Which statement best describes the difference between a fillet weld and a groove weld?

• A. Fillet welds join surfaces at a right angle without a groove
• B. Groove welds fill a groove between members
• C. Fillet welds require backing
• D. Groove welds require post-weld heat treatment

Answer: (B)

The key idea is how the joint is prepared and how the weld metal sits in the joint. A fillet weld is placed in the corner where two surfaces meet without creating a groove; the weld fills a triangular space at the intersection. A groove weld requires a groove cut into one or both members, and the weld metal fills that groove to join the parts, which is common for thicker joints and can allow deeper penetration. So the statement that groove welds fill a groove between members is the best description.

Fillet welds do not require a groove and can join surfaces at various angles, not just a right angle. Backing is not inherently required for fillet welds, and post-weld heat treatment is not a general requirement for groove welds.