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Welding is a complex task with many intricacies, and these intricacies are often communicated in the unique language of welding symbols. One of the first things a new welder must learn is how to read a welding symbol. Without an understanding of how to read a welding symbol or welding symbol chart, it is impossible to understand instructions for even the simplest welds. If you are somebody who is new to welding and would like to improve your understanding of how to read welding symbols, this guide will cover most of the basics for you.
The first distinction to make is between welding symbols and weld symbols. A weld symbol specifies the type of weld being performed (fillet, plug, projection, etc.). It communicates one piece of information within a larger diagram of information. This larger diagram is the welding symbol. A welding symbol communicates all of the information necessary to carry out a welding job. This includes the type of weld (weld symbol) along with everything else the welder must know in order to successfully complete their job. Each common type of weld is represented by its own unique symbol on a weld symbol chart. Learning to correctly identify each weld is important for understanding welding symbols.
The reference line is a single horizontal line which serves as the foundation for the rest of the welding symbol. The reference line itself does not communicate any information, but serves as the reference point to which all information in the welding symbol is attached.
The arrow is attached diagonally to the reference line. The arrow can point in any direction (left, right, up, down), but a welding symbol is always read left-to-right. The arrow connects the reference line to the joint which is being welded. The arrow points toward the joint being welded, and this joint will always have two sides. The side of the joint to which the arrow points is intuitively called the “arrow side.” The side opposite the arrow side is, also intuitively, called the “other side”. All instructions pertaining to the weld on the arrow side will be listed below the reference line on your welding symbol, while instructions for the other side will be given above the reference line.
As discussed above, the weld symbol communicates the type of weld being performed. There are many common types of welds, and each one has its own unique symbol. In almost all cases, the weld symbol must be placed on the reference line.
The tail is a V-shaped space at the end of the reference line opposite the arrow. The tail is used to convey any supplementary information about the weld which does not have its own symbol or place on the welding symbol, such as the prefered type of welding for the job. If there is no information which needs to be communicated in the tail, it can be left off the welding symbol entirely.
Crucial information like the dimensions of the weld or type of welding process can be placed on either the reference line or the tail of the welding symbol. Like weld symbols for different types of weld, each common welding process has its own shorthand in a welding symbol (“AC” for Arc Cutting, “OC” for Oxygen Cutting, etc.). The dimensions for each weld will be listed on the reference line, next to each unique weld symbol. The size of the weld is to the left of the weld symbol, while its length goes to the right of the weld symbol.