ALT-1 How to Choose the right Auto Body Sandpaper
For the right sandpaper to use on auto body we will first need to identify the surface it is to be used on. The type of sandpaper you will need depends on the extent of the job in sanding. In this regard, we will categorize the job to be done and what type and grit of sandpaper is to be used. For any sanding job on auto body, wet type of sandpaper is best recommended. Water with some detergent, on occasion, subdues sanding dust and helps prevent in inhaling them even with a mask. Second, wet type sandpapers cool the sandpaper and surface. Third, it helps ‘clean’ or unclog the sandpaper thus prolonging its use.
Metal surfaces that need to be sanded and remove traces of rust, it is recommended to use the rough 120 grit sandpaper. This is really rough and would leave scratches on the metal surface for the Bondo to properly adhere to. For scrape-to-metal entire body jobs, initial sanding of bondo filled areas will require the dry type 120 grit or lower to do the job quicker and to prevent rust to build up or propagate. Rust has tentacles or roots where it could start from dry-sanding will stunt rusting.
When Bondo has been applied the same 120 grit sandpaper will be need to form the Bondo according to the desired shape. The desired shape should be at least a couple of millimeters from the true shape. At this point, the next sandpaper to use is either the 240 to 360 grit sandpaper, classified as Microgrit, to smoothen the “scratches” left by the 120 grit. Having done this, the bondo should have ‘feathered’ with the metal surface. This means there is no significant ridge felt by the tips of your fingers between the metal and bondo.
The area being repaired will need to be prepared for primer. Assuming that all is perfect, used 360 grit sandpaper will do the work of smoothing the primer. The area with bondo will have some minute porosity that will need to be covered with putty. Again, sanding the putty can be done with 400 grit sandpaper. A surface primer will have to be sprayed again after this. The area should now be ready to get its first coat of color. The color coat, once dry, should be light sanded with 600 to 800 grit sandpaper, just enough to level or even out small imperfections.
The second coat up to the final color coat, usually up to the sixth coat, should be lightly sanded with used 800 grit sandpaper. Sanding in between coats is just to remove particles or insects that might have accidentally landed while spraying. After the last color coat, it will be followed by a clear coat with a slight mix of the color. From here on, use 1000 grit or higher sandpaper. There will be two more clear coats after that and sanding them with used 1000 grit or finer sandpaper will leave a glossy finish.
After the last clear coat has been sanded, it advised to use rubbing compound on the finish. This is actually a sanding process but not as paper but cream that is coarser than toothpaste. Care and even rubbing should be observed to get a glass-like finish. All the sanding process above, except for the rubbing compound, water should always flow consistently on the area being sanded. To save on water, use a large sponge that slowly dispenses water in the process. Following the procedure should yield excellent results on the car’s paint finish.
In the above process, determine from what point you have to work on to determine the right grit of sand paper to use. Minor scratches might just require rubbing compound while cracked or chipped off paint might require 120 grit sandpaper for proper adhesion. Now, you know what grit of sandpaper to use on what type of surface you have work on.
