Welding blueprints are one of the most important tools in the welding process. They are used to communicate design plans and specifications between Welders, Fabricators, Engineers, and Manufacturers.
To produce high-quality welds, Welders must understand and interpret welding drawings correctly. In this welding blueprints guide, we will discuss the basics of reading and using welding drawings. Let’s get started!
Why is it Important to Know How to Read Blueprints?
Welding blueprints provide critical information about a welding project. This information includes the dimensions of the parts to be welded, the types of materials to be used, the location of the welds, and any special instructions. Without this information, it would be very difficult to produce high-quality welds.
In addition to providing essential information about a welding project, blueprints also help Welders save time and money.
As a result, Welders who know how to read blueprints can work more efficiently and effectively.
What Are the Parts of a Welding Blueprint?
Welding blueprints are technical drawings that show how to construct a weld joint. The main purpose of welding blueprints is to provide clear and accurate instructions to the welder so that they can create a safe and sound weld joint.
Welding blueprints typically consist of three parts: the welding symbols, dimensions, and notes.
- The welding symbols are graphical representations of the various types of welds that can be made. These symbols are used to indicate the type of weld, its size, and other important characteristics.
- Dimensions are used to specify the size, shape, and location of the weld joint.
- Notes provide additional information about the welding process or joint that may be helpful to the welder.
Welding blueprints are an essential tool for welders, as they provide clear and concise instructions on how to create a safe and sound weld joint. By understanding the various parts of a welding blueprint, welders can more easily interpret and follow the instructions.
Welding Blueprint Symbols: What Are They, and How Do You Read Them?
While there are many welding blueprint symbols, understanding a few of the basics will help you interpret most Welding Drawing. Here are some common Welding Blueprint Symbols:
- Arrow: An arrow is used to show the direction of movement on a drawing.
- Leader Line: A leader line is a short line with an arrow at one end that is used to point out something on a drawing.
- Dimension Line: A dimension line is a line with small arrows at each end and numbers in between that show the size or measurement of an object on a drawing.
- Center Line: A centerline is a thin continuous line used to divide an object evenly into halves, quarters, or eighths.
Welding Symbol Basics
Most welding symbols contain the following elements:
- The reference line is the main horizontal or vertical line to which all other Welding Blueprints lines and arrows are connected.
- The arrow points to the side of the Welding Blueprint that should be facing up.
- The tail, contains information about the type of weld, size, depth, angle, etc.
Some common welding symbols you’ll see on Welding Blueprints include:
- Butt joint welds
- Fillet welds
- Plug or slot welds
- Spot welds
- Flare bevel groove welds
Each of these Welding Blueprint symbols will have a specific meaning and purpose.
Arrowhead and reference line
The arrowhead is always placed on the reference line. It points in the direction of the view. Welding symbols are often located near the arrowhead. The Welding Blueprint Reference Line can be found at different locations on the drawing.
A leader line is a thin, dashed line that connects the welding symbol to the feature it represents. Leaders can be straight or curved, and they may have an arrowhead at the end closest to the welding symbol.
When multiple leader lines connect to a single welding symbol, they should be arranged so they do not cross each other.
Type of weld
The tail of the welding symbol is always placed on the reference line, and it includes information about the type of weld, size, material, etc. Welding symbols can be located anywhere on the drawing as long as they are not obstructed by other features.
Placement or orientation of the weld
When reading welding blueprints, it is important to pay attention to the placement or orientation of the weld. This will give you an indication of where the weld needs to be placed about the rest of the structure.
The placement of the weld can be shown in two ways; either by an arrow or by a leader line. An arrow will show the direction that the Welding Symbol is pointing, while a leader line will show the specific location of the Welding Symbol.
There are three types of weld contours that you will find on drawings, and each one indicates a different Welding Procedure Specification (WPS).
- The butt joint is the most common type of weld joint, and it is used to join two pieces of metal together at right angles.
- A fillet weld is used to join two pieces of metal together at an angle other than 90 degrees.
- A groove weld is used to join two pieces of metal together along a groove.
When reading welding blueprints, you will also need to pay attention to the symbols that indicate the type of welding process that should be used. The most common welding processes are:
- Shielded Metal Arc Welding (SMAW)
- Gas Metal Arc Welding (GMAW)
- Flux Cored Arc Welding (FCAW)
Each of these welding processes has its own set of symbols, and you will need to be familiar with them to interpret the drawing correctly.
