On a fillet weld symbol, what does the size number represent?

• A. The weld length along the axis of the joint.
• B. The leg length of the fillet weld; the throat is smaller than or equal to leg length.
• C. The weld throat thickness.
• D. The angle of the fillet weld relative to the base metal.

Answer: (B)

On a fillet weld symbol, the size number is the leg length of the fillet weld—the distance along each welded leg where the weld sits on the faces meeting at the joint. The throat, which is the shortest distance from the weld root to the face of the weld, is derived from that leg length and is always smaller than or equal to it (for a standard 90-degree fillet, roughly 0.707 times the leg length). The overall length of the weld along the joint and the weld angle are specified separately and do not come from this size number.