A plug weld is a type of weld that is used to join two metal plates together. It is a very simple weld to make and can be done with a few basic welding tools.
In this blog post, we will discuss the four easy steps that are involved in making a plug weld. We will also provide some tips on metal preparation and clamping.
So, if you're new to welding and want to learn how to make a plug weld, read on!
Table of Contents
What is a plug weld?
A plug weld is a type of welding that bonds two pieces of metal together by fusing them in a small, round hole. The outer metal will have the hole while the back metal will be solid.
This type of weld is common in metal fabrication and typically used to join thinner pieces of metal together and is often used in automotive and construction applications.
If you're a new welder, don't worry - making a plug weld is quite easy. Here are four easy steps to follow:
Steps to perform plug welds-
1. Clean the metal to be welded.
This is an important step because it ensures that there is no dirt, grease, or other contaminants that could prevent the weld from taking hold.
Use a flap disc on an angle grinder to clean the metal and then wipe it down with a rag. I use acetone for this.
If you're plug welding outdoors, blowing the area with compressed air can also help to remove any gross contaminants.
2. Drill the holes to be welded.
The plug welds will be holding the two pieces of metal together, so you need to drill holes for the plugs.
How big should a plug weld hole be?
The hole for a plug weld hole should be a minimum of 2 times the thickness of the workpiece. It's preferable to have 2.25 times the thickness of the piece. You can use the following weld plug hole size calculator.
Plug Weld Hole Size Calculation-
Example: 1/4" steel would be equivalent to .25"
You would multiply .25 X 2.25 = .5625
.5625 is then converted to a fraction of 9/16"
You would therefore drill your holes for welding with a 9/16" drill bit.
If math ain't your thing, double your wall thickness and it'll be good enough for the average home DIYer's project.
Here is a picture of it cleaned up from the inside.
3. Clamp metals to be welded.
You need to clamp the two pieces of metal together so that they don't move while you're welding.
4. Welding the two metal pieces together.
Now it's time to weld the two pieces of metal together. Start by welding the plug in the first hole and then welding the plug in the second hole.
You want to make sure that you are welding around the entire circumference of each plug so that it's fully fused to the metal. If it's a thicker material, you'll want to fill the holes up to slightly above the original thickness of the metal.
There you have it! You've now successfully completed a plug weld. Practice the plug welding technique a few times and soon you'll be a pro.
What is the difference between a spot weld and a plug weld?
Plug welding is drilling a hole in one piece of metal so that it can be laid over the top of another piece. The welder then fills the hole with filler rod or wire to join the two pieces.
Spot welds are where two pieces of sheet metal are pressed together really tight. After clamping the two, a spot welder is used to join the two metals together by running a current through both metals. This current melts the two metals together without the use of filler material.
When would you use a plug weld?
A plug weld is often used when joining two pieces of metal together that are too thin to be butt welded. It is also a good way to join two pieces of metal together when you don't have access to both sides of the joint.
- Control arms
Welding threaded bungs into tube ends is an excellent example of when I use plug welding. I drill a small hole in the tube and then insert the bung.
You can then weld the plug. Once you've finished the plug welding, you can then come back and weld the joint all around the tube.
- Floor panels
Plug welds can be used when installing thin floor panels when restoring a vehicle. You essentially trim the floor panels to fit.
Clamp the panel in place using magnets. You can also drill small holes through both pieces of sheet metal and use blind hole panel holders for a precise fit-up.
- Frame stretch
A frame stretch is where you cut the frame in half. Add a section of frame in between the cut to lengthen the wheelbase. This is a common Jeep modification.
You'll have but welds along the frame, but a common practice to strengthen the joint will be to weld an insert into the frame. This is where plug welds come in to play. Some builders will then add fish plates on the sides for even more strength.
What are the benefits of plug welding?
Plug welding is a strong way to join two pieces of metal together. It is also quick and easy to do, which makes it a good choice for many welding applications.
That's it! Those are the four easy steps to making a plug weld. Plug welds have a purpose and are some of the easiest welds that you will make.
If you're new to welding, we recommend practicing on some scrap metal before trying this technique on your project pieces.
We also suggest reading our other welding tutorials for stitch welding, safety tips, tools, and more tips. Thanks for reading and good luck with your welding project.