For welders, it is very important that they are able to interpret welding symbols correctly. In this way, they can get the job done faster and with higher quality.
As well as reducing costs, understanding blueprints correctly also enhances the quality of the project by getting it done the right way the first time.
A great deal of welders has a difficult time reading blueprints correctly, which is unfortunate. It is important to note that many welders do not take vocational training in order to be competent.
It seems that those who take classes either don’t learn about blueprints or decide not to pay attention to the written materials that are presented.
The result is a small number of welders who are adept at reading blueprints and who are able to use them to their advantage.
This article will review how to read welding blueprints like a pro and the benefits they can offer when it comes to improving the quality and reducing the cost of your project.
The Role of Welding Companies
The lack of qualified welders in today’s market prevents companies from imposing strict criteria for hiring since they simply aren’t feasible.
You can still train a welder if they are not good at following blueprints just because you hire them. To help their welders improve their technical skills, welding companies can conduct training sessions for their employees.
Coaching classes can be held on the premises of the company and welding symbols can also be posted on posters in the workshop.
It is a common problem among welding manufacturers that they don’t have someone on staff who can train others how to read blueprints.
Many small and medium-sized businesses experience this problem. Professional welding trainers can be hired from outside if your organization needs this training.
Vendors of welding supplies, especially industrial wholesale distributors and representatives of welding equipment manufacturers, have this kind of expertise.
You should ask them if they can train your staff on welding equipment usage. Most of the time, they are more than happy to do so at no cost to your business.
Fundamentals of Welding Blueprints
A glance at a welding blueprint will show that there are three basic types of views in a blueprint. They are the front view, the top view, and the right-side view. There are also a number of welding symbols on the sketches that can be seen in specific places.
There are different types of symbols that represent the different types of work that must be performed in order to finish a welding job.
The following is a more detailed explanation of the symbols and each type of view.
Welding Symbol Basics
An example of a welding symbol could be a line that is drawn following a specific structure that describes the direction of the weld and the type of this weld. Whenever weld symbols are shown, there is an arrowhead next to it, pointing to the location where the weld needs to be made.
An arrow is attached to what is known as a leader line. There are additional horizontal reference lines connecting this leader line to this line. Depending on where the arrow points, the weld can either be made upwards or downwards.
At the end of the reference line there is a tail at the opposite end of the line. This tail may have more than one fork, each pointing in a different direction. A tail like this indicates the welding procedure should be specialized.
In the center of the reference line, you will see either parallel lines or a geometric shape – depending on what you want to see. The lines on the metal frame indicate what kind of weld you need to make on the metal frame.
In total, there are more than a dozen different types of welding that can be done. If you want to do an accurate job, you need to avoid confusion between the weld symbols.
It is indicated on the reference lines that there is a specific type of weld that should be performed whereas the overall welding symbol can give you complete welding instructions for the project.
It is very important to pay close attention to the placement of the symbols on the reference line as you read a welding diagram. Welding should be performed on the side of the joint pointing towards the arrow if the weld symbol is present below the reference line.
In contrast, if the weld symbol is located on top of the reference line present on the diagram, it is recommended that the weld is performed on the opposite side of the joint from where the arrow is pointing.
In the event that the welding symbol is marked on both sides of the reference line, then multiple welds must be made on the two sides of the joint.
In order to differentiate between the various types of welds that can be used on your project, various welding symbols have been developed. In the example above, a “V” shaped symbol indicates that a V weld is to be used, while a “S” represents a square weld.
Due to the large number of symbols, it can take some time for welders to learn the differences between the symbols.
In order to make it easier for you to recognize the symbols on your welder, it is possible to print out a few of the most basic symbols.
You can then move on to memorize symbols that are not very common once you have memorized the most common symbols.
Letters on the Welding Symbols
When you start reading welding blueprints, you will also find some letters on the charts. These letters show you important information to consider when making the welds, such as length and root openings. Here is a reference to use for the letters.
