In welding, a set of basic weld symbols are used to describe the information of the size, quality, type of weld, starting and finishing.

American National Standards Institute (ANSI) and the American Welding Society (AWS) have listed and published a set of welding symbol elements that are necessary to recognize. Fabricators and welding engineers need to do the job as per instruction.

“ANSI/AWS A2.4, Symbols for Welding and Nondestructive Testing” is the publication that contains all important and complex welding symbols. We are going to introduce you with the most used and basic welding symbols so that you can understand them well and use them in your welding planning.

Basic Of Welding Symbols
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Weld Symbol Vs Welding Symbol

People often make mistakes mixing weld symbol and welding symbol definition. Most of the welder’s even professional one, mix that two connotation and consider as one. But weld symbol and welding symbol have differences to some extent.

Weld symbol indicates the type of weld required for a particular joint. For example, Fillet weld, Groove weld, Slot weld or Plug weld. Take a look at the common weld symbols published by

AWS (American Welding Society).

On the other hand, welding symbol indicates the complete picture of joint design. It provides all the information necessary to make a weld. In other word we can say welding symbol contains weld symbol and other supplementary & complimentary information required for a complete weld.

So we see that weld symbol is a part of welding symbol.

Structure of Welding Symbol

welding symbol
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Figure: 1.1

Here we can see a horizontal line. It is called the Reference line. All other welding information and symbols are tied along this line.

We can see an arrow pointing to the down left side of the welding symbol. This one is called the arrow line. This represents the direction of welding to be made. The arrow can point either of two sides of reference line which means two potential weld.

For example if you are said to weld two pieces of metal plates together into a T shape, welding may be operated at either even both side of the stems of T. Below are some different types of arrow frequently used in welding.

T joint arrow
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Arrows to the joint
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Figure 1.2

There are two sides above and below the reference line (in figure 1.1). The former is called the ‘Other side’ and the latter is called the ‘Arrow side’. They signify the joint direction, in other words to which direction the weld is to be applied.

In short, below the reference line is arrow side and above the reference line denotes other side in all case regardless of direction in welding symbol.

There is a flag on the left of reference line (figure 1.1). This flag symbolizes that the weld is to be made on work field during erection of the project. And if the flag is missing in symbol that means the welding project is to be made in work shop.

The circle around the left edge of reference line represents that, weld is to be made all-around the joint. See the picture below (figure-1.3) for better understanding.

circle around the joint
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Figure 1.3

At last we can see a tail on the other edge of horizontal line. It contains all supplementary information projected by engineer for welding worker or inspector.

For example it can contain the information on type of welding process, electrode requirements, detailed drawing or any other information that may aid in making the weld.

Weld Symbol

weld symbol
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Figure-2.1

Weld symbols are drawn below and above the reference line. It provides direction of weld. You can see a triangular shape on reference line. It directs whether to do groove weld or filet weld on the work piece.

Also it provides information on size of weld, length of the weld and pitch. You can see ‘X’ on the left side of reference line (see figure 2.1) that represents the size of weld. Size can be expressed in millimeter, centimeter or inches.

And to the right, you can see ‘Y’ that represents the length of weld. Length can be full depth penetration or partial. These information appears on the mentioned area.

Then lastly we can see ‘Z’ at the right most of reference line. It represents the pitch of weld in other word it describes the distances between welds on the work piece. It is optional to use.

We can see letter ‘F’ on top and bottom of the triangular shape (see figure 2.1). It is called a finish symbol. It symbolizes how the final weld is expected according to the plan. It describes the finishing phase of weld.

Types of Weld And Their Symbols

The weld symbol is drawn according to the weld type the welder is going to follow. We know there are 4 types of weld that are; Groove weld, Filet weld, Slot weld and Plug weld. Symbols are different for each weld types.

Let’s discuss the matter in detail-

Filet Weld

filet weld symbol
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Figure- 2.2

Fillet weld makes most of the joints like lap joint, corner and T joint. The symbol used for intermittent fillet weld symbols are in a triangular shape.

As we discussed above, the weld symbol contains information on size, length and pitch. Weld size can be expressed in inches, millimeter or centimeter. 

