Concave contour
Applied to joint
Supplementary symbol applied to fillet weld
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Description
A supplementary symbol indicating that the weld face is to be finished or left with a concave (dished, slightly hollow) profile. Often specified on fillet welds to improve fatigue performance.
In plain English
The weld face dips slightly inward -- like a shallow dish. A curved line (dip side up) across the weld symbol means 'concave finish'. On fillet welds, a concave profile gives a smooth transition at the toes, which is great for fatigue life. Some welders can achieve this naturally with the right technique and parameters; otherwise, it requires grinding. Very common on offshore and fatigue-critical fillet welds.
Symbol position
Concave curve drawn across the top of the weld symbol.
Size notation
No additional dimensions for the contour. Throat thickness still must meet minimum.
Common uses
- Fatigue-critical fillet welds (smooth toe transition)
- Offshore structural connections
- Welds subject to cyclic loading
- Applications where stress concentration at toes must be minimised
