Using Bondo to Fix a Dent
How To Fix A Dent With Bondo
Repairing dents in a vehicle body with bondois very easy to do. The materials required to do the repair can be purchased at most auto supply stores and would include the following materials.
Bondo, cream hardener, glazing compound, fine grit rubbing compound, sand paper (dry and wet), thinner, primer and paint.
Depending on how you are going to apply the primer and paint will determine what you will need to apply them.
If you use the aerosol can type you wont need any painting equipment other than the number of cans of primer and paint you will need to do the job. However, if you use a spray painter you will need the paint gun, air hose, air compressor and air regulator. For the person who likes to do the job themself, the aerosol type is by far the easiest to use.
You will need to pull the dent out to within about one eighth of an inch below the surrounding area of the body. If the back of the dent is accessible you can use a soft face hammer and a block of wood to hammer the dent out.
If you cannot get to back of dent, drill some small holes in the dented area and put self tapping screws in the holes, leaving enough of the head of the screws extended so that you can use locking pliers to grip the head and pull the dent out as far as you need.
Once you have the dent pulled out you can remove the screws. Sometimes the screws will leave a small rise in the dented area. To fix this problem use the hammer and block of wood again, only when you hammer the area this time put the block of wood on the inside. That is assuming you can get at the back side of the dent.
If you cannot then I recommend using a grinder to grind the burrs down smooth.
When you have the dent pulled out and the screws removed, you will need to sand the area to expose the metal. I recommend using 40, 60, or 80 grit dry sand paper to do this part of the sanding. The sand paper is coarse and will get through the paint and primer that is still in the dent fairly quickly. It will also will help to remove any rust that may have formed.
If there are any small areas that are still lower than one eighth of an inch, you can still cover them with bondo by putting a layer of screen over the entire area. First cut a piece of the screen the size of the area. Apply a thin layer of bondo and place the screen over the bondo before it hardens. Press the screen down and into the bondo so that it ( the screen ) will be held in place, and allow the bondo to harden. After the first layer of bondo with the screen has hardened, you can continue to apply thin layers of bondo until you have the area level with the rest of the vehicle body. Be sure to allow each layer to harden.
Once you have the dented area to the level you need, you can start sanding the bondo to get it smooth. Sand at least one inch around the entire dented area. I recommend wrapping a piece of 40 grit dry sand paper around a block of wood to do the sanding. The block of wood will help to avoid grooves in the bondo. When you finish using the 40 grit sand paper, change to a finer grit. I recommend using either 60 or 80 grit, by doing this, it will help to smooth the bondo better.
If there are any small holes or pits they can be filled in with glazing compound and sanded smooth using a fine grit sand paper. When you have the bondo (and glazing compound if used), as smooth as necessary, wet sand it with 220 wet/dry sand paper to get it a little smoother.
After you have sanded the bondo as smooth as possible you will be ready to apply the primer.
I recommend wiping the entire area with a soft cotton cloth that has been dampened in thinner. This will help to remove any dust left after the sanding.
Since primer can be purchased in different colors, I recommend using a primer that will match the color of the vehicle. If the vehicle is a dark color then use a dark primer, if the vehicle is a light color, use a light color primer. This helps to match the final color of the paint to the rest of the vehicle. I personally use a primer which has a rust sealent in it.
Apply the primer in thin layers allowing each layer to dry before applying the next. If runs form in the primer because to much was applied in one place, the runs can be sanded out using 220 wet/dry sand paper, and then primer the area again. After you have applied enough coats of primer and it has dried, you can wet sand the primer to get it smooth. Use a fine grit wet/dry sand paper to do this. I use 400 to 600 grit fine wet/dry sand paper for this part of the job.
After the area has been sanded smooth again and dry, use a soft cotton cloth dampened with thinner again to wipe the entire area.
The paint can now be applied. As with the primer, apply the paint in thin layers until it is level with the surrounding area. Allow about two weeks for the paint to harden. When the paint has hardened you can buff it with a fine grit rubbing compound and apply wax to the finished area.
