Lesson 6 – Auto Welding – Part 1. Below are the videos included in this lesson. Click on the video to watch.
MIG Basics
Set-Up
Replace Bedside
Plug Weld
Butt Weld
How To Use Drill
Seam Buster
Repair Flanges
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MIG Basics
This video tutorial discusses the different parts of a MIG Welder. Starting with the gun,it consists of: gun, nozzle, contact tip, gun liner and welding wire. -
Set-Up
Students demonstrate how to replace a shielding gas cylinder and wire on a MIG Welding Machine -
Replace Bedside
This is a weld-on panel, which involves cutting or drilling out spot welds and welding the new part on. Below is a brief list of the steps we took for this procedure. -
Plug Weld
Students recorded for http://ABRN.com Our collision repair technology program partnered with ABRN to provide ABRN HOW2 Tip. This is a digital edition highlighting collision repair training tips. This ABRN How2 is how to performa plug weld using a MIG welder. -
Butt Weld
This DIY video demonstrates how to perform a butt weld on thinner metal, such as welding car panels in auto body repairs. Students demonstrate how to perform a butt weld, which is a student led demonstration. -
How To Use Drill
In this video we are demonstrating how to use a drill and drill bits to remove spot welds in this 1966 Mustang. We are removing a quarter panel and drilling all of the spot welds to remove it. There are other methods for removing spot welds, but this is an easy method to use and most people have a drill and drill bits. -
Seam Buster
This video demonstrates how to use a seam buster to remove weld on panels. In this video we were using it to remove quarter panel on a 1966 Mustang. -
Repair Flanges
This video demonstrates how to clean and repair flanges before installing a new panel
Introduction
In this lesson, we’ll explore key welding methods—spot welding, plug welding, butt welding, and lap welding—discussing their applications and the tools required. You’ll also learn about the importance of heat management and practice to achieve strong, reliable welds.
Lesson Objectives
These objectives will help learners grasp fundamental welding concepts and techniques essential for success in auto body repair.
Most of the welds from the factory consist of spot welds, where a machine compresses the pieces of metal together. Then a high-voltage spot welds the two pieces together. In this process, there is no additional filler metal used to complete the weld process, which does not add any extra weight to the vehicle, unlike nuts and bolts.
We do have spot welding machines that can reproduce a spot weld similar to the factory spot weld. However, some places are difficult to reach and may need to be welded with a MIG welder. And these machines are expensive, and not all shops have one. The majority of this lesson will focus on using a MIG welder to replace factory spot welds and other welds needed in collision repair.
Welding In the Auto Body Shops
Collision repair shops have machines that will produce spot welds as well. Still, many of the areas that need to be repaired are hard to get to, which may require an alternative welding method. The welding method used in this situation is called a plug weld. This is done by punching an 8 mm hole in the top piece of metal, similar to a hole in notebook paper, and placing it on top of the piece of metal to be welded. Once clamped in place, weld the hole with a MIG welder while getting good penetration into the bottom piece. Sound easy enough? Well, it is easy to learn, but hours need to be spent perfecting these welds before making actual welds on a car. Just like in baseball, you don’t stop throwing and catching as soon as you learn how. No, you keep on practicing to become better and better. Well, if you don’t practice catching, you may miss the ball. However, suppose you don’t have the welding down. In that case, your welds may not hold up in an accident, which could lead to unnecessary injuries. Note: Check the vehicle recommendation to determine the hole size recommended for plug welds. Some suggestions may require different sizes, but the most common is 8 mm – 5/16″.
There are three types of welds used in auto body repair: plug welds, which are used to join two pieces of metal together; butt welds, which may or may not have a backing plate, and are used when sectioning parts together; and lap welds, which is when one piece of metal laps over the other piece of metal. Each type of weld has its own specific use in auto body repair.
A butt weld is used when sectioning parts together. This is achieved by butting the two pieces of metal together so that they are flush and level. This will allow you to grind the weld when completed, so the weld can be filled and smoothed out without the repair being visible. This is when you would use the fiberglass filler over the welded area.
Quarter Panel Example
Let’s look at a situation where a butt weld would be used. We’re going to section a quarter panel. You want to find a small area, such as the dog leg or sail panel. Mark and cut the damaged quarter panel, and remove all spot welds and adhesive. Clean and dress the inner quarter to prepare it for the new quarter panel. Drill a hole in the new panel where you are going to plug-weld it. Next, cut the new quarter panel about 1 inch past the section area cut on the vehicle. This will give you a little extra to make your final cut. Pre-fit the new panel and clamp it in place. Now you can scribe a mark where the new panel meets the old panel with a scratch awl. Take the new quarter back off and make the final cuts where you scribed the marks. The new quarter panel should be a perfect fit and butt up to the section splice areas. At this point, the panel can be welded in place using a plug weld and a butt weld to join the splice area.
There are more detailed steps to replacing a quarter panel. Still, I just wanted to give you a quick idea of how welding can be applied to an actual auto repair.
