Sandpaper, An Indispensable Shop Tool

Whether it's in woodworking or in metal refinishing such as auto body repair, one tool has been indispensable to the workings of these shops, yet is taken for granted. We're talking about the lowly sandpaper. From penetrating the substrate, evening out chipped material from a scratch to leveling old surfaces or paints, the sandpaper is indispensable. And in the finishing stage of a paint job, sandpaper is also a very important tool in providing a proper surface for new paint to adhere.

Most sandpapers have paper backing on them, although there are some variations with cloth backing. Newer types of sandpaper for automotive use have plastic backing, and this new type seems to be highly suited for use in waterborne paints. This is because waterborne paint technology allows for thinner coats. Being thinner, it's critical that the sanding material does not cut through the thin coat. A plastic film-backed sanding sheet is so much flatter, compared to traditional sandpaper backing materials. The effect of this is that the peaks and valleys on the sanding surface are minimized, which allows for more consistent cutting.

Natural minerals like emery, garnet and flint are used in fingernails, wood and soft metals, but these are too soft and degrade easily for automotive refinishing use. This is especially true when a painter needs to refinish a car that uses coatings like urethane paint. What's needed is an abrasive that's harder, sharper and more durable. It turns out that the materials suitable for these types of sandpaper are all man-made, and these are silicone carbide, ceramic and aluminum oxide. Ceramic-based abrasives are the most expensive, but are the longest lasting, so a good shop manager will take these factors into account when choosing which abrasive to buy. Labor costs are one of the highest cost items in auto body repair, so if the cheap paper discs wear out more quickly, the time spent replacing the sandpaper (and possibly fitting it to a sander or other tool) may add up to a significant amount of time that would have been more productive, if a much longer-lasting abrasive had been used.

When using sandpaper in an automotive refinishing environment, wetting the sandpaper is highly advised because it is what sweeps away the abraded surface and grit material. In a dry environment, this grit, technically called swarf, clogs the sandpaper prematurely, thus forcing the worker to change sandpaper more often. As with most things, you get what you pay for when buying sandpaper. Lightweight paper, softer minerals and cheaper glues do cost less, but the tradeoff in more time, labor and materials being used can actually be more costly for an auto body repair shop.