How To Read Welding Blueprints – The Ultimate Guide

A large number of welders struggle to read blueprints. Many market welders do not receive vocational training. Those who do attend classes don’t get trained on blueprints or neglect to read the written material. Only a handful of welders are able to read and use blueprints correctly.

This article will show you How To Read Welding Blueprints and understand welding blueprints. It will also explain the benefits these can bring to your project’s quality and cost reduction.

The Role of Welding Companies:

Welding companies play a significant role in the adoption and maintenance of welding blueprints. Only a few companies require that welders know how to read symbols. Companies are reluctant to place strict requirements on hiring welders because they are not practical.

But just because a welder isn’t proficient at reading blueprints doesn’t mean they can’t be trained to do better. To help improve their technical skills, welding companies can offer training sessions to their welders. They can hold coaching classes within their premises. 

Additionally, they can attach posters to the workshop with welding blueprint symbols. Many welding companies have a problem: they don’t have anyone who can teach others how to read blueprints.  This is a common problem for small- to medium-sized businesses. 

This type of training is available to organizations through the hiring of professional welder trainers. This knowledge is available to welding supplies suppliers, particularly industrial wholesale distributors, and welder equipment manufacturer’s sales representatives. 

This training can be offered to your employees by you asking them. Most likely, they will be willing to offer this training and it won’t cost you anything.

Fundamentals of Welding Blueprints:

Three types of views will be apparent in typical welding blueprints. These views are the right side, top, and front. There are also a variety of welding symbols located in specific areas of the sketch. 

These symbols indicate the type of work required to complete the project. Let’s take a closer look at each type of view and the symbols.

Basics of the (Welding Blueprints) Symbol:

The structure of welding symbols is specific and describes the type and direction of the weld. Each welding symbol you see will include an arrowhead that points to the spot where the weld should be made.

Welding Symbols

The arrow connects to what we call the leader line. The line intersects with horizontal reference lines. The arrow can point either upwards or downwards to indicate where the weld should be made. The tail is located at the other end of the reference line. 

signifying where to make the weld

There may be several forks on the tail that point in different directions. This tail may indicate that you need to follow specific instructions when welding. You will find either parallel lines or a curved shape at the center.

specialized instructions for the weld

These lines will indicate what type of welding you should do on the metal frames. There are many types of welds you can make. 

metal frames

It is important to not confuse the weld symbols in order to do a good job. The reference lines have symbols that indicate which type of welding should be performed, while the overall symbol for welding gives complete instructions.

complete instructions for the welding project

Pay attention to where the symbol is placed on the reference line when you read a welding diagram. The weld symbol should not be placed below the reference line. Instead, it should be on the arrow side. If the weld symbol is located above the reference line, it is best to weld on the opposite side from the point where the arrow is.

Supplementary Symbols

Multiple welds should be done on each side of the joint if the weld symbol appears on both sides. Different welding Blueprints are available to distinguish between different types of welds. Welders have to learn the meaning of each symbol. 

To make it easier to remember the basic symbols, you can print them out and place them on your welder. Once you’ve memorized the most commonly used symbols, you can move on and learn more.

additional welding symbols

Letters on the Welding Symbols:

You will find letters on the Welding Blueprints when you begin to read them. These letters will provide important information that you need to know when welding, such as the length and root openings. 

This is how to refer to the letters.

  • A: Angle of Countersink
  • C: Chipping Finish
  • F: Finish Symbol
  • G: Grinding Finish
  • L: Length in the Weld
  • M: Machining Finish
  • N: The number of spot or projection welds
  • P: Pitch for Welds (Center to Center Spacing)
  • R: Root Opening; Depth Of Filling
  • S: Depth and Strength
  • T: Specification Process

These letters will be displayed with the symbol of welding when there is a particular weld required to complete the project. You may also find the letter on some blueprints.

Dimensions and Angles:

It is important to pay attention to the dimensions and angles of the Welding Blueprints. They make it easier for you to understand the blueprint. 

A blueprint is packed full of information. An experienced user will only need to read a few lines. These blueprints can be used for communicating length, width, depth, and the opening of a weld.

The weld’s diameter, or width, is usually noted on the left side of the symbol. It will then be broken down into fractions in inches. On the right side of the weld symbol is the length. It can also be expressed in inches.

Welding symbols indicate whether welds should be mirrored or offset on each side. Mirrored welds are those that are exactly the same location as sheets on opposite sides. If they are made in the exact same location as the frame, they will be considered to be offset.

The weld symbol includes the angle of the welding, the root opening, and the root face dimensions. The identification of the weld depth, angle specifications, and root opening is sided by numbers. These numbers help to clarify the need for beveling on the base metal in order to weld successfully above or below the reference lines.

above or below the reference line

The dimensions written below the reference line refer to the joint on that side, while the dimensions marked over the line refer to the joint on that side. The welds can be identified on both sides of the joint. Sometimes, it may be necessary to specify a series or multiple welds for a project. 

