What is Butt Welding or Butt Joints?
It doesn’t matter if you only want to weld for a hobby or as a career choice, you will eventually have to learn about welding joints. They are the basic foundation of welding and something you will come across daily. According to the American Welding Society, there are five different types of welding joints. These include the corner, butt, lap, edge, and tee joints.
Learning about only five joints sounds easy but, each one comes with many different types of welds, welding symbols, requirements, etc. For this guide, we’re going to focus on one of the more common ones, the Butt Joint.
What Are Butt Joints?
A Butt Joint simply refers to when two components are connected together while also being on the same plane. Like I mentioned earlier, this is one of the most common joints you will come across in your welding career. One of the reasons the butt joint is more common is thanks to the many advantages it brings to the table. These include:
- Can be automated or done manually.
- Is economically smart, especially in factories where a butt joint can save time and money.
- Butt Joint preparation is easy.
- Simple joint to learn and perform.
- When done right, a Butt Joint is a very structurally strong weld.
However, just like with anything in life, the Butt Joint is not perfect and does come with some disadvantages. These include:
- Prone to excess cavities in the weld or Porosity.
- Slag entrapment and cracking can be more common.
The Different Types of Butt Joint Welds
Just going by the definition we gave earlier, Butt Joints may seem like a pretty simple weld to perform. However, things get a little more difficult once you start learning about all of the different types of welds that a Butt Joint has.
The American National Standards Institute (ANSI) term for these welds is Groove Welds. You may also hear them referred to as Butt Welds, which is the International Organization for Standardization (ISO) term. They can sometimes even be called a Bevel Butt Weld. No matter what you call them though, they all include the same welds.
As you can tell in the figure above, there are quite a bit of Groove Welds you’ll need to memorize. But before you start that you will need to know the basics of a Groove Weld and what a bevel is.
What Is A Groove Weld?
A Groove Weld or a Butt Weld simply refers to the type of weld used in a Butt Joint. Depending on the penetration of the groove weld, it could fall into one of two categories. These include:
Complete Joint Penetration (CJP) - The weld material goes all the way through to the root opening and fills the gap.
Partial Joint Penetration (PJP) - The weld material does not reach the root opening and only fills the gap partially.
What is a Bevel?
When you need a deeper penetration for a groove weld, you will need to use a bevel. For those unfamiliar, a bevel simply refers to the slanted edge of an object or structure. Beveling the edges of a component will reduce the thickness of the metal while still letting you get a strong joint.
The angle and depth of the bevel are extremely important in determining the strength of the joint. Without getting too off-topic, here are a few important things to keep in mind regarding the angle and depth:
- The angle will commonly be around 45 degrees but can vary.
- The angle needs to be wide enough to comfortably lay your first bead.
- The Angle can’t be a 90-degree angle.
- The depth will need to be deep enough in order to get almost full penetration. Be careful not to go too deep or else you might blow through the bottom while welding.
If you’d like to know more about how to bevel the edge of metal, we’ve listed a video below that should be helpful.
Square Groove Weld
Now that we are done with the basics, we can get into learning about the first groove weld, the Square Groove Weld. Thankfully this is one of the easiest Butt Joints to learn.
To start with, this weld is typically done on thinner metals up to 4.5mm or 0.1772 inches plate thickness. Since this is only performed on thin metals, there is no need to bevel the metal’s edges or modify it at all.
How To Weld A Square Groove Butt Joint
Bevel Groove Weld
So now that you know what Butt Joint to use on thinner metals, what if the metal you’re using is too thick? This is where a bevel comes in handy. It also brings us to the next Butt Joint, the Bevel Groove Weld.
As you can see in the image above a Bevel Groove Weld has two main variations. These include:
Single Bevel Groove Weld - A joint where one of the metals being welded is beveled on one side. Plate Thickness: 3⁄16–3⁄8 in (4.76–9.53 mm)
Double Bevel Groove Weld - A joint where one of the metals being welded is beveled on both sides. Plate Thickness: Over 3⁄8 in (9.53 mm)
How To Weld A Bevel Groove Butt Joint
Just like the Bevel Groove Weld, a V-Groove Weld requires a beveled edge. However instead of just one of the metals having a beveled edge both metals do. The bevels together will form a “V” shape, hence the name of the joint.
You have the choice between two variations of a V-Groove Weld, which you can find below:
Single V-Groove Weld - Edges of both metals are beveled, forming a “V”. Plate Thickness: Up to 3⁄4 in (19.05 mm)
Double V-Groove Weld - The edges on both sides of the metals are beveled, forming a “V” on both sides. Plate Thickness: Over 3⁄4 in (19.05 mm)
How To Weld A V-Groove Butt Joint
A J-Groove Weld is a different type of Butt Joint weld that doesn't use a beveled edge. It uses a groove in the shape of a “J”. Even though it doesn’t have a bevel like the previous welds, the J-Groove does have the same two different types to choose from, single and double.
Single J-Groove Weld - This weld requires one of the metals to have the J-Groove edge, with the other metal having a regular square edge. Plate Thickness: 1⁄2–3⁄4 in (12.70–19.05 mm)
Double J-Groove Weld - For this weld, one of the metals has the J-Groove made on both sides of the edge, with the other metal also having a regular square edge. Plate Thickness: Over 3⁄4 in (19.05 mm)
Just like how the V-Groove is similar to the Bevel Groove, the U-Groove is similar to the J-Groove. With the U-Groove you’ll be making the same “J” shaped groove, but instead of only having one of the metals with the J-Groove both metals will have it. This is where the weld gets its name since this groove forms a “U” shape.
You have probably already guessed but, that there are two different types of U-Groove Welds you can make.
Single U-Groove Weld - Edges of both metals have the J-Groove, forming a U-Groove when brought together. Plate Thickness: Up to 3⁄4 in (19.05 mm)
Double U-Groove Weld - Edges on both metals on both sides have the J-Groove, forming two U-Grooves. Plate Thickness: Over 3⁄4 in (19.05 mm)
Helpful Links & Sources
As with every one of our articles or guides, we almost make it a priority to remind people about the dangers when welding. Any experienced welder will tell you how stupid it is to not take it seriously. It doesn’t take much either to properly protect yourself.
One of the easiest ways to protect yourself from a lot of dangers is with a welding helmet. Simply having a welding helmet will protect you against welders flash, UV welding burns, and even stray debris. Some other easy ways to protect against other dangers include wearing proper welding gloves and making sure you have proper ventilation.