What Is A Tack Weld? (How To Properly Use It and Why It Is So Important)

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Have you ever wondered what is a tack weld? Tack welding is a seemingly small step in the welding process, but it plays a major role in a welder’s finished product and its integrity.

During welds, it is important to ensure that the components you are working on are fixed in place and won’t shift or misalign during the rest of the welding process.

What is a tack weld? Tack welding is a process in which you set your welding material in place by applying short welds or tack welds that act as fixtures or joints. These welds are placed along the metals being soldered together before making the initial and final root pass.

There are two methods that a welder can use to keep the components in place.

This can be done by binding the material together with binding wire or by tack welding them.

Why is it Important? (Why do you need tack welds?)

There are several reasons why the use of proper tack welding is important. It helps to ensure proper alignment of the material.

If your welds are placed at appropriate intervals it also aids in preventing the metal from warping out of place during the welding process.

It also allows the welder to set the joint gap.

With your tack weld acting as a fixture, it allows you to reduce workplace clutter or can even be used to help reinforce fixtures for added security against misalignment or distortion.

They are also easily disassembled to allow for realignment if the weld happens to be incorrect.

For such a small step, the benefits of properly applying a tack weld have an impact on the entire process and the quality of the finished product.

Not only can it help to eliminate unnecessary equipment from the work area by acting as a fixture but it has the ability to strengthen or weaken a weld.

Eliminate Contamination Risks

Appropriately applying tack welds are an important step for welding metals together. At any time during welding, there is a risk of contamination.

If the metal is exposed to contaminants, it will compromise the integrity of a weld. This is no different with tack welds.

That is why it is important to treat tack welding the same as you would any part of the welding process.

No matter how small the tack area, the integrity of the whole project could be compromised. So, before applying your tack weld, always check your consumables and equipment for any possible loose fittings or defects.

If you are using TIG welding, this is an important step in ensuring that your gas shield is not compromised and will adequately protect the work area from contamination by oxygen.

You also want to make sure that the work area is properly cleaned by sanding or grinding away any grime or possible coatings that are on the metal being weld.

 Are You Using the Correct Equipment?

Tack welds can literally take less than five seconds to perform, but those five seconds can result in weld defects if not properly applied.

Depending on whether or not you have the equipment, welders have the option to create the tack welds manually with their welding torch or to use a tack welding machine specifically designed for this step of the welding process.

If you are using a tack welding machine, it is imperative to make sure you are using the correct machine for the job. A tack I machines is ideal for tacking metals such as gold while a tack II machine can tack platinum, silver, brass, and titanium due to its higher power input.

What Are the Requirements for Making a Tack Weld?

When you are tack welding, it is important to follow appropriate welding requirements when spacing out and applying tack welds.

According to The National Board of Boiler and Pressure Vessel Inspections, the ASME code requires that all tack welds are to be inspected and qualified for both procedure and performance.

If a tack weld is not adequately installed during the welding process, it is known to cause entrapped slag, porosity, lack of penetration, leaks, and cracks.

That is why meeting the required code and job specifications for the type of weld you are performing are so important.

It helps to ensure a quality weld that won’t fail or disassemble after the final weld.

If any defects go undetected during testing, it can potentially cause harm to both property and people.

That is why tack welds should only be performed by qualified welders.

How to Make a Tack Weld

More often than not the tack size will be left up to the welder’s professional opinion if they are directed to use “a sufficient number of tack welds to maintain alignment during welding”.

The sufficient number will then be dependent on the qualified welder’s best judgment and should be based on the thickness of the metal being worked on as well as the complexity and length of the weld.

There is also a misconception that tack welds are always short or small welding applications.

Although tack welds are typically between ½ inch to ¾ an inch in length and do not exceed one inch, that is not always going to be the case

This will depend on what you are working on and the job specifications given to you.

In some instances, a tack weld could be required to be up to twelve inches in length while also needing to being completely fused to the root.

It really depends on the project at hand, but most importantly when you make a tack weld it should always be free of any defects.

Tack Welding Defects

At times, tack welding is often overlooked for its importance, but the improper application of it could result in the tack weld becoming the weakest point of your weld.

It is important to ensure that the tac weld does not degrade or compromise the quality of the final weld. It also should not contain any type of defects.

After tacking welding be sure to check it for visual defects such as any discoloration from contamination, whether there are any heat distortions, craters, arc strikes, graining, sugaring, or signs of rapid cooling. 

Related reading: 11 Common Welding Defects And How To Prevent Them

What is Rapid Cooling?

Rapid cooling or quenching occurs when the temperature of the metal cools too quickly.  

