Making a circle

You can select the Circle command from the Draw panel in the Home tab, or you can also use its command, C. When you click the Circle flyout, you will find six different methods for making a circle in AutoCAD:

Figure 2.23: The six draw tools in the Circle flyout

We will talk about all of these methods in the following sections.

Center, radius, and diameter

The first option in the Circle flyout will let you make a circle with center and radius values. The following is the workflow for making a circle using a center and radius:

1. Select the first option from the Circle flyout. The command line will now prompt you to specify the center of the circle:

Figure 2.24: The circle command in the command line

2. Click on any point in the drawing area and this will be selected as the center of the circle.
3. Now, the command line will prompt you to specify the radius of the circle. Type the radius value in the command line and press Enter to make the circle, or you can also move your cursor in the drawing area and click on a point to make your circle.
4. The circle will be made with a specified radius and center point.

Let’s repeat the preceding example again to make a circle with a diameter value this time:

1. Type C and press Enter to start the Circle command, or use the Circle tool from the Circle flyout.
2. Click on a point to specify the radius of the circle and then the command line will prompt you to specify its radius:

Figure 2.25: The radius prompt in the circle command line

3. Don’t add the radius value at this point. In the command line, you will also see that after or, Diameter is highlighted with D in uppercase. Using this option, you can convert the radius input of the command line to the diameter. So, instead of radius, type D and then press Enter.

4. The command line will change again and this time it will prompt you to specify the diameter instead of the radius. You can also click on the highlighted Diameter option in the command line to select it instead of typing D and pressing the Enter key:

Figure 2.26: The diameter prompt in the circle command line

5. Now, type the value of the diameter in the command line and press Enter and your circle will be rendered with the required diameter. In the Circle flyout, the second option, Center, Diameter, will also let you make a circle with a center and diameter.

So, these two methods are nearly identical, the only difference being the radius or diameter value that you need to make the circle. The methods shown in the next section are, however, completely different and you don't even need the radius or diameter value for them.

2-Point and 3-Point

The next circle option, 2-Point, requires you to specify two points for making the circle. For this, I will use the triangle shown here. Here, AB is 10 units and AC is 8 units in length:

Figure 2.27: A triangle with 10 and 8 unit side lengths

In the following example, I will make a 2-point circle on the AC line of our sample triangle:

1. Select the 2-Point option from the Circle flyout.
2. Click on the A point, then click on the C point, and you will end up with a circle that looks like the one in the following diagram.
3. In this case, the AC line is on the diameter of the circle and the length of the AC line will be equal to the circle's diameter:

Figure 2.28: A 2-point circle on the AC line

The next example, a 3-Point circle, will need three points to make the circle:

1. Select the 3-Point circle command from the Circle flyout and then click on the A point, then the B point, and finally, on the C point of our example triangle.
2. The circle will be made by connecting all three points of the triangle, as in the following diagram:

Figure 2.29: A 3-point circle on triangle ABC

The next set of options in the Circle flyout will let you make the circle with the tangent and radius as references. We will discuss this next.

Tan, Tan, Radius and Tan, Tan, Tan

The next example will require you to specify two geometries on which the circle will be tangent and then the radius of the circle:

1. Select the Tan, Tan, Radius circle option from the flyout.
2. Click anywhere on the AB line and then click anywhere on the AC line. Now, the command line will prompt you to select the radius of the circle, as in the following screenshot.
3. Type 2 and press Enter and you will have your circle that is at a tangent to the AB and AC lines. The radius of the circle will be 2 units, as demonstrated in the following diagram:

Figure 2.30: A circle tangent to two lines

In the last circle option, Tan, Tan, Tan, you need to only specify three geometries on which the circle will be tangent:

1. Select the Tan, Tan, Tan circle tool from the Circle flyout.
2. Click on the AB line, then click on the BC line, and finally, click on the AC line.

3. You will get a circle that is tangent to all three lines and it will look like this:

Figure 2.31: A circle tangent to three lines

So, in this way, you can make circles using different methods and the selection of the method depends on the dimensions provided and the type of geometry you are required to make. In the next section, we will explore the arc tool, which is basically a part of the circle, but the workflow of making an arc is very different from that of a circle.