The Basic Elements of AutoCAD 2 (Part 2): How to Draw Circles and Arcs 

In the previous part of the workshop on computer-aided design with AutoCAD, you have read about the LINE and POLYLINE tools of AutoCAD, which happen to be the first two tools that you see in the application toolbar. Now, you can head over to the CIRCLE and ARC tools. 

Circle 

As the name suggests, the CIRCLE tool creates a perfect circle in the model space when the center point and the radius are given as inputs by the user.  

When you click on CIRCLE, the application opens up a drop-down menu with the following options: 

  • Center, Radius
  • Center, Diameter
  • 2-Point
  • 3-Point
  • Tan, Tan, Radius
  • Tan, Tan, Tan

Center, Radius Circle 

In this option, the AutoCAD software will first prompt you to specify a point in the model space to be the center point of the circle. You can identify this point either by typing in the coordinates or clicking anywhere in the model space.  

Once you have specified the center point, you will be prompted to enter a radius value. If you do not choose to enter a precise value, you can eyeball it just like you did with the LINE tool in the model space. You can change the dimensions at any point in the future.

Center, Diameter Circle 

This option to draw a circle in AutoCAD is very similar to the previous one. You should select a center point just like in the last step. Then, instead of entering a radius value, you will be prompted to enter a diameter value. 

2-Point Circle 

The 2-Point circle can be seen as a variation of the center-diameter circle. 

Upon selecting this option, you will first specify a point in the model space. This point would be one of the endpoints of the diameter of the circle you are going to draw. You can specify this point by either manually entering the values or by choosing a point in the workspace using your mouse.  

Then, you will specify another point on the model space. This point would be the opposite endpoint of the diameter of the circle you are going to create. It can be chosen the same way as that of the first point.

3-Point Circle 

The 3-Point circle lets you define or create a circle in the model space by specifying any three arbitrary points.  

Each of the points can either be specified by manually entering the coordinates or by eyeballing using your mouse.

Tan, Tan, Radius Circle 

Beginners in AutoCAD do not commonly use this option. It essentially allows you to create a circle that is tangent to any two objects and also specify a radius as the third point.  

The first two points that you have to specify are bodies or objects in the model space, while the third point can be determined by choosing arbitrarily or by entering coordinates. 

Tan, Tan, Tan Circle 

This circle tool creates a circle in the model space that is tangent to three objects. Hence, you would be prompted to specify three elements in the model space when you choose this tool.  

Like the previous tools, this is also uncommon for beginners to use.  But it will be very beneficial when drafting complex geometry such as that of a base plate. 

Arc 

Arc is nothing but a portion of a circle. When you click on the ARC tool in AutoCAD, you will see a drop-down menu consisting of the following options: 

  • 3-Point
  • Start, Center, End
  • Start, Center, Angle
  • Start, Center, Length
  • Start, End, Angle
  • Start, End, Direction
  • Start, End, Radius
  • Center, Start, End
  • Center, Start, Angle
  • Center, Start, Length
  • Continue

Most of the arcs are similar in their creation methods. Therefore, let us just take a look at the most commonly used types. The rest would then be self-explanatory. 

3-Point Arc 

The 3-Point arc is similar to the 3-Point circle. It creates an arc upon specifying three points in the model space. 

Start, Center, End Arc 

Here, you are required to first specify the starting point of an arc, then a center point of the imaginary circle that it is a part of, and another point that is on the circumference of this imaginary circle. 

Start, Center, Angle Arc 

This feature is similar to the previous arc. The only difference here is that instead of an endpoint, you would specify the angle that the arc subtends. 

Start, Center, Length 

This type of arc requires you to specify a starting point, a center of the imaginary circle that it is a part of, and the length of the arc. 

Continue 

This arc type is very different from the rest because it can be used only when there is a pre-existing object like a line or an arc in the model space. 

This tool allows you to make an arc from the endpoint of the object that you last stopped at. 

Other Features 

Other features in the geometry toolbar include: 

  • Rectangle
  • Polygon
  • Ellipse
    • Centre Ellipse
    • Axis, End Ellipse
    • Elliptical Arc
  • View Controls
    • Hatch
    • Gradient
    • Boundary

The RECTANGLE and POLYGON tools are an extended feature of the POLYLINE tools.  

If you choose the POLYGON tool, you must enter a number, and AutoCAD draws a polygon of the given number of sides of arbitrary size. The size can be adjusted later by the users themselves.  

The polygon you choose to draw can either be inscribed in a circle or circumscribed about a circle. This feature enables you to better define the size of the polygon. 

Conclusion 

You have now read all about the creation of basic geometric shapes for computer-aided design with AutoCAD. We looked at how the profiles of each geometric tool in AutoCAD are different in terms of editing. As a result, you can now create a bare-bones 2D design in the application.

In the subsequent parts, you will learn more about modifying objects in the model space. To check out more courses and workshops on CAD, visit Skill-Lync today. 


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