If rapid cooling occurs it could pose a serious risk for any type of weld as it can cause the weld to develop brittle, crack-sensitive microstructures where the heat was applied.

These cracks can potentially be small enough to go unnoticed during the inspection, allowing the crack to grow over time and risk fracturing.

This could lead to failure of the structure and risk harm to people and property.    

Tips for Tack Welding

If you are looking to make a successful tack weld there are a few things you can do to set yourself up for success.

Tip#1: One of the main factors in the quality of any weld is the type of welder being used. As mentioned above, it is important to make sure you are using the correct machine for the job. 

Different metals require different voltage to reach their melting points, and like any product, the quality of the welder will affect the quality of the weld.

If you plan on making a career out of this is it advisable to invest in some quality welders.

Tip#2: You also want to make sure that the tac weld is not the only thing holding the two pieces of metal together for too long a period of time.

Tack welds are not meant to be a substitute to a final weld and the project should not be used until properly and fully welded.

So even though welding takes time and patience, you want to make sure you finish the project within a reasonable amount of time from starting it.

Tip#3: Distortion prevention is one of the perks of using tack welds so you want to pay attention to the order in which you place them.

When placing your tack welds make sure to alternate between sides when welding them on. The heat used to create the tack weld is capable of warping the metal out of alignment.

This can happen if you are starting from one end of the metal and go straight down to the other end.

To prevent the alignment from being off, you want to tack weld one end of the material and then the other opposite end, working inward as you alternate between tack welding sides. 

Tip#4: When checking your equipment before use, make sure to check your contact tips. You want to double-check that it is not worn as that can make the process more of a challenge for the welder.

This is especially important with TIG welding as it uses a brass fitting and collet that are worn down from assembly and disassembly after each use.  

You also want to make sure that you aren’t using the wrong size contact tip for the wire size being used. 

Tip#5: Try using a smaller diameter filler wire, this will allow for a faster burn and will keep the wire from balling.

Always be Safe!

Since tack welding uses the same heat application as the actual weld, it requires the same precautions.

Always make sure you are using the appropriate safety gear with an ANSI (American National Standards Institute) certified welding helmet and gloves.

You will also want to ensure that your work area has proper ventilation and that all of the equipment is free of any damage.  

Related Article: Personal Protective Equipment for Welders – PPE | List, and Requirements

Mastering Tack Welding – Salary & Career

It takes both time and patience to become a qualified and masterful welder.

If tack welds prove anything it is that even the simplest function/step to a good weld must be made with precaution and precision.

They can create and pose challenges for even the most skilled welders so if you are new to the world of tack welding don’t be disheartened.

The more comfortable you get with the process and equipment, and the more you understand how things can go wrong and how to prevent them the better you’ll be for the next weld.

Read also: Welding As A Job: 16 Crucial Facts Why Welding Is A Great Career Choice

If you are interested in tack welding there are courses out there to become certified in tack welding specifically.

Whether it catches your interest or you find that you are actually quite good at applying tack welds, it can be a lucrative career to dive into. Tack welders can average making upwards of $43,000 a year.

What Is the American Welding Society Standard for Tack Welding?

The AWS A3.0 Standard Welding Terms refers to the following “Tack weld. A weld made to hold the parts of a weldment in proper alignment until the static welds are made.”

The code, however, does not limit the length as, generally speaking, there are no specific American Welding Society standards with regard to tack welding in particular.

There have been numerous “rules of thumb” over the years regarding the regulations in connection with what a good tack weld consists of, but no actual code.

Although there are no specific limits on the lengths of tack welds, it goes without saying that a 6-inch tack weld on a 6-inch plate would actually no longer be considered to be a tack weld.

A sound judgment is required by the welder. Tack welds should also comply with the visual acceptance regulations if they have not been ground or embedded into the weld.

The tack weld can even be a multiple pass weld when it is used to hold large parts together until the final production weld is carried out.

How Do You Tack Weld with a Stick Welder?

Tack welding requires you to weld two pieces of metal together in order to hold them in place.

This is an aid to reducing joint distinction which is often caused by the metal expanding and contracting as it is subjected to heat or cold.

When using a stick welder, the weld direction can move from the top to the bottom or the bottom to the top, but it is usually a lot easier to weld in an upwards direction.

Use a backing plate that has been tack welded on if required. If using thicker materials, it makes sense to bevel the edges.

Related reading: Stick Welding – Ultimate SMAW Guide You´ll Ever Need [Updated]

In manual welding short production runs, the use of tacking welding is perfect for setting up the pieces without permanently fixing them.

Usually, the welds are short. In most cases, a number of tack welds are provided at a good distance from one another so as to keep the edges together.

