Sandpaper Tech

Selecting the correct sandpaper grit for the job not only makes the work go easier, it produces a better finished product. Sandpaper has a literally a million uses, but we're concentrating here on automotive use, specifically body and parts finishing.


First and foremost, use quality, name-brand sandpapers. The best type for finish work is the wet/dry variety. It's used with water as lubricate between the paper and metal surface. The most popular grits for bodywork are 60, 80, 400 and 600. For final sanding prior to buffing fresh paint, 1200 or 1500-grit is made. To cut body filler, 60 or 100-grit on a sanding board is normally used. This coarse paper has excellent cutting capabilities. For sanding primer, the 400 to 600-grit works best; the surface isn't terribly hard. After painting, "color sanding" is usually performed with 1200 or 1500-grit, which is very fine and doesn't leave sanding scratches. We'll show you the various papers in use on appropriate auto parts to give you an idea how to use them.

Body Panel
This body panel is in progress—body filler and primer have already been applied. To smooth the surface, we are using 60-grit paper on a sanding board. When using a coarse paper like this, water is normally not used. It can be done by hand or using a power sander to cut the surface. Several coats of primer are usually applied, then each is sanded smooth after drying. The last few coats will be cut with 400-grit on the same board. The 400 will leave minute scratches, which the new finish coat can adhere to and will fill. When you see sanding scratches in polished paint, it means that the body shop didn't take the time to remove them with 400-grit paper.

Shield
This flywheel cover needs a treatment with 400-grit to cut an uneven paint surface caused by a heavy paint application. We will use 400-grit wet/dry paper to smooth the unevenness. Normally on a part with contours like this, using your hand as the sanding block with plenty of water will accomplish the job. This is a good, all-purpose grit that can be used on the body and most parts prior to finish color being applied. Most hardware or auto-paint supply stores carry the full gamut of papers and can recommend a particular grit for your project.

Color Sanding
After the final color coats of paint are applied, "color sanding" takes place. This hand-sanding smoothes any orange-peel from the surface and any foreign matter that might have settled on the paint during the drying. It also provides a good surface for polishing out the color. A very fine paper is required here, usually between 1000 and 1500-grit, depending on the type of paint used. Again, plenty of water for lubrication and constantly changing paper will allow ease of cutting the surface and a smooth, straight body panel. The best way to buy the paper is in individual sheets; bulk packs usually have several grits that you won't use. Select the sheets according to your project and you'll always have the true grit you need.