Weld Fillet or Fillet Weld is a basic type of weld for welding two or three members using a ‘T’ joint, Lap joint, or Corner Joint configuration. Fillet Welds account for the bulk of weld type in every welding construction although they are not used for critical welding joints.

Fillet welds are not complete penetration welds (CJP), and weld penetration is limited only to the root.

In a Weld Fillet, the plates or pipe or other material shapes are usually welded perpendicular to each other or overlapping plates (in the case of a lap joint).

One exception of skewed joint where fillet welds welded on members joined at an angle. Fillet Welds are easy to weld ad require the least welder skills. Welding codes such as ASME Section IX or AWS D1.1 allows a welder who is qualified with a groove weld to weld fillet welds of any size on any material thickness.

What is a Fillet Weld Used For?

Fillet welds are the most predominately used type of weld in fabrication. They are easy to make as they do not need any particular welding joint preparation such as bevel making, root face & root gap preparation, etc. Fillet welds are used for shear loading application or for providing strength to structures. Weld fillets are not applied in cases of load-bearing joints as they are not full penetration welds.

Fillet welds are subjected to limited non-destructive testing as they are not suitable for ultrasonic or radiographic. Mostly penetrant testing and magnetic particle testing is used for fillet welds.