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What Is Tack Welding?

Jul 16, 2021 ·

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The history of welding dates back centuries, and to this day the process of joining materials together through the use of heat and pressure is important in a range of industries.

There are many types of welds and processes used by those in the field, depending on what kind of project they’re working on. One of the methods welders are likely to use is tack welding.

Tack welds are small and temporary welds used to hold parts together before a final weld occurs. Tack welds help keep the right alignment and distance between the parts that are being fused together.

It’s safe to say tack welding is pretty important. Keep reading to find out more about how these welds are used in the welding industry, as well as more on how the process works.

Tack Welding Process

During the process, small tack welds are usually placed throughout the two joining metals to properly fit and prepare them post-weldment. Fit-up (the step between producing the parts needed for a weld and welding them) and tack-up (the application of the weld) are keys to a successful weldment.

Two or more metals are pieced together through heat and pressure just like other welding processes. Tack welding works by joining the metals using electrodes that send electrical current through work pieces, which are locally heated.

Small tack welds are ideal for keeping work pieces looking good, as well as preventing warping and overheating before a permanent weld is made. They are usually between one-half inch to three-fourths inches in length, and they never exceed one inch in length.

In many different welding processes, the materials and parts will be clamped to fixtures that will prevent movement and keep the alignment correct. Tack welds are convenient because they help eliminate the need to clamp these materials. Often, tack welds are used for low-volume production jobs that don’t justify the need to purchase fixtures.

Tack welds can also be removed if you find that the parts being welded are not properly aligned. You can redo tack welds and refine them fairly easily.

Other benefits to tack welds include:

  • Reinforcing the function of features
  • Reducing distortion that can come from welds
  • Maintaining the proper joint gap
  • Helping to reinforce the strength of a weld

Tack Weld vs. Spot Weld

There can be confusion between spot welding and tack welding and whether the two are the same. Spot welding, unlike tack welding, is about securing the final and permanent joints in the welds.

Spot welding does not use any filler material to fuse pieces of material together and is mainly used on thin materials, like foil or wire mesh. Spot welding works by connecting electrodes to the surfaces of the metal, then current and pressure are applied to bond the materials.

To help remember the difference between the two, just remember that spot welding is permanent, whereas tack welding does not have to be. Spot welding does not allow the user to remove pieces.When it comes to symbols, the one for spot welding is a circle placed above the reference chart on a blueprint for a project. There is no official tack weld symbol.

spot welding symbol

The Right Way to Tack Weld

The American Welding Society (AWS) offers guidance through its standard terms and definitions to help explain tack welds and how the process should be completed. As mentioned before, AWS states that tack welds are joints holding weld parts in correct alignment until final welding is complete.

Tack welds are able to be made both inside and outside the welding joints. They are able to be melted again during the final welding process, and if desired they can become a part of the final weld. This goes for welds made both inside and outside of the weld joint.

Tack welds should be strong and sized appropriately so they are able to hold up and manage the weight of the materials.

It’s also important to clean tack welds before starting the final welding process, which ensures harmful oxides are removed.

Risks of Improper Tack Welding

The most important thing welders need to remember during the tack welding process is to not let these welds affect the quality of the final weld. Tack welds need to be performed by trained welders familiar with the process to ensure quality.

Performing tack welds improperly can result in:

  • Craters
  • Cracks
  • Arc strikes
  • Excess slag (a layer of byproduct that takes time to be removed after a weld)
  • Hard spots
  • Buildup of weld oxides

Moving metals or hoisting them during the tack welding process can cause them to fall apart, as tack welds are not meant to permanently hold the metals together. You don’t want to cause damage to the pieces you’re working on or risk injury.

Get Welding Training at UTI

If you’re considering a hands-on career in a growing industry, now might be the time to consider training to become a welder.

The Welding Technology program at Universal Technical Institute (UTI) can help give you the experience you need to perform a range of welds, including MIG, TIG, stick and flux-cored arc welding. You’ll also learn how to perform tack welds, which will come in handy during these processes.

In less than a year, you can gain the skills and education desired by employers across the country.1 You can pursue an in-demand career that you’re passionate about! Learn more about tack welding and other welding processes at one of our campuses nationwide.

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