Welding Blueprints 101: How To Read Them

We’re going to take a close look at things you need to know when learning how to read welding blueprints. If you’ve been working as a welder for a while now, but never quite got around to learning how to read blueprints properly it might surprise you to know you’re not alone. It’s pretty common for experienced welders to have little or no expertise when it comes to reading blueprints. If you’re ready to take yourself off this list you’re in the right place – read on.

understanding welding blueprints and symbols

Option 1: In-House Training

If you’re the owner of a medium to large-sized business with a focus on the welding industry or if you have a division with a welding shop its always a good idea to consider your options for helping your staff welders increase their knowledge and skills.

Having an in-house trainer is a great idea if you employ a significant number of welders. When taking advantage of an in-house trainer you can help your employees to upgrade their skills whenever time permits without having to compromise your business schedule.

Option 2: Outside Help

For a small business, hiring a dedicated trainer may not make a lot of financial sense. That doesn’t mean you shouldn’t help your staff welders fill in any gaps that they may have when it comes to reading blueprints. It’s always a good idea to help employees with training to make them better at their job.

The solution is to bring in outside help when needed or to offer incentives and help for welders to take welding blueprint courses to further career goals and to help the company grow.

Workplace Posters, Videos & Literature

Even welders that can read blueprints may not have all welding blueprint symbols memorized – that shouldn’t come as much of a surprise as there are many of them. A simple way to get around this is to make sure that your workplace has reference books, a collection of accessible videos and strategically located posters to help a staff welder track down a symbol that they’re not familiar with.

The 3 Basic Views Or Perspective Found In Welding Blueprints

It doesn’t matter whether you choose to offer blueprint training in-house, seek outside help or if you decide to take on the training roll yourself – the fundamentals of how to read blueprints for welding remain the same. First, let’s take a look at the view or perspective you can expect to find on welding blueprints.

There are three of them:

  1. Front
  2. Top
  3. Right-side perspective

If there’s one area of understanding welding blueprints that doesn’t require a lot of explanation, it’s this section. There’s no trick language here – the front view shows a picture of the object to be welded from the front of the object. The top view looks like an aerial view if you were standing over the object and the right-side view shows the object or objects from the perspective on the right side.

Understanding Common Symbols

So now that we know which points of view blueprints can be drawn from the next step is to become more familiar with the various symbols drawn on a welding blueprint. There are tons of them and that’s why we suggested earlier to keep reference material around the workplace.

We’re going to review some of the more common symbols and how they’re used so that you can use this document as a great starting point.

In the image below you’ll notice a depiction of a horizontal line with an arrow angling downward at the end of the line. The diagram may seem a little busy, but it does a good job of covering the fundamentals of welding blueprint reading.

welding symbols chart
Image credit: Pinterest

The Arrow & Leader Line

The arrow points to the area on the blueprint where the weld should be applied. Unless you have a set of basic blueprints, your document will probably have a number or arrows on it pointing to multiple different areas that need to be welded. Each arrow will lead to a set of instructions and we’ll talk about that below. The leader line is simply the line that connects the arrow with the horizontal reference line.

Reference Line

The reference line is the heart of the information on a welding blueprint. In the middle of the line, there will always be a shape such as a triangle, a V or parallel lines for example. These symbols indicate what type of weld should be performed on the joint.

If the shape is located on the bottom side of the reference line, that means the weld should be applied on the same side of the joint as the arrow is located. Alternatively, if the shape is located on the top of the reference line you should apply the weld on the opposite side of the joint.

It’s also possible you’ll see an identical symbol on both the top and bottom of the reference line – this tells the person reading the blueprints that it’s necessary to apply the same weld on both sides of the joint.

Tail

Most of the time you won’t find an arrow that ends with a tail – usually, it’s just the arrow, leader line and the reference line. When you do see a tail used on welding blueprints, they’re used to indicate that there are special instructions you need to know about. It might be just to let you know what type of welding should be used on the type of metal in question or something else that isn’t found on the reference line.