- A: Angle of Countersink
- C: Chipping Finish
- F: Finish Symbol
- G: Grinding Finish
- L: Length of the Weld
- M: Machining Finish
- N: Number of spot welds or projection welds
- P: Pitch of Welds (Center-to-Center Spacing)
- R: Root Opening; Depth of Filling
- S: Depth of Preparation; Size of Strength
- T: Specification Process
You will see these letters along with the symbols of welding if there is a specific weld that must be done to complete the project. The letter may also be found on some welding blueprints on its own.
Dimensions and Angles
The welding symbol’s angles and dimensions are very important to note as they make it easier to understand the welding blueprint.
The blueprints are packed with information and provide a lot of information with just a few lines to an experienced user. They can be used to communicate length, width, depth and the opening of the weld.
The diameter or width of the weld is generally noted on the left of the weld symbol and will be written down as a fraction in inches. The length, also expressed in inches, is written on the right of weld symbol.
Welding symbols also indicate whether the welds should be offset on both sides or mirror each other. Welds are mirrored when they are made on the exact location of a sheet on opposite sides.
They are considered to offset one another when they are not made on the exact opposite location of the frame.
The welding symbol also includes the angle of the weld, its root opening or root face dimensions. Numbers are a big part of identifying the weld depth and angle specifications.
They help clarify the beveling required on the base metal before welding can be performed successfully above or below the reference line.
Dimensions written under the reference line are used for the joint on the arrow side while dimensions noted over the line apply to the joint on the opposite side. If we look at the image above, welds are identified for both sides of the joint.
In some cases, a series of separate welds may be specified for a project that should be used instead of a single long weld.
When working with heat-sensitive or thin metals that can get damaged with a long and consistent weld, this is a common practice. If you read the welding diagram shown below, you’ll see that a string of 3-inch intermittent fillet welds is recommended for the project:
If you ever see a flag at an intersection of the reference line do not perform the weld inside a workshop. The flag is used to indicate that the weld must be carried out in the field.
Common Symbols and Their Meanings
There are dozens of cryptic symbols used in welding blueprints for identifying the weld. These symbols help the welder understand the size and other finishing and processing information for the project.
In this section, we will go over some of the common symbols and their meaning. You can find the complete set of symbols through the American National Standards Institute (ANSI) for welding.
Welding a fillet (pronounced “fill-it”) is commonly used, in construction, to make 90-degree lap joints, T-joints, or corner joints. This welding is almost triangular in cross-section as you can see from the symbol.
Occasionally, there may be some variation in the shape of the triangle and the weld may not always be a 90-degree right-angle triangle.
In order to weld the two pieces of metal together, a small quantity of welding metal is deposited in the corner of the joint. As it penetrates the material of the frames, it forms a joint which is fused with the frame material.
No matter what the orientation of the welding, the perpendicular leg of the triangle will always appear on the left side of the symbol.
There is a size indication on the left side of the weld symbol, and that is the leg length.
When the two legs of the weld are expected to be the same size, the symbol will only display one of the dimensions of the weld.
In the case that the weld has legs of different sizes then both dimensions will be given if the weld is supposed to have legs of different sizes. The drawing will also illustrate which leg is supposed to be longer.
The groove weld is generally used to create joints that are connected between the edge of two different metal frames or sheets.
As can be seen by the image above, the groove weld can be made in a variety of ways. This type of weld is also used in T joints, corner joints or joints between curved and flat pieces of metal.
The difference in welding mainly depends on the geometrical shapes of the parts that are to be joined together and how they are prepared at their edges.
During the welding process, the joining metal is deposited within the groove as it penetrates and fuses with the base metal on different sheets to form the joint.
The groove weld can be further classified into the following categories.
Square Groove Welds
A groove of this type may be formed either by creating a slight parting between the metal edges or by creating a tight fit between two metal frames. It is possible, if there has been a space created by using this method, to view the diameter of the space on the weld symbol.
The groove is created when one or both sides of the metal pieces are chamfered in order to create the groove, and it is similar to a square weld, with the exception that the edges of both metal pieces are chamfered. In addition to the degree of the V angle, you can also see where the root of the weld is separated, where applicable.
