geometric - los rios community college...

Learning Objectives

GeometricConstructions

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 placepoint 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 JThe OFFSET command is used to draw concentric circles, concentric arcs, concen

tric curves, parallel polylines, and parallel lines. This command is accessed by pickingthe 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 OffsetThe 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 offsetdistanceused is the defaultand is shown in brackets. Forexample, if you want to drawtwo 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=currentSpecify offset distance or [Through/Erase/Layer] <cnrrent>: .USelect 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)Selectobject to offset or [Exit/Undo] <current>: (select another object orpress [Enter])Command:

OFFSET

2D Draw

> Offset

Modify

Offset

BEModify

> Offset

Through

LayerMultiple

HLJ

C/)U_

245

246

Figure 8-1.Drawing an offsetusing a designateddistance.

Pick box

Select Object

Pick side to offset

/

Side to Offset Offset

If you do not know the offset value, but two reference points exist in the drawingarea, you can pick a first point and then a second point instead of typing in an offsetvalue. 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, thecursor turns into a pick box. After the object is picked, the cursor turns back intocrosshairs. No other selection option (such as window or crossing) works with theOFFSET command.

The other option is to pick a point through which the offset is drawn. Type T, asfollows, to produce the results shown in Figure 8-2:


Current settings: Erase source=current Layer=current OFFSETGAPTYPE=a<rrenfSpecify offset distance or [Through/Erase/Layer] <current>: TJSelect 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>: JCommand:

Object snap modes can be used to assist in specifying the offset distance. Forexample, suppose you have a circle and a line and want to draw a concentric circletangent to the line. Refer to Figure 8-3 and the following command sequence:


Current settings: Erase source=current Layer=current OFFSETGAPTYPE=n/rre/7fSpecify offset distance or [Through/Erase/Layer] <current>: QUAJof (pick the existing circle)Specify second point: PERJto (pick the existing line)Select object to offsetor [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>: JCommand:

Figure 8-2.Drawing an offsetthrough a givenpoint.

Pick box

Select Object

Pick throughV point

Through Point

AutoCAD and Its Applications—Basics

Figure 8-3.Using OFFSET todraw a concentriccircle tangent to aline.

Originscircle

QUA

A

\L

PER

Select the

object to offset

Side to

offset

Erasing the Original ObjectWhen 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 thesource objectwhen it is offset.After initiating the OFFSET command, select Erase andYes from the shortcut menu to erase the source object. TheYes option remains as thedefault until it is changed to No. Be sure to change this option back to No if you do notwant the source offset object to be erased the next time the OFFSET command is used.

Changing the Layer of the Offset ObjectThe 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 offsetobject needs to be placedon the Lighting layer, this can be done during the command ifLighting is the current layer by following this command sequence:


Current settings: Erase source=current Layer=current OFFSETGAPTYPE=cnrrentSpecify offset distance or [Through/Erase/Layer] <current>: I iEnter layer option for offset objects [Current/Source] <current>: CJSpecify offset distance or [Through/Erase/Layer] <current>:

When Current is specified, the offset object is placed on the current layer. To havethe offset object remain on the same layer as the offset source object, use the Sourceoption.

Offsetting Multiple TimesAfter 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 withouthaving to reselect the objectto offset. Initiate the OFFSET command, specify the offsetdistance, and pick the source object. You can then select Multiple and begin picking tospecify the offset direction. See Figure 8-4. Whenever the Undo option is available, itcan be used to undo the last offsetwithout exiting the command. Using the Exitoptionby typing Eor Exit, pressing [Enter], or right-clicking exits the OFFSET command.

Exercise 8-1Complete the exercise on the Student CD.

Chapter 8 Geometric Constructions 247

i-z

o0.

POINT

PO

2D Draw

> Point

Point

Draw

> Point

DDPTYPE

Format

> Point Style.

248

Figure 8-4.The Multiple optioncan be use to create

multiple offsets withthe same distance,without picking thesource object again.

c

,4, ,4, ,J,

1

Drawing Points

Points are useful for identifying specific locations on a drawing and, as you will seein the next section,for marking positions on objects. You can draw points anywhere onthe screen using the POINT command. To access this command, pick the Point buttonfrom the Draw toolbar or from the 2D Draw control panel in the Dashboard, type PO orPOINT, or select Draw > Point and one of the options. You can pick or type coordinatesto place the points.

If you need to placeonly a singlepoint object, use the keyboard command or selectthe Single Point option from the Point cascading menu. If you need to draw multiplepoints, use the Point button on the Draw toolbar or the Multiple Point option from thePoint cascading menu. Press [Esc] to exit the command.

