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What Is Undercut in Welding and Why Is It Used?

Welding is joining two pieces of metal or other material such as concrete, plastic, or fiberglass. "Undercut welding is a process used to create a fillet weld, which is the joining of two flat surfaces by melting and flowing filler metal in the space between them. The resulting weld has a V-shaped notch at the edge opposite the direction of travel." Undercut welding is a complex and delicate process that requires costly machinery. In automotive applications, it can be used to weld thin metal sections together where the piece being welded has a smaller cross-section than the filler metal. 

In aerospace applications, weld undercutting is also used to join panels together and also for buildpro table, such as wing sheeting to skin or fuselage panels to stringers. This article looks at welding undercut, a form of welding that is used in the construction industry.

What is Undercut Welding? 

Undercut welding is a type of welding where the discount welds metal is deposited below the parent metal. It can be done using a lower welding current, creating a smaller weld bead. Alternatively, it can also be accomplished by using a higher welding speed, which will create a narrower and deeper weld pool. Undercut welding has many benefits, such as increasing the strength of the weld, improving its fatigue resistance, and preventing cracking. Additionally, it can also be used to repair damaged or broken welds. If you're looking for a way to improve the quality of your welds, then consider giving undercut welding a try.

Why is it used?

Undercut welding creates a stronger weld joint between two pieces of metal. The undercut creates a smaller area for the weld to attach to, which makes the joint stronger. Additionally, the undercut helps to prevent cracking and warping in the weld joint.

Types of Undercut Welding

There are three types of undercut welding:

  1. Manual Undercut Welding
  2. Machine Undercut Welding
  3. Automatic Undercut Welding
  • Manual undercut welding is the most common type of undercut in welding. It is performed by hand, using a torch or welder.
  • Machine undercut welding is performed by a machine using a torch or welder.
  • Automatic undercut welding is performed by a machine using an automated system.

Different Options for Undercut Welding

There are many reasons why you might want to consider using welding undercutting for your next project. This type of welding can offer several advantages, including:

  1. Increased Strength: Undercut welding supplies can create a stronger joint than other types of welding, making it ideal for projects that require a high degree of strength and durability.
  1. Improved Aesthetics: Undercut welding can create a much cleaner and smoother joint than other types of welding. It can be particularly beneficial if you're working on a project that will be visible to the public.
  1. Greater Flexibility: Undercut welding can be used on various materials, giving you more options for your project.
  1. Faster Welding Time: Because undercut welding creates a smaller and narrower weld, it can often be completed faster than other types of welding. It can save you time and money on your project.
  1. Easier to Repair: If you make a mistake while undercut welding, it's often easier to repair the error than it would be with other types of welding.

If you're considering using undercut welding for your next project, be sure to talk to a professional welder and welding supply stores to discuss.

How Does It Work?

Undercut welding is a type of welding in which the weld metal is deposited below the surface of the base metal. It creates a strong bond between the two metals and helps to prevent cracking and other forms of damage. Undercut welding is often used in applications where high temperatures are a concern, such as a boiler making.

Signs of incorrect undercut welding

If you're welding and you notice any of the following signs, likely, you're not creating an undercut weld:

-The weld is too broad.

-The weld is too shallow.

-There are voids in the weld.

-The edges of the weld are ragged.

-The weld is porous.

Principles of Undercut Welding

Undercut welding is a type of welding that involves creating a groove in the base metal before depositing the weld metal. It helps improve the weld's mechanical properties and increase its resistance to cracking and corrosion. Additionally, undercut welding can create a seal between two pieces of metal, which is often important in critical applications such as aerospace and nuclear industries. 

There are several advantages to using undercut welding:

  • It can help improve the weld's strength by increasing its cross-sectional area.
  • It can help to prevent cracking by providing additional support to the welded metal.
  • It can improve the weld's resistance to corrosion and wear.
  • It can create a seal between two pieces of metal, which is often important in critical applications such as aerospace and nuclear industries. 

Inert tungsten gas (TIG) welding equipment include welding jacket is often used for undercut welding. The welder first cuts a groove in the base metal using a pointed electrode. The welder then uses a filler rod to deposit the weld metal into the track. Depending on the application, the depth of the way and the size of the filler rod will change.

Equipment Needed for Undercut Welding

You'll need a few items if you conduct any undercut welding. An angle grinder with a metal cutoff wheel is the first thing you'll need. Additionally, you'll want a welder that can do MIG or Tig welds. Finally, you'll want a mask and a pair of welding gloves.

