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It can be confusing learning how to read welding blueprints and symbols, but welding programs like Professional Welding or Welding Specialist with Pipefitting at Tulsa Welding School (TWS), covers everything you need to know. Let’s scratch the surface of this topic and go over some of the basics now.
What Are Welding Blueprint Symbols?
Welding blueprints rely on symbols to communicate precise instructions for welders to create structurally sound welds. These symbols are a standardized language used in technical drawings and governed by the American Welding Society (AWS)1 and the International Organization for Standardization (ISO)2. Welding symbols provide crucial information about joint types, dimensions, welding processes, and finishing details, allowing you to create the perfect weld.
Common Weld Types Represented in Symbols
● Fillet Weld (Triangle Shape): Used for corner or lap joints.
● Groove Weld (Rectangular or V-Shaped): Used for butt joints and edge preparations.
● Plug/Slot Weld (Circular or Rectangular): Joins overlapping parts through a hole or slot.
● Spot Weld (Circular Dot): Indicates a localized weld between two surfaces.
What Are the Different Welding Joint Types?
Welding joints are the points where two or more metal parts are welded together. Each joint type serves specific structural purposes, and they all have their own welding requirements. Here are the five welding joint types:
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Butt Joint
A butt joint aligns two metal pieces in the same plane, joined at their edges. Commonly used in pipelines and structural applications, butt joints require groove welds to pass non-destructive testing. For example, the welding blueprint may specify a double V-groove weld for thick plates, requiring precise edge preparation.
Corner Joint
Corner joints join two pieces of metal at a 90-degree angle, creating an L-shape. These joints are found in frame structures and sheet metal assemblies. On a welding blueprint, you might see a fillet weld symbol that indicates a triangular weld bead needs to be applied to the inside or outside of the corner.
T-Joint
In a T-joint, one piece of metal is positioned perpendicular to another, creating a T-shape. T-joints are common in structural supports and frames. On a welding blueprint, a staggered intermittent fillet weld may be specified to reduce stress concentration.
Lap Joint
Lap joints are created when two pieces of metal overlap . Lap joints are commonly used in thin sheet metals or automotive applications. On a welding blueprint, a plug weld symbol may appear, indicating that welds will be applied through drilled holes.
Edge Joint
In an edge joint, the pieces of metal are placed side by side with their edges aligned. Edge joints are often used when creating boxes or tanks, where minimal load-bearing is required. When you are reading a welding blueprint, a single-bevel groove weld symbol may be used for thicker materials, providing additional weld penetration.
How to Read Welding Blueprint & Symbols
Reading welding blueprint symbols is a step-by-step process that you will learn about during your education at TWS. Here are the steps to reading welding blueprint symbols:
Step 1: Understand the Reference Line
The reference line is the horizontal line in a welding symbol where information about the weld is anchored to it. The arrow line points to the joint, and the tail can specify things like the weld type (i.e. MIG or TIG). Weld symbols placed above the reference line indicate a weld on the opposite side of the joint, while symbols below the line represent a weld on the side the arrow points to.
Step 2: Identify the Weld Symbol
The weld symbol on the reference line specifies the type of weld required. For instance: (create images of weld symbols)
● A triangle indicates a fillet weld.
● A half-circle denotes a backing weld.
● A rectangular symbol represents a square groove weld.
Step 3: Analyze Dimensions and Specifications
Dimensions are important to ensure that welds pass non-destructive testing.
Welding symbols on a blueprint may include:
● Weld Size: A number on the left side of the symbol.
● Length and Spacing: Numbers to the right of the symbol specify the length of each weld and the spacing between intermittent welds.
Step 4: Recognize Additional Instructions
The tail of the welding symbol may include details about the process, welding position, or filler material. For example, MIG or TIG in the tail indicates the welding process to be used.
Step 5: Apply to Real-World Examples
Consider a blueprint for constructing a steel frame with T-joints and corner joints. The welding blueprint might include fillet welds on T-joints to reduce stress on the welds. The corner joints may use beveled groove welds for deeper penetration and added strength.
Practice, Practice, Practice
Reading welding blueprint symbols takes practice. The good news is that during the Professional Welding program at TWS, you get plenty of hands-on training to practice welding different joint types and reading different types of welding blueprints. In the meantime, we recommend reviewing industry standards from the American Welding Society (AWS A2.4)3.
Want to Learn More?
The Professional Welder & Welding Specialist with Pipefitting programs at Tulsa Welding School’s Houston campus starts by helping you know what it’s like to be a welder in interactive workshop courses and welding booths. You’ll be trained in structural, flux core, and pipe welding in as little as seven months. You’ll also be prepared to excel in job interviews and welding tests for various certifications.
Read about the types of welding careers you can pursue with your skills. Ready to start a Professional Welding program or Welding Specialist with Pipefitting program? Contact us today about our welding certification preparation program.
1) https://www.aws.org/
2) https://www.iso.org/home.html
3) https://www.aws.org/standards-and-publications/guides-and-handbooks/
