How to Weld a Large Body Seam

Welding automotive sheet metal is delicate work.

Welding a body seam on a car that has been damaged is a process that takes care and deliberation to accomplish successfully. The reason for this is that the heat generated by the welding process can warp the metal panel if you aren't careful. Another consideration that must be taken into account is the placement of insulation in the vehicle's body. If the panel you are welding up has insulation behind it, the insulation may catch fire when you attempt to weld the panels together.

Things You'll Need

• Welding clamps
• Mig welder
• Clean rag
• Bucket
• Water
• Welding helmet
• Fire extinguisher

Instructions

1. Align the panels that are to be welded, and then secure them in place with the welding clamps. The two edges of the panel should match up as closely as possible in order to achieve the best quality weld. When this is complete, check behind the panel to make certain that there are no flammable materials touching the panels, such as insulation. Keep a fire extinguisher within arm's reach, though, just to be safe.

2. Attach the negative clamp from the welder onto a clean patch of metal near the place where you will be welding, and then set the welder to its second-lowest setting. This will help prevent you from burning through the sheet metal while you weld it.

3. Turn on the welder, and then position the welding gun's electrode over the seam that is to be welded. Lower your welding helmet.

4. Produce a spot weld near the top of the seam being welded. When you have done this, move the welding gun 6 inches down the length of the seam and produce another spot weld. Move 6 inches further down, and then produce another spot weld. Continue in this manner until there are a series of spot welds positioned 6 inches from one another along the length of the seam.

5. Position the welding gun next to the first spot weld that you produced, and produce another spot weld just below or above it. The process of producing spot welds every 6 inches will help prevent the panel from getting too hot in one place at a time. In essence, it will spread out the heat to make the panel less likely to warp.

6. Put down the welding gun every five minutes or so and wet a clean rag with water. Apply the rag to the panel to help cool it, and then use a second, dry rag to dry the panel seam off. When you have thoroughly cooled the panel, continue producing staggered spot welds along the length of the seam until the two panels have been completely joined together.

Tips & Warnings

• If you are unfamiliar with welding, you may find it to be more comfortable to wear a long-sleeved shirt and gloves while welding. While the sparks produced won't necessarily harm you, they are quite uncomfortable without protection.

• Always put the welding gun down before reaching for the wet rag. Not doing so could result in an electrical shock. Never attempt to weld without a welding helmet in place. The intense light produced by the welding process could permanently damage your eyesight.

References

• "Auto Body Repair Technology"; James Duffy; 2008
• "The Complete Guide to Auto Body Repair"; Dennis Parks; 2008
• "Welding Manual"; John Haynes; 1995