Distinguish between a groove weld and a fillet weld.

• A. Both groove and fillet welds involve triangular cross-section.
• B. Fillet welds require a root opening to be present.
• C. A groove weld is formed at the corner of two members with a fillet; A fillet weld is along a groove.
• D. Groove welds join two members along a groove; fillet welds join two surfaces at an angle with a triangular cross-section.

Answer: (D)

The distinction hinges on where the weld is placed and how the joint is prepared. A groove weld is made in a groove cut into one or both pieces, so the weld metal fills that groove and fuses the parts along the joint line. A fillet weld, by contrast, sits at the intersection of two surfaces that meet at an angle, creating a triangular cross-section between the members without a groove being cut into the parts. Fillet welds are used at corners or intersections, while groove welds are used for butt or edge joints where the joint is prepared with a groove to allow penetration and fusion along the joint. The remaining statements either describe incorrect cross-sections or requirements (such as a root opening for a fillet weld) and don’t match how these welds are actually formed.