Resto Series Number 1: Bodywork Basics Page 2

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Was it Hit Straight on, or From an Angle?

    If a victim was mysteriously shot by a gun, one of the elements of solving the crime would be to determine the angle of trajectory. The same holds true when the victim is a smashed car. The bodyman can only start the repair properly if he knows from what direction the car was hit. “Now how the heck would I know this?” you ask. “I didn’t see the accident!” Let me explain how to use a bit of “impression forensics” to help you read or “reverse-engineer,” the damage. Damage assessment is usually a simple matter of applying some common-sense and logic.

    If the dent is somewhat symmetrical without a scrape mark on the painted surface, all indications point to an impact from a straight perpendicular hit. If, on the other hand, the paint is scraped and the dent is non-symmetrical or pushed up on one side, the dent was obviously caused by an indirect hit, and by looking at the direction of the paint scratches as well as the shape of the dent, you can assume that the impact came from one side or the other. To be more specific, if a panel is hit from a direction other than straight on, the affected metal will be left with somewhat of a wave-like impression. The metal was pushed ahead of the impact area. If the dent is new, you can also look at the scraped paint and see which way it hit because the paint will curl up on the end of the direction of the impact.


Within a few days the body is looking as it did when we first built the car.
Notice the car is raised up to a comfortable working height using a
Bend Pak scissor lift. This way we can lift or lower the car for working
on different parts without having to sit on cold concrete.

    When I first got into body repair, my unadulterated curiosity for anything related to fixing a dent had me going to the local wrecking yard to study a variety of totaled-out cars just to see if I could figure out how the accident occurred. The reason that this is so important (figuring it out, not going to wrecking yards!) is that it will help you figure out the direction that the panel must be worked as well as where to look for hidden damage. For example, if a car suffered a rear-end hit and the gap between the door and front fender is closed up, that tells you there’s much more damage than a smashed rear. Did you know that if a car is hit hard from behind, you could tell if the driver had the brakes on at the time of impact even if the car was towed from the scene of the accident (where you could have just looked for skid marks)? The clue can be found in the taillight bulbs.

    The bulb filaments get soft and weak when the light is on and a sudden impact is oftentimes enough to break the filament. So by seeing which bulb is out, a sharp repairman can tell if the brakes or headlights were on. This doesn’t necessarily relate to body repair, but it proves that looking closely at certain parts of a car can tell you what it’s been through.

    If you look closely, a hit on a panel will very likely cause a series of deep ridges in the metal that radiate out from the point of impact. The ridge, or crease, that is furthest away from the main point of impact is where to begin the basic body repair. A smooth undamaged sheet of metal tends to be flexible to a degree. However, once an indentation is made into that sheet, the panel becomes more rigid. A dented fender or door panel exhibits the same characteristics. Therefore, once you begin to work the creases out, the damaged panel will gradually become easier to work with. These radiant creases are actually holding the dent in. As long as you remember to work the damage from the outermost point towards the center of the impact, the metal will be much easier to hammer and dolly back into its original form.

    The objective as you begin to hammer and dolly the metal is, at first, to relieve the stress of the creases and indentations. The initial body working is strictly rough-shaping until the metal is free of any sharp indentations. The goal is to work the panel back into shape without stretching the metal unnecessarily. Hammering directly at the center of the dent will cause the most stretching and make it almost impossible to return the metal back to original form. In most cases, there will be a small degree of stretch to contend with, but we’ll get into that later.

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    The process of body repair and painting consists of individual steps that take you progressively closer to a finished job. The number of steps and the actual techniques involved will, of course, vary from car to car. When you begin your repair, you’ll have to make the final call regarding which steps are needed and which are not. The following is a general outline of basic dent repair steps to use as a guide.
 

