8
FEATURE SANDING
Understanding sandpaper All sandpapers are not equal and hardware retailers should know that each piece of sandpaper has its own intended purpose.
S
anding products come in many
are applied – the first is applied to the backing and
shapes and forms – each with its
the second is applied after the abrasive material is
own intended purpose. Make sure
attached, and covers the entire surface.
you know what you are selling.
THE TYPES OF SANDING PRODUCTS INCLUDE: • Coated abrasive rolls
THE GRIT
• Coated abrasive sheets
UNDERSTANDING SANDPAPER
The third layer is the grit, which is the material that
If you dissect a piece of sandpaper, you will
does the actual sanding. It can be natural, such as
• Coated abrasive discs
find it is made up of three layers.
garnet, or man-made, such as aluminium oxide or silicon carbide. Some sandpapers are better suited
THE BACKING
for sanding certain materials. The two grits used
Layer number one is the backing material. The
most often by woodworkers are aluminium oxide
backing for sandpaper can be made from a variety
and garnet, while silicon carbide and ceramic are
of materials, with paper being the most common.
best suited for sanding metals.
Other materials include polyester, cotton and rayon, The abrasive aggregate is selected according to
backings are used for sanding belts and discs.
the hardness of the material being cut. • Aluminium oxide
categories. For paper backing, the weight categories
• Silicone oxide
range from A to F, with A being the lightest and F
• Zirconia.
the heaviest. The weight of cloth-based backings is indicated by the letters J, X, Y, T and M, with J being
Aluminium oxide
the lightest and M being the heaviest.
(light brown in colour) has a high
ABRASIVE MATERIAL
degree of friability. What
Layer number two is the adhesive that binds the
this means is that the
abrasive material to the backing. This adhesive should
sandpaper renews itself
be durable; otherwise the sandpaper won’t last very
when heat and pressure are
long. Nowadays, the first choice in adhesive is resin.
applied. The aluminium oxide
There are a few others, but the two used most often
fragments and creates new sharp
are urea resin for handheld sandpaper and phenolic
edges. This property allows the
resin for power sanding. The reason phenolic resin
sandpaper to last longer than other
is used in power sanding is because it holds up
types of sandpaper. It is especially good
much better against the heat that is generated. It is
for stripping old varnish and paint
strong and water resistant. Two coats of adhesive
when sanding hardwoods.
MAY 2019 DIY & INDUSTRIAL TRADE NEWS
• Vulcanised fibre discs • Narrow and wide abrasive belts • Cylindrical sleeves with holding fixtures • Flap wheel with flange
which are more durable than paper. These cloth-like Backings are classified in different weight
• Coated abrasives for hand held grinding machines with or without holes for dust extraction
• Flap wheels with shafts.
