Different Types of Welded Joints: Lap, Fillet, Butt, Square, Corner, Groove, Bevel

You just bought your new TIG or engine-driven welder. You’re trying to become a better pro. Well, this is the article you need.

Contrary to what most would think, the joints formed by welding come in different types. But they may all look the same for anyone with an untrained eye.

You probably don’t realize that these varying types are not just about style or aesthetics. They serve legitimate purposes. Metals and plastics are fused using either a butt or a fillet method in different positions. These specific joints meet specific needs and forces, but the joints they form are varied.

Don’t have a clue what these different types are? We’ve got you covered! According to the American Welding Society, you will know about each of the five major types of welding joints present. You’ll learn about what sets them apart from each other.

You can choose which one to use for your next project. We hope you get as much excitement out of reading about this topic as we have pride in publishing the article on it. We spent a great deal of time on it, and we hope that its quality reflects it.

If you’re a beginner, we encourage you to read this article on the very basics.

Here’s a quick overlook before we start digging into it.

Types
ButtTeeLap
EdgeCorner 

Butt Joints

If you have ever seen metals or plastics lying flat whose parallel edges are fused, the joint you are looking at is a butt. This consists of welding the edges or “butts” of the material placed side by side and in the same plane. Doing a butt is considered the simplest method. That is why it is also considered the most popular.

They may be done as it is, or weld preps or cutting off sections of the edges may be necessary. They are created through different styles, namely:

  • Bevel– only one of the materials has a diagonally straight bevel that extends from top to bottom.
  • Flare-bevel butt is the same as the bevel groove but has a groove.
  • Flare-V-groove butt – each parallel sides of two materials have grooves running from top to bottom.
  • Square-groove butt– no bevels or grooves are made. The parallel edges are fused together.
  • J-groove butt – only one material has a groove at the edge. This groove only passes through around 3/4 the entire length of that edge, thus forming a ‘J.’
  • U-groove butt – both materials have parallel edges with grooves that take up 3/4 of each edges’ length.
  • V-groove butt – bevels on both parallel edges are made from top to bottom.

This type is often used for various materials and equipment. Examples include:

  • pipes
  • fittings
  • flanges
  • and valves.

It should not be used for those that will receive loads at high impact.

Butts can be done for metals and plastics with a thickness ranging from 3 mm to 12 mm. But if it is 5 mm thick or more, you need to bevel one or both edges before welding them.

Some also opt to have a double butt for those involving bevels. Unlike a traditional butt that only involves one side, a double butt involves making the same bevels on both sides of the edges. They are mirror images of each other. This allows the parallel edges to be fused on both sides.

Aside from doing a double butt, you can also opt for a full penetration weld to strengthen the bond formed. Beveling the materials and a full penetration option will result in a strong butt joint. Excessive heat can result in a twist or bow, not a straight finish.

Edge

An edge joint is made when the edges of two metals are placed parallel. Their adjacent edges are fused using a butt. This edge welding joint is formed either with the metals stacked on top of each other. It can also be welded at the side. Otherwise, it’s placed next to each other and welded at the top. Instead of being on the same plane as a butt, they are fused at parallel planes.

The edge joint is highly similar to the butt. That is why many of the styles used to create this type are the same:

  • U-groove
  • J-groove
  • V-groove
  • Square groove or butt
  • Bevel-groove

You can also use the edge flange and corner flange styles to form an edge joint. An edge flange typically consists of two curved metals with their edges welded at their parallel points. At the same time, a corner flange involves one straight metal and one curved metal also welded at parallel points.

They are weaker because they are shallow and do not completely penetrate the joint. They are typically used on sheet metal plates less than 6 mm thick, such as mufflers. It is also not recommended if the materials are expected to undergo a lot of pressure, tension, or bending.

To strengthen the edge, you can either do a full penetration weld or add filler material as you do the work. The materials must be clamped together before starting because they can separate as you work and start opening up like a clam.

Tee

You might have guessed that the Tee joint has something to do with the letter ‘T.’ A tee is sometimes referred to as at-joint. It consists of two metals or plastics intersecting to form a right angle and fuse.

The upright material is typically placed at the center of the flat one where it forms a ‘T.’ It is done using a fillet at both corners formed by their intersection at the base of the upright material.

The different  styles used are:

  • Plug – a hole is made on one of the metals or plastics. The edge of the other one must intersect with the hole. This hole is then filled or plugged up through welding, bonding the materials together.
  • Slot– it has similarities with a plug, but the hole made is larger and can extend to one edge.
  • Fillet – both corners made by the intersecting materials are fused.
  • J-groove is similar to fillet, but the base of the upright material has a groove.
  • A bevel groove is the same as a J-groove, but it has a bevel instead of a groove at the base of the upright material.
  • Flare-bevel groove – it involves a tube-shaped material placed above a flat material. These are fused at their intersecting points.
  • Melt-through – only one side is welded, but it fully penetrates to reach the other side of the upright material.

