AWS A2.4 weld symbol
Spot Weld Symbol
A spot weld symbol is a circle, calling for a discrete fused nugget between two overlapping sheets — usually made by resistance welding with no filler metal.
How to read the spot weld symbol
- For resistance spot welding the circle is centred on the reference line, because the process has no arrow-side or other-side significance.
- For arc spot welding the circle is placed on the arrow side or other side, because the process is applied from one side.
- The nugget diameter or the required shear strength per spot is written to the left of the symbol.
- The number of spot welds appears in parentheses.
- The pitch, the centre-to-centre spacing, is written to the right.
Where the dimensions go
| Position | What it specifies |
|---|---|
| Left of the symbol | Nugget diameter, or minimum shear strength per spot |
| Right of the symbol | Pitch — centre-to-centre spacing |
| In parentheses | Number of spot welds |
| In the tail | Process reference, for example RSW or GMAW |
Joint types
- Lap joint
- T-joint
Practical notes
- Resistance spot welding is the dominant joining process in automotive body construction.
- Because a centred symbol has no side significance, the process reference in the tail matters more here than on most symbols.
- Spot welds carry shear well and peel poorly, which is why the strength is usually specified in shear.
Spot Weld symbol — common questions
Why is the spot weld symbol sometimes centred on the reference line?
Resistance spot welding fuses the sheets from both sides at once, so there is no arrow side or other side. When the symbol is centred, it means the process itself has no side significance. Arc spot welding, which works from one side, does place the symbol on a side.
What does the number to the left of a spot weld symbol mean?
Either the nugget diameter or the minimum acceptable shear strength per spot, depending on the drawing's conventions.
What is the difference between a spot weld and a plug weld?
A spot weld fuses two overlapping sheets at their interface, normally by resistance heating and with no filler or hole. A plug weld fills a pre-cut hole with deposited weld metal.
What does the tail on a spot weld symbol usually say?
The process — RSW for resistance spot welding, GMAW or GTAW for arc spot welding. Since the symbol itself does not distinguish them, the tail is how the drawing does.
Welding symbol anatomy
Every weld symbol attaches to the same framework. If any part of the diagram above is unfamiliar, the full guide to reading welding symbols walks through the whole system.
| Reference line | The horizontal backbone of every welding symbol. Everything else attaches to it, and it is always drawn horizontal on the drawing. |
|---|---|
| Arrow | The leader and arrowhead that connect the reference line to the joint. The side of the joint the arrow touches is the arrow side. |
| Weld symbol | The shape that says which kind of weld is required — triangle for a fillet, V for a V-groove, circle for a spot, and so on. |
| Arrow side (below the line) | A weld symbol drawn below the reference line calls for a weld on the side of the joint the arrow points to. This is the convention that catches people out most often. |
| Other side (above the line) | A weld symbol drawn above the reference line calls for a weld on the far side of the joint. |
| Both sides | Symbols drawn above and below the reference line call for welds on both sides of the joint. |
| Tail | An optional fork at the far end of the reference line, used to reference a specification, process or procedure such as GMAW or a WPS number. |
| Dimensions | Size is placed to the left of the weld symbol; length and pitch are placed to the right. |