Distance from the joint root to the weld face. The theoretical throat of an equal-leg fillet is about 0.707 times the leg size; the effective throat used in design adds any credited penetration, and the actual throat is measured on the real profile. Strength calculations use throat area, so a wide but concave fillet can be weaker than its leg size suggests.
Concave fillet like that cheats the throat, measure it with the concave side of the gauge.
Also heard as
- effective throat
- theoretical throat
- actual throat
Related terms
Leg
How far a fillet weld reaches along each member from the corner, the dimension used to call out fillet size.
Fillet weld
Weld with a triangular profile laid in the corner where two members meet, the usual weld on T, lap and corner joints.
CJP
Complete joint penetration: a groove weld that fuses through the full thickness of the joint.