What is a fillet weld, and how are its leg length and throat defined?

What is a fillet weld, and how are its leg length and throat defined?

• A. Fillet weld is triangular at the intersection of two members; leg length is the distance from root to toe; throat is the minimum thickness between weld root and face
• B. Fillet weld is a straight weld; leg length equals depth; throat is distance from root to toe
• C. Fillet weld is the same as a groove weld; leg length is measured along the weld axis
• D. Fillet weld is triangular but leg length is the distance from weld face to toe; throat equals root-to-face distance

Answer: (A)

A fillet weld forms a triangular cross-section where two members meet. The size is described by the leg length, which is the distance from the weld root up along each leg to the toe (basically, from the root to the outer edge along the member surfaces). The throat is the minimum distance through the weld from the weld root to the opposite face of the weld—the shortest cross‑section that carries the load. For a typical 45-degree fillet, the throat is about 0.707 times the leg length. This description matches the idea of a triangular weld whose leg length runs from root to toe and whose effective thickness through the weld is the throat.

A fillet weld forms a triangular cross-section where two members meet. The size is described by the leg length, which is the distance from the weld root up along each leg to the toe (basically, from the root to the outer edge along the member surfaces). The throat is the minimum distance through the weld from the weld root to the opposite face of the weld—the shortest cross‑section that carries the load. For a typical 45-degree fillet, the throat is about 0.707 times the leg length. This description matches the idea of a triangular weld whose leg length runs from root to toe and whose effective thickness through the weld is the throat.