Weld Dimensioning — How to Dimension Welded Joints (ISO 2553)
Introduction
Dimensioning a weld means indicating its size on the technical drawing: throat thickness, leg length, weld length, spacing and other geometric parameters. ISO 2553 defines precise rules.
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Fillet Weld Dimensions
Leg Length (z) and Throat (a)
- Leg length (z): Side of the inscribed triangle in the fillet weld cross-section
- Throat (a): Minimum distance from root to face. a ≈ 0.7 × z for symmetric welds
In the symbol: a5 = 5 mm throat; z7 = 7 mm leg
Length and Spacing (intermittent welds)
z5 △ 50 (100) → leg 5 mm, each segment 50 mm long, 100 mm centre-to-centre spacing.
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Butt Weld Dimensions
- s = penetration depth
- Full penetration: may not be dimensioned — complete joint penetration is assumed
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Supplementary Symbols
| Symbol | Meaning |
|---|---|
| ⌒ | Convex face |
| — | Flush face |
| ⌣ | Concave face |
| ○ | All-around weld |
| ⊏ | Field/site weld |
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Practical Rules
- Dimensions on the same line as the elementary symbol
- Left of symbol: cross-section dimensions (a, z, s) with prefix letter
- Right of symbol: length × (spacing) — numbers only
- No units: millimetres assumed
- No dimension: continuous weld over full joint length assumed
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*Article based on ISO 2553:2019. Published on WeldFC Academy.*