Guide To Reading Welding Blueprint Symbols

Whether you’re an experienced welder or have considered pursuing a career in welding, you’ve most likely heard of welding blueprint symbols. Welding blueprint symbols are used as a shorthand code to describe the type of weld, its size, and other information. Similar to how a web designer uses code when creating a website or a CNC machinist follows blueprints for their designs, welders rely on blueprints to guide their work and ensure precision in their welds. Welders interpret and decipher the symbols when creating their work.

If you’re unfamiliar with welding symbols, don’t panic! While they can look intimidating at first, learning the basics behind what they mean can transform your welds. Welding symbols consist of several elements, including a reference line, an arrow to show the joint and a tail for additional information. There are different types of welding joints, including butt, corner, T, lap and edge joints.

To pursue a career in welding, completing a welding training program is recommended, such as the Welding Technology program at Universal Technical Institute (UTI).¹

Keep reading to learn all about what welding blueprint symbols are, the basics of how to read them and more.

What Are Welding Blueprint Symbols?

Welding blueprint symbols are used as a means of communication between a designer, such as a shop foreman, welding engineer or supervisor, and a welder. Essentially, they are a set of symbols used as a shorthand code for describing the type of weld, its size and other processing and finishing information. They appear on engineering and fabrication drawings, which the welder will refer to in order to create their weld.

Welders live by the 1/16th rule—meaning their welds can be larger or smaller than what is specified by no more than 1/16th of an inch. Precision is key in this industry, so it’s important for welders to understand blueprints and how to follow them to create welds that are up to standard.

Before starting their weld, welders will typically look at a Welding Procedure Specification (WPS), which is a document that gives direction to the welder by providing information such as material thickness, the general position the part needs to be welded in, the electrodes to use and more. From here, the welder will look at the welding blueprint, which contains weld symbols, specific measurements and other information needed to complete the task. These blueprints come in different forms, such as isometric, orthographic and 3D.

There is a wide variety of welding blueprint symbols that represent all types of welds. These symbols aren’t used in every industry—however, they are commonly used in industries such as construction, which require parts and pieces that meet exact specifications. Welders in these industries rely on blueprints to guide their work every day.

Understanding the Basic Structure of a Welding Symbol

According to the American Welding Society (AWS), a welding symbol consists of several elements. The skeleton of a welding symbol contains a horizontal line, called the reference line, which acts as an anchor that all welding symbols are tied to. The instructions for making the weld appear along this reference line. From here, an arrow connects to this horizontal line to show the joint that is to be welded.

In addition to these two elements, welding symbols may include other elements to convey specific welding information. Welding information may also be conveyed in other ways, such as by drawing notes or details, specifications, codes, standards or other drawings, which eliminates the need to include corresponding elements in the symbol.

The tail of a welding symbol is used for designating the welding, brazing and cutting process in addition to the welding or brazing specifications, procedures or supplementary information to be used in making the weld or braze. The process, identification of the filler metal to be used and other important data are placed in the tail of the symbol.

All elements have specific locations within a welding symbol, which can be seen in the image below:

Image Credit: AWS A2.4 

Weld symbols, which are drawn in contact with the reference line, include the following:

Image Credit: AWS A2.4 

Finally, supplementary symbols, which are used in connection with welding symbols, appear as the following:

Image Credit: AWS A2.4

Joint Types

Another important concept for welders to be familiar with is basic welding joint types, which include butt, corner, T, lap and edge joints. A joint is an edge or point where two or more plastic or metal pieces are joined together. A visual representation of each type of joint can be seen below:

Image Credit: AWS A2.4 

To learn more about the structure of welding symbols, download the AWS A2.4:2007 Standard Symbols for Welding, Brazing, and Nondestructive Examination.

How To Read 6 Welding Blueprint Symbols

Welding blueprint reading starts with understanding the different types of welds and their symbols. Each welding position has its own symbol, which is often placed near the center of the reference line. This symbol appears as a drawing that represents a simplified cross-section of the weld.

While there are many different types of weld symbols, there are six basic types of welds.

1. Fillet

The fillet weld symbol is one of the most recognized. It is used to make corner joints, lap joints and T joints. It appears as a triangular shape; however, its shape is not always an isosceles or right triangle. Formed by fitting up two members, weld metal is deposited in a corner and penetrates and fuses with the base metal to form the joint.

Image Credit: AWS Symbol Chart

2. Groove

Groove welds are used to make edge-to-edge joints. However, they are also often used in T joints, corner joints and joints between flat and curved pieces. These welds can be made in many ways, depending on the geometry of the parts being joined and the preparation of their edges. Essentially, weld metal is deposited in the groove, which fuses with the base metal to form the joint. There are various types of groove welds, including square, double-bevel and V-groove welds.

Image Credit: AWS Symbol Chart

3. Plug or slot

Plug and slot welds are used to connect overlapping parts by drilling holes in one of the parts. Weld metal is deposited in the holes and fuses with the base metal of the two parts to form the joint. For plug welds, the holes are round, and in slot welds, the holes are in a slot shape.

Image Credit: AWS Symbol Chart

4. Spot

Spot welding connects overlapping pieces of metal at small points by applying pressure and using electric current. First, electrodes are brought to the surface of the parts to be joined and pressure is applied. Current is then applied through the electrodes to melt the material, and finally, the current is removed while the electrodes stay in place as the material cools and solidifies.

Image Credit: AWS Symbol Chart

5. Seam

A seam weld uses a similar process to a spot weld. Essentially, the weld projects through the top surface and melts into the other part with the use of heat input. The symbol is also similar yet has two parallel lines running through it.

Image Credit: AWS Symbol Chart 

6. Stud

Stud welds are commonly practiced in many shops. In this process, a metal stud is joined to a metal workpiece by heating both parts with an arc. This is a highly reliable method that provides the fastening used by a variety of applications.

Image Credit: AWS Symbol Chart
To view more about welding symbols and blueprint reading, download the American Welding Society Welding Symbol Chart.

Pursuing a Career in Welding

If you’re considering a career in welding, you might be wondering, “How do I learn welding symbols?” or “How do I read a welding blueprint?” A great place to start is by completing a welding training program, like the Welding Technology program at UTI. In just 36 weeks, students are taught the fundamentals of what it takes to become a welder, including stick, MIG, TIG and flux-cored arc welding.

This program gives students the hands-on training needed to prepare for a career in a variety of industries, including:

• Aerospace
• Construction
• Shipyards & Shipbuilding
• Fabrication
• Manufacturing
• Transportation

To learn more about welding job types, visit our welding career guide.

UTI’s program was built in conjunction with Lincoln Electric and focuses on teaching students what the industry says matters most. According to Chris Hershman, UTI Welding Instructor and Certified Welding Inspector (CWI), this focused and accelerated program allows students to go further in their training in a shorter amount of time. In nine months, students gain skills that might otherwise take years of on-the-job training to acquire.

“We want our students to be smart welders,” says Chris. Upon completion of this program, students have the skills they need to be self-sufficient welders, which includes reading some of the most common structural and pipe welding symbols. To demonstrate this, students can build a blueprint of their own using welding symbols. “Knowing these symbols builds students’ confidence, and being a confident welder is being a great welder,” Chris shares.

Overall, a career in welding can be an exciting one. Total welder employment is expected to exceed 463,000 by 2033,⁵⁰ which means the industry will be looking to the next generation of welders skilled in the latest technologies to fill those positions.

The UTI program helps prepare you for the industry with the skills and knowledge employers are looking for. Interested? To learn more details, visit our program page and request more information today.