How To Read Welding Blueprints 101

Last Updated on Apr 17, 2022

Learning how to read welding blueprints is essential if you’d like to pursue a career in this field or maybe want to improve your knowledge as a veteran welder. While sometimes they are unnecessary, welding blueprints can help you complete the projects you’re currently in charge of. These blueprints contain symbols that you must be familiar with so that you’re able to complete such a project.

However, not everyone is familiar with the ways of reading welding blueprints. If that’s the case for you, please, don’t worry. We will be teaching you how to read welding blueprints like a professional in today’s article, starting from the very basics.

What are welding blueprints?

Welding blueprints are known as technical drawings of a structural design. It contains welding symbols that will indicate how they must complete the work to the welder. Hence, reading welding blueprints is all about being familiar with the symbols.

There are diverse welding symbols, and they all refer to something different. Furthermore, a welding blueprint will have different views of the project (top, front and side views). Each side will showcase a different variety of welding symbols that will indicate to you how you must complete the project correctly.

We can say that welding blueprints act as the “expectations” the client has about the project. If you’d like to meet those expectations or even surpass them, it is important for you to be familiar with each of these aspects and what they mean.

Parts of a welding blueprint

Before we move on to the explanation of each welding symbol, let’s learn the different parts of a welding blueprint. At first, it may seem like a weird combination of drawings and letters. However, you will likely find six parts in a welding blueprint. These parts include revision blocks, bill of material, scale and title block. Additionally, you will find drawing numbers, reference numbers and dash numbers.

You won’t get lost the first time, as welding blueprints are very similar to the common shop plans there are out there. However, being familiar with each option is important so you can complete the work correctly.

Revision blocks

Revision blocks may not be present all the time, but that doesn’t make them less important. They are typically included in the documentation whenever drastic changes occur. It can be simple or complex, such as a date that specifies the time of the revision or specific numbers that refer to the changes made in the blueprint.

Bill of material

This area will show you the list of materials needed to complete the project. It is one of the essential parts of a welding blueprint, as it contains how much of a determined material you’ll need to complete the current project.


The next part is the scale. This area will show you how big the current project is, preventing you from measuring the blueprint instead. Although it may seem trivial, it is essential to ensure that the welder is building the project in the correct size.

Title block

The title block area identifies the current portion of the blueprint. It may contain different elements, including the project name or a number that refers to it. This part of the welding blueprint can be especially useful when a single project has various parts and, therefore, multiple blueprints to work with. This way, the welder can keep track of the project and complete it correctly.

Drawing number

The drawing number will differentiate one part from the other. It works like the pages of a book and is especially useful when the current project is considerably “big.” This helps the welder keep in mind the different parts of the project, allowing them to complete the project correctly.

Reference numbers and dash numbers

These numbers are used to bring in more organization to the project. For instance, sometimes, you may encounter a project requiring the same process to be completed in different parts of the blueprint. Hence, dash numbers will provide you guidance, so you know the project’s continuity is.

However, sometimes you won’t need to complete such a process so many times. In that case, there will be a reference number instead.

What are welding symbols?

Now that we know how the different parts of a welding blueprint can help you stay organized and keep the current project constant let’s talk about the welding symbols. The first time you get your eye on a welding blueprint, it may feel quite overwhelmed due to the many letters and coders found. That’s why it is necessary for you to learn how to read welding blueprints if you’re looking forward to working on considerably large projects in the future.

This section is divided into two parts:

  • Letters on the welding symbols
  • Welding symbol basics

Both parts are co-related. Hence, you will benefit from memorizing them in the future. At first, you may forget one thing or two, but these letters and symbols will get stuck in your head with practice.

Letters on the welding symbol

Besides the symbols, you will find eleven letters on a welding blueprint. Each letter refers to a certain piece of information that will become key while completing the project (i.e., length).

The following chart showcases the information that each letter will provide to the welder and how they relate to the symbols.

These letters will often be found in certain parts of the project whenever you need a specific weld to be completed for the project. Sometimes, the letters will be on their own throughout the welding blueprint, but these cases are less common.

Welding symbol basics

Now that we know what each letter refers to, let’s learn about the symbols. For starters, there are two types of symbols:

  • Weld symbols: These symbols give the welder information regarding the weld type needed in that specific area.
  • Welding symbols: While the previous symbols refer to the type of weld, the welding symbols refer to the method required to complete that specific task.

It’s also worth noting that there are diverse welding symbols out there, and the welder must be familiar with those, so they’re capable of completing the project with precision. The Universal Technical Institute says that there are 11 welding symbols classifications every welder must be familiar with. We explain each one below.

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Fillet welds

This symbol is utilized to indicate corners, laps or T-joints.

Groove welds

There are diverse types of groove welds. These symbols are prominently used whenever you’re connecting two edges (edge to edge joint). You need to memorize diverse types of groove welds, as you will likely find many of them in a single project.

Plug and slot welds

Plug and slow welds can be confusing at first, as they refer to the drilling and filling of holes. It can be quite complicated to memorize these symbols, as both types of holes can overlap from time to time.

Spot or projection welds

Spot or projection welds are the most usual type of weld used in the industry. Therefore, you’re likely to find many of them in the same project. The technique implies connecting two items with a minimal dot of welding material.

Seam welds

Seam welds refer to the virtual creation of a seam between two metal pieces while fusing them.

Back welds

As the name suggests, a back weld is typically found in the back area of a single groove weld.

Melt through welds

While the weld is only present on a determined side of the metal, it’s still possible to see where the metal melts on the other side.

Surfacing welds

You will find surfacing welds whenever you need to build up a particular area. It’s typically used to prepare such areas to be connected.

Flag toward tail field weld

This symbol indicates where the welder needs to pick up the welding whenever it reaches the final location.

Flange weld

It is usually found on pipes, and it refers to the end of the pipe that will be fitted to either a flat surface or a different pipe.

Contour welds

This type of weld is typically used in construction or engineering projects. It has remarkable importance, as it will be one of the final weld processes of the project and will be easily observed on the surface. You can find flush (straight line), convex (smiley face) and concave contour welds (frown symbol).