Grinding tools are handy things to keep in your workshop, whether or not you intend
to do any metal work. If you do intend to work with metal materials, they are essential.
There are three main types of grinders, bench, angle, and die. They all can do more
or less the same thing, but are designed for different situations. Bench grinders
are designed to sit in one place and are going to be the most convenient for sharpening
your tools and shaping or finishing small metal pieces. Die grinders are specifically
made for getting into small, tight corners and the inside of pipes or other cylindrical
shapes. Angle grinders are the most versatile and are made to travel. They can be used
in or out of the workshop.
All of these grinders are designed to cut, shape, polish, or hone material. They
are usually used on metal, but you can also use a grinder on stone, tile, concrete,
or plaster.
Types of Grinders and Polishers
Bench Grinder
These grinding machines are stationary tools, meant to sit on a bench or table.
The bench grinder may have one or two grinding wheels, driven by the motor. A tool
rest, located next to the wheel, helps support your tool or other material, allowing
you to touch it lightly to the wheel, sharpening the edge, or grinding it down as
you prefer.
The grinding wheel will usually be made of some abrasive material, but can also be replaced with a buffer or a wire brush, allowing you to accomplish other tasks
as well. Having two wheels is very convenient, since it allows you to switch between
two different grinders without having to change the wheel.
Some grinders come equipped with lights that can illuminate your task. Some come
with cooling systems, which keep the sparks to a minimum, and help extend the life
of the wheels and the machine itself.
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Angle Grinder
Also known as disc grinders, angle grinders are the most versatile of the grinding
tools. They can be used in the workshop or on-site. They can be used to cut, shape,
or polish, depending on the speed and type of disc used.
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An angle grinder is a hand tool with a small motor that
spins a disc parallel to the handle. (A straight grinder is similar to an angle grinder, but with the disc set perpendicular rather than parallel.)
The discs available for angle grinders range from various grades of abrasive grit
for polishing and shaping, to diamond-cut blades that can cut into tile or masonry,
to wire brushes that make cleaning dirty or rusty tools a breeze.
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Die Grinder
The distinction of a die grinder is that it uses tiny drill-shaped bits instead
of discs or wheels. One of the main purposes of a die grinder is to file off the
sharp metal shards that inevitably stick out of a metal pipe after it's cut. But
these tools are handy for any finishing or grinder that needs to be done in a small
spot.
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Sharpener
Sharpeners are bench grinders made specifically for tool sharpening. They may not
have as many features as a bench grinder, but if you are only interested in sharpening
your tools, they can be a cost-effective option. Some of these machines are "wet"
systems, using water to keep the grinding stone from heating up or creating sparks
as it hones the metal edges of your tools.
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Wall Chaser
This machine is used for creating "chases" (narrow slots) in solid walls so that
power cables can be laid into the wall, rather than over it. The most common type
of wall chaser uses two twin discs to cut into the material at once, creating two
perfectly parallel cuts. The depth of the cuts can be set precisely as well, and
the closed carriage allows for dust collection--something difficult with other grinders.
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Polisher
Polishers, as the name implies, are designed specifically for polishing finished
surfaces. They can be fitted with soft buffing or waxing attachments. A power polisher
takes most of the elbow work out of putting that final touch on a metalwork project--or
waxing your car.
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An orbital polisher is especially nice, since it uses random pattern movement to prevent creating swirls in your
wax finish, creating a more lustrous glow.
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Features to Consider
Pneumatic Power
Many grinders are pneumatic tools, meaning that they use air power instead of electricity.
This is a better option for grinding tools, as air tends to cool the tool down,
while electricity creates heat. As the friction of grinding is already heating things
up, any cooling is good.
But the downside is that you need an air compressor to provide the power for any
pneumatic tool. Unless you have one, or plan to purchase one, make sure that you
are getting a grinder that runs on electricity.
Cordless Tools
There are battery-powered grinders. As with all cordless power tools, these trade
convenience for length of use. Grinding takes a lot of power, and you may need to
keep extra batteries on-hand if you plan on using your grinder for long periods
of time.
Variable Speed
Speed is an important factor when you are grinding. Different tasks require different
RPMs (Revolutions Per Minute) to be done most safely and effectively. For large angle
grinders, a "slow start" feature is good, as it can be dangerous for the discs to
go suddenly into the high speeds that the tool can generate.
Safety Tips
In order to effectively cut, polish, or shape metal, grinders
run very fast. Safety is paramount.
-You must use safety goggles and ear muffs. The grinders are going to throw off
tiny, sharp shards of metal. You don't want one of them penetrating your eye. Nor
do you want to imperil your eardrums. These machines are noisy.
-Be sure that you are wearing gloves and other protective clothing, especially
if you are working with a wire brush or wheel. The bristles can easily become dislodged
and fly out, becoming tiny metal spears.
-Wear a face mask when using a grinder. Unlike woodworking tools, most grinders have
no dust collection system.
-Get a grinder that has an emergency shutoff switch or pedal and make sure you know
how to turn the machine off quickly.
-If you are using a bench grinder or sharpener, make sure that it is very securely
fastened down.
-Make sure that the tool rest on a bench grinder is as close to the wheel
as possible. Otherwise, the material you're working on can jam between the wheel
and tool rest, causing kickback. Do not adjust the tool rest while the wheel is
in motion.
-Lastly, not as much a safety tip as a general piece of advice: follow manufacturer specifications, especially the ones about which grinding wheel or pad to use for your materials and purpose. Using the wrong abrasive can damage your work or the grinder. It can be an expensive mistake to make.
Price Range
Bench grinders generally cost from between $70-$150. Expect the higher costing machines
to come with extras like built in lights or cooling systems.
Angle grinders start at around $30 for a basic small (4 1/2") disc capacity. You
can find both pneumatic and electric angle grinders. The most expensive air-powered
angle grinders run around $250. There are more expensive electrical angle grinders,
usually labeled either heavy duty or industrial, which can cost as much
as $1,000.
Die grinders generally cost from about $50-$250, although, like the angle grinders,
industrial versions can cost between $500-$1,000. Most die grinders seem to be pneumatic.
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