What is the fillet weld throat?

• A. The width of the weld at the surface.
• B. The distance from weld toe to weld root along the leg.
• C. The shortest distance from the weld root to the weld face across the cross-section.
• D. The interior volume of the weld metal.

Answer: (C)

The main idea is that the fillet weld throat is the minimum thickness of the weld across its cross-section. It is defined as the shortest distance from the weld root to the weld face, measured across the weld cross-section. This description precisely captures the cross-sectional “thickness” you use when assessing the weld’s strength. The other ideas describe the weld’s width at the surface or the leg length along the joint, or the weld’s volume, which are not the throat. In practice, the throat is typically smaller than the leg length; for a fillet weld with equal legs, the throat is about 0.707 times the leg length.