For plug welds, what must be true about the hole after welding?

• A. It should be left partially open
• B. It should be widened after welding
• C. It must be completely filled
• D. It should be filled partially and then ground

Answer: (C)

Plug welds rely on filling the punched hole with weld metal so the two sheets are fused together with a solid, through-penetrating joint. The hole must be completely filled after welding because any remaining void weakens the connection, can trap moisture, and may lead to corrosion or failure under load. A fully filled plug weld provides the necessary strength and seal, and then you can grind flush if needed to blend the surface. Leaving it partially open, widening after welding, or only partially filling and grinding would all leave gaps or reduce strength, which is why complete fill is the correct approach.