Doing body work can be challenging, frustrating, and time consuming if not properly prepared. There is almost not right or wrong way in achieving the proper shape to a panel after it's been damaged, body work is an art form that normally takes years to master, but with some helpful tips in this article you'll be on your way to getting that damaged body panel as flat as possible and saving yourself from the enormous bill that a body shop would charge you.
Things you will need: Stripper, palm sander, stud welder or screw slide hammer, body hammer (in case you pull the dent out too much), air compressor , 40, 80, 120 grit sand paper, sanding block or inline pneumatic sander, body filler and spreaders, and a catalyzed primer with primer gun.
**Before you begin doing any body work you are going to need to get down to the metal, this can be done in a number of ways, by using a stripper (such as a Dewalt), a DA (dual action sander), or a palm sander, or aircraft stripper if necessary; when stripping off paint to get down to the metal make sure you wear a dusty mask, you do not want to breath in body dust.
**Using a stud (or shank) welder is the contemporary proper way to pull out dents, but there are some things that you should know before you use one of these welding tools. First of all you should remove any interior parts that can be behind the panel in question such as interior panels and sound deadening material because stud welders are known to start fires, also place wet towels near the interior of the car where the panel in question is to have a stud welded into it. A hot cherry can fall into the interior of the car and a fire may be a result. Always use proper eye protection also. Begin welding your shanks in the very middle part of the panel where the dent is the deepest and space them about a ¾ to an inch apart depending on the length of the dent. After using your stud pulling slide hammer you may not get the desired results as far as pulling the dent out, so you might have to repeat the process again to get the desired results.
**Some people still use a drill and a slide hammer with a screw to pull out dents, although this method is still effective it can leave you with some nasty holes to fill. Make sure that you use a new good quality screw when pulling out the dent. Some screws are not the same quality as other and the screw in question should be very course threaded, this will give it the optimal opportunity of pulling out the dent. You should use a drill bit that is the same diameter as the body of the screw not the threads, drilling to big of a hole will be useless if you can't pull out the dent. Similar to a stud welder you will most likely have to drill multiple holes in the panel to get the desired effect and space them out just as you would a stud welder.
**Keep in mind also that some damaged panels are just beyond fixing and may need to be replaced, unless you're working on the roof of a car or the rear quarter panels you will most likely be in luck for easy removal and replacement of the said part with basic hand tools and of course all major collision damage should be done by a professional.
**After getting down to bare metal you should have probably used 80 or 40 grit to do this, the next thing you will want to do is feather the layers of paint approximately six inches in diameter from where the damage is, you will do this with 120 grit sanding discs on your palm sander; the desired result should look like something similar to the rings a tree has on a piece of fire wood that's cut in half.
**Now you'll need body filler, don't get Bondo brand (it dries to hard and too fast and it is never used by real body men), instead buy something like Evercoat EZ sand filler. This is a process is going to have to go fast because once you mix the blue catalyst in the filler you wont have much time before you have to put it on the metal. The biggest mistake people do is taking their sweet time to mix up the filler and spread it on. This leaves them with a clumpy, chunky, and half dried wipe of body filler on the panel. As a rule the body filler that you pour on your mixing board (card board) should only require squirting in one line of catalyst that is the length of the diameter of the puddle of filler. Mix it up like the world is ending and quickly wipe it on the panel. Make sure you mix up enough and put enough filler on the panel or you will have to repeat the process, which is somewhat typical; keep in mind it's better to have more filler than less and that filler shrinks as it dries.
**Wait two or three minutes while the filler begins to setup, when it does and you can feel the heat of the filler when you touch it, it's time to pick up your inline sander with 40 grit air file paper and get to sanding. You want to sand as much as you can before the body filler completely sets up, if your tearing off chunks of filler that expose the metal then you need to wait a little longer.
**Your hand is your eye when it comes to body work, after sanding the filler on the panel in question (which you should have done in all directions including: up and down, side to side, and diagonally) you will need to feel it with your hand. If it doesn't feel flat, it isn't; so you'll need to repeat the process again.
**When laying on your second coat of filler you should upgrade your paper to 80 grit which is finer and won't create such big sanding grooves; hopefully you didn't have to put on near as much filler as the first time, so sanding the second coat back down shouldn't take entirely too long. If you feel you need a third light coat of filler buy a product at your local auto body supply shop called Icing, it is a very thin viscosity filler used for the final layer of body work and is also used to fill pin holes.
**Now that you have the body filler work completed it's time to smooth the whole panel out with your palm sander using 120 grit paper, remove all of the deep grooves and make sure the pad of your palm sander sits flat against the surface of the panel; if not you will make small valleys and ripples by holding it at an angle.
**Now that you've completed the sanding process it's time to prime, make sure you have a good face mask handy (not a dust mask), mix up the primer per the directions; you may want to reduce it slightly more if it does not come out of the gun well (the primer that you should be using should be primer, a catalyst or hardener, and a reducer; if you're using any primer other than this and you get your car wet before it's painted it will most likely leach into the metal and cause it to rust. You must use high quality primer, not lacquer primer). Make sure to mask off the parts of the car that you do not want to get primer on (contractors plastic is good), also the gun that you are using should be a siphon feed cup gun specifically for primer; most gravity HVLP guns do not have a tip big enough for primer.
**Make sure to put on three full coats of primer, unwrap the paper and plastic from the car; your done.