Final answer:
In welding, a gap of 3 mm or greater in a fillet weld requires the weld size to be increased by the amount of the gap to maintain structural integrity.
Step-by-step explanation:
In the context of welding, particularly when dealing with fillet welds, there is a noticeable cost to poor fit-up. For a fillet weld, a gap of 3 mm or greater necessitates an increase in the size of the fillet weld equivalent to the gap's measurement. This is to ensure that the joint's integrity isn't compromised and can carry the required load as intended. In practice, this means that if the gap measures 3 mm, the weld size must be increased by an additional 3 mm to fill this void properly. This is critical in maintaining the structural integrity of the welded assembly and avoiding potential weld failure due to under-sizing of the weld.