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parallel
flush
fit
gap
bevel
groove
root
edge

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If you want to maintain a smooth surface, use a butt weld  joint. Because butt welds require deep penetration and only work across one plane, it’s easy to weld your pieces and grind any excess bead flat. For this reason, butt welds are plentiful and often used in fabrication. Butt welds are used in pipes, fittings, and frames, and if you look around, butt welds shouldn’t be hard to spot. Butt welds are easy for automated welders since there’s very little skill involved, so you’re likely to have more butt welds in your life than you might imagine.

Butt joints...

join two metal pieces that meet at their edges on the same plane

used in applications where a smooth weld face is required

fillet or groove welded; groove welding requires added expertise and expense

improper design/welding risks distortion and residual stresses

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adjacent
fusion
low stress
pressure
impact
flare
groove
reinforce

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Arc Welding 2 | Butt Joints | Welding Rods

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Edge joints are not the strongest joints. In fact, you might be better off moving towards pieces that utilize a T-joint instead. With a T-joint, you don’t have to weld as much material and it’s easier to achieve deeper penetration. In some cases, however, edge joints are both necessary and unavoidable. In those instances, direct stress to other points of the final piece as much as possible. Edge joints do not hold up well to stress and are often the most replaced joint because of it.

Edge joints...

Join two parallel, or nearly parallel, workpieces

Not recommended if either piece will be subject to impact or high stresses

Square groove is most common, but other groove configurations are possible

Very deep penetration is impossible

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overlap
thickness
strength
sheet metal
fillet
slot
rigidity

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intersect
intersection
angle
mechanical
structural
horizontal
vertical
overhead
45 degrees

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90 degrees
assemble
square
open corner
boxes
frames
structures
thinner
burn-through
distortion

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There are 2 main types of corner welding joints: open and closed. Differentiating between the pair relies on positioning. In both cases, you’ll want to weld on the inside seam of the 2 pieces of material, and some applications might require you to stitch the pieces together along the entire joint surface. Corners tend to take a lot of stress and wear and tear, so a solid initial weld is critical. Corner weld joints are complex, but when welded (and ground down) properly, they can become invisible.

Corner Joints...

Join two workpieces that meet at an angle

Two main types: open corner and closed corner

Easily welded with little or no joint preparation

Increase travel speed on lighter material to avoid burn-through

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A butt weld is one of the simplest and versatile types of weld joint designs. The joint is formed simply by placing two pieces of metal end-to-end and then welding along the join. Importantly, in a butt joint, the surfaces of the workpieces being joined are on the same plane and weld metal remains within the planes of the surfaces. Thus, workpieces are nearly parallel and do not overlap, unlike lap joints, for example.

Butt weld diagram

Depending upon the thickness of the metal pieces, different types of grooves can be prepared. Groove preparation is also called weld edge preparation and is necessary for thicker metals. Examples of types of grooves, depending upon their shape are V groove, J groove, and U groove. Groove design changes depending upon full penetration or partial penetration weld requirements. Groove welding can be carried out using different types of welding - whether manual, mechanised or automated processes. Thin sheets are usually welded without any weld edge preparation, such joints are referred as square butt joint.

Butt joints can be welded using arc welding, resistance welding and high energy beam welding and it can even be part of a brazing operation.

At the start, weld pieces can be held together with a tack weld, which is a temporary joint that ensures components stay in a proper alignment while the butt welding is performed. Pre-heating might be required for joining parts at the butt joint area.

Butt welding is commonly employed in various industry sectors varying from piping systems, automotive, energy, power, etc.

Types of Butt Weld Joints

As mentioned earlier, various types of butt welding joints are named for their particular shape. The different types of joints include single V, double V, single and double bevel, single and double U, single and double J joints, square butt joints and even combinations of these. The simplest of these, with regards to alignment, is the square butt weld.

In all cases, the welds are performed with the pieces end-to-end with the thickness of the parent metal. To control distortion of the welded assembly, it is important to control weld penetration by using a double penetration joint design.

For butt welds, depending upon various factors, there is typically a gap of about 2 to 3mm (1/8") between the workpieces, which is called a root gap. The gap is to ensure that the filler metal fully penetrates the joint. If the gap is too small or too large, it will produce weld defects.

Advantages

Butt welds provide several advantages, including:

High strength with complete fusion

Easy to machine

Distortion control

Easy to inspect

Disadvantages

There are some disadvantages such as:

Welding geometry can limit applications

Fixturing or backing may be required

Sensitive to faying surface conditions

Butt Weld vs Fillet Weld

The main difference between a butt and a fillet weld is the angle between the joining workpieces. If the surfaces to be joined are on the same plane, then it is a butt weld. If the surfaces are perpendicular (with an angle of 90°), then they are usually joined with a fillet weld. Weld preparation is not required for fillet welds as with a butt joint.

In fillet weld joint, filler metal is deposited at the joint in a triangular section so that it creates an angle of 45° with both the joining workpieces. To achieve the required weld joint thickness, welding is carried out in several passes.

Distortion occurs in both fillet and butt welds as a result of shrinkage as the filler metal cools down. This can be mitigated against by pre-heating and/or by making successive passes on opposite sides of the joint.

