There is a lot of confusion between the spot welding and tack welding. A lot of beginner welders are asking what is tacking in welding. Actually, tack welding is very important as it is used to hold the parts to be welded in the correct position and alignment while welding.
Spot welding, on the other hand, is one of the eldest welding processes in which two sheets or more are welded together, usually without using filler materials.
If you’re one of the many people who is confused about these types of welds then read on. In this post, we will discuss almost everything that you need to know about tack weld and spot weld.
Let’s get started!
What is Tack Welding?
Tack welding is a crucial step wherein the welder bonds base metals with few separate short beads to position, secure, and align the workpieces together properly before the final welding.
This form of welding always comes in handy if you’re placing and aligning the details in place especially in short-term welding processes
Tack welds are short/small bursts of welds and often they’re utilized in construction. Such welds are created between small distances in order to hold the base metals in one place.
Moreover, tack welding has a lot of benefits. For instance, if there is a problem or misplacement of base metal, you can undo the beads, take the pieces apart easily and reposition the items. And then they could then be tack welded for a second time.
Why and When Tack Weld Is Used?
Tack weld is perfect to use when positioning individual parts in order and to keep them in place, especially if you are doing precise work or working on small projects.
One reason why the weld tack is used is that it will keep the joint intact. Also, it will boost the mechanical strength of the pieces for just a short span of time for more operations.
Lastly, with tack weld, you will be able to take apart and reposition the pieces if there is a problem.
TACK WELDING SIZE AND SPACING
The purpose of tack welding is mainly to hold the metal pieces in place while the rest of the weld is completed, therefore your tack sizes should not exceed that of the final weld. The size will change according to the size of the weld and the metal thickness.
If you have enough space available, then you should try to avoid making multiple tacks in heat affected area of the previous weld. This spacing between the welds usually revolves around 25-30mm or one inch. This distance can change obviously.
In summary, your tack welds have to be large enough to hold the metal pieces in place while you work on the final weld but small enough to be conspicuous in the final weld.
The spacing should not be more than 20 metal thicknesses apart and the tack weld should not exceed one inch in size.
How to Tack Weld with MIG?
- Always begin with a tack weld to prevent metal separation or displacement from the original spot when you start the welding process. Lay the welding gun’s edge down on the workpiece with the nozzle resting on the upper part of the metal.
- Next, point the gun where you want to place the weld then pull the gun’s trigger. This starts the wire feed and activates the flow of gas.
- For tack welds, you need to hold the trigger for about two seconds, in fact, it’s enough for molten puddles to form and join two pieces together. Make sure that the tack weld is 2-inch to 3-inch apart, no more, if needed they can be closer to each other.
Once the tack welds are completed, you can lay the bead.
What is Spot Welding?
Spot welding is actually a resistance welding process which is primarily utilized for welding two or more sheets (metal) by applying heat and pressure to the weld area.
This process works by contacting copper alloy electrodes to the metal sheet surfaces where electric current and pressure are applied while heat is being made through the way of current over resistive materials, thus melting the metal and bonding it together.
Spot welding, however, isn’t ideal for small sections of base materials. The ideal material for this process is low carbon steel, because unlike other materials, it’s more resistant to electricity. What’s more, it comes with a lower thermal conductivity compared to the copper electrode utilized in creating the needed electrical current.
Additionally, high carbon steels, as well as aluminum alloys, may form fragile welds that do not last long with spot welding method.
Why and When Spot Weld Is Used?
Typically, spot weld is utilized when welding certain kinds of wire mesh, sheet metal, or welded wire mesh. Further, it is used to weld sheet metal and construct a car.
However, spot weld has also applications in different industries like electronics, construction, medical building, aerospace, and metal furniture.
One reason why spot weld is used is that it is an easy and quick process. In fact, you don’t have to use filler materials or fluxes to make a joint.
How to SpotWeld with MIG?
- Start by marking out flat spacing where you want to make spot welds on the material. Then you can drill or us a round chisel to create a hole in the upper layer of the metal.
- With the holes drilled or punched, clamp the panel back together and then take vice pliers and tightly clamp it.
- Lastly, place the gun on the metal and start to weld. Make sure to turn the voltage/heat up on the MIG welder because the thickness of the material is doubled. Also, make sure to fill the hole perfectly.
Tack Weld vs Spot Weld
Spot welding and tack welding are two of the most common welding processes that can be used in attaching metals. While both processes can accomplish this task, they still are used for different purposes.
If you’re having a hard time deciding, keep in mind that the easiest way to remember the difference between a spot tack weld is that the tack weld is an initial step for positioning and securing items for welding, while the spot weld is the permanent and final join, mostly used for sheet metal.
And since it is permanent, with spot weld you cannot remove the pieces with ease whereas in tack weld you can.
When it comes to the symbols, actually, there is no official tack weld symbol, but the spot weld symbol is just a circle that could be placed below, above, or centered on the reference line.
As you can see there is a huge difference between tack weld and spot weld. Hopefully, this content helped you decide which process you should use and when.
If you have any questions, feel free to comment below!