The grinding wheel is a cutting
tool. It's an abrasive cutting tool.
In a grinding wheel, the abrasive
performs the same function as the
teeth in a saw. But unlike a saw,
which has teeth only on its edge,
the grinding wheel has abrasive
grains distributed throughout the
wheel. Thousands of these hard,
tough grains move against the
workpiece to cut away tiny chips of
material.
Abrasive suppliers offer a wide
array of products for a wide array
of grinding applications in
metalworking. Choosing the wrong
product can cost the shop time and
money. This article presents some of
the fundamentals of selecting the
best grinding wheel for the job.
Abrasives—Grits and Grains
Grinding wheels and other bonded
abrasives have two major
components-the abrasive grains that
do the actual cutting and the bond
that holds the grains together and
supports them while they cut. The
percentages of grain and bond and
their spacing in the wheel determine
the wheel's structure.
The particular abrasive used in a
wheel is chosen based on the way it
will interact with the work
material. The ideal abrasive has the
ability to stay sharp with minimal
point dulling. When dulling begins,
the abrasive fractures, creating new
cutting points.
Each abrasive type is unique with
distinct properties for hardness,
strength, fracture toughness and
resistance to impact.
Aluminum oxide is the most common
abrasive used in grinding wheels. It
is usually the abrasive chosen for
grinding carbon steel, alloy steel,
high speed steel, annealed malleable
iron, wrought iron, and bronzes and
similar metals. There are many
different types of aluminum oxide
abrasives, each specially made and
blended for particular types of
grinding jobs. Each abrasive type
carries its own designation-usually
a combination of a letter and a
number. These designations vary by
manufacturer.
Grinding wheels are generally
labeled with a maximum safe
operating speed for various
equipments. Don't exceed this speed
limit. The safest course is not even
to mount a given wheel on any
grinder fast enough to exceed this
limit.
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