Welding Symbols, Drawings and Documentation
What you must know
Read the standard welding symbol: reference line, arrow, tail, and the elementary symbols placed above (other side) and below (arrow side) the line. Know groove symbols (V, bevel, U, J), fillet, plug, slot, spot, seam, and backing symbols, plus supplementary symbols for weld-all-around, field weld, contour, and finish. Understand dimension placement: size to the left of the symbol, length and pitch to the right, with parentheses for reference dimensions. Know that the tail carries process or specification references and that omitted tails mean the process is defined elsewhere.
Traps in questions
- Reversing arrow-side and other-side placement.
- Reading a fillet size as leg length when the symbol specifies throat, or vice versa.
- Ignoring the all-around circle or the field weld flag.
- Misreading pitch (spacing) versus length in intermittent welds.
- Treating a reference dimension as a required inspection value.
Worked example
A fillet symbol below the reference line with size 6 and length 75–150 means a 6 mm arrow-side fillet in 75 mm increments with 150 mm pitch. If a circle sits at the junction, the weld continues all around the joint. Rule of thumb: below the line means the arrow side; length and pitch always sit to the right.
Inspection link
Documentation control matters: verify the drawing revision matches the work order before accepting geometry.