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Double-V groove weld symbol: what it means on a drawing

Fillet Gauge editorial teamSources checked 4 min read

The double-V groove weld symbol is a V-groove mark drawn on both sides of the reference line, one pointing up and one down. It calls for a joint in which both members are beveled from both faces, leaving a root face in the middle, and welded from both sides. Each V carries its own dimensions.

A butt joint drawn end on with both plates beveled from top and bottom, leaving a short root face in the middle, both grooves filled with weld metal, beside a V below and a V above the reference line, each with 3/8 on its left and 60 degrees beyond its open end
One V per side, and each side writes out its own numbers. Numbers are invented.
Use this diagram

How to read it

  1. Read the arrow side first. The V below the line is the arrow side of the joint. Its depth, weld size, root opening and groove angle apply to that face.
  2. Read the other side. The V above the line is the far face. Read its numbers separately. They often match the arrow side, but they don't have to: a double-V can be deeper or wider on one side.
  3. Check every number is there. When both sides are the same, both sides are still dimensioned. If one side's depth is missing, that side's preparation is unknown. Ask, don't copy the other side.
  4. Work out the root face. Take both groove depths away from the plate thickness and what's left is the root face. On 3/4 plate with 3/8 each side the root face is zero; with 5/16 each side it's 1/8.
  5. Look at the line itself. A rectangle that breaks the reference line between the two Vs is a spacer, a strip set in the root between the members. Its material and size come from the tail or a note.

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Symbols - Welding and NDE

On a welding symbol, what does a circle at the junction of the arrow and the reference line indicate?

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Why double-V

Beveling from both faces halves the depth of each groove, so a thick joint takes much less weld metal than one deep single V. Welding alternately on each side also balances the shrinkage, which helps hold the joint flat. The cost is access: the part has to be turned or reached from both faces, and the second side's root is often gouged back to sound metal first.

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Every answer comes with a full explanation.

Common mix-ups

  • Double-V or single V. A V-groove on one side of the line is welded from that face only. Two Vs mirror across the line for a double.
  • Double-V or X. The two Vs meet at the line and can look like an X. Read them as two Vs, each opening away from the line, and read each one's numbers on its own side.
  • Double-V or double square. Two strokes on each side is a square groove welded from both faces, with no bevel at all.
  • Groove angle or bevel angle. 60° beyond a V is the whole included angle on that side, so each member is beveled about 30° on that face when the bevels are equal.

Double grooves on the CWI exam

Reading two sides of one symbol is core to Symbols, Welding and NDE, at least 10% of closed-book CWI Part A, and the root face arithmetic is a quick calculation worth having cold. Part B, where Utilization of Specifications and Drawings is at least 8% of the practical, is where you read symbols like this off a full drawing.

Practice it

In the welding symbol builder, pick the V-groove, set it to both sides and read back how each side is described. Compare it with the double-V box among the supplementary marks on the welding symbols chart.

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Take the free 10-question check. It's weighted to the Part A outline, scored by domain and needs no signup, so you see whether symbols or another domain costs you the most points. The Part A course gives you a lesson on reading welding and NDE symbols and on every other exam subject, two full-length timed practice exams, and a worked explanation with every answer.

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Facts checked 24 October 2026 against the sources listed above. If something has changed, tell us and we will correct it within 2 business days.

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