Lap Weld
A lap weld is when one piece of metal laps over the other piece of metal. You may need to do this type of weld when replacing structural parts that recommend this weld type. These welds are generally in areas that do not require an invisible repair. Therefore, the fiberglass and body filler are not necessary. However, you may need to apply seam sealer to seal the area and prevent moisture and corrosion properly.
Heat Management
One thing that differs in automotive welding is the heat concerns. You must monitor your heat to prevent warping a panel or compromising its structural integrity. Especially when welding high-strength steel. Therefore, to avoid these problems, you should not weld continuous welds. Skip welds, stitch welds, and triggering techniques must be practiced to prevent overheating the weld locations.
Skip welding is welding a 1/2 inch and moving to another area to make the next weld. This allows each weld area to cool. Continue these small welds until all welds meet, creating a solid weld. This does not make a pretty weld like you would see on thicker metal, but the weld is going to be ground off. It’s necessary to make sure you have proper penetration to both pieces of metal being welded.
The most important thing to do is to practice. Welding takes much practice. Get your welder out and some scrap metal about the thickness of body sheet metal. Then practice, practice, practice. This consistent practice will prepare you for any welding task, boosting your confidence in your skills.
There is one last thing that I would like to mention. When you are welding a panel or patch onto a car, you may not be able to re-enter the enclosed area that you are welding. You cannot use a regular primer to protect the metal, as it would burn off due to the heat of welding. However, you can purchase a product called weld-thru primer that can be used. Spray inside the area that you will be welding. The heat will not destroy the zinc-rich primer, and the metal will be protected, promoting corrosion protection.
Safety
Safety is something you always need to consider when working on cars. Still, welding has a few additional things to be aware of. It’s crucial to adhere to safety measures to ensure your security and protection while working with welding equipment.
Heat
Of course, welding produces heat, but every welder has burned themselves at one point or another. Therefore, clothing should be worn to protect oneself from the hot molten metal.
Personal Protective Equipment
PPE should be worn at all times when welding to protect you from being burned. This includes a welding helmet with a proper shade, welding gloves, a flame-resistant jacket, and closed-toe shoes. Besides accidentally grabbing a hot piece of metal you just welded, there are other ways you can be burned.
Any time you are welding, you will have sparks and molten metal splatter falling. If a piece of molten metal falls on you, it will burn through a regular shirt like you didn’t even have a shirt on. Leather is the best way to protect yourself from being burned. Leather gloves, leather jacket, leather boots, etc., will eliminate an unnecessary burn.
Ultraviolet Rays
UV rays are another thing to consider and a reason to keep your skin protected. Oxy/Acetylene does not produce UV rays, but other types of welding, such as MIG, TIP, or arc welding do. Just like the sun, a welder can give you a massive sunburn, too.
Eye Protection
Eye protection should always be worn when working on cars, but the UV rays from the welder can damage your eyes. If you have ever had welders burn you, you know how bad this can hurt. It may not hurt your eyes immediately, but I have woken up at midnight before with some of the worst pain from welder’s burn. Not only can the light from the welder cause eye irritation, but it can also result in medical issues.
A welding helmet with the proper shade lens should be worn when welding or when watching someone else weld. Dark shaded sun glasses will not work. You need a lens that will filter out the UV rays. Welding thin metals, such as car bodies, produces lower UV rays than arc or TIG welding, but the lowest lens you want to use for any welding is shade 9. When welding thicker metals, you will use more voltage, which will require a darker lens.
Lungs
You will also want to wear an approved respirator when welding to protect your lungs. Many of the metals used on cars have coatings that produce harmful fumes. Galvanized coatings are one of the coatings that produce harmful fumes when welding or cutting. Always wear the respirator to keep yourself safe.
Hair
You may not have thought of protecting your head, but if slag drops on your hair, it’s going to hurt. That is why you see welders wearing welder’s caps. This is a cap that will not catch on fire easily and allows the helmet to fit on top of the cap easily. There are many more safety concerns that I am not going to cover, but remember to keep your skin, eyes, lungs, and head protected and safe by using the proper PPE.
Oxy/Acetylene Welding
We use oxy/acetylene for brazing in the collision repair industry. Still, it is not used for cutting much in the automotive industry, as it can create too much heat and can warp or ruin today’s metals. MIG welding has replaced oxy/acetylene for welding purposes.
There are still certain weld types that recommend brazing for the sealing properties brass provides. Still, MIG welders are also being used with brass, which is called MIG brazing.
Even though oxy/acetylene is not used much in the automotive industry, there may be times you need to do a rough cut, heat a bolt, or perform a little brazing. Therefore, I’m going to touch on the subject.
Bottle Pressure
Regardless of what type of bottle—oxygen, acetylene, argon, etc.—there are going to be two gauges to read the pressure. One gauge will tell you how much pressure is in the bottle. Of course, you cannot use the equipment with that much pressure, so you will have to regulate the pressure. The second gauge tells you the regulated pressure. You can think of it like an air compressor. The tank may have 150 psi, but you must reduce the pressure to 40 psi using a regulator to operate a tool properly.