Setting Point StyleThe 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 typingDDPTYPE.

The Point Style dialog box contains twenty different point styles. The currentpoint style is highlighted. To change the style, simply pick the graphic image of thedesired style.

Figure 8-5.The Point Styledialog box. This is aquick way to selectthe point style andchange the pointsize.

Pick to —-

change style

Point size

options ~

IPointStyle

DDfflKo] 1^ LS IS Lc[• • ffl m m

ffl h ra

Point Size: 5.0000

© Set SizeRelativeto Screen

O Set Size inAbsoluteUnits

1*-

Help

_ Current pointstyle highlighted

_ Adjustpoint size


cThe point style is stored in the PDMODE system variable. Thisvariable can be changed at the Command: prompt. The PDMODE valuesofthepointstyles shownin the toprowofthe Point Style dialog boxare 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 basicPDMODE value. Add 64 to draw a square (third row), and add 96 todraw a circle andsquare (bottom row). For example, apoint displayof an X inside a circle has a PDMODE value of 35. This is the sum ofthe 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 Styledialog box. Pick the Set Size Relative to Screen option button if you want the pointsize to change in relation to different screen magnifications. Picking the Set Size inAbsolute Units option button makes the points appear the same size no matter whatscreen magnification is used. Theeffects of these options are shownin Figure 8-6.

CThepoint size and relative/absolute settings can also be modified bychanging the PDSIZE (point display size) system variable. PositivePDSIZE values change size in relation to different display options(relative to screen).Negative PDSIZE values make the points appearthe same size no matter how much you zoom the drawing (absoluteunits).


Figure 8-6.Points sized with

the Set Size Relative

to Screen settingchange size as thedrawing is zoomed.Points sized with the

Set Size in Absolute

Units setting remaina constant size.

Size Setting Original Point Size 2X Zoom 0.5 Zoom

Relative to

Screen K/X

/

H

Absolute

Units

V

8 KJ


250

c Dividing an Object

A line, circle, arc, or polyline can be divided into an equal number of segmentsusingthe DIVIDE command. To start the DIVIDE command, select Draw > Point > Divideor type DIV or DIVIDE. The DIVIDE command does not break an object into multipleparts. Itplaces point objects or blocks at the locations where the breaks would occur ifthe 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 ofsegments. See Figure 8-7.

The Block option of the DIVIDE command allows you to place a block at eachdivision point. To initiate the Blockoption, type Bat the Enter the number of segments

block: a previously or [Block]: prompt. AutoCAD asks if the blockis to be aligned with the object. A blockshape Symb°' °r isapreviously 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. Bydefault, however, points are displayed as dots, which may not show very well. Changethe point style to make the points more visible.

Figure 8-7.Using the DIVIDEcommand. Note that

the default marks(points) have beenchanged to Xs.

^<—X—X—X—X—>

Points divide

the object intoequal-sized parts

c Marking an Object at Specified Distances

Unlike the DIVIDE command, in which an object is divided into a specified numberof parts, the MEASURE command places marks a specified distance apart. To activatethe MEASURE command, pick Draw > Point > Measure from the pull-down menu ortype ME or MEASURE. Pick the object and type in the distance. The line shown inFigure 8-8 is measured with .75 unit segments.

Measuring begins at the end closest to where the object is picked. All incrementsare equal to the specified segment length, except the last segment, which may beshorter. The point style determines the type of marks placed on the object, just as itdoes with the DIVIDE command. Blocks can be inserted at the given distances usingthe Block option of the MEASURE command.



.75 .75 .75 .75 .75< >•

.75 .75 .75•< >•

Figure 8-8.Using the MEASUREcommand. Notice

that the last segmentmay be shorter thanthe others,dependingon the total length ofthe object.

-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 electronicsdrafting, symbols are placed in a schematic diagram to show a circuit layout. In civildrafting, contour lines are used to show the topography of land. Mechanical draftinguses multiview drawings.

Multiview drawings are based on the standard ASME Y14.3M, Multiview andSectional View Drawings. The viewsof a multiview drawing are created through orthographic projection. Orthographic projection involves projecting object features ontoan imaginary planecalledaprojection plane. Theimaginaryprojection plane isplacedparallelto the object. Thus, the line ofsight is perpendicular to the object. This resultsin 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 arrangement 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 thisfigure that the horizontal and vertical edges illustrated in the front view are alignedwith the corresponding edges in the other views. You will create the other viewsfrom the front view by using the object snapping and tracking features covered inChapter 7.

