Spot and Seam Weld Symbols
Spot welds create localized welds at discrete locations; seam welds create an elongated weld along a line or path. Their callouts can include size or strength, number, length, and pitch depending on process and drawing requirements.
- Distinguish spot, seam, and plug/slot instructions
- Read count, pitch, size/strength, and process information without borrowing fillet rules
- Connect the symbol to a lap-joint production decision
A correct icon is not yet a correct decision.
Spot and seam symbols often appear on sheet assemblies where joint preparation, electrode access, process, and spacing matter more than a conventional weld bead profile.
What each mark tells you—and what it does not.
Use the third column as a stop-check. It prevents a familiar mark from turning into an unsupported assumption.
| Visual cue | What it tells you | What you must still verify |
|---|---|---|
| Circle elementary symbol | Spot or projection weld family in the illustrated convention | A circle does not mean weld-all-around when it is centered on the reference line. |
| Two parallel lines | Seam weld family | Required seam length, spacing, and process still come from the full callout. |
| Parenthesized count | Number of spot welds where that notation is used | Do not treat count as diameter or strength. |
| Pitch to the right | Center-to-center spacing of repeated spots or seam segments | Confirm the layout and whether the seam is continuous or intermittent. |
A sheet-metal lap joint shows a circle with (6) and 2 pitch
The assembly needs repeated localized welds rather than a continuous bead.
Recognize a spot-weld instruction, then verify whether the left-side value controls size or strength, whether (6) is the required count in this callout, and whether 2 is center-to-center pitch. Confirm process in the tail or notes.
The callout is not misread as a plug weld or as a fillet weld with six-inch length.
How to read it without guessing
Identify the circle for spot or the seam symbol first. Then read the values by position and verify whether the symbol has side significance for the process and convention used on the drawing.
- Distinguish the spot and seam elementary symbols.
- Identify process or specification information in the tail or notes.
- Read size/strength, number, length, and pitch according to the applicable symbol convention.
- Confirm side significance and member arrangement from the drawing.
Similar-looking instructions, different fabrication decisions
Spot weld
A localized weld at a discrete location
DECIDING CHECKLook for count, pitch, size/strength, and electrode access.Seam weld
An elongated weld along a line or path
DECIDING CHECKConfirm continuous versus intermittent extent.Plug weld
Weld metal deposited into a prepared opening
DECIDING CHECKLook for a hole/slot detail; do not infer one from a spot circle.Three mistakes that change the instruction
Spot versus plug
A plug weld fills a prepared opening; a spot weld creates a localized joint, commonly between overlapping members, without that plug opening.
Assuming continuity
A seam callout can include length and pitch. Read the complete instruction instead of assuming an uninterrupted seam.
Reusing fillet rules
Dimension meaning and placement depend on the elementary symbol and process. Do not transfer fillet conventions blindly.
Spot & Seam Welds practice
Skill: weld comparison
Which feature most clearly separates a plug weld from a spot weld?
Five checks for this symbol
This is a drawing-reading checklist, not an acceptance standard. Use it before fabrication, fit-up, inspection, or answering a test question.
- 01Name spot or seam
- 02Check size versus strength notation
- 03Read count and pitch
- 04Confirm continuous/intermittent extent
- 05Find process and access requirements
Standards and editorial basis
This guide teaches common AWS-style drawing interpretation. It is educational material, not a substitute for the purchased standard, project specification, code, WPS, or qualified engineering direction.
Editorial method. Original training diagrams, worked decisions, misconception checks, and questions are written for learning—not copied from a standards table. Production interpretation must still follow the governing documents.
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Related symbol guides
Plug & Slot Welds
Size, Length & Pitch
Symbol AnatomyEducational practice only. Verify production work against the governing drawing, applicable standard, WPS, and qualified instruction.