Symbol Filter
Welding Symbol Reference
| Symbol | Name | Description | When Used |
|---|---|---|---|
| Fillet Weld | Triangular-shaped weld filling the corner between two surfaces at roughly 90°. | Joining perpendicular or angled surfaces (90°+ angles) | |
| V-Groove | Two beveled edges forming a V-shape. Common for thick plate. Requires beveling on both sides. | Thick materials (>1/4"), full penetration welds | |
| Bevel Weld | One edge beveled (angled), the other edge square. Creates asymmetrical V-groove on one side only. | Medium thickness, one-sided access, cost savings | |
| U-Groove | Both edges rounded with a minimum root opening. Reduces heat input and distortion compared to V-groove. | Thick materials, heat-sensitive metals (aluminum, stainless) | |
| J-Groove | One rounded edge and one square edge. Similar advantage to bevel but with rounded instead of angled side. | One-sided beveling, reduces stress concentration | |
| Plug/Slot Weld | Circular or elongated hole in one plate filled with weld to fuse two plates together. Common in lap joints. | Lap joint overlap connections, high shear stress areas | |
| Spot Weld | Circular weld joining overlapped plates. Made by resistance welding, no filler metal. Creates a nugget. | Thin sheet metal, lap joints, high-speed production | |
| Seam Weld | Continuous weld line joining overlapped plates. Made by resistance or arc welding. Creates airtight/watertight seam. | Containers, tanks, pipes, watertight joints | |
| Back Weld | Weld applied to the opposite side of a joint after the primary weld. Improves penetration and quality. | Critical joints, full penetration assurance, pipe work | |
| Surfacing | Weld metal deposited on a surface (not joining edges). Used for buildup, cladding, or wear resistance. | Hardfacing, wear surfaces, restoration, cladding |
Reading Welding Symbols (No Guessing)
The Three Parts You Need to Know
If you can't read a welding symbol, you can't weld to print. Period. Every shop test starts with blueprint reading. The symbol has three parts:
- Reference line + arrow: Horizontal line with an arrow pointing to the actual joint on the drawing. That arrow location matters.
- Weld symbol: The shape (triangle, V, circle, etc.) that tells you the weld type. Goes above or below the reference line.
- Tail (optional): End of the line. Notes about process, electrode, anything else needed.
Master these three and you read 90% of symbols correctly.
Below the Line vs Above the Line
This is critical. Symbol below the reference line? Weld on the side the arrow points to. Symbol above? Opposite side. Both sides? Symbols both above and below. That's the whole language.
Prevent confusion. If it's written clearly, you don't misread it. No ambiguity. Either side of the joint.
Extra Symbols That Change Everything
Sometimes there's more than just the basic symbol:
- Circle at the arrow-line junction: Weld-all-around. Goes completely around the joint. Common in pipe work.
- Flag symbol: Field weld—make it on-site, not in the shop.
- Backing weld indicator: Second weld pass on the back for full penetration.
- Numbers: How many passes, which direction, how spaced.
Dimensions (Size and Length)
Weld size goes to the left of the symbol (like 1/4" or 3/8" for fillets). Length goes right. These numbers matter. A 1/4" fillet is half the strength of a 3/8" fillet. Not close.
For groove welds: root opening and bevel angle get noted. Intermittent welds show spacing center-to-center. Read the dimensions or you'll get it wrong.
Weld Symbol vs Welding Symbol (The Distinction)
Weld symbol: Just the shape. Triangle = fillet. V = groove. Circle = spot.
Welding symbol: The entire package. Arrow, reference line, shape, dimensions, supplementary stuff, tail. The whole thing.
When someone says "see the welding symbol," they mean read all of it. When they say "fillet weld symbol," they mean just the triangle.
Real-World Reality
Fillets make up about 80% of structural welds. Fast, no prep, strong enough. Grooves are for thick material and critical joints. Plug and slot welds are automotive lap joints. Spot and seam welds are resistance processes for production.
Symbols must be placed directly on the arrow-line. If it's floating weird on the drawing, ask. A misread symbol = weld in the wrong place. Not acceptable.
Standards (AWS A2.4)
American Welding Society sets the standard. Everyone follows it. Keep a symbol chart at the workstation. Faster work, fewer mistakes, get paid right.
