Utilizing Sandpaper’s Fine Points

Sandpaper probably is one of the most important tools you can have in your workshop. Sandpaper technically is known as a “coated abrasive.” Those numbers printed on the back of sandpaper provide a wealth of information.

Today, four types of abrasives are used: aluminum oxide, silicon carbide, garnet and ceramic grit.

* Aluminum oxide papers are most common and are excellent when used on wood.

* Silicon carbide also is sharp, but doesn’t crack and break like aluminum oxide, making it more appropriate for surfaces such as plastic and metal.

* Garnet is the old, economical standby. Unlike aluminum and silicon, garnet gets dull as it is used. It can be used for a rough sanding first and then, as it wears down, for finer work.

* Finally, there’s ceramic abrasive. It isn’t as sharp as the others and generally is used for machine papers, such as those used in disk, belt and drum sanders.

As to the numbering code on the back of the sheet: The lower the number the more coarse the grit and the more surface will be removed with each pass.

Sanding is a multi-step process. We recommend at least four grits for most jobs. First, we like to do a coarse sanding using 30-to 50-grit paper to remove deep gouges and imperfections.

Next, 60-to 80-grit paper removes the deep scratches from the first sanding, followed by 120-to 150-grit and finally by 220-grit. For oiled or varnished finishes, 220-grit paper is necessary.

Sandpaper can be used for metal polishing as well. The protective coating (usually clear lacquer) must be completely removed before sanding. Use paint remover. Then sandpaper is used to remove the oxidized surface layer, including any pitting. The last sanding step should be with 400-to 600-grit paper. Then apply polish.

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