What are the types of welding joints?

Figure 1 Butt Joint

Figure 2 Lap Joint

Figure 3 T Groove

Figure 4 T Fillet

Figure 5 Corner Groove

Figure 6 Corner Fillet

Figure 7 Edge Joint

AWS A3.0(2010) Standard for Welding Terms and Definitions defines a weld joint as “the junction of the workpieces that are to be joined or have been joined.”  The welding codes recognize two basic types of joints. They are grooves and fillets. There are several variations of each, however, the easiest way to tell them apart is where the weld is going in relation to the two workpieces. If the weld is between the two workpieces, it is a groove weld. If the weld is beside the two workpieces, it is a fillet weld.

Groove welds extend through the thickness of at least one of the workpieces. The most common groove weld is known as a butt joint (Figure 1). This joint is formed by taking the two workpieces and “butting” the ends together. The weld will be placed in between the two workpieces. When the weld extends completely through the thickness of the joint, it is called complete joint penetration (CJP). When it extends only part of the way through, it is called partial joint penetration (PJP).

The other type of joint is a fillet weld. As mentioned earlier, fillet welds are placed beside the junction of the workpieces. One of the most common fillet welds is the lap joint (Figure 2). This joint is formed by laying one of the workpieces on the other and welding where the edge of the first meets the side of the second.

Another common joint is the T joint. This joint is formed by butting the edge of one workpiece against the side of the other making a T shape. T grooves are welded through the thickness of the one workpiece (Figure 3) while T fillets are welded beside where the two workpieces meet (Figure 4).

Corner joints are very similar to T joints. The only difference is the intersection of the two workpieces does not occur in the middle of the one but at the end or “corner”. Corner grooves are represented in Figure 5. Corner fillets are represented in Figure 6.  

​The last joint is the edge joint (Figure 7). It is formed by laying the sides together so that the edges are next to one another. The joint is then welded along the two edges. Edge joints have partial joint penetration.

Ben weatherford

Welding Engineer and CWI at Earlbeck Gases & Technologies