Seam Weld Symbol
The seam weld symbol is a circle with two parallel lines running through it. It calls for a continuous weld between lapped sheets, usually made with roller electrodes. For resistance seam welding it is centred on the reference line (no side); for one-sided processes it goes below for arrow side or above for other side. Width goes left and length right.
How to read the seam weld symbol
A seam weld is a continuous line of fusion between overlapping sheets, often a row of overlapping resistance nuggets made by wheel electrodes. It is used where a joint must be leak-tight.
As with spot welds, side depends on the process: centred on the reference line when the weld forms at the interface (resistance seam welding), below or above the line when it is made from one face, such as laser or electron beam seam welds.
What each dimension position means
| Position | Meaning |
|---|---|
| Left (S) | Width of the seam, or a required strength per unit length. |
| Right (L) | Length of the seam. For intermittent seams, length-pitch. |
| Tail | Process such as RSEW (resistance seam welding) and any specification. |
Example callout, read aloud
“Make a resistance seam weld 0.30 inch wide and 6 inches long between the lapped sheets.”
Example: reading the callout piece by piece
- Seam symbol across the line: no side significance, resistance seam weld.
- 0.30 left: seam width 0.30 inch.
- 6 right: seam length 6 inches.
- RSEW in the tail: resistance seam welding.
Result: Make a resistance seam weld 0.30 inch wide and 6 inches long between the lapped sheets.
When it is used
- Fuel tanks, mufflers, radiators and drums that must be leak-tight.
- Long lap joints in sheet metal made at high speed with wheel electrodes.
- Laser seam welds in thin-walled enclosures and battery cases.
Common mistakes
- Drawing a spot symbol for a leak-tight joint. Spot welds leave gaps. Use the seam symbol for a continuous joint.
- Putting a resistance seam weld on one side of the line. Centre it; side has no meaning for resistance seam welding.
- Reading the left value as sheet thickness. It is the seam width (or a strength).
- Leaving out the process. Name the process in the tail so the placement is clear.
Related weld symbols
- Spot weld: A spot weld is a single nugget rather than a continuous seam.
- Edge weld: Edge welds can also seal sheet edges.
- Plug and slot weld: Slot welds give a longer weld through a hole in a lap joint.
- Fillet weld: Lap fillets seal thicker material along an edge.
- Weld-all-around: All around closes a seam right around a part.
Every weld symbol page: welding symbols chart
Calculators and further reading
Frequently asked questions
What does the seam weld symbol look like?
A circle with two parallel horizontal lines passing through it.
What is the difference between a spot and a seam weld symbol?
Both are circles; the seam symbol adds two lines through the circle, showing a continuous weld.
Why is the seam symbol sometimes centred on the line?
For resistance seam welding the weld forms between the sheets, so there is no arrow or other side.
What does RSEW mean?
Resistance seam welding.
Sources
- AWS A2.4 Standard Symbols for Welding, Brazing, and Nondestructive Examination, American Welding Society
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