AWS A2.4 Section 6.3, AWS A2.4 Section 7.3 · AWS D1.1:2025 Figure 5.1

J-Groove Weld Symbol

The J-groove symbol is asymmetric, so AWS A2.4 Section 6.3 keeps the perpendicular leg on the left, while AWS A2.4 Section 7.3.3 requires radius and root-face details in cross-section, detail, or tail-referenced data. Use AWS D1.1:2025 Figure 5.1 for structural CJP values.

How to read a J-groove weld symbol — perpendicular leg left, J-curve right, tail-referenced radius/root-face data, broken arrow convention, and D1.1:2025 prequalified CJP joint details.

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J-Groove Weld Symbol — Anatomy

Single-J — 45°, D=3/4"

Joint cross-section

Broken arrow convention

Double-J groove

Key rule: Per A2.4 §7.3.3, groove radii and root faces of U- and J-groove welds are specified by cross-section, detail, or other data with reference in the tail of the welding symbol.

How to Read

J-Groove Symbol Dimensions

The J-groove symbol has a vertical line (perpendicular leg) on the LEFT and a J-curve on the RIGHT. Per A2.4 §6.3, the perpendicular leg is always on the left regardless of which side of the reference line the symbol sits on.

What Goes on the Symbol

Root opening (R) — INSIDE the symbol.

Groove angle (α) — above or below the weld symbol as appropriate (A2.4 §7.3.2).

Groove depth (D) — to the LEFT for PJP.

Weld size (S) — in parentheses to the LEFT for PJP.

Where Radius and Root Face Are Specified

Root radius (r) and root face (f) — per A2.4 §7.3.3, these are specified by cross-section, detail, or other data with reference in the tail. Use the tail reference to identify the controlling J-groove radius/root-face data.

Broken Arrow

Like the bevel groove, the J-groove prepares only one member. The broken arrow points to the member that receives the J-preparation. A straight arrow means the fabricator may choose which member to prepare.

Perpendicular leg rule: The vertical line is always on the LEFT of the symbol shape. This applies to J-groove, bevel, and all asymmetric groove welds per A2.4 §6.3.

D1.1:2025 Figure 5.1

Prequalified J-Groove CJP Joints

D1.1:2025 Figure 5.1 Type 8 (single-J) and Type 9 (double-J) specify prequalified CJP joint details. All prequalified J-groove CJP joints require backgouge.

Parameter	SMAW	GMAW / FCAW
Joint designation	B-U8	B-U8-GF
Groove angle (α)	45° all positions	30° all positions
Root face (f)	1/8" (3mm)	1/8" (3mm)
Root radius (r)	3/8" (10mm)	3/8" (10mm)
Root opening (R)	0–1/8" (0–3mm)	0–1/8" (0–3mm)
Backgouge	Required	Required

Economy note: J-groove preparation reduces weld metal volume compared to V-groove on thick plate. For material >1", the savings in filler metal, heat input, and distortion justify the higher preparation cost.

Common Questions

J-Groove Weld Symbol FAQ

What is the difference between a J-groove and a bevel groove weld?

Both prepare only one member while the other stays square. The difference is the shape of the preparation. A bevel groove has a straight angled cut. A J-groove has a curved (J-shaped) preparation with a defined root radius. The J-groove reduces weld metal volume on thick plate compared to a bevel, making it more economical for material over 1 inch thick. Both use the broken arrow convention and have the perpendicular leg on the left.

Can root radius and root face appear on the J-groove symbol?

AWS A2.4 §7.3.3 says groove radii and root faces for U- and J-groove welds shall be specified by cross-section, detail, or other data with reference in the tail of the welding symbol. Use the J-groove symbol for the groove type and the tail reference to point to the controlling radius/root-face data.

What is the prequalified J-groove root radius in D1.1?

Per D1.1:2025 Figure 5.1, all prequalified single-J CJP joints (B-U8) specify a root radius of r = 3/8 inch (10 mm) with a root face of f = 1/8 inch (3 mm) and a root opening of R = 0 to 1/8 inch (0 to 3 mm). Any other root radius requires qualification by testing (PQR). The groove angle is 45° for SMAW all positions and 30° for GMAW/FCAW all positions. All prequalified J-groove CJP joints require backgouge.

Why use a J-groove instead of a V-groove?

J-groove preparation reduces the volume of weld metal needed compared to V-groove on thick plate. For material over 1 inch thick, the curved preparation removes less base metal than a full V-opening, resulting in less filler metal consumption, less heat input, less distortion, and faster welding. The tradeoff is that J-groove preparation requires machining or special cutting equipment, while V-groove can be flame-cut.

Related Reference

J-Groove Weld Symbol

J-Groove Symbol Dimensions

What Goes on the Symbol

Where Radius and Root Face Are Specified

Broken Arrow

Prequalified J-Groove CJP Joints

J-Groove Weld Symbol FAQ

More Weld Symbol Pages