What Grit Sandpaper to Use when Painting a Car

Body work and car prep before paint can be very labor intensive, hard on the hands and back; especially if you're not familiar with what grits of sand paper you should be using when doing body work or sanding the car. In this article I am going to describe the correct sand paper grits to use when doing these tasks which will save you much time and effort. We will be going over 36, 80, 120, 240, 320, 400, 600, 1500, and 2000 grit sanding applications, so you can choose the one that's right for you.

36 Grit- 36 grit sandpaper is only used when doing heavy body work with filler, this is the kind of grit that you would use on a Dewalt stripper ( 8 inch sticky back paper) to grind through paint down to metal or multiple layers of paint to metal. 36 grit scratches in metal or fiberglass on a cars body are what is necessary for body filler to properly adhere. 36 grit is also use for rough shaping after the filler has been applied while it is still soft; thios is a good idea to do if you're going to be doing multiple layers of filler work. Be warned though, while cutting down curing filler with 36 grit you will get the job done faster, but you will also go through paper pretty fast. They also have 36 grit in sticky back air file (in-line sander) format-this makes getting straight panels much easier than blocking by hand.

80 Grit-this grit should be used on your last wipe of body filler; you don't want heavy deep scratches in the cured filler like you will have with 36 grit. 80 grit is ultimately the best grit to use for final blocking to get a panel as straight as possible before going onto the next step.

120 Grit-you should always finish out your body filler work with 120 grit and it is also optimal for using products such as Icing (low viscosity filler, used for pinholes and slight surface straightness imperfections left behind from heavy filler work); you want to make sure you go over the body filler work with 120 grit very well, removing all of the 80 grit scratches. 120 grit should also be used initially after stripping the paint away down to metal with 36 grit to feather edge the surrounding layers of paint that are not in the damaged area; this will create a smooth transitional area for filler work and primer work to be bridged together yielding a smooth panel. 120 grit is also great for removing oxidized clear coat to get down to the base coat or sealer before priming work is done.

240 Grit-some people finish a car out with 240 grit before they begin to seal and paint; however I find that it will yield a paint job with orange peel and imperfections after the paint solvents evaporate a few days to a couple of weeks later. 240 grit is really best used when you're sanding through heavy primer with the intentions of re-priming the area (such as in the case where there has been heavy filler work).

320 Grit-minimum grit before sealing and painting a car, this is known as a finishing grit.

400 Grit-this is perhaps the most widely used finishing grit by autobody shops pre-sealing and paint; it provides a smooth surface, yet is rough enough for great paint adhesion.

600 Grit-this is most typically used when attempting the ultimate paintjob with a very skilled painter in a climate controlled booth. 600 grit is is used with water and the surfaces of the car are wet sanded smooth. This is the highest grit you can go pre-sealing and paint; any grit higher than this will create to smooth of a surface and there will be paint adhesion problems and most likely peeling will result.

1500 Grit-this grit is used in your first step of cutting and buffing a base coat/ clear or solid color single stage paint jobs. This grit is not really used to cut the top layer of paint for flatness, rather it is used to remove trash, debris and top surface imperfections such as: flies that land in the last coat, hair, dust, possible moister that found its way onto the surface of the paint when painting is completed. In the case of heavy orange peel 1500 grit can be used to remove most of it pending there are at least three full coats of paint on the vehicle.

2000 Grit-this grit is used to ultimately make a painted panel as smooth and as flat as possible after painting; a soft sanding block should always be used and one should stay clear of edges so as to not burn through (there is less paint material naturally on edges). This is your final step before buffing with an extra cut compound. Following an extra cut compound should be as follows: regular cut, swirl remover, polish, wax.