Very few products require all six views. The number of views needed dependson the complexity of the object. Use only enough views to completely describe theobject. Drawing too many views is time-consuming and can clutter the drawing. Insome cases, a single view may be enough to describe the object. The object shown inFigure 8-11 needs only two views. These two views completely describe the width,height, depth, and features of the object.

Figure 8-9.Obtaining afront view with

orthographicprojection.

Chapter 8 Geometric Constructions

Two-dimensional

drawing N.

Three-dimensional

object

Projection plane

©

multiview

drawings:Presentation of

views of drawingscreated throughorthographicprojection.

orthographicprojection:Projecting objectfeatures onto animaginary plane.

projection plane:The imaginaryprojection planethat is parallel to theobject.

251

252

Figure 8-10.Arrangement of thesix orthographicviews.

Figure 8-11.The views youchoose to describe

the object shouldshow all height,width, and depthdimensions.

Projectionlines

Three-dimensional

view

Bottom

Selecting the Front ViewThe 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 theviews needed to completely describe the object's features.

Showing Hidden FeaturesHidden features are parts of the object not visible in the view at which you are

looking. Avisible edgeappearsasa solid line. Ahiddenedgeisshownwith a hiddenline.Hidden lines were discussed in Chapter 5. Notice in Figure 8-12 how hidden featuresare shown as hidden lines. Hidden lines are thin to provide contrast to object lines.



Figure 8-12.Hidden features areshown with hiddenlines.

Figure 8-13.A one-view drawingof a gasket. Thethickness is given ina note.

Visibleedge

Jf^ X "\—

__^__

\

' /Front view

Hidden edges

NOTE: THICKNESS 1.5mm

One-View DrawingsIn 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 givenas a note in the drawing or in the title block.

Showing Symmetry and Circle CentersThe 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. Inthe other view, centerlines cross to show the center in the circular view. 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.

C

Small dashes cross

Centerline axis

Centerlines of a Cylinder

Centerline of hole

J-Axis of hole '

Centerlines of a Hole

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 notenough to properlyidentifysome object surfaces. It may then be necessary to draw anauxiliary view.

An auxiliary vieiv is typically needed when a surface on the object is at an angleto the line of sight in all of the standard views. This slanted surface isforeshortened ina standard view, meaning it is shorter than the true size and shape of the surface. Toshow this surface in true size, an auxiliary view is needed. Foreshortened dimensionsare not recommended.


auxiliary view:View needed when

a surface on an

object is at an angleto the three principalprojection planes.

foreshortened:

Shorter than the

true size and shapeof the surface.

253

partial auxiliaryview: An auxiliaryview that shows onlya single surface ofan object, ratherthan the entire

object.

viewing-plane line:Line identifying theviewing direction ofa related view.

world coordinate

system (WCS): X,Y, and Z coordinatevalues measured

from the origin(0,0,0).

user coordinate

system (UCS): Acoordinate systemwith a user-defined

origin location andaxes rotation.

254

An auxiliary view is drawn by projecting lines perpendicular (90°) to a slantedsurface. Usually, one projection line remains on the drawing. It connects the auxiliaryview to the viewwhere the slantedsurface appearsas a line. The resultingauxiliaryviewshows the surface in true size and shape. For most applications, the auxiliary viewneeds only to show the slanted surface, not the entire object. This is called a partialauxiliary vieiv and is shown in Figure 8-15.

In some situations, there may not be enough room on the drawing to projectdirectly from the slanted surface. The auxiliary view is then placed elsewhere. SeeFigure 8-16. A viewing-plane line is drawn next to the viewwhere the slantedsurfaceappears as a line. The viewing-plane line is drawn with a thick dashed or phantomline 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" isplaced under the auxiliary view. When more than one auxiliary view is drawn, labelscontinue with B-B through Z-Z (if necessary). The letters I, O, and Q are not usedbecause they may be confused with numbers. An auxiliary view drawn away from thestandard view retains the same angle as if it is projected directly.

Using the User Coordinate System for Auxiliary ViewsAll the features on your drawing originate from the world coordinate system

(WCS). This system includes the X, Y, and Z coordinate values measured from theorigin (0,0,0). The WCS is fixed. A usercoordinate system (UCS), on the other hand,can be moved to any orientation. User coordinate systems are discussed in detail inAutoCAD and Its Applications—Advanced.

In general, a UCS allows you to set your own coordinate origin. The WCS 0,0,0origin has been in the lower-left corner of the screen for the drawings you have doneso far. In many cases, this is fine, but when drawing an auxiliary view, it is best tohave the measurements originate from a corner of the view. This, in turn, makes allauxiliary view features and the coordinate display true, as measured from the cornerof the view. This method makes it easier to locate and later dimension the auxiliaryview features.

