Flush contour symbol

The contour symbol is drawn just beyond the weld symbol's outer face, on the same side of the reference line. When it is a straight bar, the requirement is a flush face: the finished weld is to sit level with the surrounding base metal rather than standing proud with the crown a weld naturally forms.

A bar on its own says what shape is wanted but not how to get there. That is the job of the finish letter written alongside it. Without a letter, the flush face may be produced by welding technique alone, which is achievable on some processes and positions and unrealistic on others. With a letter, the method is fixed and there is no argument on the shop floor about grinding versus machining.

Flush faces are asked for when something has to sit against the weld, when flow across the surface must not be disturbed, or when the joint sees fatigue loading and the abrupt change in section at a weld toe would concentrate stress. Removing the reinforcement smooths that transition considerably, which is why fatigue-critical joints so often carry this bar.

There is a cost to it. Dressing a weld face flush removes the reinforcement that gives a joint its margin, so a weld ground flat must be full and sound underneath before dressing, not built up and then cut back. Grinding into the base metal below the surrounding surface turns a finishing operation into a defect, which is why depth control matters as much as the shape.