A tee may seem simple. Bonding them together is complicated. The material placed vertically can move around when you work the one side first or even be distorted. This upright material must either have a brace to hold it in place. Otherwise, you’ll have to allow it to stand at a slight angle to move in the right position while welding.

If the Tee is misaligned after welding, use a soft hammer to tap the section into place. Do it quickly while it is still hot to be easier to move.

They are normally used for materials whose thickness does not exceed 3 mm and even for bonding a pipe to a metal. All four sides of the intersecting sections are typically welded to give it strength. Some opt to join either the lengths or ends of the materials only, resulting in a weaker bond.

Corner Joints

A corner joint is done similarly to a tee. The upright material is typically placed at the edge of the other one lying flat, forming an L-shape or right angle. This type is also known as a square joint. It is one of the most popular methods, especially for sheet metals. It also allows you to fuse two materials with varying thicknesses or widths.

Its strength is uneven because it involves a fillet on the intersecting side and a butt on the parallel side where the edges meet. It is generally weaker than a tee. Some of its most common uses are for creating boxes and frames using light and thick materials.

These styles used in butt and tees are also used to form a corner:

  • Bevel-groove
  • Fillet
  • Square groove or butt
  • J-groove
  • U-groove
  • V-groove
  • Flare-V-groove

The following styles also form corners. The resulting appearance does not form the ‘L’ shape. That is why they are often mistaken for edge joints:

  • Corner-flange involves one flat and one curved material, but only the corners of their parallel edges are welded.
  • Edge is done similar to a basic edge joint where the edges are placed parallel to each other and then welded.
  • Spot – only small spots at the sides of the intersecting edges are welded

They are typically made with the entire edges of both materials touching each other. It is also possible to weld only their corners. You can also only do a butt for a corner joint and leave the inside corner without a weld. Preps are done on the sides butt welded to strengthen it.

Lap

Suppose you need to fuse two materials with different thicknesses. A lap joint is another way to do it if a corner one is not suitable. A lap one involves stacking two materials together to overlap. The fusing is done on either the top or bottom only or both. While fillets are mostly used, the style that creates a lap is also known as a lap weld.

Aside from the fillet, you can choose among the following styles if you need to create a lap:

  • J-groove
  • Slot
  • Plug
  • Bevel groove
  • Flare-bevel-groove
  • Spot

You can typically see these when resistance spot, laser beam, and electron beam welding is used. They’re typically used for exercise and industrial equipment. They are among the easiest to create because there is hardly any preparation needed aside from positioning the materials. Not only that, but they also often have the smoothest finish. However, it is also prone to warping if there is too much heat.

Now that you are aware of the five different types, you can identify which are most suitable for your project. Yes, you can use various types in a single project.

But aside from choosing the suitable one, always make sure to wear the appropriate personal protective equipment as you work. It can be done easily. There are always various safety and health risks present, no matter how small your project is.

Safety first! Did you manage to learn what it was you came here to learn? We sure hope so and that you didn’t just spend the time reading in vain.

worker at construction site

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For now, that includes various things like helping pros choose the best plasma cutters and wide belt sanders. As we continue to develop this site, we hope to be adding more and more information for you to take advantage of.


What is the strongest welding joint?


Many types of welding joints can easily qualify for the best type of joint welding. Some like Metal Inert Gas(MIG). Others like Gas Tungsten Arc welding(TIG) and Flux Cored Arc Welding(FCAW). However, TIG welding joints have proven to be the strongest type of weld. It is also the neatest type of welding that creates the least amount of splatter.


What are the basic joints in welding?


The most common type of joint is five in total. The first is the butt joint which consists of two pieces of metal joined together in the same plane by welding. This type of joint is commonly used in piping structures.

The second basic joint is a tee joint where two pieces of metal are at a 90-degree angle. Since it forms a T-like shape, it is known as a Tee joint. Another basic joint is the lap joint which is somewhat like the butt joint. It consists of two different metal pieces that are overlapped and welded together. It is most commonly used to join metals of different thicknesses together.


What are the various welding joints?


Apart from the Tee joint, the butt joint and lap joint are popular types. The corner joint weld is mostly found in the sheet metal industry. This type of weld resembles the L shape. Another type of joint is the edge joint, in which metals are placed together by edges bent together at an angle.

Before choosing the types of joints to be employed in your project, consider many factors. They are listed below for your reference.


How to choose the right welding joint?

  1. The Overlap factor


    As a rule of thumb, you should remember that the overlap should result in twice the weld size with an additional 1.5mm for the tolerance. This size is dependent on the size of the nugget. It is also the deciding factor for the type of joint to be employed.

  2. Distance from edge


    It is the distance from the center of the nugget to the edge of the metal sheet.

  3. Accessibility


    The welding machine’s electrode points should be able to access all the joints.

  4. The type of project


    Piping projects will require butt joints, while lap joints are used in the sheet metal industry. T- joints are used in all types of welding applications. Corner joints are used outside, while edge joints are used on the inside of the metal pieces. You will determine the types of joints you need in your home project with the above factors.