Figure 8-17shows an example of aligning the UCS to the auxiliary view. Draw theprincipal views, such as the front, top, and right side. Move the UCS origin to a locationthat coincides with a corner of the auxiliary view.

Figure 8-15.Auxiliary viewsshow the true size

and shape of aninclined surface.

This surface not

shown on the

auxiliary view

Projectionline

//

V./

Foreshortened

surface

Auxiliary viewis true

size and shape

Foreshortened

surface

/ oCircle

appears

as an

ellipse


Figure 8-16.Identifying anauxiliary view with a viewing-plane line. If there isnot enough room, theview can be moved to a different location.

Viewing-plline

View is

moved if

needed

Figure 8-17.Relocating the origin and rotating the Z axis of the UCS system. A—Rotating the UCS toalign with the auxiliary view angle. B—The UCS icon is displayed at the current UCS originat the corner of the auxiliary view.

Select as

origin ofUCS

UCSicon

-&-X

o

A B

UCS icon

displayedat new

origin

o

Tomove the UCS origin, type UCS, select the 3 Pointbutton on the UCS toolbar, orselectTools > New UCS > 3 Point. The command sequence is as follows:

Command: UCSJ

Current ucs name: ^current*

Enter an option [New/Move/orthoGraphic/Prev/Restore/Save/Del/Apply/?Mor1d] <World>: NjSpecify origin of new UCS or [ZAxis/3point/OBject/Face/View/X/Y/Z] <0,0,0>: 3JSpecify new origin point <0,0,0>: (select Point A, asshown inFigure8-17)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:


UCS

UCS

k33 Point

lfllD«lMTool

New UCS

> 3 Point

oD

255

construction line

(xline): A line inAutoCAD that is

infinite in both

directions.

256

The icon is rotated and moved, as shown in Figure 8-17B. If you want the UCSdisplayed 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 UCScommand 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 [?]: AUXJCommand:

Now, proceed by drawingtheauxiliary view. Whenyouhave finished, select the WorldUCS button from the UCS toolbar or enter the UCS command and use the default Worldoption 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:

C

J

Polar tracking is another method that can be used to draw auxiliaryviews. It can be used in place of or in addition to the UCS methoddescribed in this section. Polar tracking was covered in Chapter 7.


Construction Lines and Rays

The tracking vectors and alignment paths you used in the previous sectionsare efficient methods of creating geometry because these types of lines appear onlywhen they are needed. Sometimes, you may want the lines to stay visible while youcontinue 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 XLINEcommand has more options and flexibility than the RAY command.

Using the Xline CommandA 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 otherediting operations. Editing commands such as TRIM or FILLET change the object type.


For example, ifone end of aconstruction line is trimmed off, itbecomes a ray. Aray isconsidered semi-infinite because it is infinite in one direction only. If the infinite endofa ray is trimmed off, itbecomes a line object.

Construction lines and rays are drawn on the current layer and plot the same asother objects. This may cause conflict with other lines on that layer. Agood way tohandle thisproblem is to setup a special layer justfor construction lines.

The XLINE command canbe accessed bypicking theConstruction Line button onthe Draw toolbar or from the 2D Draw control panel of the Dashboard, picking Draw >Construction Line in the pull-down menu, or typing XL orXLINE. You can specify twopoints through which the construction line passes. The first point of a constructionline is called the root point. After you pick the first point, you can select as manypoints 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 featuresbetween views. After picking the first point, right-click the drawing area to see thefollowing XLINE options in the shortcut menu:

• Hor. Draws a horizontal construction line through a single specified point.• Ver. Draws a vertical constructionline through a specifiedpoint.• Ang. Draws a construction line at a specified angle through a selected point.

The default lets you specify an angle and thenpick a point throughwhich theconstruction line is to be drawn. This works well if you know the angle. Youcan alsopick two points in the drawing to describe the angle. The Referenceoption allows you tousetheangle ofan existing line object as a reference anglefor construction lines. This option is useful when you donotknow theangle ofthe construction line, but you know the angle between an existingobject andthe construction line. Figure 8-19 shows the Ang option used to draw construction lines establishing the location of an auxiliaryview.

• Bisect. This option draws a construction line that bisects a specified angle. This isaconvenient tool for usein some geometric constructions, asshownin Figure 8-20.

• Offset. This XLINE option draws a construction line a specified distance from aselected line object. You have the option ofspecifying an offset distance or usingthe Through option to picka point through which to draw the construction line.