Oxygen
First of all, we’ll talk about an oxygen cylinder. It is a high-pressure bottle (up to 2200 psi), and oxygen is one of the elements needed to make fire. The three elements to make a fire are a fuel source, an ignition, and oxygen. So the oxygen is highly flammable. The more oxygen that you add to a fire, the hotter it will get. A lot of care needs to be taken when handling the oxygen bottle because it is highly concentrated and highly flammable. Dirty, oily rags or wrenches that you may be using to change the cylinder bottle may cause an explosion. Therefore, you need to make sure that the equipment used is clean and free of oil. Also, note that you never want to use any lubricant or similar substances. This can be dangerous and may result in an explosion.
Acetylene
The other bottle, which is commonly used as a fuel source, is the acetylene bottle. It is a low-pressure bottle. It only has up to 250 pounds, but care must be taken when handling this bottle as well.
Secure Bottle
When storing bottles that are not in use, always have the lid screwed on to protect the valve and secure the bottles to prevent them from being knocked over.
What Oxy/Acetylene May Be Used for in a Body Shop
Oxy/acetylene may be used for brazing. You may do some rough cuts and things like that, but plasma torches have replaced the cutting, and oxygen/acetylene is being phased out with new repair methods. As I mentioned, there are some recommendations for areas on a vehicle that need to be sealed well, like sail panels. Recommendations are to braze the joint, since brass provides superior sealing properties over other types of welds. This helps keep moisture out and helps fight corrosion with its superior sealing properties. Brass is also more flexible, and there are other benefits to brass.
Brass Is Not a Fusion Weld
Brass is not a fusion process like when something is welded with oxygen/acetylene or MIG welding. Fusion means that the two pieces are melted together, forming a single piece. When brazing, it is like gluing or soldering something together, as it does not melt the metals together. One benefit of brass is that it requires lower heat to melt. The amount of heat used is always something to consider because too much heat in the automotive industry can ruin the metals, such as high-strength steel.
Benefits of Brass
The benefit of brass is the sealing properties it provides to prevent corrosion and the lower heat required to join the metals.
MIG WELDING
MIG welding may be referred to as GMAW, which stands for gas metal arc welding. MIG stands for metal inert gas, but may also be known as wire feed welding. A MIG welder is used to replace many of the factory spot welds with a plug weld.
Work Clamp
First of all, we’ll talk about a few things that you need to know when welding on a vehicle. You always want to keep the work clamp close to where you are welding on the car. For example, you certainly wouldn’t want to have the work clamp on the back bumper and be welding on the front section! Try to keep the work clamp just as close to you as possible. Another thing you want to do when welding on a car is to disconnect the battery. Whenever you are welding on the vehicle, you are making a circuit, and you don’t want to have your battery connected, as this could damage electrical components on the car. Disconnect the battery by disconnecting the negative cable. Then isolate the negative battery cable by wrapping it with a rag or plastic to prevent it from accidentally grounding itself to the car.
Quiz
1. **Open-Ended Question**: Why is it important to choose the appropriate welding technique (plug, butt, or lap weld) for different areas of auto body repairs? Discuss how this choice affects the overall quality and safety of the repair.
2. **Scenario-Based Question**: Imagine you are tasked with repairing a car with significant damage to the rear quarter panel. Given your knowledge of different welding techniques, how would you approach this repair? Outline the steps you would take and the rationale behind your choices.
3. **Comparative Question**: Compare and contrast the advantages and disadvantages of using MIG welding versus spot welding in auto body repair. In what situations would one method be favored over the other?
4. **Critical Thinking Question**: What potential risks could arise from improper heat management during welding? Provide specific examples of how these risks could impact the safety and longevity of an auto repair.
5. **Reflective Question**: Consider the practice requirements highlighted in the lesson. How can developing proficiency in welding techniques impact your career in the auto body repair industry? Reflect on both short-term and long-term benefits.
Lesson Summary
This lesson focuses on the various welding techniques used in auto body repair, primarily spot welding, plug welding, butt welding, and lap welding. 1. **Spot Welding**: Most factory welds are spot welds, created by compressing metal pieces together and applying high-voltage electricity without additional filler metal, which avoids adding extra weight.
2. **MIG Welding**: Due to accessibility issues in some repair areas, MIG welding is often used to replace factory spot welds. A plug weld is created by punching a hole in the top metal piece, clamping it, and welding through the hole for proper penetration.
3. **Weld Types**: – **Plug Welds**: Join two metal pieces together by creating a hole in the top piece. –
**Butt Welds**: Used for sectioning parts together by butting the pieces flush, allowing for grinding and a smooth finish. –
**Lap Welds**: Involve overlapping metal pieces, typically in structural repairs that don’t require invisible seams.
4. **Quarter Panel Example**: The lesson includes a practical example of using a butt weld to replace a quarter panel, outlining the steps from cutting and preparing the damaged area to clamping and finally welding the new panel.
5. **Heat Management**: Managing heat is crucial to avoid warping and compromising structural integrity, especially with high-strength steel. Techniques like skip welding and stitch welding help control heat build-up by alternating weld locations.
6. **Practice**: Emphasizing that proficiency in welding requires extensive practice to ensure strong, durable welds that can withstand the rigors of automotive use. Overall, mastering these welding techniques is essential for effective and safe auto body repair.