Tack welds are indispensable in many welding operations. Whether you are working on a small project or trying to assemble complex components, tack welding will take your metal welding skills to the next level. Though these welds serve temporary functions, they are important as they help prepare the workpieces for bigger welding processes. Tack welds help to align parts and reduce distortion during welding.
As a beginner or DIY enthusiast, it is not a surprise if you are looking to learn how to properly make tack welds at home. This article will explain what tack welds are, the common types of tack welds, and a stepwise guide to tack weld various metal types.
What Are Tack Welds
Tack welds are temporary welds that hold two or more metal pieces in place before the main technique. Tack welds are small, dot-like, and used in place of clamp pins and rivets. They have limited strength and are made with a relatively low heat input. Tack welds are either consumed during the final operation or removed using a grinder or chisel. They are applicable to different engineering materials including aluminum, brass, stainless steel, and iron.
The functions of tack welds during product development are endless. These welds help to properly align and position workpieces during fabrication. They prevent unnecessary movement and vibration that can lead to warping and distortion. Furthermore, tack welds provide support during part assembly. They keep the components stable and maintain the needed joint gap until the full weld is complete.
Types of Tack Welds
Before going into how to make tack welds in detail, let’s discuss the six major types of tack welds you can use
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Standard Tack Welds
Standard rack welds are the most common type available. They are usually large and can be between half to one inch long. The main function of standard tack welds is to align complex structures and components. This type of weld is strong and straightforward to make even for beginners. Furthermore, it is possible to remove them by grinding after the final welding.
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Bridge Tack Welds
Bridge tack welds are more sophisticated than the standard type. While the way you make both tack welds are similar, they have different objectives. Bridge tack welds aim to close unwanted small gaps between two workpieces. Additionally, bridge gap welds help to correct alignment issues and are perfect where perfect fit-up is necessary.
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Hot Tack Welds
When making hot tack welds, you carry out the process at a high temperature. The temperature you use depends on the particular welding technique and material properties. Hot tack welds are useful when working with parts that are susceptible to cracking under stress. They also have applications when pre-welding strong and heat-sensitive materials.
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Ultrasonic Tack Welds
Ultrasonic tack welds are formed when high-frequency acoustic vibrations temporarily join two or more workpieces. The ultrasonic waves convert electrical energy to heat which carries out the welding action. The whole process is fast and it takes just seconds to successfully make an ultrasonic tack weld. Furthermore, the welds are of high quality and can join dissimilar materials with ease.
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Induction Tack Welds
This type of tack weld is the end product of the induction welding process. It involves using electromagnetic induction to heat portions of workpieces to temporarily join them together. This process is noncontact and the heat input is localized. Hence, the surrounding material remains intact after tack welding. Furthermore, induction tack welds are strong and properly align the parts.
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Thermit Tack Welds
Thermit tack weld is another type of tack weld. They are produced when an exothermic chemical reaction heats workpieces to join them temporarily. It involves igniting the thermite mixture to form molten metal that fills the gap joint after solidification. Thermit tack welds are very strong and may be difficult to remove. You should use them in places where they can get consumed by the final welding operation.
Step-by-Step Process on How to Tack Welds at Home
It is relatively easy to create tack welds at home even as a beginner. It involves gathering the necessary equipment and carrying out the operation. Let’s look at a stepwise approach you can employ when creating tack welds as a DIY enthusiast.
Step 1- Preparation
Before starting the welding process properly, you have to prepare yourself and the workpiece to avoid errors. Gather necessary tools such as the welding machine, PPEs, clamps, grinder, and measuring tools. Thereafter, prepare the surface of the workpieces by cleaning them using suitable agents which can be neutral or alkaline based. This helps to remove contaminants that can affect the integrity of the final weld. After cleaning the parts, align and clamp them using a vise.
Step 2- Machine Setup
The next step is to choose the right welding technique. There are different techniques you can use with the most common being MIG, TIG, and stick welding. The one you go for will depend on your budget and the available skill level. You then set up the machine. Check the gas flow and ensure it is sufficient to prevent oxidation. If necessary, select the right filler material based on the properties of the part you are working with. If you are joining dissimilar materials, ensure the filler metal is compatible with both to avoid different types of welding defects.
Step 3- Begin to Tack Weld
Once everything is set, adjust the welding parameters and start to tack weld. Position the welding torch at the right distance and angle from the workpiece. The tack welding process should take an average of 2 seconds depending on the workpiece thickness. If you need multiple tack welds, ensure that they have the same distance along the joint. If the joint is long, consider tacking in a zig-zag pattern to minimize distortion.
Step 4- Finish and Inspect
When you are done, inspect the tack welds individually and be sure they are strong enough. You can try to gently pull them apart and check for how well they resist the force. Note that there are instances where you have to remove and reapply tacks. This can happen if they are in the wrong position or are not strong enough.
Step 5- Apply the Final Weld
After performing the inspection, you can now carry out the main welding technique to complete your project. Join the workpieces along the tack welds to consume them. For those still bulging out, use a grinder to smoothen them. You then carry out the final inspection and reweld if needed.
Conclusion
Before going into welding properly, it is important to make tack welds to temporarily hold the workpieces. Note that the tack weld usually becomes a part of the final weld. However, there are situations where you have to grind them when finishing the part. When making tack welds, ensure they are consistent and not too big. To get the best results, always clean the workpiece and use proper amperage and voltage. Additionally, avoid overheating and use the correct electrode size.
