Weld symbol
Edge weld symbol
Two parallel lines calling for a weld along the abutting edges of parts lying face to face. It shares its glyph with the square groove, and only the joint the arrow points at tells them apart.
Reads as: Arrow side: edge weld, 1/4 size.
How to read it
An edge weld joins parts whose surfaces lie against one another, welded along their common edge. Think of two sheets flanged up together, or a pair of plates stood side by side and welded across their tops. The weld runs along the edges rather than into a gap between the members, so the parts are joined at their extremity rather than through their thickness.
The symbol is a pair of short lines perpendicular to the reference line, the same glyph the square groove uses. That overlap is deliberate historically but confusing in practice, and the thing that resolves it is the joint the arrow lands on. An arrow pointing at two members meeting edge to edge across a gap is a square groove; an arrow pointing at two members lying face to face is an edge weld.
The number to the left is the weld size, meaning how deep the fusion goes down from the edge into the thickness of the stacked members. On thin flanged sheet the weld often consumes the whole flange height, while on thicker parts it is a controlled depth that leaves material unfused below.
Edge welds show up constantly on formed sheet metal, where flanging two pieces up and running a weld along the top is far quicker than fitting and welding a butt joint. They also appear on the ends of laminated or stacked plates. Because the members are already in contact, fit-up problems show as unequal flange heights rather than as gaps.
Where each dimension goes
- Weld size (left of the symbol)
- Depth of fusion down from the edge into the thickness of the stacked members.
- Length (right of the symbol)
- Run length along the edge, or full length when omitted.
- Side of the reference line
- Which face of the stacked assembly the weld is made from.
- The joint itself
- The only thing distinguishing this glyph from a square groove is what the arrow points at.
Worked examples
Edge weld on flanged sheet
“Weld along the flanged edge to a depth of 1/8 from the top.”
The parallel lines are the edge weld symbol and the 1/8 to the left is how far the fusion reaches down from the edge into the stacked flange thickness.
Edge weld with a stated length
“Run a 3/16 deep edge weld four inches along the stacked plates.”
The size to the left sets the fusion depth and the 4 to the right limits the run, so the remainder of the stacked edge is left unwelded.
Common mistakes
- Reading an edge weld as a square groove because the two share a glyph.
- Treating the size as a leg dimension the way a fillet's is read.
- Assuming the weld must consume the full flange height when a smaller size is called for.
- Fitting the members with a gap between their faces, which turns an edge weld into something else entirely.
Typical joints
Related symbols
Practise reading welds, not just symbols
The drawing tells you what the weld should be. The gauge trainer is where you find out whether you can tell what it actually is.