Weld symbol
Double V-groove weld symbol
A V above and below the reference line prepares the joint from both faces, giving an X-shaped cross section that halves the weld metal of a single V on thick material and balances shrinkage.
Reads asArrow side: V-groove weld, 5/8 size, 60° groove angle, 1/8 root opening. Other side: V-groove weld, 5/8 size, 60° groove angle.
How to read it
Two vees on one reference line describe one joint prepared from both sides. In cross section the result looks like an X or an hourglass, with a land in the middle where the two preparations meet. Each vee is dimensioned independently: its own included angle beyond the open end, its own depth to the left, and the root opening written once inside the joint.
The two halves are not always equal. Where access is better from one face, or where the joint has to be welded mostly in position, the designer may specify a deeper preparation on one side and a shallower one on the other. Read both sets of numbers before assuming symmetry, because welding an unbalanced double-V as though it were symmetric leaves either unfilled groove or wasted metal.
The reason to reach for a double-V on thick plate is volume and distortion. Filling a single vee through a two-inch plate takes an enormous amount of weld metal and pulls the joint angularly as it cools. Splitting the preparation across both faces roughly halves the volume and lets passes be alternated side to side so the shrinkage on one face is offset by shrinkage on the other.
The first side is normally welded, the joint turned, the root cleaned back to sound metal, and the second side filled. That sequence is not encoded in the symbol. If the drawing needs a specific order or a specific back-gouging step, look for it in the tail, in a note, or in the written procedure the tail points at.
Where each dimension goes
- Included angle on each side
- Total angle across the two prepared faces on that side of the joint. The two sides can differ.
- Depth on each side
- How deep that face's preparation is cut and filled, measured inward from that face.
- Root opening
- Gap between the two root faces at the middle of the joint, where the two preparations meet.
- Root face or land
- The unbevelled thickness left between the two preparations, usually dimensioned on the joint detail rather than on the symbol.
Worked examples
Each one is a drawing, the sentence it comes out as, and then the mark-by-mark account of why. Read the sheet first and say the sentence yourself before you look down.
Example 1: Symmetric double-V
TitleSymmetric double-VRefDouble V-grooveEx1 / 2Reads as
Prepare 60 degree vees on both faces, each 1/2 deep, with a 1/8 root gap.
Which mark says so
- V-groove symbolBelow the reference lineA V-groove weld on the arrow side of the joint
- 1/2Left of the arrow-side symbolGroove weld size - how deep the weld itself goes
- 60°Beyond the outer face of the arrow-side symbolIncluded angle the joint is prepared to
- 1/8Inside the arrow-side symbolRoot opening - the gap left between the members before welding
- V-groove symbolAbove the reference lineA V-groove weld on the far side of the joint
- 1/2Left of the other-side symbolGroove weld size - how deep the weld itself goes
- 60°Beyond the outer face of the other-side symbolIncluded angle the joint is prepared to
Both symbols carry the same angle and depth, so the preparation is symmetric about the mid-thickness and passes can be alternated face to face to balance shrinkage.
And what it does not say
- No length is given, so each weld runs the full length of the joint.
- There is no circle at the elbow, so the weld does not continue around the joint.
Example 2: Unbalanced double-V for restricted access
TitleUnbalanced double-V for restricted accessRefDouble V-grooveEx2 / 2Reads as
Cut a 3/4 deep vee on the arrow side and only a 1/4 deep vee opposite.
Which mark says so
- V-groove symbolBelow the reference lineA V-groove weld on the arrow side of the joint
- 3/4Left of the arrow-side symbolGroove weld size - how deep the weld itself goes
- 60°Beyond the outer face of the arrow-side symbolIncluded angle the joint is prepared to
- 1/8Inside the arrow-side symbolRoot opening - the gap left between the members before welding
- V-groove symbolAbove the reference lineA V-groove weld on the far side of the joint
- 1/4Left of the other-side symbolGroove weld size - how deep the weld itself goes
- 45°Beyond the outer face of the other-side symbolIncluded angle the joint is prepared to
The two depths differ, so most of the joint is filled from the accessible face and the far side gets a shallow preparation just deep enough to clean out and cap the root.
And what it does not say
- No length is given, so each weld runs the full length of the joint.
- There is no circle at the elbow, so the weld does not continue around the joint.
Common mistakes
- Assuming both halves are equal without reading the depth on each symbol.
- Filling one side completely before back gouging, which can lock in the distortion the double preparation was meant to avoid.
- Adding the two depths and treating the total as a single-side groove weld size.
- Expecting the symbol to specify which side is welded first - it does not.