Stitch Weld Symbol
"Stitch weld" is a field term — AWS A2.4 calls it an intermittent fillet weld. No special symbol exists. The standard fillet weld triangle with length-pitch notation to the right is all that appears on the drawing.
How to Read the Symbol
The intermittent fillet weld symbol uses the same right triangle as any fillet weld. The intermittent character is specified entirely by the notation to the right of the symbol. Per A2.4 §8.4.2, the pitch is specified to the right of the length dimension following a hyphen.
| Element | Position | Meaning | Citation |
|---|---|---|---|
| 3/16 | Left of symbol | Fillet weld leg size (3/16 in) | §8.2.1 |
| △ | On reference line | Fillet weld symbol — right triangle, vertical leg on left | §6.3 |
| 2 | Right of symbol | Weld segment length (2 in) | §8.3.1 |
| 6 | After hyphen | Center-to-center pitch (6 in) | §8.4.1, §8.4.2 |
Pitch vs Unwelded Distance
The single most common misread on intermittent fillet weld symbols is treating the pitch number as the gap between welds. It is not.
Pitch = center-to-center distance between adjacent weld segments on one side of the joint.
Unwelded distance = pitch minus weld segment length.
For a 2-6 symbol: 2 in welds, 6 in pitch, 4 in unwelded distance between segments. AWS A2.4 does not use the word "gap" — pitch is the governing design parameter throughout the standard.
| Notation | Weld Length | Pitch (c/c) | Unwelded Distance |
|---|---|---|---|
| 2-6 | 2 in | 6 in | 4 in |
| 3-12 | 3 in | 12 in | 9 in |
| 50-150 mm | 50 mm | 150 mm | 100 mm |
Chain vs Staggered Intermittent Fillet Welds
When intermittent fillet welds appear on both sides of a joint, they are either chain or staggered. The symbol tells you which.
Segments on both sides of the joint are directly opposite each other. Symbols appear aligned on both sides of the reference line, per the general alignment rule in §6.2.3.1.
Segments on opposite sides are offset by half a pitch — symmetrically spaced on both sides of the joint. Symbols are staggered on the reference line. This is an explicit exception to the §6.2.3 alignment rules, stated in §6.2.3.1 and §6.2.3.2.
Staggered welds produce less concentrated heat input at any single cross-section, which can be beneficial for distortion control on thin plate. Chain welds are simpler to lay out and inspect. Neither is inherently superior — the drawing specifies which applies.
Maximum Pitch Requirements
D1.1:2025 §4.13.2 sets maximum longitudinal spacing for intermittent welds in built-up members. These limits prevent buckling between weld points. The governing limit depends on the member type.
| Member Type | Maximum Pitch | Citation |
|---|---|---|
| Built-up plates — plate to component | 24 × thinner plate thickness, max 12 in [300 mm] | §4.13.2.1 |
| Built-up — rolled shapes to rolled shapes | 24 in [600 mm] | §4.13.2.1 |
| Compression members — outside plate | Lesser of 12 in [300 mm] or t × 0.730√(E/Fy) | §4.13.2.2 |
| Weathering steel (unpainted, exposed) | 14 × thinner plate thickness, max 7 in [180 mm] | §4.13.2.3 |
The §4.13.2.2 limit for compression members is not a flat 12-inch cap. The governing limit is the lesser of 12 in or plate thickness times 0.730√(E/Fy). For A36 steel (Fy = 36 ksi, E = 29,000 ksi): 0.730√(29000/36) = 0.730 × 28.4 = 20.7 × t. The 12 in cap governs for thick plate; the formula governs for thin plate. Always calculate both and use the smaller value.