CWI Welding Symbols Study Guide (AWS A2.4) for Part A

Why symbols get their own topic

Welding and NDE symbols are one of the larger topics on CWI Part A. The governing document is AWS A2.4, Standard Symbols for Welding, Brazing, and Nondestructive Examination. Part A is closed book, so you need its rules memorized, and some questions include a figure. AWS's own sample Part A question shows a double fillet weld symbol with unequal sizes, so expect that level of detail.

Weld symbol versus welding symbol

These are separate terms:

• The weld symbol is the small character for one weld type, such as the triangle for a fillet weld.
• The welding symbol is the whole assembly: reference line, arrow, weld symbols, dimensions, supplementary symbols and an optional tail.

Arrow side and other side

Learn this rule first:

• A weld symbol below the reference line means the weld goes on the arrow side of the joint.
• A weld symbol above the reference line means the other side.
• Symbols on both sides mean welds on both sides.
• Some symbols are centered on the line when side has no meaning.

The rule does not change with the arrow's direction or the tail's position. The tail never indicates a side.

Fillet weld dimensions

Around a fillet weld symbol:

• Size goes to the left. An unequal-leg fillet is written leg by leg, such as 1/4 x 3/8. The drawing must show which leg goes where.
• Length goes to the right.
• Pitch follows the length with a hyphen. Pitch is the center-to-center spacing of increments, not the gap between them.

Example: a fillet symbol below the line has 5/16 on the left and 3-8 on the right. It calls for a 5/16 in. intermittent fillet on the arrow side. The segments are 3 in. long and spaced 8 in. center to center.

With intermittent welds on both sides:

• Symbols directly opposite each other mean chain intermittent welds.
• Symbols offset from each other mean staggered intermittent welds.

If no length is shown, the weld runs the full length of the joint, between abrupt changes in direction. Going around corners needs the weld-all-around symbol or separate symbols.

Groove weld dimensions

Groove symbols carry more information. The terms used here, such as root opening and groove angle, are defined in the terminology guide.

• Depth of groove preparation goes to the left with no parentheses.
• Groove weld size (effective throat) goes to the left in parentheses. So 3/8 (1/2) means a 3/8 in. bevel depth and a 1/2 in. weld size. The weld size can exceed the bevel depth when root penetration is expected.
• Root opening goes inside the symbol.
• Groove angle goes outside the symbol, on the side away from the reference line.

For single-groove and symmetrical double-groove welds, if neither depth nor weld size is given, the symbol calls for complete joint penetration. "CJP" may also appear in the tail.

Orientation and the broken arrow

The perpendicular leg of fillet, bevel, J-groove and flare-bevel symbols is always drawn on the left, whichever way the arrow points.

For bevel and J-groove welds, an arrow with a break points to the member that gets the preparation. The break can be left out when it is obvious which member is prepared.

Supplementary symbols

Know these by sight:

• Weld all around: a circle at the junction of the arrow and reference line.
• Field weld: a flag at the junction. The weld is made at the site, not in the shop.
• Melt-through: a filled semicircle on the side opposite the groove symbol. It calls for visible root reinforcement on a joint welded from one side.
• Backing: a rectangle opposite the groove symbol. An R inside means remove the backing after welding. Backing material and size go in the tail or a note.
• Consumable insert: a square.
• Contour: a straight line for flush, or an arc for convex or concave.

Finishing method letters go with the contour symbol: C chipping, G grinding, H hammering, M machining, P planishing and R rolling. A flush contour with G means grind flush. A convex contour with M means machine to a convex shape.

Other weld symbols

• Plug and slot welds use a rectangle on the reference line. For plug welds, the hole size goes to the left and pitch goes to the right. A number inside the symbol gives the depth of filling when it is less than full. A number in parentheses gives how many welds.
• Spot welds use a circle; seam welds use a circle with two lines through it.
• Stud welds use a circle with an X and go on the arrow side only.

Don't confuse the backing rectangle with the plug and slot rectangle. The backing rectangle is a supplementary symbol opposite a groove weld; the plug and slot rectangle is the weld symbol itself.

Combined symbols, tails and multiple reference lines

When several weld symbols are stacked on the same side of the line, all of those welds are required on that side. Take a bevel groove with a fillet on top, both below the line. It means a groove weld reinforced by a fillet on the arrow side.

The tail holds a specification, process, welding procedure specification (WPS) number or other reference. Leave it off when nothing is needed.

With multiple reference lines, the operation on the line nearest the arrow is done first, then the next line out, and so on.

NDE symbols

Examination symbols follow the same side rules as welding symbols. Method letters to know:

• VT visual, PT penetrant, MT magnetic particle.
• RT radiographic, UT ultrasonic.
• ET electromagnetic (eddy current), LT leak, AET acoustic emission.

Letters below the line mean arrow side, above mean other side, and centered on the line means no side preference. A number in parentheses gives the number of examinations. A length to the right gives how much to examine. What each method can find is covered in the NDE methods guide.

A reading routine

On every symbol, work in the same order:

1. Which side or sides? Check above or below the line.
2. Which weld type?
3. Size or depth to the left; length and pitch to the right.
4. For grooves: root opening inside, groove angle outside.
5. Supplementary symbols: all around, field, melt-through, backing, contour and finish.
6. Tail notes and sequence of reference lines.

Mark J. Curry's tip: sketch the joint before you look at the answer choices. Many wrong answers swap arrow side and other side, or treat pitch as the gap between welds.

Related: the welding symbols chart, with labelled diagrams.

Work through the free welding symbols practice questions. To see which Part A topic to study first, take the free CWI diagnostic test.

Sources

The Symbols: Welding and NDE questions cite these documents, by document and, where we can confirm it, chapter or section. We never reproduce them.

1. AWS A2.4 (28 questions)

Found a mistake? Use "Report a problem" under any question, and Mark J. Curry checks it.

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