Welding Symbols and Terminology
Welding symbol questions test whether you can transfer a drawing instruction into a real weld: side, size, length, pitch, process and finish. You must know the reference line, arrow, tail and basic weld symbol.
Core rules
- The arrow points to the joint. The reference line carries the symbol. The tail may name the process or procedure. A circle at the junction means weld all around; a flag means field weld.
- A fillet weld symbol is a triangle. A groove weld symbol shows the preparation shape, such as V, U, J or square. Supplementary symbols show finish, backing, spacer or root opening.
- Under AWS A2.4, a symbol below the reference line is on the arrow side; above the line is on the other side. ISO 2553 uses a different reference-line convention, so always identify the standard used on the drawing.
- Size, length and pitch must be placed in the correct positions. For a fillet, size is the leg length unless throat is stated.
Worked example
An AWS fillet symbol below the reference line has 6 on the left and 100 on the right. This means an arrow-side fillet weld with 6 mm leg length and 100 mm weld length. If a tail note says “SMAW”, the welder uses shielded metal arc welding. The reasoning is positional: below the line fixes the side; left fixes size; right fixes length.
Traps that cost marks
- Putting the weld on the wrong side of the joint.
- Reading 6 mm as throat when the drawing means leg length.
- Missing an all-around circle or field-weld flag.
- Confusing ISO and AWS symbol conventions.