Freeman's
Guide To Abrasives
Part 1 of 2: Abrasives Overview
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directly to Part 2: Freeman's Line of Abrasives
Abrasives
are most commonly used to precisely remove small amounts of
material to achieve a specific dimension, smooth or polish
a surface, or roughen materials for gluing applications.
When
selecting the proper abrasive for an application, the
following criteria need to be considered…
#1 - Type of abrasive required:
This
decision is made by knowing what type of material you will
be working with.
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| Garnet
- A reddish brown mineral. It is of medium hardness with
good cutting edges and has the tendency to break or fracture
when used, thus creating new cutting edges. Used primarily
for fine finishing of wood. |
Aluminum
Oxide - A synthetic brown-colored mineral that
is tough and durable and is the most widely used abrasive
grain. It is ideal for both woodworking and metalworking.
(Non-Ferrous) |
Silicon
Carbide - A very hard and shiny black-colored
mineral. This product has a brittle quality that allows
it to fracture into sharp sliver-like wedges as it works.
Can be used for everything from sanding non-ferrous and
ferrous metals, plastics, composites, and wood products. |
#2
- Type of backing required:
This decision is made by the type of abrasive and grit you
have selected or the type of process you will be performing
with the abrasive.
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| Paper -
Used mainly for wood finishing in weights from A, C,
D, E and F. “A” is the lightest weight. |
Cloth -
Produces a flexible backing in a wide range of weights.
The more popular “J” and “X” weights
are standard stock items. The “J” weight is
the lightest and most flexible whereas the “X”
weight is a heavier backing providing the widest range
of use. |
#3
- Type of glue required:
This
decision is made by the type of abrasive you have selected
or the type of process you will be performing.
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Glue - A straight animal hide glue that
is used to adhere the abrasive particles to the backing.
Referred to as “Glue Bond”.
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Resin - A synthetic resin that is used
to adhere the abrasive particles to the backing. This
type of bond is resistant to heat and moisture and is
referred to as “Resin Bond”.
#4
- Coarseness of the abrasive mineral:
Commonly
referred to as “grit”, this number designation
is determined by the amount of abrasive mineral that
can pass through a mesh screen with specific size openings.
Therefore, a 40 grit abrasive particle will pass through
a mesh screen that has 40 openings in one linear inch.
Consequently,
the higher the “grit” number results in a finer
abrasive and will produce a smoother surface finish. The
lower the “grit” number results in a coarser
abrasive that will remove material much faster.
#5
- Amount of abrasive applied:
This
decision is made by knowing the type of material you will
be working with.
- Open
Coat – Here, the abrasive granules cover
from 50% - 70% of the backing and are set at pre-determined
spacing to reduce loading. Used on softer surface materials
that tends to load or fill the abrasive surface.
-
Closed Coat – Here,
the abrasive granules cover virtually the entire backing
surface. Used where loading of abrasives is less of a
problem.
#6
- Form and shape of the abrasive:
This
decision is made by determining how the abrasive will be
used by the individual. Abrasives are sold in forms such
as sheets, large/small discs, belts, and large/small rolls.
Selecting the right form is determined by whether the abrasive
will be used for hand sanding, applied to a large disc sander,
attached to a small hand grinder, or installed on a large
belt sanding machine.
Sanding
of concave shapes probably requires round or cylindrical
shaped abrasives. Flat or convex shapes probably require
flat abrasives.
Continue
to Part 2 of 2: Freeman's Line of Abrasives
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