Welding symbols are how the designer communicates information to the craftsman performing the welding or brazing. The American Welding Society (AWS) publishes and maintains a national standard for welding symbols. The standard’s official name is “ANSI/AWS A2.4 Standard Symbols for Welding, Brazing, and Nondestructive Examination”.
The welding symbol is the most effective, compact, and standardized way to communicate required welding information. It is also common to convey welding information by drawing notes or details, specifications, codes, and welding procedures.
Welding symbols have a standardized but often poorly understood system; this is mostly due to the lack of access to properly structured training, access to reference materials, and access to the welding symbol standard itself. The following article thoroughly covers the basics that anyone working with welding symbols would need to know.
Arrow Side: Welds on the arrow side of the joint are specified by placing the weld symbol below the Reference Line.
Other Side: Information placed above the Reference Line is associated with the side of the joint on the other side or opposite side from the arrow
The arrow side and other side of a joint are determined by their respective side position along the joint’s plane in respect to the placement of the welding symbol arrow.
Fillet weld dimensions primarily consist of Size, Length & Pitch, as depicted in the diagram below. If “L” or “P” are not defined, the weld is meant to be continuous for the joint’s length.
Fillet weld applications include continuous or intermittent conditions. Intermittent fillet welds can be specified as chain or staggered. A Stitch Weld is a common nonstandard term for intermittent welds.
Chain intermittent layouts place the fillet welds opposite each other through the length of the joint.
Staggered intermittent layouts place the opposing fillet welds in a staggered position, where fillet welds are approximately centered between the gap on the joint’s opposite side.
The pitch of intermittent fillet welds shall be the distance between the centers of successive and adjacent weld segments down one side of the joint. For example, a 4” pitch places the center of adjacent fillet welds at 4” center to center. In the example of a 2-4 intermittent fillet weld, that will leave 2” between the end of one weld and the start of the next.
Care should be taken to prevent the incorrect practice of the pitch being the distance between the end of a weld and the start of the next. This creates a condition where an insufficient amount of weld is placed in the joint and will not meet the necessary strength requirements.
Fillet weld size specifies the length of the legs of the fillet weld. A fillet weld inspection gauge is used to measure the leg length.
The size of a fillet weld is specified on the left side of the fillet weld symbol.
CJP or a Complete Joint Penetration weld is a weld in which weld metal extends through the full thickness of the base material being welded.
PJP or Partial Joint Penetration weld is a weld in which the weld metal does not reach the full thickness of the base material being welded but extends only through a portion of it.
Omitting the depth of bevel and groove weld size dimensions from the welding symbol requires complete joint penetration.
The following table demonstrates how the weld symbol dimensions are applied across the standard groove symbols.