How Wide Should a TIG Weld Be?


Whether you are just starting out as a manual welder or you have been welding like a pro for years, getting your work done both quickly and well is a top priority. With welding, room for error is very low, since a weld that is too wide or narrow can compromise the structural integrity of the entire project.

This begs the question: how wide should a TIG weld be?

A proper TIG weld requires extreme precision, and the width depends on the size of the fill material you are using. Since metal shrinks as it cools, it is recommended to make each pass at least twice the size of the fill rod you are using, but be careful not to go much wider than that, either. 

Since the width of the weld depends on the size of the fill rod, it is important to understand the fill options you have so you can make the right choice for your project. 

How Is The Fill Metal Turned Into A Proper Weld?

Manual TIG welding is incredibly tough to master because it requires the welder to be both precise and dexterous. This type of welding requires the use of both hands – one feeds the metal fill rods into the area being welded, and the other wields the welding torch. The trick is keeping the tungsten electrode close enough to the surface that a proper heat arc is formed without actually touching the tool to the metal surface.

If the tungsten electrode touches the metal you are welding, several things will likely happen:

  1. You will likely receive an unwelcome shock.
  2. The tungsten will become contaminated, and will not work properly moving forward.
  3. The weld will become weakened at the point of contact, possibly leading to pressure areas that could crack or separate down the road.

Argon-helium gas mixtures are the most commonly used heating elements in TIG welding. It is easy to keep them at a constant flow, which is essential for maintaining a consistent heat supply to the electrode. Without this consistency, your weld line will become sloppy, and it is more difficult to maintain a steady width.

Remember: your goal is to create a TIG weld that is approximately double the width of you fill metal, so if you are using a 1.6 mm aluminum fill rod, you need your finished weld to be approximately 3 mm to 3.4 mm in width.

Hold the rod at a 20-30 degree angle, making sure to point the tip of the electrode in the direction you want your weld to go. Just as you want the width of your weld to be close to double the width of the fill rod, a good rule of thumb is to keep that same distance between the tungsten electrode and the metal fill. This will ensure proper arc connection without the danger of the two actually touching.

Once you have finished your weld line, pause briefly to let the welding torch turn off and briefly cool before lifting the electrode; this will prevent an uneven end to your work, which can lead to decreased structural integrity and even cracks in the material.

How To Properly Adjust Your Weld Width and Troubleshoot Inconsistencies

Be careful about your speed when welding. Rushing things can cause craters, which are usually formed when you reduce the welding heat and power too quickly. This then rapidly changes the texture of flow of the melted metal weld area. Sometimes craters can also be caused when you remove the tungsten electrode too quickly at the end of a weld line. 

These craters are essentially weak spots where the width or depth of the weld is not the same as everywhere else. This puts unnecessary tension on the two pieces of metal being fused together; depending on their eventual use, this structural imbalance could cause major issues such as rust, cracking, or even a full separation. 

Also, mind your voltage. Voltage that is too high will create excessive spatter and a flatter, wider bead that is porous. Additionally, high voltage can cause undercutting, a groove melted into the work piece that is not properly filled with weld metal. Voltage set too low produces a narrow weld bead that lacks proper penetration and fusion.”

When in doubt, the best way to troubleshoot inconsistent weld width is to slow down, take your time, and practice. Practicing on scrap metal is a great way to build up your hand-eye coordination and muscle memory; after all, TIG welding requires extreme precision and a steady hand – both of which are usually developed skills, not things that come naturally to most people.

What Are the TIG Welding Fill Options?

Often called gas tungsten arc welding, TIG welding is a common practice that involves heating metal to a melting point and using a pen-like tool to draw a thin line of molten filler metal to attach to other metal pieces together. This is helpful both when repairing existing metal items and when building new ones from scratch.

There are three primary types of fill rods available:

  1. Stainless Steel: This material is popular because of its incredible resistance to both corrosion and rust. There are several different types of stainless steel used in welding, one of which has magnetic properties. It is important to select your steel fill based on the materials you are trying to connect together. 
  2. Aluminum: Lightweight and versatile, aluminum is the most commonly used welding fill. As with the stainless steel, choose the aluminum fill option that best matches the composition of the two pieces of metal you are trying to attach, as this will produce the best, most binding result.
  3. Titanium: Less common than stainless steel or aluminum fill, titanium nevertheless has a proper place and time to be used. Watch for overheating, however, as this metal has the capacity to become extremely brittle.

It is important to note that when TIG welding steel, using a filler rod with copper coating inhibits rusting of the rod. This effect is similar to the types of filler rod used in oxy-acetylene welding. Because the copper layer is very light, the coating has no negative effect on the weld (when welding steel). If you are however using a non-coated rod, it is important to note that it needs to be kept rust free for optimal results.

On average, you will need to find fill rods that are between 1.6 mm and 4.8 mm in diameter. This will get you through most projects. Should something larger or smaller be required, it is likely that you will also need to adjust the welding tools you are using to accommodate the uncommon width of the rods. 

The end result you want to see is a smooth weld in a straight line that does not vary in width even a millimeter. This intense precision requires focus, muscle control, and the ability to tune out distractions. 

It also goes without saying that you need your protective gear to accommodate a clear line of sight to your project workspace, so of your safety visor becomes cloudy or scratched you will need to replace it as soon as possible, so it does not compromise your ability to focus on your weld width.

Alexander Berk

A bit about myself: I am a certified international welding engineer (IWE) who worked in different welding projects for TIG, MIG, MAG, and Resistance Spot welding. Most recently as a Process Engineer for Laser and TIG welding processes. To address some of the questions I frequently got asked or was wondering myself during my job, I started this blog. It has become a bit of a pet project, as I want to learn more about the details about welding. I sincerely hope it will help you to improve your welding results as much as it did improve mine.

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