Fillet (mechanics)

In mechanical engineering, a fillet is a rounding of an interior or exterior corner of a part design. An interior or exterior corner, with an angle or type of bevel, is called a "chamfer". Fillet geometry, when on an interior corner is a line of concave function, whereas a fillet on an exterior corner is a line of convex function (in these cases, fillets are typically referred to as rounds). Fillets commonly appear on welded, soldered, or brazed joints.
Design process.
Fillets can be quickly designed onto parts using 3D solid modeling engineering CAD software by invoking the function and picking edges of interest. Smooth edges connecting two simple flat features are generally simple for a computer to create and fast for a human user to specify. Once these features are included in the CAD design of a part, they are often manufactured automatically using computer-numerical control.
Terminology.
Different design packages use different names for the same operations.
Other 3D solid modeling software programs outside of engineering, such as gameSpace, have similar functions.