How to Read Welding Symbols

Learning how to read welding symbols is crucial to welding projects. Understanding the parts of a welding symbol and what they mean can help you create joints successfully and efficiently. Welding symbols can range from straightforward to complex, depending on the type of weld.

Understanding welding symbols takes time, and many welders use cheat sheets for assistance as they gain experience. If you’re new to welding or just need a refresher, read on to learn the basics of reading welding symbols.

What Are Welding Symbols?

Welding symbols are a way to visually convey information to the welder about a welding joint. Engineers include welding symbols on welding blueprints to note the type, size and location of the weld, plus other supplementary information.

The primary purpose of welding symbols is to provide the welder with information on where to weld, the joint type, how much metal or filler material to use, and how much of that material to apply in or on the joint. The American Welding Society is responsible for creating the symbol standards.

Specifying welds with standardized symbols instead of pictures and text streamlines the welding process, as engineers don’t have to spend time explaining the weld, and welders don’t have to spend time reading instructions. For this reason, most engineering drawings for welding jobs incorporate welding symbols to denote pertinent information associated with a weld.

Understanding the Difference Between a Welding Symbol and a Weld Symbol

While you may hear the terms “welding symbol” and “weld symbol” used interchangeably, the two are distinct.

The welding symbol is an overall representation of what’s required to produce a welded joint. Weld symbols are graphic characters connected to the reference line of a welding symbol that specify the weld type. In essence, weld symbols are one element of welding symbols.

The Anatomy of a Welding Symbol

You’ll find three main components in every welding symbol, regardless of the type of weld — the reference line, arrow and tail.

1. Reference Line

The reference line is a horizontal line that forms the body of the welding symbol. This line serves as an anchor for the rest of the information, with shapes, numbers and letters positioned in specific locations on or around it. Essentially, the instructions for creating a weld are strung along the reference line.

2. Arrow

The arrow connects the reference line to the joint in which the weld is to be made. The arrow can point in any direction — left, right, up, down or toward the tail. Some welding symbols contain multiple arrows.

Many times, the arrow points to a joint that has two sides, meaning there are two potential places to weld. For example, when linking two metal pieces to form a T-shape, welding may be done on each side of the T’s stem.

The welding symbol differentiates between each joint side using the arrow and the spaces above or below the reference line to indicate a weld on the following:

  • The arrow side: The arrow side of the reference line is the side of the weld joint the arrow points to. Symbols on the reference line’s arrow side refer to the weld joint’s arrow side. Welders perform arrow-side welds based on the instructions under the reference line.
  • The other side: Symbols on the other side of the reference line refer to the other side of the weld joint. Welders perform other side welds according to the instructions above the reference line.

3. Tail

The tail is a sideways “V” attached to the reference line on the opposite side of the arrow. The tail provides supplementary information, such as which welding or cutting process to use and general notes or specifications that apply to the joint.

Understanding Welding Symbol Dimensions

Welding drawings use dimensions to specify the weld’s length, width, depth and opening.

You’ll find the weld’s width or diameter expressed in inches on the weld symbol’s left side and its length on the weld symbol’s right side. Say, for example, a blueprint instructs you to perform a weld that’s a 1/2 inch wide and 4 inches long. These instructions will appear as “1/2” followed by the weld symbol and the number “4.”

If the project requires welding on each side of a joint, you’ll see a symbol on each side of the reference line. Note where these symbols are on the line — if they align and are on the same side of the reference line, the welds should do the same. Alternatively, if the symbols are offset, the welds should also be offset.

It’s important to take note of the numbers beside the symbols. While a joint may need welding on each side, the length and width may differ. Remember that figures under the reference line designate what to do on the side of the joint to which the arrow points. Figures above the reference line designate what to do on the other side of the joint.

Finally, some welding blueprints may contain a flag shape at the junction of the reference line and the arrow. A flag stipulates that you should complete the final welding procedure in the field rather than in the shop.

Understanding Welding Symbol Letters

In addition to lines, shapes and numbers, you’ll find various letters on a welding blueprint. These letters specify pertinent information like the weld bead’s length or the root opening.

If you’re new to reading welding symbols, it can be helpful to keep a copy of letter meanings handy as you perform welds. Here is a brief list of welding symbol letter meanings:

  • A: Angle of the countersink
  • C: Chipping finish
  • F: Finish symbol
  • G: Grinding finish
  • L: Length of the weld bead
  • M: Type of machining finish
  • N: The number of spot welds or projection welds required
  • P: Pitch of welds
  • R: Root opening or depth of the filling
  • S: Depth of preparation required
  • T: Specification process

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