How to Fillet Corners of Rectangles in AutoCADby Kay Ireland ; Updated February 10, 2017
Straight lines are default in AutoCAD, since most mechanical and architectural drawings require straight edges. Still, if you need to create a fillet or curved edge, AutoCAD offers a specific command that allows you to control the radius of a fillet. The command also allows automatically remembers your settings to repeat the command when necessary. By creating a rectangle first, it's simple work to curve the edges for a more elegant drawing.
Draw a rectangle with a rectangle tool by selecting the rectangle icon from the home tab. Click anywhere on the template and then specify the opposite corner to insert the rectangle.
Click the "Fillet" button, depicted as a rounded corner above the Home tab's "Modify" panel.
Type "R" into the command line to specify the radius, then press "Enter."
Type the radius of the fillet, including unit of measure. For instance, for a radius of 10 inches, you'd type 10" without spacing. Press "Enter."
Click directly on one of the lines of the rectangle and then select the line perpendicular to the first. The fillet will automatically appear. Repeat the action by clicking the fillet icon once more, then clicking two perpendicular lines. Your settings from the first fillet will still apply. To create new settings, repeat the process and enter a new radius.
Typing "0" as the radius makes the corners of a rectangle square without a visible fillet.
To create bevelled corners, use the CHAmfer command instead of the Radius command.