There is a cost to poor fit-up since a gap of ____ mm or greater in a fillet weld requires the size of the fillet weld to be increased by the amount of the gap.

• A. 1 mm
• B. 2 mm
• C. 3 mm
• D. 4 mm

Answer: (B)

Gaps in fillet weld fit-up reduce the effective throat of the weld, so to achieve the required throat thickness you must compensate by enlarging the weld size by the same amount as the gap. For a gap of 2 mm or greater, the fillet weld size is increased by the exact gap amount to maintain joint strength. If the gap is 2 mm, you would add 2 mm to the weld size; 3 mm would require a 3 mm increase, and so on. This is why a 2 mm gap is the threshold in this item—the increase mirrors the gap to preserve the joint’s intended reinforcement. A smaller gap, like 1 mm, would not meet this threshold, and larger gaps require proportionally larger increases, which is why the number 2 mm is the correct choice here.