How is fillet weld size typically measured and what dictates acceptance?

• A. Leg length is not used; arc length determines size and is accepted by visual inspection.
• B. Leg length measured with a fillet gauge or ruler; acceptance per WPS or drawing tolerances
• C. Fillet width measured with calipers; acceptance by color
• D. Weld height measured with a micrometer; acceptance by weight

Answer: (B)

Fillet weld size is defined by the leg length of the weld cross-section—the distance along each leg of the weld where it meets the base metals. To check it, use a fillet gauge or a ruler to measure the length of each leg at the weld face. The weld is accepted only if that measured leg length matches the size specified on the WPS or in the drawing within the allowed tolerances. The throat thickness is related to strength, but it’s the leg length that determines nominal size and acceptance. Measurements like arc length, width with calipers, color, or weight don’t define or judge fillet weld size.