The options contained within the Modify>Fillet submenu can be used to add fillet curves either with trimming to a tangency, or without trimming.

Quick Trim:

Use Quick Trim to create a fillet, but not a chamfer, with a single cursor selection. The Quick Trim feature is available from the Edit>Settings submenu. Select Quick Trim to turn quick fillet on. When using Quick Trim and prompted to select entities, make your selection as far away from the intersection of the entities as possible to prevent errors.

When adding fillets, it will be important to keep the following in mind:

• In 3D construction mode, the program will attempt to create a plane from the selected entities. If both selected entities are lines, polylines, or vectors, then the program will always be able to create a plane. This plane will be at the depth of the first entity selected if the entities are at different depths with respect to this plane.

• If a plane cannot be created and the program is in 3D construction mode, a non-planar fillet curve will be created. If a plane cannot be created and the program is in 2D construction mode, an arc will be created using the active CPlane.

• You can trim or extend the selected curves to the intersections with the arc fillet. You cannot trim closed curves, such as circles, ellipses, or closed splines.

• You can trim or extend the selected curves to the intersections with the chamfer. You cannot trim closed curves, such as circles, ellipses, or closed splines.

To view information on a feature available from the Fillet submenu, click the appropriate link below:
Trim
No Trim