The Many Methods of Auto Body Repair
Cars often end up dented, creased, or partly crushed by impacts of different kinds. When this occurs, auto body repair is used to restore the car’s exterior, as well as its frame and structure. Auto body work is designed to straighten bent frames, remove dents and creases, and return the car to its original condition when possible. Rust is another problem that can cause damage to a car’s body in a much more peaceful and quiet manner. Nonetheless, this, too, requires repair.
Old-Style Auto Body Repair with Plastic Filler
For many years, lots of auto body repairmen contented themselves with filling in dents, no matter how large, with plastic filler. This body filler was then sanded smooth, primer was applied, and the paint job was restored. This method, though quick, easy, and cheap, is a poor idea from the car owner’s perspective, because the filler can eventually scab off. Even worse, rust often develops behind these thick cakes of filler, which serve as a trap for water. This technique should not be used to fix an auto body, though some repairmen still make use of it when their clients don’t know any better.
Hammer and Dolly Dent Repair
Frequently, minor-to-moderate dents can be fixed using a hammer and dolly. A dolly is a shaped piece of metal that is held in the hand and used as a miniature sort of anvil upon which a hammer is used to slowly tap dented metals back into shape. The dolly provides control and may be placed at the point of impact or nearby to limit the effects of hammering. When using a hammer and dolly to repair dented body panels, the secret is to go slowly and move the metal back into place in small increments, since just smashing away at full force with the hammer will reduce the panel to a dented, twisted, ruined mess. There are many types of hammers, including ordinary body hammers, trim hammers for narrow spaces and fine crownwork, shrinking hammers for stretched metals, and so on.
When the back of a dented panel is inaccessible and thus impossible to use a hammer and dolly to restore the car’s original surface, many methods of dent pulling are also available. Some dent pulling is accomplished by drilling a hole in the sheet metal, inserting a screw, and then carefully pulling the metal out using a slide hammer.
This, of course, produces a hole in the car’s metal exterior, which must then be patched and could become a source of future rust. Suction cup dent pullers are an alternative that does not penetrate the exterior of the car, but they are usually too weak to deal with anything other than small dents. Sometimes coins with a wire attached are tack-welded to the surface of the metal (after it is cleaned of paint), and the metal is pulled out using pliers or a slide hammer. There are many options for dent pulling on panels that cannot be easily removed by hammer and dolly restoration.
Patching a Damaged Panel
Sometimes a panel has a hole, as opposed to a dent, either because the panel tore during a collision, something punched through it, or rust ate away part of its surface. If the hole covers 20 percent of the panel area or less, it can probably be patched. Larger holes mean the panel should be replaced entirely. Circular patches are best, because tension is distributed equally to all the welds around the edge. For practice, the patch must often be square, rectangular, or irregularly shaped.
A paper template is prepared to duplicate the shape onto a new piece of metal from which the patch will be cut, and the damaged metal is then cut away with pneumatic nibblers by drilling holes and cutting with a hacksaw or by cutting with an angle grinder. Multiple tack or spot welds are then used to secure the patch, since a continuous weld would heat the thin sheet metal enough to warp it.
Replacing a Damaged Panel
If the panel has been gouged, smashed, holed, or rusted to pieces, it is usually advisable to remove it and insert a new panel. Replacing a damaged panel is a regular auto body repair technique, but it can be quite involved. Different procedures are used for various sections of the auto body, with quarter panels being the easiest to repair (the large front and rear panels forming the side near the wheels), and door panels being quite difficult. A replacement panel should either be bought or cut and bent from appropriately weighted sheet metal. Then, the old panel is cut away with an angle grinder, its last remnants removed, and the new panel fitted, which may involve trimming it down slightly to fit. Finally, the new panel is welded in place, primed, and painted to match the car’s color.
Straightening Bent Frames
Not every collision results in a bent frame, but a reputable repair shop should always check for frame damage. A damaged frame can weaken a car’s structure, making it more dangerous to occupy, should another collision occur. It can also cause steering problems or irregular wear on the car’s tires. The frame’s alignment is usually checked with a tram gauge. This may be a physical gauge or a laser gauge, but it measures the distance between fixed reference points on a car. This technique can easily reveal even subtle warping of a car’s frame.
A huge range of specialized tools and techniques are available today for auto body repair, meaning that practically any ding, dent, or cavity can be fixed. A battered or rusty car can be transformed into a sleek and gleaming automobile again with the right applications. Though it will not be worth as much as a new car, such a vehicle is less likely to succumb to rust than one that is neglected after sustaining damage. In the long run, getting repairs done to a car body is cost-effective and will save you from many headaches later.