How to Choose Auto Body Sandpaperby Tom Keaton
During a body work project various grades of sandpaper will be used. It is important to choose the correct grit paper depending on the job. The goal is to let the sandpaper do the work for you and yet only leave minimal scratching so you can end up with a very smooth surface for new paint to lay on. Even after paint is sprayed on the car there is still more sanding involved, called wet sanding, where very fine grits are used. Coarse grits of paper have a lower number, such as 60 grit being very coarse, and the higher the number , the finer the grit, such as 2000, which is a very fine grit.
Use 60 to 80 grit paper to sand down below rust, deeper scars or to sand down and begin to shape body filler, such as bondo. These are very coarse grits and should only be used in specific areas where you really need it since it will leave sanding marks.
Use 120 grit , which is still coarse, when rust spots or scratches are not that severe but you still need to cut below damage or use 120 to follow up after 60 or 80 grit was used to flatten out scratches from the heavier grit. This is also a good grit for further shaping and forming of body filler.
Use 220 grit , still in the coarse grit group, to bring down any rough edges from body filler after using the 120 grit. 220 is also great to sand down and begin to feather edge glazing or spot putty that was applied. This grit will also serve to remove surface lighter rust with minimal scratching.
Use 320 grit to complete feathering edge of any compounds and as a block sand before application of any primers. You may also use a 400 grit which is a bit less coarse. Block sanding is when you wrap the paper around a long sanding block and sand the entire area flat. These grits are typical used just before primers.
Use 600 grit after a standard or high build primer has been applied to remove imperfections and runs from the primer using a block sanding technique.
Use 800 grit for sanding the final finish primers just before primer sealers or paint. Again using the block sanding technique.
Use 1000 or 1200 grit over new paint to sand down runs, but sand very lightly using a "wet sand" technique. Wet sanding is when you wet the surface and paper with water and use a sanding block to insure an even sanding. Even though 1000 and 1200 grit is in the fine grit group it will still create scratches in paint and should always be followed up with at least 1500 or even 2000 grit.
Use 1500 grit for wet sanding over new paint to bring the entire surface smooth and level removing any surface imperfections. 1500 grit can be followed up with rubbing compound or you may even use a finer grit such as 2000 before the compound.
Use 2000 grit for a very final wet sanding to create an ultra smooth finish and as a final remover of any small scratches left behind from 1000, 1200 or 1500 grit papers. This is the final sanding before rubbing compound.
Very fine Rubbing Compound, even though not in the sandpaper family, is still used after wet sanding of new paint to bring back the shine that was dulled during wet sanding to create a smooth to the touch finish, flattening out the paint and removing even the smallest imperfections from the finish. Rubbing compounds do contain ultra fine grits which is not labeled as a grit type but as fine and very fine for instance, which is also available in medium and coarse used for other jobs, but not as a final compound for a new paint job since they can easily cut through your paint and ruin the finish.
- When sanding be careful not to sand very hard on edges since paint or primers can be easily cut and removed. You can run painters tape over the edges as an option to be sure to avoid them.
- If you have sanding scratches from a coarse grit you can simply sand with finer grits to remove the scratches.
- Very fine Rubbing Compound, even though not in the sandpaper family, is still used after wet sanding of new paint to bring back the shine that was dulled during wet sanding. Rubbing compounds do contain ultra fine grits which is not labeled as a grit type.
Tom Keaton has been writing professionally since 2007. His background includes experience in mortgage banking, pest control and classic-car restoration. Keaton has also worked as a licensed stock broker.