Fillet welds are particularly suited for which joint configurations?

• A. T-, lap-, and corner joints
• B. Butt joints with full penetration only
• C. T-, lap-, and corner joints
• D. Shear joints with no backing

Answer: (C)

Fillet welds are used where two members meet at an angle, forming a triangular throat that can be deposited along the intersection from one side without extensive joint preparation. This makes them ideal for T joints (where a plate meets another at right angles), lap joints (plates overlapping), and corner joints (two pieces meeting at a corner), because the weld can fill the gap along the joint efficiently and provide good strength in those configurations.

They’re not the right choice for butt joints that require full penetration through the thickness, since a fillet weld doesn’t provide the through-thickness penetration groove welds offer. And while fillet welds can be used in various joints, they’re not the standard or most typical solution for shear joints with no backing, which is why the other option is less representative of fillet-weld applications.