Most Common Symbols Used On The Reference Line

common symbols on the reference line of welding blueprints
Image credit: Welding Insider

The diagram above is a great summary of the most common symbols used on the reference line of welding blueprints. We’ll go through each one of them briefly below.

Two Parallel Lines

If your weld indicates two parallel lines on the reference line this indicates the need for a square butt weld. In essence, two pieces of metal are placed back to back with a minimal amount of space between them and the weld is applied so that they butt up against each other.

Two Parallel Lines

If your weld indicates two parallel lines on the reference line this indicates the need for a square butt weld. In essence, two pieces of metal are placed back to back with a minimal amount of space between them and the weld is applied so that they butt up against each other.

A “V” Shape

When a V-shaped weld is specified the two pieces of metal that are to be joined together will have a slanted end. When the two pieces are joined together the area to be filled in by the weld is in the shape of a V.

A “V” With A Stem

When you see a symbol that looks like a V with a stem on the bottom, each piece of metal that is to be welded starts with a straight line and then angles off to the left or right. When you place the two pieces of metal together, the joint that will be welded looks like a V with a straight stem at the bottom.

A Straight Line With An Adjoining Angled Line

A unique variation of the V weld joint is more of a half V. One of the two adjoining pieces of metal has a straight vertical edge, the other slants to the left or right in a half V pattern. This is referred to as a Single Bevel Butt in the chart above.

A Straight Line With An Adjoining Angled Line Raised On A Stem

When you add a stem at the bottom of the Single Bevel Butt this indicates a weld that has a straight horizontal edge that branches off to the right or left at the end of the stem. The other piece of metal will feature a straight horizontal edge. When reading welding blueprints this type of weld is known as a Single Bevel Butt with Broad Root Face.

A “U” On A Stem

The symbol of a U placed on top of a short horizontal stem is known as a Single U Butt. Each piece of metal that will be joined together is characterized by a half U and a straight horizontal stem.

A Raised “J” Branching Off A Straight Line

The last symbol in our helpful diagram above is the Single J Butt. Here you’ll notice a symbol that features a straight horizontal edge on one side and a J that branches off about a 1/4 of the way up the stem.

Other Information To Look For On The Reference Line

We’ve only really touched the surface of how to read welding blueprints. For anyone in your organization that is responsible for at least some welding tasks, they should now have at least have a basic grasp of how to read welding blueprints. There are a couple of other symbols that someone learning how to read blueprints should know about early on in their educational journey though.

The Field Weld Symbol

If you see a symbol of a flag on the end of a pole at the junction of the Leader Line and the Reference Line you should follow its instruction before moving forward. That’s because this symbol is an indicator that the weld should be performed in the field and not in the shop. You will need to wait until you’re on the job site before performing this task.

The Weld All Around Symbol

If you see a circle at the joint of the Leader Line and the Reference line the blueprint is indicating that you should weld all around the joint. You won’t see this often, but you will see it a lot if you’re welding pipes or other similar objects. 

When The Symbols On The Top Of A Reference Line Are Offset From The Ones On The Bottom

If you notice that the symbols on a reference line in your blueprint are offset or staggered instead of lined up this is meant to indicate that smaller welds with space between them will need to be applied on either side of the joint. This is commonly used when working with lighter metals.

Understanding Numbering

On the reference lines of a welding blueprint, you’ll usually see numbers as well. These are used to indicate the depth of the weld, the width and also the appropriate angle to be used on a joint. Normally you’ll find the specifications for the width on the left and the depth on the right.

What’s Next?

As we’ve already indicated above, this article isn’t an all-inclusive manual for reading welding blueprints. It’s meant to be used as an introductory tool for welders with some experience, but for one reason or another never got around to learning how to read welding blueprints. When used as a springboard in combination with in-house literature and regular training it can be a great piece of the puzzle to help learn how to read welding blueprints.

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