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 asArrow 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
Each one is a drawing, the sentence it comes out as, and then the mark-by-mark account of why. Read the sheet first and say the sentence yourself before you look down.
Example 1: Edge weld on flanged sheet
TitleEdge weld on flanged sheetRefEdge weldEx1 / 2Reads as
Weld along the flanged edge to a depth of 1/8 from the top.
Which mark says so
- edge symbolBelow the reference lineA edge weld on the arrow side of the joint
- 1/8Left of the symbolGroove weld size - how deep the weld itself goes
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.
And what it does not say
- No length is given, so each weld runs the full length of the joint.
- Nothing sits above the reference line, so the far face of the joint stays bare.
- There is no circle at the elbow, so the weld does not continue around the joint.
Example 2: Edge weld with a stated length
TitleEdge weld with a stated lengthRefEdge weldEx2 / 2Reads as
Run a 3/16 deep edge weld four inches along the stacked plates.
Which mark says so
- edge symbolBelow the reference lineA edge weld on the arrow side of the joint
- 3/16Left of the symbolGroove weld size - how deep the weld itself goes
- 4Right of the symbolLength of each weld
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.
And what it does not say
- No pitch follows the length, so the weld is continuous over that length.
- Nothing sits above the reference line, so the far face of the joint stays bare.
- There is no circle at the elbow, so the weld does not continue around the joint.
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.