Autocad 2d Module 07 PDF

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AutoCAD Self-paced Learning Modules ®

AutoCAD 2D Module 7 Circles and Arcs Learning Outcomes: When you have completed this module, you will be able to:

1. Describe a circle and an arc and their characteristics. 2. Describe and use the CIRCLE and ARC commands to draw circles and arcs.

Geometry Lesson Circles A circle is defined as a closed curve in which all points are the same distance from its center point. The center point is a single XY coordinate. Study the drawings in Figure 7-1 for a description of the characteristics of a circle.

Figure 7-1 Circle Geometry Circles and Arcs

The CAD Guys Ltd. Copyright © 1993 - 2007

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AutoCAD Self-paced Learning Modules - AutoCAD 2D - Revised 2007-04-11

AutoCAD Command:

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CIRCLE

The CIRCLE command is used to draw circles.

Shortcut: C

2004-2008

2000-2002

Geometry Lesson Arcs An arc is defined as an open curve in which all points are the same distance from its center point. Study the drawings in Figure 7-2 for a description of the geometry of an arc.

Figure 7-2 Arc Geometry Circles and Arcs


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AutoCAD Command:

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ARC

The ARC command is used to draw arcs.

Shortcut: A

2004-2008

2000-2002

When you are drawing arcs, you should know that AutoCAD wants to draw arcs counterclockwise. To AutoCAD, this is the positive arc angle. When you use the Center-Start-End option to draw arcs, there is no way to draw the arc clockwise or in the negative arc angle. If you use the Angle option, AutoCAD does allow you to enter a negative angle and it will draw the arc for you.

Circles and Arcs


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Using the CIRCLE and ARC Commands Step 1

Start a new drawing using the template Module Template A.

Step 2 Save and name the drawing AutoCAD 2D Workalong 07-1. Step 3 Create layer Object, color red, as shown in Figure Step 3.

Figure Step 3

Step 4 Set layer Object as the current layer and enter the LINE and ARC commands shown below to draw the object shown in Figure Step 4.

Command: LINE Specify first point: 2.5,5 Specify next point or [Undo]: @4,0 Specify next point or [Undo]: Command: ARC The Object to be Drawn Specify start point of arc or [Center]: C (If possible, always draw arcs starting with the center point first.) Specify center point of arc: 2.5,5 (Enter the center point.) Specify start point of arc: @4,0 (Enter the start point. Here the trick is to give AutoCAD the start point and the radius of the arc at the same time.) Specify end point of arc or [Angle/chord Length]: A Specify included angle: 90 (Enter the angle of the arc. In this case, it is 90 degrees.) Command: LINE Specify first point: 2.5,5 Specify next point or [Undo]: @0,4 Specify next point or [Undo]:

Command: Figure Step 4

...continued on page 7-5

Circles and Arcs


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Using the CIRCLE and ARC Commands - continued Step 5 Enter the CIRCLE commands shown below to complete the object. See Figure Step 5. Command: CIRCLE Specify center point for circle or [3P/2P/Ttr (tan tan radius)]: 3.5,6 (Since this is the first circle inserted, enter an absolute coordinate for the center point.) Specify radius of circle or [Diameter]: D (Circles are usually dimensioned with diameters rather then a radius, enter D) Specify diameter of circle: .65 Command: CIRCLE (Press enter or space as that will repeat the last command. Specify center point for circle or [3P/2P/Ttr (tan tan radius)]: @1,0 (Notice here, since AutoCAD always remembers the lastpoint, use an @. The lastpoint was the center of the first circle placed.) Specify radius of circle or [Diameter] <0.3250>: D Specify diameter of circle <0.6500>: .75 Command: CIRCLE (Press enter or space as that will repeat the last command. Figure Step 5 Specify center point for circle or [3P/2P/Ttr (tan tan radius)]: @0,1.5 (Again use an @ which is from the center of the last circle placed.) Specify radius of circle or [Diameter] <0.3750>: D Specify diameter of circle <0.7500>: 1 Command: CIRCLE (Press enter or space as that will repeat the last command and save you entering it again.) Specify center point for circle or [3P/2P/Ttr (tan tan radius)]: @-1,0 Specify radius of circle or [Diameter] <0.5000>: D Specify diameter of circle <1.0000>: .5 Command: Completed

Step 6

Save and close the drawing.

