Weld Joint Types and Geometry
Fillet welds, groove welds, CJP, PJP, throat dimensions, root openings, and root face.
- Define fillet weld geometry including leg size and theoretical throat
- Describe groove weld types, root opening, and root face
- Distinguish between CJP and PJP joint penetration
Leçon 1
Fillet Weld Geometry
What Is a Fillet Weld?
A fillet weld is a triangular weld joining two surfaces at approximately right angles. It is the most common weld type in structural fabrication, used for T-joints, lap joints, and corner joints. Fillet welds do not require groove preparation - the pieces are simply positioned and welded.
Leg and Throat Dimensions
The leg of a fillet weld is the distance from the root to the toe along the fusion face. For an equal-leg fillet, both legs are the same size. The weld symbol specifies the required leg size.
The throat of a fillet weld is the shortest distance from the root to the face of the weld. For an equal-leg fillet weld, the theoretical throat dimension is 0.707 x leg size. This mathematical relationship comes from the geometry of a 45-degree right triangle.
Critical Formula
Theoretical throat = 0.707 x leg size. For a 3/8" fillet weld: throat = 0.707 x 0.375 = 0.265". The throat is the critical dimension for calculating weld strength.
A fillet weld joins two surfaces at right angles with a triangular cross-section. The leg is the distance from root to toe. The theoretical throat is 0.707 x leg size for an equal-leg fillet. The throat dimension determines weld strength.