metal straightening and body filler info

This is a class project about different types of metals used in vehicle construction, some possible repair methods, and some information on body fillers.

The three most common steels used in vehicle construction are mild, high-strength, and ultra-high-strength steel. Mild steel can be easily formed and is generally easy to work with. High strength steel is more heat sensitive than mild steel and should be straightened cold, and ultra high strength steel is used for intrusion beams and bumper reinforcement, and its strength is destroyed by heat.

Once the metal has been determined then you can focus on the tools and the way it must be repaired. The way you will be able to repair the damage depends on how accessible the damage is.

For example it may be accessible from either both sides, both sides but limited access to the back side, and just one side. When damage is accessible from both sides many repair methods may be used. You also must determine where the direct damage and the indirect damage.

The size of the direct damage will depend on the size of the object that struck the panel. The amount of indirect damage depends on the amount of force used to strike the panel. The most common tools used for dent repair is the hammer and dolly. Before you begin the task make sure that you select the correct hammer and dolly.

Dollies are usually held on the back side of the damage and are used to work the highs down and the lows up. There are two different techniques to consider when working with the hammer and dollies. One way is the hammer on dolly the other is the hammer off dolly method.

Body fillers are applied to minor damages and should not be relied on for proper damage repair. Body filler is applied to bare metal. There are three types of body fillers, fiberglass, polyester, and all metal.   Fiberglass is applied anywhere that has been welded and is used to prevent corrosion in the finished repair. Polyester fillers include conventional, lightweight, premium, and glazing putty.  All metal body fillers are used for corrosion protection and restoration projects.

To prepare for body fillers you need to remove the paint. Some putty’s are epoxy and made to go over a primer.  When applying body filler use the makers recommendations.  The thickness should be a maximum of 3mm. Use firm strokes to ensure the putty goes into the sand scratches. The total body filler build up should be higher than the contour to allow for additional sanding.

Shaping of the body filler includes using a “cheese grater”, orbital sander, air files, hand sanding boards, or contour matching objects. After sanding, if there is bare metal there might need to be additional filler added to the project. If there is a high spot tap it down and apply additional filler.

Body filler problems include pinholes which are caused from trapping air. This may also be caused by improper mixing of the filler and adding too much hardener. To ensure this doesn’t happen, fold the putty, don’t stir it. Cracks caused by adding to much hardener, if this occurs it should be removed and added back on. Another problem can be poor featheredging and sandpaper clogging.

The Steps

1. Access the damage
2. Wash with soap and water or wax and grease remover
3. Determine direction of damage
4. Develop a repair plan
5. (First In Last Out)- reverse damage
6. Straighten metal and remove dents with easiest determined repair method
7. Prepare metal for body filler by grinding or DA depending on metal thickness
8. DO NOT  TOUCH METAL WITH BARE HANDS
9. Apply body filler after mixing hardener into body filler.

10.  DO NOT STIR, WILL CAUSE AIR BUBBLES OR PIN HOLES. Adding too much hardener will result in body filler hardening at an excessive rate do not use a porous mixing board

11.  When spreading body filler smooth your edges to eliminate some of your feather edges

12.  Using a cheese grater to rough up the area and find your high points

13.  Sand down high points with 36 or 80 grit sandpaper before the filler is cured

Use guide coat to find imperfections in metal and then sand with 150