Objective of Chapter 4: Basic Drawing Commands

1) Create a new drawing

2) Establish the drawing units

3) Set the drawing limits

4) Create lines, circles, and arcs

5) Create ellipses and elliptical arcs

6) Create point objects and control their size and appearance.

7) Divide and measure using point objects

 

 

Create a new drawing

Drawing templates A drawing file used as a starting point when creating drawings
have the file extension: DWT­

Establish the drawing units

Decimal

 

This is the default format for displaying units. The decimal setting is unitless in that decimal units can represent any unit of measurement. In general, you should note on your drawing which drawing units you are using.

Engineering

 

Engineering units are based on Imperial feet-inch units. 1 unit is 1"

and 12 units are 1'. Inches are displayed in decimal units. For example, 15" would be displayed as 1 '-3.5".

Architectural

 

Architectural units are similar to engineering units except inches are displayed as fractions. For example, 151." would be displayed as 1'-31.".

Fractional

 

Fractional units are similar to decimal units except that numbers are represented as fractions. For example, 15.5 units would display as 15. Like the decimal setting, the fractional setting is unitless.

Scientific

 

Scientific unit display uses exponential notation. For example, 15.5would display as 1.5500E+01 (1.55x101). Like the decimal and fractional unit display, scientific unit display is unitless.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Decimal
Degrees

This is the default format for displaying angular measurements. 1 unit equals 1 degree.

DeglMin/Sec

Degrees Minutes and Seconds. With this format, there are 360 degrees in a full circle, 60 minutes in 1 degree, and 60 seconds in 1 minute. A 30-degree angle would display as 30dO'0" where d denotes degrees,, denotes minutes, and" denotes seconds. Latitude and Longitude are

typically displayed using Deg/Min/Sec.

Grads

400 grads = 360 degrees. 1 grad is roughly 0.9 degree.

Radians

Radians are measured as multiples of pi ([I). 2pi radians (-6.28r) equals 360 degrees. Pi radians (3.14r) is 180 degrees.

Surveyor Units

 

Surveyor's units show angles as bearings, using N or S for north or south,

degrees/minutes/seconds to denote how far east or west the angle is from

direct north or south, and E or W for east or west. For example, N 45dO'0"

E represents 45 degrees from North in the East direction (45 degrees in

decimal units).Angles are always less than 90 degrees and are displayed in the Deg/Min/Sec format. You can simply use E, N, W, and S to represent 0,90,

180, and 270 degrees, respectively.

 

 

 

Create lines, circles, and arcs

Cartesian coordinate system A system of locating points using an X- and Y-axis

 

6 Lines  Drawing Methods

n        Relative coordinate entry The @ symbol is used to denote  @  3,4

n        Polar coordinate entry  The < (less than) symbol is used to denote measurement < degree   symbols is used to denote

 

Circle A drawing object define by a center point and radius

6 Circle  Drawing Methods 

n        Center Radius

n        Center, Diameter

n        Tangent, Tangent, Radius

n        Tangent, Tangent, Tangent

n        2 Points

n        3 points

 

6 Arc Drawing Methods

n        3 points

n        Start, Center, End

n        Start, Center, Angle

n        Start, Center, Length

n        Start, End, Angle

n        Start, End, Direction

n        Start, End, Radius

n        Center, Start, End

n        Center, Start, Angle

n        Center, Start, Length

n        Continue

 

Start

The start option defines the start point of the arc.

End

The end option defines the endpoint of the arc.

Center

The center option defines the center point of the arc.

Radius

The radius option defines the radius of the arc. This option can only be used after

the start points and endpoints of the arc are defined.

Angle

The angle option defines the included angle of the arc. This is the difference between the starting angle and the ending angle. The angle option is available only

after the start point and either the endpoint or the center points have been picked.

Length

The length option defines the length of the chord between the start point and end point of the arc

Direction

The direction option defines the direction of a line tangent to the starting point

of the arc The direction option can only be used after the start

and endpoints of the arc have been defined.

Continue

This is not technically an option, but a behavior of the ARC command. When you  start the ARC command, if you press <Enter .J> at the first prompt, AutoCAD will start drawing an arc segment tangent to the previous line or arc segment drawn. AutoCAD uses the last specified point as the start point and determines the tangent direction from the previous line or arc segment. AutoCAD then prompts you for the endpoint of the arc (see Figure 4-23).

 

 

Create point objects and control their size and appearance.

Points -Are stored as a single coordinate in space. They don’t Plot

 

Divide and measure using point objects

2 Points Drawing Methods

 

n        DIVIDE Command used to place points at equal distances an object

n        MEASURE- Command used to place points at a specified interval along an object

 

 

SUMMARY.

You have now covered some of the basic drawing objects in CAD. Lines, circles, and arcs are the building blocks of drawings. The majority of AutoCAD drawing objects are variations of these basic objects. Learning how to create ~ modify these objects effectively is key to becoming proficient with AutoCAD.