Size of weld
The size of the weld is stated in two ways, first the length and then the throat thickness. The length is always Welding blueprint shown as an inside dimension. The throat thickness is how deep the joint should be, and it’s shown as an outside dimension.
Welders often come across supplementary symbols on their drawings that are meant to provide more information about a specific joint. While these are not always present, it’s important to know how to interpret them when they are. Here is a quick guide to some of the most common supplementary symbols you might see:
- Field Welds: These are welds that cannot be made in the shop and must be performed in the field. They will usually be indicated by a note that says “field weld required” or something similar.
- Weld All Around (WAA): This symbol indicates that the welder should make a complete welding bead around the entire circumference of the pipe or other object.
- Shop Welds: These are welds that can be made in the shop and do not require field welding.
- Back Welds: Back welds are Weld All Around symbols that have been rotated so that they are facing the other way. This indicates that the welder should start at the end of the pipe and work its way back towards the beginning.
- Pipe Welds: Pipe welds are similar to Weld All Around symbols, but they only apply to circular objects.
- Partial Joint Penetration (PJP): This symbol indicates that the welder should only make a partial penetration weld. This means that the welding bead will not go all the way through the metal plate.
- Root Welds: Root welds are partial joint penetration welds that have been rotated so that they are facing the other way. This indicates that the welder should start at the end of the pipe and work its way back towards the beginning.
- Flat Welds: Flat welds are similar to partial joint penetration welds, but they only apply to flat surfaces.
- Plug Welds: Plug Welds are small welding beads that fill in holes in metal plates. They can be round or oval.
- Slot Welds: Slot Welds are similar to plug welds, but they are elongated and rectangular.
What Do the Letters Mean on a Welding Blueprint?
The letters on a welding blueprint show the different types of welds that are required for the project. Here is a quick guide to what each letter stands for:
- T – Welds that are required to be made on the inside of a tube or pipe.
- P – Welds that are required to be made on the outside of a tube or pipe.
- R – Welds that are required to be made on the root pass of a joint.
- G – Welds that are required to be made on the cap pass of a joint.
- S – Welds that are required to be made in a lap joint configuration.
- L – Welds that are required to be made in a butt joint configuration.
A welding engineer or supervisor will determine which type of weld is needed for each part of the project. The welder must then follow those instructions carefully to ensure a strong, high-quality weld.
Dimensions and Angles
There are three types of lines used to indicate dimensions and angles on drawings:
- Extension lines are used to show the size or location of an object. They extend from the object being measured and terminate in arrowheads.
- Dimension lines are similar to extension lines, but they also include numbers that specify the size of an object. The numbers appear next to arrows pointing toward the object being measured.
- Leader lines are used to point out specific features on a drawing. They consist of a short line with an arrowhead at one end and a dot at the other end. Welding symbols often include leader lines pointing to the various parts of the symbol.
Common Symbols and Their Meanings
Welding symbols are often seen on drawings or blueprints. They are used to indicate the type of weld, size, and other important information. The most common welding symbols and their meanings are.
A fillet weld is used to join two pieces of metal at right angles. The most common fillet weld symbol is an arrow with a line next to it. This indicates the size of the weld.
The other common fillet weld symbol is two arrows pointing towards each other. This means that the Weld will be on both sides of the joint.
Some symbols indicate how much material will be removed during welding, this is known as chamfering or beveling.
- Chamfer – A 45-degree angle cut made on the edge of the material, usually before welding.
- Bevel – A sloped cut made on the edge of the material, usually before welding.
One of the most important aspects of reading welding blueprints is understanding the symbols used to represent different types of groove welds. Here are some of the most common symbols you’ll see on welding drawings:
- Butt Weld: This is the most basic type of groove weld, created by joining two pieces of metal together at right angles. The symbol for a butt weld looks like two half-circles connected by a straight line.
- V Weld: A V weld is created by joining two pieces of metal together at an angle, forming a “V” shape. The symbol for a V weld looks like two half-circles connected by a curved line.
- Lap Weld: A lap weld is created by overlapping two pieces of metal and welding them together. The symbol for a lap weld looks like two half-circles connected by a wavy line.
As you can see, the symbols used to represent different types of groove welds are fairly simple and easy to remember.
Plug or Slot
Another common type of weld you’ll see on welding drawings is the plug or slot weld. A plug weld is created by welding a metal disk to the surface of another piece of metal. The symbol for a plug weld looks like a circle with a cross in the center.
A slot weld is similar to a plug weld, but instead of using a metal disk, a slot is cut into the surface of one piece of metal and then welded shut. The symbol for a slot weld looks like two rectangles connected by a line.
