Different Types of Welds and Joints

Types of Welds 

Before we can get into different types of joints, we have to take a moment to explore different weld techniques. Welds describe how pieces form to make joints. We'll be using these terms throughout the article. 

Groove welds involve joining two plates with a bead. Several varieties, usually named after shapes or letters, describe the resulting groove. You'll find groove welds in each joint discussed in this post. 

Bevel welds only occur when the pieces used have angled edges. The angles allow you to make welds with a thickness equal to that of the parts.

Fillet welds join the pieces so that they are perpendicular. Such welds are prevalent in arc welding.

Square welds are similar to fillet welds. The critical difference is that the ends of the pieces touch where the weld occurs.

Spot weld is less about technique and more about tools. When spot welding, electrical currents generate the heat that joins the metal pieces together in a weld.

Slot welds fill an elongated hole in one plate to affix the two parts together.

Plug welds are nearly identical to slot welds, except they use smaller holes and expose less of the underlying piece. 

Square welds join two pieces together at their edges. However, to be a square weld, the edges can't be bevelled.

Finally, melt-through welds occur when you intentionally melt your weld through one piece to join it to another.

The above is by no means complete. They are, however, amongst the most common welds used. After each joint described below, we've listed relevant welds to help you picture the final product.

Types of Joints

Joints are merely two or more pieces of metal welded together to form a support structure. How you join the pieces and the resulting shape can determine their strength and durability. As we outline below, some joints are best suited for specific structures.

1. Butt Joint

The most common type of weld seen in fabrication is the butt joint. To make this joint, two parts lie together end to end evenly on the same plane. Butt welds are a popular choice because they are easy to make and offer multiple variations for different welding solutions.

The area that you melt during the weld is called the faying surface. Because the butt joint has such a simple setup, you can easily shape the faying surface at different angles, resulting in welds with varying strengths for different needs. 

Common types of butt weld joints are:

• Square
• Single or Double Bevel
• Single or Double J Groove
• Single or Double U Groove
• Single or Double V Groove
• Flare V Groove

Buttweld joints are ideal for metal and plastic but can be prone to cracking during the weld. If this happens, try to adjust the angle of the faying surface.

2. Tee Joint Welding 

The tee weld joint sees two pieces joined together at a 90-degree angle, forming a T-shape. The intersection must occur at the center of one component for the resulting joint to be effective. The tee weld joint has fewer variables and uses than the butt weld joint because it doesn't create a groove. 

When making a tee joint weld, your primary consideration is creating deep enough penetration for the intersection to hold. If it isn't deep enough, the joint could lose shape and eventually break. You should also use thicker pieces for a more durable weld. 

Common tee joint welds include:

• Fillet weld
• Plug weld
• Slot weld
• Melt-through weld
• Single bevel
• Double bevel

Due to their unique shape, tee weld joints are very porous and trap more moisture than other joint welds. As a result, they are prone to corrosion. 

3. Corner Joint Welding

At first glance, corner joints look very similar to tee joints, as both form a right angle. However, corner joints do not intersect and are joined together at their ends instead. As a result, welders sometimes classify it as a butt weld joint due to its simplicity. 

Corner joints are commonly used with sheet metal and wood. A welder can choose to join the corners without intersection (called half-open) or by having two ends intersect (called flush). Both require different approaches to ensure the joint is strong enough to hold its form. 

Corner joint welds include:

• Corner-flange weld
• Square weld
• Fillet weld
• J groove weld
• U groove weld

Corner joints are easy to weld, but distortion can become an issue if the joined plates aren't equally thick. Even slight differences in gauge can cause the joint to lose strength and warp. Consider too that the more contact the components of a corner joint have with each other, the stronger it will be.

4. Lap Joint Weld

Like corner joints, these welds are very similar to butt joint welds. The only difference (at least visually) is that the ends of the plate don't join together. Instead, one overlaps the other. 

Unlike other joints, lap joints can use pieces of different thicknesses without issue. However, professionals usually avoid using heavy materials for this for quality concerns. If one part is much heavier than the other, the joint can bend or break. 

Different types of lap joint welds are:

• Spot weld
• Plug weld
• Slot weld
• Bevel-groove weld

5. Edge Joint Weld

Despite their name, edge joint welds do not involve joining the ends of metal sheets. Instead, you weld pieces of the same thickness together surface-to-surface. Therefore, the contact areas should completely overlap with an edge joint weld. 

Edge joints are unique in that one, or both plates can be bent. Such a design can help distribute the stress placed on the joint differently and give the joint better strength and durability. It's best to form any bends before welding the plates together. 

Edge joint welds include: 

• Square
• J groove
• U-groove
• V-groove