The Different Parts of A Weld – Explained With Diagrams

Wondering what is the anatomy of a weld? Here are the different parts making up weld.

It saddens me when I hear and see seasoned professionals and engineers and tradespeople referring to butt joints as butt welds as if it is the custom and usage of the industry—an exact search proves my claim.

Such instances are clear proof of discontinuing education. Using this blog post as a medium, I would explain to you the different parts of a weld

Groove Weld

If I were to choose between welded or seamless parts, I would choose the latter. Every joint makes my design vulnerable, weak, and prone to failure. While it is not always possible to go seamless, the next best option is a groove weld. 

There are two major types of groove welds. A complete joint penetration (CJP) joins the two workpieces throughout the entire thickness. The other type is the partial joint penetration (PJP) groove weld. (Read more here)

Groove weld shapes

A groove is like a cavity awaiting filling. But for the electrode to reach the bottom, the top must be like a funnel. It can be a V-shape (or J and U for higher thickness).

To make it more clear using 3D, I made this CAD model of a single V groove.

Below you will find how other groove welds look.

A single V groove is the only option when the other side is inaccessible. But quite often, complete penetration is difficult to achieve. 

To overcome this disadvantage, double V groove welds come useful. To make it, the welder makes a single V groove from one side and welds it. The welder repeats the same procedure but from the other side. Such a process ensures full penetration. 

Compared to single V, a welder needs to deposit half the amount of electrode in a double V groove. This not only reduces cost and distortion but also ensures 100% penetration.

Groove angle

Each tapered side of the groove is the groove face, and the groove angle is the angle between both the groove faces. A large groove angle requires a small root gap and vice versa. 

Root Gap

Before welding starts, the welder keeps the workpieces apart at a distance known as the root gap. If they are not, then the electrode won’t be able to reach the root—the place where the weld starts. A smaller gap requires a small electrode, but welding time increases. A wide root gap is fast but increases distortion.

Root Face

If the edge of the workpiece is knife-shaped (no root face), the welding heat would cause a burn-through. To prevent this, the designer provides more material at this place by making a root face. 

Weld reinforcement

The excess weld metal present beyond the base metal is the “weld reinforcement.” It serves no functional purpose but increases the stress level, so it is best to remove it.

Fillet Weld

The second type is the fillet welds. They are very popular and for a good reason. You don’t need any joint preparation—put the parts in position and weld. Fillet welds have another advantage. Welders can join perpendicular workpieces using fillet welds. The disadvantage of fillet welds is that they are weaker compared to groove welds.

Welding is like casting—melting the metal and then solidifying and fusing them. A liquid takes the shape of its container. In fillet welds, it looks like a right-angled triangle. Two perpendicular sides lie along each workpiece and the third is the hypotenuse.

Fillet face

The hypotenuse is the “fillet face” and can be convex, concave, or straight. The intersection of the hypotenuse with each workpiece is the “toe.” 

Fillet Legs

The two sides of the fillet are the “legs.” And this is the value welders want to know. But they shouldn’t deposit more thinking that it will add to strength. It won’t. Read more in this article by TWI.

Fillet Throat

The most critical parameter of fillet welds is not the leg but the throat. The throat is the distance between the root and hypotenuse. The designer designs fillet weld using the throat value. 

The throat and leg values have a relation. If you know one, you can find the other. Throat size equals fillet leg size multiplied by 0.707 (for an equal-leg fillet weld).

What is next? 

I hope you have enjoyed learning about the parts of a weld. After learning the different parts of a weld, Its always a good idea to learn about the welding joint types and their styles.



Mechanical Project engineer (M Eng., C Eng.) with 8 years’ experience in the EPC industry (oil/gas/chemicals) and another 8 years experience as a mechanical chartered Engineer. Authored six books on project management, piping, and pressure vessels. Former member of American society of Mechanical engineers, pressure vessels and piping division. Acted briefly as a welding coordinator.
Arc Welding

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