Converting Between Rounded Edges and Chamfered Edges
Click Pull in the Edit group on the Design tab.
Select the edge or edges you want to convert to chamfers or rounded
edges.Double-click to select a tangent chain.You can't
convert a chamfered edge if you have changed the setback
distance(s).
Select the Chamfer option or the Round option in the Options panel or from the
mini-toolbar.The rounded edge is converted to a chamfered edge.
Note: You cannot convert a chamfer to a round if you have
changed its setback distance(s).