Abrasives for Woodworking
Abrasives: Which One Should I Use?
Thankfully, most woodworkers don't need to do extensive testing to determine the best abrasive for their use. Keeping just a few basic facts in mind
makes choosing an abrasive product relatively easy for most woodworkers.
Abrasive Materials
Of primary importance is selection of the abrasive grain. Four different materials are commonly used: Garnet, Aluminum Oxide, Silicon Carbide, and Alumina-Zirconia.
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Garnet
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Golden orange colored sandpaper that has been a
woodworking favorite for years. It is a natural mineral that cuts fast, but
wears out rather quickly. It is a good choice when sanding woods that tend
to "load" up the paper before the grit has lost its bite. It has been
largely replaced by Aluminum Oxide. |
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Aluminum Oxide |
Familiar brown or reddish brown sandpaper that has become
the standard for production woodworking. It is a synthetic abrasive which is
very hard and tough, providing good abrasive life for both metal and
woodworking applications. |
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Silicon Carbide |
Shiny black man-made abrasive most often used for
"wet-or-dry" sanding products. Its grains are very hard and sharp, but lack
the toughness of Aluminum Oxide. It is long-lasting because the abrasive
grains fracture as they wear, exposing sharp new edges. It is most often
used as a finish sanding paper. |
|
Alumina-Zirconia |
Blue colored abrasive. It is also man-made, and is
extremely hard, sharp, and tough. It is used chiefly in abrasive planing operations, where its superior life offsets the higher cost. |
Obviously, the abrasives are almost useless unless they are bonded to something, and that is where the backing comes in.
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Paper Backings |
Generally provide a finer finish than cloth backings, although they are less
durable. Paper flexibility is governed by its weight. Lightweight papers are
more flexible. Finishing paper is designated as "A" or "B" weight while cabinet
or general-purpose papers are designated as "C" or "D" weight. Heavy-weight "E"
and "F" papers are used for sanding belts. |
|
Cloth Backings |
More durable than paper, and find primary use for belts or disks. Lightweight
belts are designated as "J" weight, and are suited to contour sanding. The most
common backing is "X" weight; it is available on virtually all product types.
Heavy-duty applications, such as abrasive planing, require the strength of "Y" weight backings. |
One other factor enters into abrasive selection: Open or Closed coat bond.
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"Open" |
Refers to the fact that the abrasive grains are spaced farther apart to allow
for the buildup of wood dust which, if heavy enough, can clog the paper. It is
the most common abrasive style. |
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"Closed" |
Have almost complete abrasive coverage, so that each abrasive grain abuts the
next. This leaves very little room for sanding particles. "Closed" coat bonding
is provides a very uniform scratch pattern, and is used primarily for fine grit
products. |
Reference: Klingspor Coated Abrasives Reference Manual