DIY Network

Basic Repair Techniques Basic Repair Techniques From "Trade School" episode DTRS-101

From runaway shopping-carts to pebble-spewing dump trucks, today’s vehicles are constantly in harm’s way. The good news is that even the most damaged autos can now be returned to showroom condition. Today’s autobody students are learning the skills and equipment that not only fix minor dents and dings, but also restore structurally damaged vehicles to original factory specifications ....

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Here, you’ll read about how automotive collision repair student Jason Ensz put his skills to the test by taking on the personal challenge of restoring the body of his late uncle’s 1975 Jeep CJ-5 (figure A, figure B). The Jeep is structurally sound, but much of the exterior paneling needs to be repaired before he can begin the refinishing process.

Figure A

Figure B

Basic Tools and Materials:

Body Hammers and Dollies
Dual Action Sander
MIG welder
Oxyacetaline Torch
Disc Grinder
Polyester Body Filler
Stud Welder

Jason begins by removing outer accessories such as the side mirrors, hood latches and taillight casings. (figure C, figure D) This not only allows for easier access to potentially damaged areas, but it also gives Jason the option of painting these accessories separately. During his inspection, he discovers areas where rust has completely corroded through the body panel. He also finds several dents and a rare problem where a side panel somehow became stretched. All will need to be repaired before he can begin painting.

*SAFETY ALERT: Proper training is highly recommended before using any welding equipment. Serious injuries could result from misuse. Welding equipment can produce UV and infrared rays that can damage eyes and actually cause severe "sunburns" to exposed areas of skin. Always wear a welding helmet, welding gloves and clothing that covers arms, legs and feet when using any welding device.

Figure C

Figure D

Then he removes rust with a dual action sander with 80-grit paper. He repairs any rust-corroded holes using a MIG welder (figure E, figure F). This process fills the holes with molten metal.

Figure E

Figure F

Figure G

Once the hole is completely sealed, the remaining metal burr is ground off to create an even surface (figure G).

He masks the abrasive surface with an application of polyester body filler (figure H). Once the filler hardens, he sands it flush to the adjacent surface (figure I).

Figure H

Figure I

Figure J

(Polyester body filler is a gel that chemically binds itself to metal. After adding a hardening agent, this gel is spread over scuffed areas. The gel then solidifies, and is vigorously hand-sanded until the filled area is flush with the surrounding contour. Auto body technicians use this filler frequently to bring repaired surface areas back to shape.)

Next, Jason tackles several different types of dents. (For dents that are less than 1/8th inch deep, he simply strips the surrounding paint away and uses body filler.)

*SAFETY ALERT: Safety Glasses are recommended for the following steps.

For a dent that is accessible from the backside, he reshapes it to its original contour using a hammer and dolly technique. Dollies are handheld pieces of hardened steel and come in many shapes and sizes. Body hammers also vary in size and shape. Selection is based on the nature of the dent and the contour of the panel (figure J).

While holding the dolly flush against the exterior side of the dent, he strikes the interior side of the dent with the hammer until the desired contour is achieved. He is careful to allow the dolly to bounce so that the metal panel does not stretch. He finishes these dent repairs with body filler and sanding.

For a dent that cannot be accessed from the backside, Jason uses a stud welder. After scuffing away the surrounding paint, he uses this power tool to quick-weld brass studs directly to the surface metal. In this particular instance, the dent is rather large, so Jason welds several studs spaced at about 1-2 inches apart. Then, with a slide hammer, he pulls each stud until the dent returns to the desired contour. He clips the studs at the base with wire cutters and grinds off the remaining metal with a disc grinder. He also finishes this repair with body filler and sanding.

Then, Jason repairs a panel on the side of the Jeep where the metal has been stretched. This stretching causes the panel to pop in and out, much like the base of an old-fashioned oilcan. Jason scuffs paint from the panel and exposes the sheet metal beneath. Then, with an oxyacetylene torch, he directly heats a quarter-sized area of the metal until it becomes red hot. Then, he lightly taps the center of the red-hot area with a pick-ended hammer and immediately sponges cool water over the spot. This causes the metal to shrink quickly. Jason repeats this process in several nearby areas on the panel until it returns to its original shape.

Now that all the body damage is repaired, Jason can begin the refinishing process. In the next segment, he applies primer, basecoat and clear coat to finish his project.