This is an alternative to a single, long weld. This is common when working with thin or heat-sensitive metals. A consistent, long-lasting weld can cause damage. 

The following welding diagram will show that you should use a string 3-inch fillet welds. Do not weld in a workshop if you see a flag at the intersection of the reference lines. 

3 inch intermittent fillet welds

Flags are used to signal that the weld must take place in the field.

weld must be carried out in the field

Common Symbols and Their Meanings:

Welding blueprints can contain a variety of symbols that are difficult to read. These symbols are used to help the welder determine the size of the project and any other details. This section will cover some common symbols and their meanings. 

The American National Standards Institute (ANSI), which is the American National Standards Institute for Welding, has a complete list of symbols.

Fillet Welds:

Fillet Welds

Fillet welding (pronounced fill-it) is used to create 90-degree lap joints and T-joints. Corner joints can also be made using the fillet weld. The cross-section of the weld is nearly triangular, as the symbol indicates. 

However, the shape of the weld is not always a 90-degree right-angled triangle. In the corner of the joint between the two members, a small amount of welding metal is placed. It penetrates the joints and fuses with the frames’ material to create them.


The perpendicular leg of the triangle is drawn on the left side regardless of its orientation. The leg’s size is indicated on the left side of the weld symbol.

The symbol will only show one dimension if the legs of the weld should be equal in size. The symbol will show both dimensions if the legs of the weld are supposed to be different sizes.  You will also see which leg should be longer in the drawing.

Groove Welds:

Groove Welds

The groove weld is used to connect two metal sheets or frames. This type of weld can also be used in corner joints, T joints, and joints between flat and curved pieces of metal. Welding is a process that differs from other welding methods. 

This is mainly due to the geometry of the parts and the way they are prepared around their edges.  The welding process involves the depositing of the joining metal within the groove. It penetrates the base metal and fused with it to form the joint. You can further classify the groove weld into these categories.

Square Groove Welds:

Square Groove Welds

This type of groove can be made by creating a small parting of the metal edges, or by securing two metal frames together. If this is the case, the weld symbol will show the diameter of the created space.

V-Groove Welds:

V Groove Welds

This is similar to square welding, but the edge of the metal pieces is chamfered on either one or both sides to create the groove. On the weld symbol, you will see the degree of the V angle and the separation at the root.

If the groove is made by separating the metal it may not be fully embedded in the sheet metal.

groove is created by separating the metal

Bevel Groove Welds:

This type of weld has one edge chamfered, and the other square to create a bevel groove. The perpendicular line of the bevel symbol is always drawn on either the left or right side, regardless of the direction that the weld is facing. 

Bevel Groove Welds

The arrow indicates the metal joint that needs to be chamfered. Breaking the arrow line emphasizes the importance of the direction.

U-Groove Welds:

U Groove Welds

The edges of the metal pieces are given a concave treatment. They form a U-shaped groove when they are joined. The V-groove method is used to show the depth of the edge treatment, the separation at the root, and the effective throat.

J-Groove Welds:

You create the J-groove by concaving one piece of metal while leaving the other as a square. This process is very similar to that of the bevel groove joint. The left side shows the perpendicular line. 

J Groove Welds

The arrow indicates the metal that will receive the concave treatment. The following describes the depth of edge treatment, root separation, and effective throat.

Flare Groove Welds:

Flare Groove Welds

This type of welding is used to join more than one rounded part together. The symbol shows the ideal weld depth on the left, while the weld depth is in parentheses.

Plug and Slot Welds:

To join metal sheets and frames that overlap, plug welds or slot welds can be used. Both pieces will have holes to connect them. Metal sheets with plugs are round-shaped, while slot sheets have elongated holes.

The holes are filled with welded metal as it penetrates the sheets and fuses with them to form the joint. The symbol will indicate the plug’s diameter for plug welding. 

Plug and Slot Welds 1

The right side of the symbol labels the pitch of the plugs. Slot welds show the width of each slot. The symbol is shown on the left, while the length and pitch of the symbol are illustrated to its right.

Near the tail is a reference to the detailed drawing. Below the weld symbol, which is in parenthesis, you can see the total number of slots or plugs that need to be welded. The arrow side and the other side indicate which piece has the hole.

If the hole is not completely filled with welding metal, the depth of filling it up will be noted in the weld symbol.


The metals are represented in two blocks when they join together in some of the above welding diagrams. This is to make it easier for you to understand how to weld. However, this is not always true for welding blueprints. 

This is how a real welding diagram should look.

Putting It All Together

You will see reference lines marked with a break in some welding blueprints. This means that the joints should be prepared before the pieces are joined. This design also indicates the type of preparation needed for the weld.

It may be difficult for beginners to understand the workings of welding blueprints. Even experts can find the drawings too complex and confusing. Read the drawings properly, it takes patience and time.

It will become much easier to read blueprints and create stunning and complex projects.

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