  •  Damage Assessment: Feel the panel. Note the exact shape of the dent, check for high spots, low spots, and any collateral damage. Until you become totally familiar with this step, you can identify specific points of the damage using masking tape and a marker. Tag the center point of the dent, the direction (if any) that the panel was hit, and the outer perimeter of the damage where you plan to start working the metal.
  • Access the Damaged Panel: Remove inner panel, trim pieces, molding wherever they might interfere with your work. Save all parts and hardware for reassembly when the job is complete.
  •  Tool Check: Look into your tool box to make sure you have all the tools required for the job.
  •  Rough It In: Roughing a panel back into shape can involve anything from simple hammer-and-dolly work to attaching studs or drilling holes for slide pullers, to locating clamp points for making pulls with a hydraulic post puller or “dozer.” Extensive damage requiring anything more falls into the heavy collision repair category. 
  • Fine-tune the Metal Work: More hammer-and-dolly work to bring down the high spots and bring up the lows. This step requires a lot of finesse with the hammer to avoid overworking the metal. Gentle hits are all that’s needed. Hold the handle of the hammer at the midpoint or up high on the handle near the head to increase control.
  • Prep for Filling: Prepping for body filler requires paint removal using a course-grit paper (36-grit) to expose bare metal. A high-speed sander/grinder can be used but the best paint removal tool is an orbital sander such as the Hutchins Model 2001 or a dual-action (DA) sander like Hutchins’ Model 3560. Filler should not be applied to anything other than clean, shiny bare metal.
  • Featheredge: A good bodyman always feathers all paint edges before applying filler. The hard paint edge left from grinding must be tapered to a smooth, layered edge. This can best be accomplished with 120- or 150-grit sandpaper by hand or with the dual-action sander. A hard paint edge can get overlooked during the filler and primer applications and will show through after the paint cures.
  • Applying Body Filler: The panel is ready for filling and molding as long as no high spots remain. A good- quality plastic filler such as Evercoat’s Rage Extreme will fill minor low spots, grind marks and any other imperfections in the metal. Do not overlap filler onto the featheredged paint.
  • Work the Filler: The process of smoothing the plastic filler begins with rough-shaping using a “cheesegrater” file. After grating, a sanding block mounted with 36-grit paper is used to level the filler. For large panel areas, a pneumatic air file such as the Hutchins Hustler Model 2000, 2011 or 2023 can be big time-savers. Follow up with block-sanding with 80-grit paper and the once-damaged area is ready for the first application of primer. 
  • Paint Prep or Perfection: At this point, the job can be handed off to the painter to begin the process of preparation for paint. Some body repairmen strive for perfection by taking the block-sanding stage one step further with 180-grit paper. This is a good thing!

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Roughing It In

    Most body damage will require some type of pushing or pulling device that can exert a force close to what was exerted when the damage occurred. This equipment can range from a basic slide hammer to large hydraulic equipment. In the middle-range of such body tools is a portable power jack, otherwise known as a Porto-Power. This tool can perform many of tasks, but its primary talent is undoing the main force that caused the damage. It must be applied in the opposite direction of the damaging impact. Porto-Powers have become very affordable over the last few years. I remember the first set that I bought cost so much I had to make payments on it! Now you can get a fairly good-quality unit for a little over $100. Many of them come with a set of extensions and ends made to access those hard-to-reach areas. For a bit more money, you can get a “push-pull” system that will allow you to pull with the same tool.


We often take a car off the frame for high-end paint jobs. This 1966 LeMans
was the foundation for a conversion into a 1967 xXx GTO. We set the
body on a large dolly with casters so it could be moved around to different
parts of our shop.

    Grinding the paint down to bare metal without heating it up is an art in and of itself. Grinding is a method of using a coated abrasive disk on a high-speed sander/grinder to tear the paint away from the metal. The disks utilize very small irregular abrasive particles glued to a disk in a gouging scraping motion called grinding. This method is fast, very effective and removes the paint in short order. However, the evil by-product of such friction is heat, and too much heat will cause the metal to expand and distort. This distortion is mostly temporary but partially permanent; the metal expands to a point when heated and contracts most of the way when it returns to normal temperature. Notice that I said “most of the way.” The problem is, once heated and cooled, metal will still remain a little bit larger than it started out. That’s why when a car catches fire, all the panels buckle out of shape.

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Reshaping the Metal

    As you work the dent, you will find the areas that need work getting smaller and smaller.

    The tool selection must coincide with the progress of the work. No more heavy hammers or dollies are going to be needed if you did the job correctly. Depending on the quality of the roughing job you did, you could be down to very light well-placed taps instead of hard generally placed hits, so a set of finishing hammers with polished heads as well as a slapping spoon would be handy as well.


Once the under side of the body was painted and the frame restoration
complete, we re-mounted the body back on the frame and got the car running.
It’s best to do all your heavy mechanical work before painting, or you’ll
 risk ruining your new paint job.

    Once you notice the high and low spots begin to level out, you can either start filling the lows spots with a good-quality filler, or continue working the metal until little or no filler is required.

    How do you get a feel for a low spot and what do you do about high spots? Well, this is where the “art” of bodywork comes in and “the feel” in effect becomes your guide, whereas the spraying on of a guide coat will give you a visual indicator of high and low spots by showing you where the sander went through the filler (showing the high spots) and where the sander did not touch the black guide coat (showing you the low spots).

