Use the Modify>Chamfer options to chamfer line entities with or without trimming.
When adding chamfers, 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, or if the program is in 2D construction mode, the arc will be created using the active CPlane.
Only line entities can be chamfered.
To view information on a feature available from the Chamfer submenu, click the appropriate link below: Trim No Trim