Drawing

When you are drawing arcs, it is best to specify the center point first then the start point. When you give the location of the start point, you can specify the radius and the direction at the same time, then enter the angle or the end point whichever is easier. Command: ARC Specify start point of arc or [Center]: C Specify center point of arc: 3,4 Specify start point of arc: @0,-2 (Specifying the radius and the direction for the start point.) Specify end point of arc or [Angle/chord Length]: A Specify included angle: 180 Command:

Circles and Arcs


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Using the CIRCLE Command - TTR Option Step 1

Start a new drawing using the template Module Template A.

Step 2

Save and name the drawing AutoCAD 2D Workalong 07-2.

Step 3 Create layer Object, color red, as shown in Figure Step 3.

Figure Step 3 Step 4 Set layer Object as the current layer and enter the LINE and CIRCLE commands shown below to draw the object shown in Figure Step 4A, 4B, 4C and 4D. Command: LINE Specify first point: 1.25,4.5 Specify next point or [Undo]: @6,0 Specify next point or [Undo]: @0,4 Specify next point or [Close/Undo]: @-6,0 Specify next point or [Close/Undo]: C Command: CIRCLE Specify center point for circle or [3P/2P/Ttr (tan tan radius)]: TTR Specify point on object for first tangent of circle: P1 Object to be Drawn (Using the graphic cursor, pick one of the lines the circle is tangent to. Note how the symbol that automatically appears. See Figure Step 4A.) Specify point on object for second tangent of circle: P2 (Pick the other line.) Specify radius of circle <0.7000>: 1 (Enter the radius of the circle. Be careful, since circles are usually dimensioned in diameters you will have to divide it in half.) Command: CIRCLE Specify center point for circle or [3P/2P/Ttr (tan tan radius)]: TTR Specify point on object for first tangent of circle: P3 Figure Step 4A Specify point on object for second tangent of circle: P4 Specify radius of circle <1.0000>: 1.25 (See Figure Step 4B.) Command

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Circles and Arcs

Figure Step 4B


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Using the CIRCLE Command - TTR Option - continued Command: CIRCLE Specify center point for circle or [3P/2P/Ttr (tan tan radius)]: TTR Specify point on object for first tangent of circle: P5 Specify point on object for second tangent of circle: P6 Specify radius of circle <1.2500>: 1 (See Figure Step 4C and 4D.) Command:

Figure Step 4C Step 5

Save and close the drawing.

Figure Step 4D

Completed Drawing

Drafting Lesson Reading Dimensions for Circles and Arcs When you are reading the dimensions for circles and arcs, consider the following: Circles are dimensioned as diameters. For example: 2.0 DIA. Arcs are dimensioned as radiuses. For example: 1.5 R When there is more than one circle of the same diameter, they are only dimensioned once. For example: 0.5 DIA., 4 PLACES Sometimes multiple arcs are dimensioned as typical (TYP.). For example: 2.0 R TYP. Typical simply means that there is at least one more arc of the same size.

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A useful feature in AutoCAD is the Undo/Redo feature. You can undo all the commands in the current drawing session. You can also reverse an undo with a redo. To undo the last command, use the U command and to redo an undo, use the REDO command. There are icons on the Standard toolbar to help you undo and redo. Command: U Line Command: REDO Line

For 2000-2002 Users You can use the U command to undo as many commands as you wish but the REDO command must be executed before any other commands are entered or it will not work. Redo will only undo the last undo.