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    You should learn to get the feel for high and low without having to look at the area — that is unless you are the one in a million that can see the high and low spots without feeling them. This is very possible with a surface that is painted and glossy or even wet, but as soon as the surface is sanded or multicolored it will be all but impossible to see the high and low spots.

    My shop manager, Brian Hatano, has a method of showing his helpers how he can feel the high and low spots. He will have them guide coat an area and then rub his hand across the surface and tell them where the high and low spots will appear without looking. Then he has them block sand the area and, sure enough, the metal shows where he said it will be high and the black paint stays where he said it will be low.

    This leads me to an idea that you might try…I can’t help it, it’s the inventor in me! When you are block sanding an area, try marking what you think will be a low spot with a spray can of black guide coat and do not spray the areas that you think will be high spots. After sanding, see what the results are. If the paint remains untouched, then you have the feel. If not, keep practicing because a custom fabricator or bodyman without the feel is like a blind guide on a mountain climb. You have to be able to feel the metal to know what to do next or you will be working in the dark. You can train your hand just as you do with many things. This just takes a bit of dedication and time. Practicing can save you a lot of aggravation down the road.

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When Is It Time For Primer?

    This is really a loaded question; the work is ready for a coat of primer when it is straight and smooth and no sooner. Many bodymen are too anxious to prime a job and will sometimes bury a dent, either intentionally or unintentionally, with a heavy coat of primer thinking it will fill in the imperfections and that all will be good when the paint goes on. A good painter will catch this potential for problems, but if he doesn’t, these “buried mistakes” will definitely come back to haunt both bodyman and painter as the thick primer shrinks.

    There are no shortcuts and you should not rush to apply primer to the body unless it is absolutely ready to prime. When mixing and applying primer, always read and follow the manufacturer’s recommendations for reduction, spraying tips and drying times. You can also choose a good-quality aerosol primer such as those offered by Evercoat. We use Evercoat products on a regular basis in my shop with excellent results. If the area to prime is large, you’ll most likely be better off using a spray gun. I’ll go more into gun selection later in the paint chapters, but for now, let me just say that a good-quality gun designed for primer application is recommended. I tend to favor the Devilbiss line of guns, however, there are other manufacturers such as Sata and Sharpe that will do the job with professional results. Remember, primer is not liquid filler! It is an undercoat that promotes adhesion and provides a uniform base to paint over.

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    Primers and primer-surfacers are designed to fill very small surface irregularities and also to help protect any exposed bare metal from oxidizing when it is in contact with the oxygen in the air. Another function is to provide a substrate (paintable surface) with one uniform color to facilitate topcoat coverage. Most undercoats are available in black, light gray, dark gray, red, and white, and some can be tinted to match the color of the topcoat. Selecting an undercoat color that is close in shade to the topcoat is recommended for ease of coverage and accuracy of color match.

    An important function of a primer undercoat is to provide maximum adhesion to the bare metal and properly sanded painted surfaces; the build quality allows enough thickness for block sanding. If you look into the various companies that manufacture automotive undercoatings, you’ll find a mind-boggling array of special formulations that offer specific features such as high build, easy sanding, clog-free, corrosion resistance, flexibility and more. Unless you know what you want and need, you could easily be overwhelmed. I’m sure there are some people who miss the days of all-purpose acrylic lacquer primer that worked well for just about every job. In spite of all of the special undercoatings on the market, I still try to keep things as simple as possible in my shop by using one manufacturer — Evercoat — for all fillers and undercoats. Every paint manufacturer recommends that you stick with their system of chemicals from the primer on up. This is, of course, the surest and safest way to avoid any compatibility issues when it comes time to apply paint. For those who aren’t familiar with the compatibility of different primers and paints, I highly recommend that you use the paint manufacturer’s recommended undercoat until you become more experienced.


Many times we use portable lifts to bring the car up to a better working
height. This is one of the 1967 GTOs that we built for xXx. Under the
shiny paint we found a ton of poorly prepared bodywork we needed to re-do.
Even though it was only a movie car, we often over-do the body to make
sure that body filler does not pop out during a stunt.

    Another type of primer that we use is called etching primer (also called acid-etch primer).

    As its name implies, etching primer chemically bonds, or etches, into the bare metal with the added ingredient of phosphoric acid. This special primer is used where corrosion problems exist, or when working with metals such as aluminum. Etching primer is not compatible with some sealers, primers and topcoats, so be sure to investigate compatible products before using it. Epoxy primers, or two-part catalyzed primers, cure through a chemical reaction, as opposed to solvent evaporation, when exposed to air. A catalyzed primer forms a good barrier coat between chemically unstable substrates and the topcoat. Other benefits include less shrinkage and excellent rust-inhibiting qualities.

