The minimum width of a slot weld equals the material thickness plus how many millimeters?

• A. Thickness of the material welded plus 4 mm
• B. Thickness of the material welded plus 8 mm
• C. Thickness of the material welded plus 12 mm
• D. Thickness of the material welded plus 6 mm

Answer: (B)

For a slot weld, the amount of weld metal needed to reliably transfer the load depends on how thick the joined material is and the geometry of the weld around the slot. The rule used here is that the minimum width of the slot weld is equal to the material thickness plus 8 millimeters. That extra 8 mm provides enough weld volume around the slot to achieve proper penetration and reinforcement, ensuring the cross‑section can carry the intended shear load and accommodating the weld bead shape and heat-affected zone. For example, if the plates are 6 mm thick, the minimum slot width would be 14 mm. Other added amounts (like 4, 6, or 12 mm) do not align with this standard guideline and would not guarantee the same level of weld capacity and coverage.