Welding symbols

How a welding symbol is read

The arrow connects the reference line to the joint; which way it points makes no difference to what the line means. A weld symbol below the line, on the side toward the reader, calls for a weld on the arrow side of the joint, and a symbol above the line calls for one on the other side. Symbols on both sides mean welds on both sides. Everything along the line is read from left to right.

A few rules apply to particular symbols. The fillet, bevel and J-groove symbols are drawn with the vertical leg on the left, whatever the weld. Where only one member is beveled, the arrow points with a definite break toward that member. The spot and seam weld symbols have no arrow side or other side of their own and are centered on the line.

Supplementary symbols

Small additions change what a weld symbol calls for. A circle where the arrow meets the line means weld all around. A black flag pointing toward the tail marks a field weld, one made on site rather than in the shop. A contour symbol says whether the weld's face is to be flush, convex or concave, and a finish letter such as G for grinding says how it is to be finished.

Differences by country or standard

The pages here follow the American Welding Society's system, used across the United States. Drawings made to the international standard, ISO 2553, use a dual reference line instead: a continuous line with a dashed line beside it, and the dashed line can be drawn above or below the continuous one. A symbol on the continuous line means a weld on the arrow side of the joint, and a symbol on the dashed line means a weld on the other side. India's IS 813:1986, which draws on ISO 2553, sets out the same rule.