    Electrostatic primers are what most of the factories use. The application process involves dipping the car body into a large tank of liquid primer while an electrostatic charge is sent through the body of the car, which alters the chemical properties of the liquid. The body is then cured in large ovens at about 350 degrees F until it is fully cured. This process delivers primer to every square inch of the metal’s surface and requires no sanding. There is no better method of covering the base metal of the car for extended protection but, unfortunately, it is almost impossible to perform this process without dipping the car in a large tank. This is why the best substrate to apply paint over is a properly sanded factory paint job.


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    Zinc chromate primers are basically used for aluminum or in any application where dissimilar metals are used together and have the potential of creating electrolysis. This type of primer acts as an insulator that prevents the metal from carrying a charge from one alloy to the next. Zinc chromate is used in many aircraft and marine applications and on exotic aluminum-bodied cars.

    An anti-chip primer is the soft coating that is applied on many cars along the rocker panel area and in the wheel wells. It normally cannot be applied over bare metal. Its sole purpose is to absorb the impact of road debris that might otherwise chip the paint. It is normally applied with a rough surface texture.

    Surfacers are simply the primers that are applied over the base primer and are also intended as fillers when applied in very thick high-build coats. Surfacers are formulated to provide excellent bonding with primer.


The best way to remove the old body filler on this car was with an air hammer and Ajax chisel, We did this by getting the blade under the filler and on top of the sheet metal and forcing it off the car with the air hammer.

There are a number of ways to lift a low spot in a metal fender or panel such as this. We use this method if the underside of the panel is inaccessible and time is short. This process involves drilling a few holes and using them to pull a dent out.
 
Using a Morgan Nokker or slide hammer, simply put the “screw end” into one of the holes. Slide the weight back to the stop and kinetic energy will do the rest. Take a few light pulls, instead of one large one, or you will be tapping that area back down again.
 
Another good way to bring a low spot out and an adjacent high spot in, is to leave the slide hammer in place and while pulling out on it, tap the adjacent high spot down. This is somewhat like the hammer-off-dolly technique.
 
These are pull rods which are little more than bent rods that have been hardened to retain the shape. You can insert them into pre-drilled holes and pull up while tapping down on the closest high spot, just as we showed with the slide hammer.

  Remember that even though it may not seem like you are making progress, each and every blow of the hammer is moving metal, so be patient and work thoughtfully, not quickly.
 
This area is now within 1/8 inch of perfect and ready for the next step. If it were a show car we would metal finish it to perfection but that last 1/8 inch takes longer than the whole roughing process. The closer you try to get to perfect, the longer it takes. You may find that unless you are working on a classic or a show car, this may be “good enough” for you.

 These studs can be grabbed by a special slide hammer that comes with the spot welder kit, and is used for pulling on the studs until the surface is flush. Then the studs can simply be twisted off. They are not reusable, we have tried, but they are cheap, so buy extras.
 
Another method, instead of drilling a lot of holes, is to use a hand-held stud welder and weld little copper posts to the surface of the metal in the low areas.
 
 
A Vixen file is a special file that is designed for cutting lead and steel and can be used to cut the sharp edges of the fender down with ease. Eastwood sells these as well, in both flat and round styles.
 
Many people apply too much filler, which not only will waste your filler, it takes more time to sand down. Try to get in the habit of just putting on as much as you need.

Here, Brian uses a piece of plywood for his “mixing board” and cleans it after each use, keeping it in perfect condition.
 
A large DA sander is then used to sand the surface down; or you can pre-cut it, using a sure-form rasp, or cheese grater. This will show you the high spots that are in the fender.

High spots can be picked down carefully with light hammering. Another thin coating of filler will be required.
 
The sure-form makes quick work of the excess filler on this fender, but you will need to rasp it at just the right time. If you wait too long the filler will be too hard and will have to be sanded. If you rasp it too soon, you will probably need a new rasp.

One of the handiest tools we have is this portable Bend Pak lift. We simply slide it under a car, and with 110 volts (standard plug) lift the car to a workable height. No more back problems from bending over while sanding rockers!
 
Once filed down and sanded, the fender is ready for a coat of primer. Primer is sprayed onto the panel to fill small imperfections.

Even though we seem to have every air tool known to man in our shop, we still use the long boards for finishing the surface of a custom car.
 
The fender is primed and Brian moves to the next panel and starts over with the air file. As he finishes one panel, he moves to the next one. His finishing bodywork will include wet sanding with finer grits of paper, followed by more priming and prepping the car for paint.
 
There is no tool that replaces the human feel for shaping a compound curve on a car.

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