Tack Weld

A tack weld is a temporary fastener that holds components in their final assembled position without requiring mechanical clamps or mechanical alignment aids; once the full production weld passes are completed, the tack becomes incorporated into the structure or is removed and the underlying area re-welded. Tack weld quality matters significantly because poorly executed tacks can become crack initiation sites; they must be applied using qualified procedures and by certified welders to ensure they meet the same standards as production passes.

Tack welds are particularly critical in butt joints and groove welds where fit-up cannot be maintained by gravity alone and where fixturing constraints limit the use of mechanical clamps. Many complex structural weldments employ tack welds strategically positioned to balance restraint requirements against the need to prevent distortion during full welding.