The letter G on a welding symbol means Grind — the weld face must be ground to achieve the specified contour. Full explanation of all weld finishing symbols and when they apply.
Direct Answer
G = Grind. The letter G placed above or below the weld symbol (next to the contour symbol) means the completed weld face must be ground to achieve the specified contour — flush, convex, or concave. It specifies the finishing method, not a surface roughness value. The contour symbol tells you the profile; the G tells you how to achieve it.
AWS A2.4 Finishing Methods
All Finishing Designators
AWS A2.4:2020 defines seven letters that specify the method used to finish a weld face. They always appear adjacent to the contour symbol — flush line (—), convex arc (∪), or concave arc (∩).
G
Grind
Abrasive grinding. Most common. Used to achieve flush contour on structural welds.
M
Machine
Mechanical cutting or milling. Used when precise dimensional tolerance or smooth finish is required.
C
Chip
Chipping. Less common. Used to remove weld spatter or rough slag.
H
Hammer
Hammer peening. Used to induce compressive residual stress or consolidate the weld surface.
P
Planish
Planishing roll or burnishing. Smooths by controlled plastic deformation. Uncommon in structural work.
R
Roll
Roller burnishing. Smooths and work-hardens the weld surface. Used in pressure vessels and pipe.
U
Unspecified
Method not specified — contractor may use any suitable method to achieve the required contour.
If no finishing letter appears — only a contour symbol — the method is left to the fabricator's discretion. If neither contour nor finishing symbol appears, the weld face profile is left as-welded.
AWS A2.4 — Contour Symbols
Contour Symbols — What Profile to Achieve
The finishing letter (G, M, C, H, P, R, or U) specifies how. The contour symbol specifies what profile. They always appear together — contour symbol closer to the weld symbol, finishing letter outermost.
Flush (—)
Straight line. Weld face to be flush with base metal surface.
Convex (∪)
Curved outward arc. Weld face to be convex — rounded above base surface.
Concave (∩)
Curved inward arc. Weld face to be concave — hollowed below base surface.
Symbol Placement
Where G Appears on the Welding Symbol
Symbol Stack — Arrow Side Example
Reading from inside out: fillet symbol (triangle) → flush contour (horizontal line) → G (grind). Together: make a fillet weld, then grind it flush.
The position relative to the reference line tells you which side:
Below the reference line → arrow side (same side as the arrow)
Above the reference line → other side (opposite side from the arrow)
Both sides → the same finishing requirement applies to both weld faces
Applications
When Is Grind Finish Required?
The G (grind flush) requirement appears most often in these situations:
Fatigue-sensitive structures — bridges, crane girders, offshore structures. Flush profile removes the stress-concentration of the weld toe, extending fatigue life significantly.
Surfaces receiving additional welds — a butt weld ground flush before a fillet weld is deposited over it ensures full contact and avoids incomplete fusion.
Pressure-retaining components — ASME and API require flush finish on pressure boundary welds for radiographic testing validity.
Architectural / exposed steelwork — visible welds on handrails, facades, or decorative structures where appearance matters.
Sliding contact surfaces — mating surfaces on machinery, bearing pads, or base plates where weld reinforcement would interfere with fit.
If G appears without a contour symbol, it is an error on the drawing — G alone is incomplete. A contour symbol must accompany it.
More Questions
Finishing Symbol FAQ
What does G mean on a weld symbol?
G means Grind — the completed weld face must be ground to the contour specified by the adjacent contour symbol. G specifies the finishing method. The contour symbol (flush line, convex arc, or concave arc) specifies the resulting profile. Both are required together for a complete finishing specification per AWS A2.4.
Is G only used with flush contour?
No. G can appear with any contour symbol: flush (—), convex (∪), or concave (∩). Most commonly G appears with the flush contour symbol — meaning grind the weld face flat with the base metal. But G can also mean grind to a convex or concave profile when the contour symbol indicates that profile.
What if there is no G, just a contour symbol?
If only the contour symbol appears with no finishing letter, the method of achieving that contour is at the fabricator's discretion. The fabricator may grind, machine, or leave as-welded if the weld naturally achieves the required contour. In practice, if the weld doesn't naturally meet the contour requirement, grinding is the assumed method — but specifying G removes ambiguity.
Where exactly is G placed on the welding symbol?
The sequence from the reference line outward is: reference line → weld symbol → contour symbol → finishing letter (G). So G is the outermost element. It appears below this stack for the arrow side and above this stack for the other side. G must be adjacent to the contour symbol — not floating away from it on the symbol.
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