Figure 8-18.ngure o-io.

Creatinghorizontalconstruction lines using two points and the Hor option.

Enter the XLINE command and pick twopoints for the construction line to pass through.Object snap modes are used here to help pickpoints accurately.Construction lines

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 thelocation for hidden lines in the side view.

Step 2


ray: Line thatis infinite in one

direction only.

XLINE

XL

2D Draw

> Construction Line

/

Draw

/Construction Line

B—gDraw

> Construction Line

Ver

AngBisect

Offset

root point: Thefirst point of aconstruction line.

257

LU

258

Figure 8-19.Using the XLINEcommand Angoption.

Figure 8-20.Using the XLINEcommand Bisect

option.

Enter an angle from 0° orfrom a selected object

Angle start point

Angle vertex

Exercise 8-6

Xline bisects angle

Angle endpoint

Complete the exercise on the Student CD. j

Using the Ray CommandThe 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 raypasses. In this manner, the RAY command works much like the default option of theXLINE command. The ray, however, extends beyond only thesecond pick point. The XLINEcommand results in a construction line that extends both directions from the pickpoints.

The RAY command can be accessed by picking Draw > Ray or by typing RAY. TheRAY 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 creation of multiple objects.You must press [Enter] to end the command.


Editing Construction Lines and RaysTheconstruction linesyoucreate usingtheXLINE and RAY commands canbeedited

and modified using standard editingcommands. These commands are introduced inChapter 11 and Chapter 12. The construction lines will change into a new object typewhen infinite ends are trimmed off. An xline trimmed on one side becomes a ray, andanxline trimmed onboth ends becomes anormal line object. Aray that has its infiniteend trimmed also becomes a line object. Therefore, in many cases, your constructionlines can bemodified to become partof the actual drawing. This approach can save asignificant amount of time in many drawings.

plate Many drafters rely on points created by the POINT, DIVIDE, andpment MEASURE commands to construct geometry accurately. Point

rh t o sty*es vary according to personal preference, but you can addChapter o y0Ur preferred style to your drawing templates. Refer to the

Student CD for detailed instructions toaddyour preferred pointstyle to your mechanical, architectural, and civil drawing.

Chapter TestAnswer thefollowing questions. Write your answers on a separate sheet ofpaperorcomplete 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 youdraw a single point, and how do youdraw 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 viewneeded, and whatdoes 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. Whyis 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?


^

260

Drawing ProblemsLoad AutoCADfor each ofthefollowing problems, and use one ofyour templates or start anewdrawing using your own variables.

1. Use the OFFSET command to draw the elevation of the desk shown. Do not drawdimensions. 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 andtracking. Do not draw the dimensions. Saveyour drawing as P8-2.

2X 01.15

—i .75

t1.00

1

3.50

I1.00

_L

.75

.55


3. Draw the top and front views of this hitch bracket. Use object snap modes andtracking. Do not draw the dimensions. Save your drawing as P8-3.

2X 01.25

R1.50

1 | -" .95 2.25 - .95 *•"

.75 1 I 'I I

I2't

30

i 1 i

! ' !i i i

.75

4. Draw this aluminum spacer. Use object snap modes and tracking. Do not drawthe dimensions. Save the drawing as P8-4.

.2506X (».250

2.562

6X R.250


:-•

262

5. Draw this spring using the OFFSET command for material thickness. Do notdraw 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. Drawthis gasket. Donot draw the dimensions. Save the drawing as P8-6.•1.750 —

2X R.500

R.750

(Art courtesy of Bruce L. Wilcox


7. Draw this sheet metal chassis. Do not draw the dimensions. Use object snaptracking and polar tracking toyour advantage. Save thedrawing 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

263

&

264

9. Draw this bushing. Donot draw the dimensions. Save the drawing as P8-9.

-1.250-

0.770

01.250

--.625

0.250X/0.350 X 82-

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.75R.25 — 1.25— .75

2.50

*- 02.00

2.50-


In Problems 12 through 17, draw the views needed to completely describe the objects. Use objectsnap modes, AutoTrack modes, and offsets as needed. Do not dimension. Save the drawings asP8-(problem number).

12.

Brace

13.

<**•

Connector

14.

Journal Bracket (Engineer's Rough Sketch)


266

15.

16.

Angle Bracket (Engineer's Rough Sketch)(Metric)

-Iitch Bracket

17. Draw the views of this pillow block, including the auxiliary view. Do not drawthe dimensions. Save your drawing as P8-17.

03.750

02.750


geometric - los rios community college...

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