The leg of triangle, the perpendicular one, is drawn always at the left side of symbol. And the size of that leg is written at the left side also.

side where the joint is going to be made
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Figure-2.3

If sizes of two sides are same, one dimension is given only. And conversely, if two sides require different size (which is rare), then both dimensions are given and a declaration is also attached on which one leg size is longer. See the image (figure-2.4) below where two example of fillet weld is presented.

The above one contains same dimension of size (5/16”) for both legs. And the second one has different dimension (3/8” & ¼”). Also the longer one is mentioned by an arrow sign.

same dimension filet weld
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different dimension filet weld
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Figure- 2.4

The length and pitch (distance between weld beads) are always given at the right of the weld symbol (see the figure-2.1). If no length is given, then weld must be placed between points where change can be seen in the direction.

And for pitch, spacing is drawn to detect on the weld symbol. See the example below.

pitch symbol
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Figure-2.5

Groove Weld

There are eight types of groove welds in welding. They are Square groove, Scarf, V-groove, Bevel groove, J-groove, U-groove, Flare-V-groove and Flare-bevel-groove. Each of them holds different symbols. See the image below (figure-2.6).

groove weld symbols
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Figure-2.6

Square Groove Weld

It is created as tight fit or slightly loose (slight separation) on the edges. The separation amount is given to the weld symbol. See the attachment below (figure 2.7).

square groove symbol
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Figure-2.7

The figure shows a square groove weld symbol between which 1/8 inch size is mentioned. That means the weld joint Is to be made with 1/8” root opening.

V-groove Weld

It is mostly used groove weld. It is called V grooved because of its shape it creates on work piece. If the depth of penetration thickness is full or partial, the symbol appears at the left. The groove angle is defined in the symbol and welder must follow that.

On the other hand, if the joint penetration exceeds the depth, symbol is given in a parenthesis. See the attachment below (figure-2.8).

v-groove exceeding the depth
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v-groove full thickness of depth penetration
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Figure-2.8

Why is V-groove used?

A V-groove is used in welding to create a joint with increased strength and weld quality. This configuration allows for better penetration of the weld metal into the joint, resulting in a larger bonding area and enhanced strength.

Key reasons for using V-groove weld joints include:

  1. Increased Strength: The V-groove shape facilitates deeper penetration of the weld metal, leading to a stronger and more robust weld joint.
  2. Improved Weld Quality: The V-groove design allows for better control of the welding process, reducing the likelihood of defects and ensuring a high-quality weld.
  3. Welding Thick Materials: V-groove joints are especially useful when welding thicker materials, as they provide sufficient space for proper weld penetration.
  4. Enhanced Welding Efficiency: The design of V-groove joints allows for efficient welding processes, contributing to productivity and effective use of welding resources.
  5. Structural Integrity: V-groove welds are commonly used in structural applications where the integrity and strength of the weld joint are critical for the overall performance and safety of the structure.

Bevel Groove Weld

Bevel groove weld is shaped like chamfered. Here the perpendicular portion always remain at the left of the symbol and the chamfered one at the right. The arrow points at the piece which is going to be chamfered. And to signify the single bevel groove weld symbol, it uses a break in arrow line.

Angle and depth of penetration, edge treatment, and effective throat at the root follow the same method as described in V-groove.

bevel groove symbol
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Figure-2.9

U-Groove Weld

In U-groove, both edges are treated in concave shape. Here depth of penetration, effective throat and separation follow the same rule as V-groove.

u-groove symbol
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Figure-2.10

J-Groove Weld

Here one edge is treated in concave shape and the other in left square. The perpendicular portion rests in left and the arrow to the edge that will get treatment. The depth of penetration, separation & effective throat follow the same rule as V-groove treatment.

j groove symbol
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Figure-2.11

Flare-V Groove Welds

It is used to weld carved metal. The intended depth of penetration is symbolized at the left and weld depth in parenthesis.

flare V-groove symbol
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Figure-2.12

Flare Bevel Groove

It is used for same purpose as flare v groove, and that is to weld carved and round part of metal. The intended depth penetration is symbolized at the left and the weld depth at parenthesis same as flare V-groove. The only difference is, in flare bevel groove a perpendicular line always is drawn at the left of the symbol.

flare bevel groove symbol
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Figure-2.13

Common Supplementary Symbol

Commonly two supplementary symbols are used in groove weld. They are Melt-thru and backing bar.

