A Short Guide to the Most Common Welding Symbols
You have heard it said that a picture is worth a thousand words. This is certainly the case when it comes to welding symbols.
Welding symbols are a quick way of providing welders with important information. Just like the “check engine” or “oil change” lights on your car, these symbols use images to communicate necessary messages. Paying attention to these symbols is essential to maintaining equipment and avoiding injury.
Of course, symbols are only helpful if you know what they mean. Without this understanding, even the most useful symbols will look like Greek to you.
Here are some of the most common welding symbols you need to know about, and short explanations of what they need. With this information in hand, you will be ready to get started on your next welding job.
Why Learn Welding Symbols?
To someone unfamiliar with them, welding symbols might look like some kind of strange hieroglyphics. Why go through the trouble of learning how to read them?
Welding is a profitable career that requires relatively little training. According to the Bureau of Labor Statistics, welders make on average almost $40,000 a year and don’t need a degree for an entry-level position. Many specialized jobs, however, can have a much higher salary.
But even though welding doesn’t require a college education, it does require some specialized training. Learning how to read these symbols is one of the first steps in pursuing that training. This knowledge could provide you entry into a stable career path.
Understanding Symbol Basics
Before we look at specific weld symbols, let’s look at a basic overview of what these symbols are and how they work.
Consistency of Symbols
For the most part, the use of symbols is consistent across the welding profession. There are some specifics, however, that may be specific to a certain shop or a certain tool.
Even so, it is still worthwhile to learn the basic elements of a welding symbol, since most shops are compliant with the American Welder’s Society Society standards. Whenever you start at a new shop, make sure to find out what standards they follow with their symbols. This will help you accurately read the welding drawing you have.
How Symbols Work
The purpose of a weld symbol is to give instructions about how the weld should be done. These symbols indicate the type of weld, its size, and its location. Also, sometimes welding symbols show where the welder should work, and what tools the welder should use.
Basic Elements of Weld Symbols
Every symbol used in welding is made up of some basic elements. Understanding what these elements mean can help you interpret a new symbol, even if you have never seen it before.
The first part of the symbol to identify is the arrow. The arrow is extremely important because it points to the joint that will need to be welded. It also identifies different sides of the joint.
In the drawing, the arrow will point at a joint. The side of the joint that the arrow is pointing at is called the “arrow side,” and the arrow that it is not pointing at is called the “other side.” The drawing can give instructions about how to weld either the arrow side or the other side.
Sometimes, in order to save space, a drawing will have more than one arrow coming off of the same symbol. This is permissible if more than one joint is being welded in the same way.
The Reference Line
If the arrow indicates where the weld should be done, the reference line indicates how it should be done. The reference link is a horizontal line that connects to the arrow. The arrow can be connected to either side of the line.
The reference line can give the welder information about both the arrow side and the other side of the joint. Any information about the arrow side will appear below the reference line. Information about the other side will appear above it.
In some cases, there may several tasks that the welder must perform in a specific order. To show this, the drawing may use multiple reference lines. The lines closest to the arrow are the tasks that should be performed first.
The space where the arrow and the reference line connect is called the juncture. Sometimes, there will be additional symbols attached to the juncture that give more information about how the weld should be done.
For instance, if there is a flag growing out of the juncture, that indicates that the weld should be done in the field. If there is no flag, the weld should be done back at the shop.
Another common symbol at the juncture is an open circle. This symbol indicates that the weld should go all the way around the joint.
The next part of the welding symbol to continue is the tail. The tail is a greater than (>) or less than (<) symbol. This tail is then connected to the end of the reference line opposite of the arrow.
The purpose of the tail is to provide information that cannot be communicated anywhere else on the symbol. This information can appear on the left or right side of the table.
A common reference to see on the tail is information about the approved welding procedure specification (WPS). This is a formal document that outlines how to perform a specific weld according to code requirements. Typically, the drawing represents the WPS by including specific designation letters along the tail.
Additional Information in Symbols
Most of the specific information you will need about the weld can be found in the welding procedure specification. Even so, welding symbols will often include additional information.
Different kinds of grooves, like J, V, and U grooves can increase the size of a weld on a joint. The drawing might add the groove symbol to the welding symbol.
If the groove symbol is below the reference line, it only applies to the arrow side. If it is above the reference line, it only applies to the other side. If it is on both sides, then it is a double weld. The groove weld symbol will usually include information about the depth and the angle of the groove.
Complete Joint Penetration
There are several ways that a symbol might indicate the need for complete joint penetration (CJP). The first way is to add the letters “CJP” to the tail on the symbol. This symbol indicates that complete joint penetration is required but does not specify how to do it.
A more specific way to indicate complete joint penetration is to use the symbol for a groove weld. Then, the drawing would show the need for CJP by not recording the depth of the weld.
Fillet welds are common in industries using boilers and pressure vessels. The basic symbol for a fillet weld is a right triangle.
Typically, this triangle appears on the reference line, and the perpendicular led appears on the left.If the fillet weld occurs on both sides of the joint, the symbol will appear both above and below the reference line.
Plug and Slot Welds
Plug and slot welds are used when welding two members together, one of which has holes in it. As one piece of metal is welded, the welded material fills the holes in the other piece.
For a plug weld, the drawing will show the diameter of each plug at the left. On the right, you will see the spacing between each plug.
For a slot weld, the information on the left is the length of each slot. On the right, the drawing shows the depth and width of the slot.
For the total number of plugs or slots, there is a number in parentheses below the drawing. Also, if the plugs or slots are not to be entirely filled with welded material, the appropriate depth will appear in the drawing.
Letters to Look For
We have already mentioned some letters that you may see appearing in welding symbols. There are a few more letter combinations you should be aware of.
For instance, if the weld will include air cutting, you will see the letters “AC”. Specific types of air cutting, like air-carbon, carbon arc, and metal-arc air cutting are indicated by adding an A, C, or M.
There are also common suffixes that may be added to specific types of cutting. AU indicates automatic cutting, while ME indicates machine cutting. Also, manual cutting is shown by MA, while semi-automatic is shown by SA.
Knowing Your Welding Symbols
While this list covers many important welding symbols, it is by no means exhaustive. That said, knowing these symbols will give you a good start in the industry.
If you have more questions about welding symbols or other welding issues, contact us. We’ll work with you to get you the answers you need to do your job well.