To draw an arc concentric to another arc

1. Click the Arcs > Concentric Arc icon, or choose Arcs > Concentric Arc from the Keypoint Curve Toolbox.
2. Click the arc from which the new arc will be offset.
   
3. Click the start point of the arc, or type a 3D coordinate to place the point exactly.

   As you drag the start point, the Concentric Arc tool displays the distance between the two radii.

   
4. Click the end point of the arc, or type a 3D coordinate to place the point exactly.

Tips and notes

• Concentric arcs are always drawn in the direction that creates the smallest sweep angle. If you want an arc of more than 180 degrees, open the Information Window and click the Complement button under the Attributes section.
• To create a concentric circle, set the Angle/Sweep attribute to 360 degrees in the Information Window.

Concentric Arc Options

Degree

Specifies the degree of the curve. The values range from 2 to 7. The default is 6.

Spans

Specifies the number of spans in the curve. The values range from 1 to 14. The default is 1.

Note

The sum of the degree and number of spans cannot exceed 16. When creating rational geometry, as set in Preferences > Construction Options, the Spans option is not available.