Plug Weld Symbol
How to read a plug weld symbol — hole diameter, depth of filling, pitch spacing, and countersink angle. D1.1:2025 minimum hole size per §4.5.5 and spacing requirements per §4.11.
Plug Weld Symbol Dimensions
A plug weld fills a circular hole drilled or punched in one member to fuse it to the member underneath. The hole is then filled with weld metal — either completely or to a specified depth. Per AWS A2.4 §9, all dimensions appear on the same side of the reference line as the symbol.
Where Each Dimension Goes
Diameter (Ø) — to the LEFT of the symbol, preceded by the diameter sign. Example: Ø3/4 means a 3/4-inch hole.
Depth of filling — INSIDE the rectangle symbol. When omitted, complete fill is required. When specified, it indicates how deep the weld metal goes — e.g. 1/4 inside the rectangle means fill to 1/4 inch.
Pitch — to the RIGHT of the symbol. This is the center-to-center spacing between plug welds. Example: 3 means 3-inch pitch.
Countersink angle — below the symbol (or above, depending on placement). Specifies the angle of the hole chamfer.
Number of plug welds — in parentheses, placed above or below the symbol. Example: (4) means four plug welds.
Plug Weld Requirements
AWS D1.1:2025 §4.5.5 specifies plug weld hole dimensions and §4.11 governs spacing and material restrictions. D1.1 §7.24 covers welding technique by position.
| Requirement | Value | Source |
|---|---|---|
| Min hole Ø | T + 5/16" [8mm] | §4.5.5.1 |
| Min spacing | 4 × hole diameter (center-to-center) | §4.11 |
| Q&T restriction | Prohibited in steels with Fy > 70 ksi | §4.11.4 |
| Technique | Position-specific: flat, vertical, overhead per §7.24 | §7.24 |