The groove created by separating the metal may not be deep enough to reach the entire depth of the metal sheet if the groove is created by separating the metal.
Bevel Groove Welds
A chamfer is used to define one edge of a joint and a square edge is used to define the other edge of the joint, thereby creating a bevel groove. Regardless of the direction in which the weld is oriented, the perpendicular line drawn alongside the bevel symbol is always drawn on the left side.
The arrow points to the joint that needs to be chamfered on the metal. By rearranging the arrows in this way, we emphasize the importance of this direction.
Both metal pieces are given a concave treatment at the edges, which allows the weld to be formed. The welded metal pieces form a U-shaped groove when they are bolted together.
With the same method as the V-groove, we can demonstrate the depth of the edge treatment, the separation of the roots, and the efficiency of the throat.
In order to form the J-groove, one of the pieces of metal is given a concave treatment and the other piece of metal is left as a square. The process of forming this joint is similar to the procedure of forming a bevel groove joint.
On the left-hand side of the drawing is the perpendicular line, and on the right-hand side there is the arrow pointing to the metal that will be treated with the concave edge.
A detailed description of the depth of edge treatment, root separation, and the effectiveness of a throat can be found in the following figures.
Flare Groove Welds
There are two or more rounded parts which are typically joined together using this type of weld. Welders should find it useful to note that the ideal depth of a weld is indicated on the left side of the symbol, while the actual weld depth appears in parentheses.
Plug and Slot Welds
A plug welding and a slot welding are essentially used to join or join together adjacent frames and sheets of metal. It is normal for both pieces of metal to have holes in them for connecting them. There are round holes in plug metal sheets while there are elongated holes in slot metal sheets.
In the weld joints between two sheets, the metal penetrates into the holes and fuses with the base metal in order to form the joint.
The size of the plug for each weld is given to the left of the symbol, indicating its diameter. The pitch of the plug for each weld is indicated on the right.
The width is used for each slot in slot welds, and it is indicated on the left side of the symbol while the length and pitch of the slot is shown on the right of the symbol. The detailed drawing can be found on the right side of the symbol.
In parenthesis below the weld symbol, you can see the total number of plugs or slots that must be welded. It is indicated by arrows on one side and other side which part of the piece contains a hole.
The depth at which the hole should be filled with welding metal is indicated within the weld symbol in cases where it does not need to be filled completely.
Putting It All Together
As you can see from the above welding diagrams, some of the metals have been represented as two parts that have come together. In order for the weld to be performed correctly, this information is provided in order to make it easier to understand.
It is not often the case for welding blueprints to provide this kind of information. It looks more like this in a real welding diagram.
Occasionally, you will also see the reference lines dotted with a break in welding blueprints.
The diagram indicates to the welder that the portion of the joint that must be prepared before joining the pieces together should be prepared. It is also important to remember that the design of the break represents the kind of preparation that should be performed prior to welding.
There is a good possibility that when you are just getting started with welding blueprints, you might have a difficult time reading and understanding them.
There are times where even experts have difficulty understanding and reading the blueprints. Learning how to read them can take some time and patience, but it is well worth the effort.
Once you have mastered the art of reading blueprints, creating beautiful and advanced projects will become a lot easier and you will have no problem creating them.
THE TEAM THAT WORKED ON THIS REVIEW
Hi, I’m Andrew Miller — a certified welding expert and instructor based in Long Island, NY.
With over three decades in the industry, I’m passionate about combining theoretical knowledge with hands-on experience to train the next generation of skilled welders.
I specialize in all forms of arc welding, including GMAW, GTAW, GMAW, FCAW & SAW. But my experience isn’t limited to just those—I’m also knowledgeable in oxyfuel gas welding and plasma arc cutting.
My years as a welding inspector and supervisor have honed my ability to ensure the highest standards in welding quality and safety, making me adept at executing and overseeing complex welding operations.
You can find more information about me on my website, weldingzilla.com, or connect with me on LinkedIn.