The weld bead is positioned below the metal's surface when welding using an undercut. It is accomplished by creating a metal groove and welding along it. The end product is a stronger weld less prone to fracture or break. Undercut welding is often used on critical parts or components that can't afford to fail. It's also commonly used on projects where aesthetics are important, as the weld can be ground down flush with the surface of the metal for a clean look.

Cost of the Equipment

The cost of the equipment is relatively low, making undercut welding an attractive option for many businesses. The welder uses a standard welding machine, and the only other piece of equipment needed is an undercutter. This machine is designed to create an undercut in the metal, which allows the welder to get a stronger bond. The cost of an undercutter is around $200, making it an affordable option for many businesses.

Where To Begin

Are you looking for a new welding project? Perhaps you're considering undercut welding. Undercut welding is a type of welding that involves removing a small amount of material from the base metal. It creates a V-shaped groove that helps to improve joint strength and prevent cracking. Undercut welding can be used on various materials, including aluminum, stainless steel, and even titanium.

There are several advantages to using undercut welding:

  • It can help to improve the overall strength of the weld.
  • It can help to prevent cracking and other types of damage.
  • It can provide a more aesthetically pleasing finish.
  • It can be used in a variety of difficult-to-reach places.

Considering undertaking a new welding project, consider using undercut welding. It can help improve the overall quality of your undercut welds and provide several other benefits.

How to Perform an Undercut Weld

An undercut weld is a type of weld used to improve a joint's strength and stability. It is achieved by welding material from the bottom side of the workpiece, underneath the main body of the weld. It allows for a stronger hold between the two pieces and increases resistance to stress and vibration. Undercut welding is an important method for many applications, such as automotive and aerospace industries. It can be used on ferrous and non-ferrous metals and is often used in conjunction with other welding methods to create a strong and reliable joint. 

If you're looking to perform an undercut weld, there are a few things you'll need to keep in mind:

  • You'll need a welding torch or electrode to reach the workpiece's bottom side.
  • You'll need to ensure that your welding machine is set to the correct parameters for the thickness and type of metal you're working with.
  • You'll need to practice proper technique to avoid creating weak spots in your weld.

What can be welded with this technique?

Diverse materials may be welded using the undercut welding process. It consists of metals, including copper, aluminum, and stainless steel. Additionally, it may be used to weld composites and polymers. In the automotive and aerospace sectors, undercutting welding is often employed.

What are the drawbacks to undercut welding?

While there are certain benefits to employing undercut welding, there are also some undercut welding defect. It might be challenging to regulate the level of undercutting that takes place is one of the main disadvantages. It can lead to weakened welds or, in extreme cases, structural integrity issues.

Another potential drawback is that undercut welding can be time-consuming. This is because the welder needs to be very careful to avoid creating too much or too little undercutting. It can make the overall welding process take longer than it would with other methods.

Finally, weld undercut can create more fumes and smoke than other methods. It is because creating an undercut involves burning through materials, which can release harmful fumes into the air.

Tips for Undercut Welding

There are various considerations you should make if you want to weld undercuts. Make sure the space you're working in is adequately ventilated first. Second, choose a welding rod suited for your working metal. Third, make sure to use the appropriate welding method. Fourth, test it on scrap metal before attempting it on a project piece. And lastly, be patient and take your time. Good things will come to those who wait.

Advantages and Disadvantages of Undercut Welding

A form of welding called undercut welding is used to produce a stronger weld. The procedure is fusing two pieces of metal and then trimming the extra metal from the weld with a chisel or another tool. It creates a small channel or groove in the weld, which boosts its tensile strength. The use of undercut in weld has various benefits and drawbacks. One advantage is that it results in an overall stronger weld. The disadvantage is that removing extra metal from the weld may be difficult without causing damage to the metal.

Safety Precautions for Undercut Welding

When performing undercut welding, a few safety precautions should be taken to ensure a safe and successful weld:

  • Wear proper safety gear, including gloves, a face shield, welders helmet, and protective clothing.
  • Be sure to have good ventilation in the area where you are welding.
  • Use the correct welding rod for the material you are welding.
  • Keep the site around the weld clean and free of debris.
  • Never solder on live electrical wires.

Following these safety precautions can help ensure a safe and successful undercut weld.


A common welding method with several advantages is undercut welding. Because it produces a strong weld that is less prone to fracture or shatter, it is often employed in fabrication and construction. Additionally, undercut welding is less likely to result in warping or distortion, making it perfect for tasks requiring exact specifications. A procedure called undercut welding may be used to increase the strength of a welded junction. It is often utilized in demanding applications where a high level of dependability is necessary. Even though it may not be appropriate for all applications, it can significantly improve the weld quality and the connection's strength. To achieve the most acceptable results, consult with a qualified welder before employing undercut welding on your next job.

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