Spot Weld Symbol
The spot weld symbol is a circle. For resistance spot welding, where the weld forms between the sheets, it is drawn across the reference line with no arrow or other side. When the process works from one side, such as arc or laser spot welding, it sits below (arrow side) or above (other side). Size goes left, pitch right, number in parentheses, and the process in the tail.
How to read the spot weld symbol
A spot weld is a small, round fused zone between lapped sheets. The circle on the symbol represents that nugget.
Placement depends on the process. In resistance spot welding, electrodes clamp both sides and the nugget forms at the interface, so the side has no meaning and the circle is centred on the reference line. For processes applied from one face, the circle goes below the line (weld from the arrow side) or above (from the other side).
What each dimension position means
| Position | Meaning |
|---|---|
| Left (S) | Diameter of the weld nugget, or a required shear strength per spot when the drawing specifies strength instead. |
| Right (P) | Pitch: centre-to-centre spacing. |
| Beyond, in parentheses (N) | Number of spot welds. |
| Tail | Process, such as RSW (resistance spot welding), and any specification. |
Example callout, read aloud
“Make six resistance spot welds, each 0.25 inch in diameter, spaced 2 inches centre to centre.”
Example: reading the callout piece by piece
- Circle across the line: no side significance, as expected for resistance spot welding.
- 0.25 left: nugget diameter 0.25 inch.
- 2 right and (6) beyond: six welds at 2-inch pitch, 10 inches from first to last.
- RSW in the tail: resistance spot welding.
Result: Make six resistance spot welds, each 0.25 inch in diameter, spaced 2 inches centre to centre.
When it is used
- Sheet metal assemblies: enclosures, automotive body panels, appliance cases.
- Lap joints in thin material where a continuous weld would distort the sheet.
- High-volume production with robotic or press-type spot welders.
Common mistakes
- Putting a resistance spot weld on one side of the line. Resistance spot welds have no side; centre the circle on the line.
- Reading size as electrode tip size. Size is the nugget diameter (or a strength). Tip size is set in the procedure.
- Leaving out the process. The tail should name the process so side and placement make sense.
- Confusing spot and seam symbols. Seam welds add two lines through the circle.
Related weld symbols
- Seam weld: A seam weld is a continuous row of overlapping spots.
- Plug and slot weld: Plug welds join lapped plates through a hole.
- Fillet weld: Fillets join lapped edges in thicker plate.
- Edge weld: Edge welds join flanged sheet edges.
- Field weld: The field flag can be added to any symbol, including spot welds.
Every weld symbol page: welding symbols chart
Calculators and further reading
Frequently asked questions
Why is the spot weld symbol drawn on the line?
For resistance spot welding the nugget forms between the sheets, so there is no arrow or other side. The centred circle shows that.
What does the number left of the spot weld symbol mean?
The weld (nugget) diameter, or a minimum shear strength when the drawing calls for strength.
Where does the number of spot welds go?
In parentheses beyond the symbol.
What does RSW in the tail mean?
Resistance spot welding, the most common spot weld process.
Sources
- AWS A2.4 Standard Symbols for Welding, Brazing, and Nondestructive Examination, American Welding Society
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