Creating arcs

The Arc tool, which creates circular arcs of any angle, has nine modes. The Push/Pull mode is available in 3D views for instantly extruding the arc after creation, and the Connect and Combine mode is available for use with the Tangent Radius and Tangent Locked modes.

The Arc tool and Quarter Arc tool share the same position on the Basic palette. Click and hold the mouse on the visible tool to open the Pop-out tools list and select the desired tool.

Mode	Description
Radius	Defines the arc by its center
Three Points	Defines the arc by clicking three points
Tangent to Line	Defines the arc by defining a tangent to a line
Center	Defines the arc by clicking two points and a center
Specified Radius	Defines the arc by two points and a specified radius
Point on Arc	Defines the arc by two end points and another point on the arc
Arc Length	Defines the arc by the arc length and specified chord length
Tangent Radius	Defines the arc by making it tangent to two selected arcs, circles, or lines based on a defined radius
Tangent Locked	Defines the arc by making it tangent to two selected arcs, circles, or lines based on a locked intersection point
Connect and Combine (available with Tangent Radius or Tangent Locked mode)	Used in conjunction with Tangent Radius or Tangent Locked mode; automatically connects two arcs by creating a third arc between them, then extends or trims the existing arcs before combining all three into one continuous arc
Push/Pull (3D views only)	Instantly extrudes the arc after creation; see Push/Pull mode of planar tools
Push/Pull Combine (available with Push/Pull mode)	When the shape to be extruded is drawn on the face of a solid object, combines the two objects into a single solid addition or solid subtraction; when this submode is disabled, the new extrude remains a separate object, and the existing solid object remains unchanged

Either move the mouse to draw the arc or use the Data bar to enter an angle. Degrees start on the positive X axis (the "East" direction), and increase going counter-clockwise. ("East" is 0 degrees; "North" is 90 degrees; and "West" is 180 degrees.) To draw a quarter-circle arc beginning at 0 degrees and ending at the 6 o’clock position, enter -90 (minus 90) degrees. Enter 270 to draw an arc three-quarters of a circle around.

To create a NURBS curve, draw an arc and then select Modify > Convert > Convert to NURBS.

To edit an arc, click the middle handle with the Selection tool and drag to change the arc radius. Press the Option key (Mac) or Alt key (Windows) to change the arc’s size.

Arc by radius

Mode	Tool	Tool set	Shortcut
Radius	Arc	Basic	3

To create an arc by its radius:

Click the tool and mode.

Click to set the center of the arc.

Click the start point of the arc. Move the cursor until the desired arc orientation and size are previewed.

Click to set the end point of the arc.

 

Arc by three points

Mode	Tool	Tool set	Shortcut
Three Points	Arc	Basic	3

To create an arc by three points:

Click the tool and mode.

Click to set the start point of the arc.

Click to set the point for the arc to pass through. Move the cursor until the desired arc orientation and size is previewed.

Click to set the end point of the arc.

 

Arc tangent to line

Mode	Tool	Tool set	Shortcut
Tangent to Line	Arc	Basic	3

To create an arc by tangent:

Click the tool and mode.

Click to set the start point of the arc.

Click to define the line to which the arc will be tangent. Move the cursor until the desired arc orientation and size is previewed.

Click to set the end point of the arc.

 

Use tangent snapping to assist with drawing the arc tangent to geometry; see Snapping to a tangent (2D Only).

 

Arc by center

Mode	Tool	Tool set	Shortcut
Center	Arc	Basic	3

To create an arc by two points and center:

Click the tool and mode.

Click to set the start point of the arc.

Click to set the end point of the arc.

As the cursor moves, the center of the arc is manipulated.

Click outside the arc to set the center.

 

Arc by specified radius

Mode	Tool	Tool set	Shortcut
Specified Radius	Arc	Basic	3

To create an arc by two points and a specified radius:

Click the tool and mode.

Click to set the start point of the arc.

Click to set the end point of the arc.

The Arc Radius dialog box opens. Enter the length of the radius.

 

Arc by point on arc

Mode	Tool	Tool set	Shortcut
Point on Arc	Arc	Basic	3

To create an arc by two end points and another point on the arc:

Click the tool and mode.

Click to set the start point of the arc.

Click to set the end point of the arc.

Move the cursor until the desired arc shape and size is previewed, and then click to set the arc. To constrain the angle of the line between the arc endpoints, press the Shift key when drawing the arc.

Without the Shift key, the angle of the line between the endpoints (clicks 1 and 2) is unconstrained, and the chord defining the arc height is an unconstrained line drawn from the second endpoint

When the Shift key is pressed, the angle of the line between the arc endpoints (clicks 1 and 2) is constrained, and the chord defining the arc height is perpendicular to the center of that line

Arc by arc length

Mode	Tool	Tool set	Shortcut
Arc Length	Arc	Basic	3

To create an arc by arc length and chord length:

Click the tool and mode.

Click to set the start point of the arc.

Click to set the end point of the arc.

The Arc Length dialog box opens; set the parameters.

Click to show/hide the parameters.Click to show/hide the parameters.

 

Arc tangent by radius

Mode	Tool	Tool set	Shortcut
Tangent Radius	Arc	Basic	3

To create an arc tangent by radius:

Click the tool and mode.

Do one of the following:

To trim or extend existing arcs and compose them with a third arc to create one new object, toggle Connect and Combine mode on. 

To create a new arc, toggle Connect and Combine mode off.

Select the two arcs/circles/lines to which the new arc will be tangent.

When the second object is selected, a preview of possible tangent arcs displays where the cursor is currently located. The arc's size is controlled by the radius. Move the cursor, and then click to set the radius (or enter the radius in the floating data bar).

Move the cursor until the desired tangent arc displays, and then click the preview to set the arc. If the arc is created with Connect and Combine mode on, Tangent Radius and Tangent Locked modes can no longer be used on the new arc.

In this example, Connect and Combine mode is toggled on

Arc tangent by locked intersection point

Mode	Tool	Tool set	Shortcut
Tangent Locked	Arc	Basic	3

To create an arc tangent by locked intersection point:

Click the tool and mode.

Do one of the following:

To trim or extend existing arcs and compose them with a third arc to create one new object, toggle Connect and Combine mode on.

To create a new arc, toggle Connect and Combine mode off.

Click an exact point on the first arc/circle/line to lock the intersection point.

Select the two arcs/circles/lines to which the new arc will be tangent. 

When the second arc/circle/line is selected, a preview of possible tangent arcs displays where the cursor is currently located. The second intersection point is determined by the radius. Move the cursor until the desired tangent arc displays, and then click the preview to set the arc. If the arc is created with Connect and Combine mode on, Tangent Radius and Tangent Locked modes can no longer be used on the new arc.

In this example, Connect and Combine mode is toggled off

Arc into segments

Creating quarter arcs