As with groove welds, the symbols for plug and slot Welds are fairly simple and easy to remember. With a little practice, you should be able to read these Welding drawings like a pro!
There are different types of spot symbols, each with its distinct purpose. Here is a quick overview of the most common spot symbols:
- Welding symbol: this indicates where welding is to be performed
- Grind symbol: this indicates where grinding is to be performed
- Hole symbol: this indicates where holes are to be drilled
Welding symbols can also include information on the type of weld that is to be used, as well as the size and angle of the weld. This information is typically shown in blueprint dimensions.
Hole symbols also include specific information such as diameter, depth, and type of hole to be drilled. For example, a hole symbol might show a 0.25-inch diameter blind hole that is to be drilled to a depth of 0.75 inches.
Grind symbols are typically less specific than welding and hole symbols, simply indicating where grinding is to be performed.
Spot symbols are an important part of reading and interpreting welding blueprints. By understanding the different types of spot symbols and the information they convey, you will be able to more easily use welding blueprints to complete your projects successfully.
Seam symbols are used to indicate the type of welding joint and how it is to be made. The most common types of weld joints are lap joints, butt joints, corner joints, tee joints, and edge joints. Each type of weld joint has its symbol.
- Lap Joints: A lap joint is a type of welding joint where two pieces of metal are overlapped and welded together. The lap joint symbol looks like two overlapping circles.
- Butt Joints: A butt joint is a type of welding joint where two pieces of metal are butted up against each other and welded together. The butt joint symbol looks like two rectangles that are touching each other at their edges.
- Corner Joints: A corner joint is a type of welding joint where two pieces of metal are joined together at their corners. The corner joint symbol looks like two L-shaped lines.
- Tee Joints: A tee joint is a type of welding joint where two pieces of metal are joined together at a T-shaped intersection. The tee joint symbol looks like a T-shaped line.
- Edge Joints: An edge joint is a type of welding joint where two pieces of metal are joined together along their edges. The edge joint symbol looks like two lines that are parallel to each other.
Stud symbols are used to indicate the type of stud that is to be used in the welding process. Studds are metal rods that are welded to the surface of a metal piece to provide extra support or reinforcement. The most common types of studs are threaded studs, head studs, and blind rivets. Each type of stud has its symbol.
- Threaded Studs: A threaded stud is a type of stud that has threads on its surface. These threads allow the stud to be screwed into place. The threaded stud symbol looks like a cylinder with threads running around it.
- Headed Studs: A headed stud is a type of stud that has a head on one end. The head is used to hold the stud in place. The headed stud symbol looks like a cylinder with a flat end.
- Blind Rivets: A blind rivet is a type of stud that has a head on one end and a hollow body. The body of the blind rivet is used to hold the stud in place. The blind rivet symbol looks like a cylinder with a flat end and a dashed line running through its center.
How to Read Welding Blueprints?
Welding blueprints are the instructions that tell a welder how to put together a product. The blueprint will show the dimensions of the piece, as well as where the welding symbols are located.
Welders must be able to interpret these drawings to create a quality product. To do this, they must understand the different types of lines and symbols that are used.
The first step is to identify the reference line. This is typically a thick, dashed line that runs through the center of the drawing. It is used as a starting point for all other measurements.
Next, you will need to identify the welding symbols. These indicate where welds need to be placed, as well as the type of weld that should be used.
Once you have a basic understanding of the welding blueprint, you will be able to create a quality product.
As you become more comfortable with welding symbols and reading welding blueprints, you will start to see how all of the different types of groove welds can be used in conjunction with one another.
What Type of Welding Jobs Require Reading Blueprints?
Most welding jobs require reading and interpreting blueprints before beginning work. Blueprints provide essential information about the materials to be used, the dimensions of the project, and the type of welding required. Without this information, welders would not be able to properly complete their projects.
Can All Welders Read Blueprints?
No, not all welders can read blueprints. Many welders never learn how to interpret welding drawings and symbols. However, knowing how to read welding blueprints is a valuable skill for any welder, as it allows you to visualize the final product and better understand the welding process.
Welding symbols can be confusing at first, but with a little practice, you will be able to read them like a pro!
Welding blueprints can seem daunting at first, but with a little practice, they are easy to interpret and use. By following this guide, you will be able to successfully read, interpret, and use welding blueprints on your next project.
Do you have any questions about spot symbols or reading welding blueprints? Leave us a comment below and we’ll be happy to help! Happy welding!