The Key Principles in Module 7 1. AutoCAD always draws arcs counterclockwise. 2. When you are drawing arcs, it is best to specify the center point first then the start point, which sets the radius, and then an angle or the endpoint. 3. An useful feature in AutoCAD is the Undo/Redo feature. You can undo all the commands in the current drawing session. You can also reverse an undo with a redo.

Circles and Arcs


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Lab Exercise 7-1

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Time Allowed: 30 Min. Drawing Specifications

Name

Template

Units

Text Style

Font

AutoCAD 2D Lab 07-1

Module Template A

Inches

N/A

N/A

Note: Color, Linetype, and Lineweight are all ' ByLayer ' unless otherwise instructed. Layering Scheme Objects on Layer

Name

Color

Linetype

Lineweight

All Objects Object Red Continuous Default Instructions: 1. Start a new drawing using the template shown above. 2. Save and name the drawing with the name shown above. 3. Setup the layers using the Layering Scheme shown above. 4. Draw the object shown below using the layering scheme above. In this drawing, all objects should be on layer Object and display red. 5. Check your drawing with the key. The key name is the same as the drawing name shown above. If you have trouble doing this, redo Module 3. 6. If you have any errors, correct your drawing. 7. Turn layer Key off. Completed 8. Save and close the drawing. AUTOCAD SELF-P ACED LE ARNI NG MODULES

D RAWN

D ATE

SCALE

D RAWING N O.

SHEET

Drawing

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Construction Technique The following steps are the construction technique suggested by the author to help you learn how to construct objects using AutoCAD. It is only the suggested method and if you can complete the drawing accurately using a different construct technique, that is what is important. You may want to compare your construction technique with the authors.

Construction Hints Do your best to complete the lab exercise drawing without using the following hint(s). If you get stuck and can't complete it on your own, use the following hint(s) to help you.

Hint 1 See Figure Hint 1.

Figure Hint 1

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Lab Exercise 7-2

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Time Allowed: 30 Min. Drawing Specifications

Name

Template

Units

Text Style

Font

AutoCAD 2D Lab 07-2

Module Template A4

Millimeters

N/A

N/A

Note: Color, Linetype, and Lineweight are all < ByLayer < unless otherwise instructed. Layering Scheme Objects on Layer

Name

Color

Linetype

All Objects Object Red Continuous Instructions: 1. Start a new drawing using the template shown above. 2. Save and name the drawing with the name shown above. 3. Setup the layers using the Layering Scheme shown above. 4. Draw the object shown below using the layering scheme above. In this drawing, all objects should be on layer Object and display red. 5. Check your drawing with the key. The key name is the same as the drawing name shown above. If you have trouble doing this, redo Module 3. 6. If you have any errors, correct your drawing. 7. Turn layer Key off. 8. Save and close the drawing.

Circles and Arcs


Lineweight Default

Completed Drawing

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Construction Techniques The following steps are the construction technique suggested by the author to help you learn how to construct objects using AutoCAD. It is only the suggested method and if you can complete the drawing accurately using a different construct technique, that is what is important. You may want to compare your construction technique with the authors.

Construction Hints Do your best to complete the lab exercise drawing without using the following hint(s). If you get stuck and can't complete it on your own, use the following hint(s) to help you.

Hint 1 Command: C CIRCLE Specify center point for circle or [3P/2P/Ttr (tan tan radius)]: 85,170 Specify radius of circle or [Diameter]: D Figure Hint 1 Specify diameter of circle: 10 Command: C CIRCLE Specify center point for circle or [3P/2P/Ttr (tan tan radius)]: @40,0 Specify radius of circle or [Diameter] <5.0000>: Command: C CIRCLE Specify center point for circle or [3P/2P/Ttr (tan tan radius)]: @0,20

Specify radius of circle or [Diameter] <5.0000>: Command: C CIRCLE Specify center point for circle or [3P/2P/Ttr (tan tan radius)]: @-40,0 Specify radius of circle or [Diameter] <5.0000>:

Command: Hint 2 See Figure Hint 2. Figure Hint 2 Circles and Arcs


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Autocad 2d Module 07 PDF

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