Conclusion

Butt welding is the commonly used joint design for a variety of applications in different industry sectors due to its simplicity. This basic technique has a number of different weld formations suitable for varying weld thicknesses.

TWI can offer advice on all aspects of materials and joining. You can find out more about our welding consultancy services here.

Related Frequently Asked Questions (FAQs)

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A butt weld is one of the simplest and versatile types of weld joint designs. The joint is formed simply by placing two pieces of metal end-to-end and then welding along the join. Importantly, in a butt joint, the surfaces of the workpieces being joined are on the same plane and weld metal remains within the planes of the surfaces.

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Lap joints can be found in a variety of applications such as weight and exercise equipment. The most common use, however, is in the automotive field. Lap joints are used in vehicle frames and even aircraft fuselages. They can often be used to repair unibody automotive frames where they will be subjected to a static load. Because they aren’t the strongest joint, don't rely too much on lap joints when stress levels are higher than normal.

Lap Joints...

Join two members having overlapping surfaces

Good mechanical properties, especially when welded from both sides

Usually fillet welded

Thicker material requires more overlap

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T-joints are most common in construction welding. The flat base allows for structural support. Because T-joints require welding on 2 sides of the work pieces, they are often stronger than other common types of weld joints. They may require gusseting in some cases. Drawing upon the high structural integrity of the triangle shape, gusseted T-joint welds could be stronger than even butt welds might be.

T-Joints...

Join two workpieces that meet at a T-shaped angle

Good mechanical properties, especially when welded from both sides

Easily welded with little or no joint preparation

Usually fillet welded, although J-grooves are possible

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What is a Lap Joint Weld?

Posted on September-09-2022

A lap joint is one of the five different types of welding joints. It is most commonly used when joining two different metals that have different levels of thickness. The 'lap' reflects the overlapping pattern that is formed when the two metals are joined together. The thickness of the two metals is what determines the amount of overlap needed, the thicker the metal, the more overlap required.

A lap weld can be made on one or both sides, depending on how strong you need the weld to be. You will often find this type of welding on sheet metals as it is rarely used on thicker materials.

Where would you find a lap joint weld?

Here are some examples of where you will most commonly find lap joint welds:
- Laying of pipelines and railway tracks
- Fabrication of sheet metal
- Car and aircraft industries
- Shipbuilding
- Building structures

When should you use a lap joint over a butt joint?

When you are choosing between using a lap joint or a butt joint there are a few things to consider. A butt joint will result in a contour that is more flush and will result in the workpieces being in the same plane. Whereas lap joints will result in a more noticeable contour that will not be flush. However, lap joints will provide more strength in higher stressed areas.

How do I get a good lap joint weld?

- Make sure there are no gaps between the two metals, make them as flush as possible.
- Distortion and burn through can be avoided by reducing the amperage and using a faster travel speed.
- For additional rigidity, weld both sides of the overlapping metals.
- If you are welding thicker materials, create a larger overlap between the two metals.

Advantages of Lap Joints

- Easy to prepare as it does not require the cut faces to be parallel or perfectly flat.
- It is useful for joining thin metals such as diaphragms and foils.
- The metals do not need to be the same level of thickness to be joined.
- It can be formed between two metals that are dissimilar e.g. aluminium and copper.

Disadvantages of Lap Joints

- The overlap caused can be undesirable for mechanical or aesthetic reasons.
- If the wrong welding speed is used cracks and cavity defects can happen.
- The weld can be less rigid than the metals used because it can act as a pivot.
- It can retain moisture which may cause fatigue cracking and corrosion on the shielded areas.
- In some cases, there may be lower levels of tensile strength.

Arc Welding Services

We supply a wide range of welding equipment, tools and supplies in Birmingham and the surrounding areas. With over 40 years of experience, we have worked with major clients such as British Rail and Rolls Royce. Whether you are looking for new, used or to hire welding equipment, Arc Welding is here to help.

If you would like to know more about our services, get in touch with our team today. Contact us on 0121 327 2249 or complete our online contact form and our team will be in touch as soon as possible.

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What is a Lap Joint Weld? - Arc Welding Services

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Posted on September-09-2022 A lap joint is one of the five different types of welding joints. It is most commonly used when joining two different metals that have different levels of thickness. The 'lap' reflects the overlapping pattern that is formed when the two metals are joined together.

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Edge Joint Welding: Everything You Need To Know

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Edge Joint Welding refers to the welding of a joint configuration where two or more plates are placed parallel to each other and welded on the full plate

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"Cut and butt" welding technique on fender ✅️ | This technique is known as the "cut and butt" 👩🏼‍🏭🔥 | By Bad Chad | Facebook

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252K views, 10K likes, 174 loves, 327 comments, 194 shares, Facebook Watch Videos from Bad Chad: This technique is known as the "cut and butt" 👩🏼‍🏭🔥

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Butt vs. Lap Welding for Rust Repair: The Debate Ends Here!

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Tig Welding Aluminum Tee Joint .063" (1.6mm) AWS D17.1 Certification Test Tips

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Now take the quiz about the 5 common welding joints.

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