Welding Auto Body Tips

This page offers collision repair welding tips and training.

In this photo, a patch repair panel is being welded on a bedside.

Learning How to Weld In Auto Body Repair

A vehicle consists of many parts that are attached in a variety of ways.  One of the methods used is welding.  Therefore, a technician must master welding to become a professional collision repair technician.

Most Common Welds from Factory

Most of the welds from the factory consist of spot-welds, where a machine compresses the pieces of metal together and 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 additional weight to the vehicle, as nuts and bolts would.


Welding In the Auto Body Shops


This photo is an example of plug welds

Collision repair shops have machines that will produce spot welds as well, but 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, much like a hole in a piece of notebook paper, and placing it on top of the piece of metal to be welded.  Once clamped in place, simply 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 just miss the ball.  However, if you don’t have the welding down, your welds may not hold up in an accident, which could lead to unnecessary injuries.


Some shops may have a resistance spot welding machine as shown in this photo. This welding machine reproduces spot welds similar to the spot welds at the manufacture. It squeezes the two pieces of metal together, sends voltage to the electrodes, which fuse the two pieces of metal together.

 Types of Welds Used in Auto Body

There are basically three types of welds used in auto body repair.  Plug welds as we’ve already mentioned, and we also have butt welds, which may or may not have a backing plate, and lap welds.

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.

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 normally in areas that do not require an invisible repair.  Therefore, the fiberglass and body filler are not required.  However, you may need to apply seam sealer to properly seal the area to prevent moisture and corrosion.


Coming Soon – I am in the process of writing a guide for auto body welding.  Collision Blast Basic Auto Body and Paint Training Vol. – Automotive Welding: A Guide for Welding 

This guide will be available soon at Amazon.  For other auto body  and paint guides visit: www.CollisionBlast.com/AmazonBooks

The guide will describe in detail how to properly weld on thin metals found on cars.  This guide will also include video tutorials demonstrating how to perform many of the welds.  Check back soon, as this guide is almost completed.


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