The main benefit of this procedure being that if there are any mistakes, the parts can be removed again quite easily, then placed in the correct position, and welded using the tack welding procedure once again.

What Is the Difference Between Spot Welding and Tack Welding?

While everyone tends to get a bit confused about the difference between spot and tack welding, the real confusion lies in the group of beginners.

Let’s take a detailed look at both so you can discern the differences for yourself!

Spot Welding

This is one of the oldest welding processes in the world. Here two pieces of metal are welded together without filler materials.

Technically put, it’s a resistance welding procedure.

It works by placing copper alloy electrodes to the metal sheet where the pressure and current are being applied. The resulting molten metal binds the piece together.

You should bear in mind though that spot welding isn’t usually used for small sections. Generally, it’s used on larger pieces of low-carbon steel.

Tack Welding

This is used to hold sections together in the right position while you weld. It’s an essential part of all welding.

Here, you apply small, short beads to the base components to correctly align and secure them. 

How Strong Is a Tack Weld?

Tack welding can play a crucial role in manufacture. To make a good tack weld you’ll need to use a smaller diameter wire.

Generally speaking, a little more voltage than usual is required, and you’ll definitely need to ensure that your contact tips are in perfect condition and not worn out.

You’ll also need to ensure that the arc length is kept at 3/8 or less; in fact, the shorter the better as most professionals will go in 1/4.

It’s also good practice to cut the end of your wire between the starts if you notice that a ball is forming.

A tack weld can be pretty strong but it is important that you have sufficient heat for your tack weld and that it is flat enough so as not to burn through the material you’ll welding – however, it must also have a low profile so that you don’t have to spend too much time grinding it back afterward.

It’s basically a balancing act between heat and penetration.

So, more voltage and less wire than you would tend to use on a standard weld.

Can You Tack Weld Aluminum?

Can you tack weld Aluminum? Yes, technically, you can tack weld aluminum. However, these types of welds do tend to be really weak and insufficient without the use of a filler rod.

They also have a tendence to crack really quickly.

That said, there are times when you just want to quickly tack weld so you can hold the part with the other hand, and it’s therefore not particularly easy to try and use filler metal if you’re attempting a tac weld with one hand.

There are often issues when tack welding aluminum. When subjected to certain temperature ranges it tends to be weak and rather brittle.

If you tack weld without a filler rod, the contraction and expansion stresses that come into play can actually cause the tack weld to crack. So not exactly ideal.

In short, there are three main things to consider when tack welding aluminum:

–       Keep a tight arc

–       Use a sharp electrode

–       Maintain a slight overlap but ensure there is absolutely no gap

So, not ideal but ultimately, possible.

Can You Tack Weld Stainless Steel?

Can you tack weld stainless steel? Yes, It is possible to tack weld on stainless steel, but there is a right and a wrong method. You have to ensure that the tack weld set-up is totally flush and there is definitely no gap between the two.

It’s also imperative that you prop the cup of your tig welder right alongside the joint and use a sharp tungsten electrode tip positioned less than 1/16” away from the joint.

After you’ve got all that covered, you’ll need to set the welder to attack the joint super hot and really quickly once you release that foot pedal.

What Causes Warpage or Distortion in Welding?

Warpage and distortion are common occurrences when welding since there is a lot of localized heat happening.

Therefore, the base material tends to expand and contract as the temperature varies, causing distortion of all kinds.

The good news is that you can revert some of this warping but not all kinds are reversible.

The degree of distortion or warpage does depend on a few factors. These include the following:

  • Amount of restraint — If you have been welding without any external restraint, it will warp to try and relieve itself of the stress. You can counteract this by using strong-backs.
  • Part fit-up — This should be uniform to ensure that the shrinking is consistent around the whole piece. When it isn’t, your finished item will look distorted.
  • The specific welding procedure — To prevent weld distortion here, you should keep the volume as low as possible. Plus, you should try to use techniques that balance the stress.
  • Properties of the parent material — The coefficient of thermal expansion affects the degree to which a piece will distort.
  • The design of the jointbutt and fillet joints suffer from distortion quite a lot. This can be minimized if you balance the thermal stresses against the plate.

References:

https://www.twi-global.com/technical-knowledge/job-knowledge/distortion-types-and-causes-033

https://www.millerwelds.com/resources/article-library/tack-welding-tips-from-nascar-to-your-shop

https://app.aws.org/

David Harper

David is the Co-Founder and Senior Editor at weldingtroop.com. David's an experienced fitter and tuner/welder who's passionate about helping others develop in life through new skills and opportunities.

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