The nugget hole diameter for a plug weld made through an 8 mm (5/16") hole must be at least how many millimeters?

The nugget hole diameter for a plug weld made through an 8 mm (5/16") hole must be at least how many millimeters?

• A. 3 mm
• B. 5 mm
• C. 4 mm
• D. 6 mm

Answer: (B)

For a plug weld, the weld nugget must create enough overlap with the hole to develop the joint’s shear strength without overheating or burning through. Industry practice for plug welds is to size the nugget at about 60% of the hole diameter. An 8 mm hole × 60% equals 4.8 mm, so the smallest practical nugget diameter is 5 mm. Smaller than this would reduce the weld area too much and weaken the joint, while 6 mm would still work but isn’t the minimum. So, 5 mm is the minimum nugget diameter that meets the guideline for an 8 mm hole.

For a plug weld, the weld nugget must create enough overlap with the hole to develop the joint’s shear strength without overheating or burning through. Industry practice for plug welds is to size the nugget at about 60% of the hole diameter.

An 8 mm hole × 60% equals 4.8 mm, so the smallest practical nugget diameter is 5 mm. Smaller than this would reduce the weld area too much and weaken the joint, while 6 mm would still work but isn’t the minimum.

So, 5 mm is the minimum nugget diameter that meets the guideline for an 8 mm hole.