines orpress [Enter]) Command: Both the RAY command and the XLINE command allow the creationof multiple objects. You must press [Enter] to end the command. 258 AutoCAD and Its Applications Basics

Editing Construction Lines and Rays Theconstruction linesyoucreate usingthexline and RAY commands canbeedited and modified using standard editing commands. These commands are introduced in Chapter 11 and Chapter 12. The construction lines will change into a new object type when infinite ends are trimmed off. An xline trimmed on one side becomes a ray, and anxline trimmed onboth ends becomes a normal line object. Aray that has its infinite end trimmed also becomes a line object. Therefore, in many cases, your construction lines can bemodified to become partof the actual drawing. This approach can save a significant amount of time in many drawings. plate Many drafters rely on points created by the POINT, DIVIDE, and pment MEASURE commands to construct geometry accurately. Point rh t o sty*es vary according to personal preference, but you can add Chapter o y0ur preferred style to your drawing templates. Refer to the Student CD for detailed instructions toaddyour preferred point style to your mechanical, architectural, and civil drawing. Chapter Test Answer thefollowing questions. Write your answers on a separate sheet ofpaper orcomplete the electronic chapter test on the Student CD. 1. List two ways to establishan offset distance using the OFFSET command. 2. What option of the OFFSET command is used to remove the source offset object? 3. Howdo you draw a single point, and how do you draw multiple points? 4. How do you access the Point Style dialog box? 5. How do you change the point size in the Point Style dialog box? 6. Give the command needed to divide a line into 24 equal parts. 7. If you use the DIVIDE command and nothing appears to happen, what should you do? 8. What is the difference between the DIVIDE and MEASURE commands? 9. Provide at least four guidelines for selecting the front view of an orthographic multiview drawing. 10. When can a part be shown with only one view? 11. When is an auxiliary view needed, and what does an auxiliary view show? 12. What is the angle of projection from the slanted surface into the auxiliary view? 13. Name the AutoCAD command that allows you to draw construction lines. 14. Why is it a good idea to put construction lines on their own layer? 15. Name the option that can be used to bisect an angle with a construction line. 16. What is the difference between the construction lines drawn with the command identified in Question 13 and rays drawn with the RAY command? Chapter 8 Geometric Constructions 259

Drawing Problems Load AutoCADfor each ofthefollowing problems, and use one ofyour templates or start anew drawing using your own variables. 1. Use the OFFSET command to draw the elevation of the desk shown. Do not draw dimensions. Save the drawing as P8-1. 5'-5" 2'-11" 1'-3" i ' ^i- -V CO 3- o i 1 lo i 1 r^ 1 1/2 LEGS CO ^~ ^ 2. Draw the front and side views of this offset support. Use object snap modes and tracking. Do not draw the dimensions. Save your drawing as P8-2. i.75 2X 01.15 t 1.00 1 3.50 I 1.00 _L.75.55 260 AutoCAD and Its Applications Basics

3. Draw the top and front views of this hitch bracket. Use object snap modes and tracking. Do not draw the dimensions. Save your drawing as P8-3. 2X 01.25 R1.50 1 -".75 1 I ' I I.95 2.25 -.95 * " t 30 I2' i 1 i! '! i i i.75 4. Draw this aluminum spacer. Use object snap modes and tracking. Do not draw the dimensions. Save the drawing as P8-4. 6X (».250.250 2.562 6X R.250 Chapter 8 Geometric Constructions 261

5. Draw this spring using the OFFSET command for material thickness. Do not draw the dimensions. Save the drawing as P8-5. 2X R.844 3.000 2X R.844 (Art courtesy of Bruce L. Wilcox).024 THK 6. Draw this gasket. Donot draw the dimensions. Save the drawing as P8-6. 1.750 2X R.500 R.750 (Art courtesy of Bruce L. Wilcox :- 262 AutoCAD and Its Applications Basics

7. Draw this sheet metal chassis. Do not draw the dimensions. Use object snap tracking and polar tracking to your advantage. Save the drawing as P8-7. (Art courtesy of Bruce L. Wilcox) 8. Draw this cup. Do not draw the dimensions. Save the drawing as P8-01.50 25 X.125 FILLETS & ROUNDS.10 RADIUS Chapter 8 Geometric Constructions 263

9. Draw this bushing. Donot draw the dimensions. Save the drawing as P8-9. & 0.770-1.250- --.625 01.250 10. Draw this wrench. Do not draw the dimensions. Save the drawing as P8-10. 1.00 R.50 R4.00 FILLETS AND ROUNDS =.125 11. Draw this support. Do not draw the dimensions. Save the drawing as P8-11. R.75 R.25 1.25.75 2.50 *- 02.00 0.250 X/0.350 X 82-2.50-264 AutoCAD and Its Applications Basics

In Problems 12 through 17, draw the views needed to completely describe the objects. Use object snap modes, AutoTrack modes, and offsets as needed. Do not dimension. Save the drawings as P8-(problem number). 12. Brace 13. <** Connector 14. Journal Bracket (Engineer's Rough Sketch) Chapter 8 Geometric Constructions 265

15. Angle Bracket (Engineer's Rough Sketch) (Metric) 16. -Iitch Bracket 17. Draw the views of this pillow block, including the auxiliary view. Do not draw the dimensions. Save your drawing as P8-17. 03.750 02.750 266 AutoCAD and Its Applications Basics