Melt-thru weld indicates the full penetration with single side groove weld. Here the back side of the root joint is reinforced and its height is indicated in the left side of the melt-thru symbol. This symbol exists across the basic reference line that I showed in figure 1.1.

Melt-thru weld symbol
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Figure-2.14

On the other hand, Backing bar is also a full penetration of weld using single sided groove weld. A bar is placed above the basic reference line of main symbol to indicate the backing bar weld.

When the weld is completed, the bar is removed from the symbol and a ‘R’ is placed within the bar. Its shape is same as Slot and Plug weld symbols.

backing bar symbol
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Figure-2.15

Slot And Plug Weld Symbol

Plug welds are joining two overlapping metal that has round holes on them. If the holes are elongated then the weld is called Slot weld. Metals are deposited in the holes with a view to fusing the metal with base metal for completing weld.

Plug diameter is drawn to the left and pitch is to the right in Plug weld. While the width of slot is drawn to the left and pitch to the right of the symbol at slot weld. Details for both weld type is given in the tail. The holes position is given in arrow side and other side of the symbol. Furthermore, number of weld (plug or slot) is written inside the parenthesis in the symbol either at bottom or above.

Source: ANSI/AWS A2.4, Symbols for Welding and Nondestructive Testing

Plug weld design
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Slot weld design
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Figure-3.1

Contour Symbols

Contour symbols in welding are used to specify the desired shape or profile of a weld. Common contour symbols include:

  1. Convex Contour: Represented by a curved line convex to the weld symbol.
  2. Concave Contour: Represented by a curved line concave to the weld symbol.
  3. Flat Contour: Represented by a straight line across the welding symbol.

These symbols help communicate the desired appearance and quality of the weld, providing clear instructions to the welder.

Frequently Asked Questions

1. What are the 8 elements of welding symbols?

The eight elements of welding symbols are:
a) Reference Line: The horizontal line on which the welding symbol is drawn.
b) Arrow: Indicates the location, extent, and direction of the weld.
c) Basic Weld Symbols: Represented by various geometric shapes and lines, specifying the type of weld.
d)Dimensions: Indicate the size, length, or other dimensional requirements of the weld.
e) Tail: Contains additional information, such as welding specifications, process, or reference codes.
f)Finish Symbols: Specify the surface finish or contour of the weld.
g) Process Designator: Identifies the welding process, such as SMAW, GMAW, or GTAW.
h) Supplementary Symbols: Provide additional information, such as the welding method or specific instructions.

2. What is the V symbol in welding?

The “V” symbol in welding typically represents a V-groove weld joint. It indicates that the edges of the base metals to be joined are prepared in the shape of a V.

3. What is a welding code?

A welding code is a set of rules and guidelines established by industry organizations or regulatory bodies to ensure the proper and standardized practices in welding. These codes provide specifications for various aspects of welding, including materials, procedures, inspections, and quality control.

4. What is the C symbol in welding?

The “C” symbol in welding typically refers to a fillet weld. A fillet weld is a triangular weld joint that is used to join two surfaces at right angles to each other.
The “C” symbol designates the type of weld to be applied at the joint, and the size of the weld is often specified along with other relevant information. 

5. What is AV groove?

An “AV groove” in welding typically refers to a type of groove weld joint configuration. The “AV” designation suggests a groove shape where the joint preparation resembles the letter “V,” and an additional detail, often an “A” shape, is added to one side of the groove. This configuration is also known as an “Asymmetric V-groove” or simply an “AV groove.”

Finally

Welding symbols can be confusing for newbies as they are more technical and require thorough knowhow on welding techniques. However, the symbols are important to know for any one who wants to make a career in welding.

So, if you are a beginner welder and trying to learn welding more professionally, then you should understand the essential welding symbol for better depiction of weld plan.

Also check out our guide on

Maidul Islam

I am Maidul Shakil and am a welder for more that 6 years. Welding metals and joining them is my hobby and passion. I have learnt all welding techniques, safety issues, fabrication process and rigging from SUNY Westchester Community College . I am now trying to teach beginners about welding to encourage them to come to the field.

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