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An angle grinder, also known as a side grinder or disc grinder, is a handheld
power tool A power tool is a tool that is actuated by an additional power source and mechanism other than the solely manual labor used with hand tools. The most common types of power tools use electric motors. Internal combustion engines and compressed ...
used for
grinding (abrasive cutting) Grinding is a type of abrasive machining process which uses a grinding wheel as cutting tool. A wide variety of machines are used for grinding, best classified as portable or stationary: * Portable power tools such as angle grinders, die grind ...
and
polishing Polishing is the process of creating a smooth and shiny surface by rubbing it or by applying a chemical treatment, leaving a clean surface with a significant specular reflection (still limited by the index of refraction of the material according ...
. Although developed originally as tools for rigid abrasive discs, the availability of an interchangeable power source has encouraged their use with a wide variety of cutters and attachments. Angle grinders can be powered by an
electric motor An electric motor is an electrical machine that converts electrical energy into mechanical energy. Most electric motors operate through the interaction between the motor's magnetic field and electric current in a wire winding to generate force ...
or
compressed air Compressed air is air kept under a pressure that is greater than atmospheric pressure. Compressed air is an important medium for transfer of energy in industrial processes, and is used for power tools such as air hammers, drills, wrenches, and ...
. The motor drives a geared head at a right-angle on which is mounted an
abrasive An abrasive is a material, often a mineral, that is used to shape or finish a workpiece through rubbing which leads to part of the workpiece being worn away by friction. While finishing a material often means polishing it to gain a smooth, reflec ...
disc or a thinner cut-off disc, either of which can be replaced when worn. Angle grinders typically have an adjustable guard and a side-handle for two-handed operation. Certain angle grinders, depending on their speed range, can be used as sanders, employing a sanding disc with a backing pad or disc. The backing system is typically made of hard plastic, phenolic resin, or medium-hard rubber depending on the amount of flexibility desired. Angle grinders are standard equipment in metal fabrication shops and on
construction Construction is a general term meaning the art and science to form objects, systems, or organizations,"Construction" def. 1.a. 1.b. and 1.c. ''Oxford English Dictionary'' Second Edition on CD-ROM (v. 4.0) Oxford University Press 2009 and co ...
sites. They are also common in
machine shop A machine shop or engineering workshop (UK) is a room, building, or company where machining, a form of subtractive manufacturing, is done. In a machine shop, machinists use machine tools and cutting tools to make parts, usually of metal or pl ...
s, along with
die grinder Die grinders and rotary tools are handheld power tools used for grinding, sanding, honing, polishing, or machining material (typically metal, but also plastic or wood). All such tools are conceptually similar, with no bright dividing line betwe ...
s and bench grinders.


Uses

Angle grinders may be used for removing excess material from a piece. There are many different kinds of discs that are used for various materials and tasks, such as cut-off discs (
diamond blade A diamond blade is a saw blade which has diamonds fixed on its edge for cutting hard or abrasive materials. There are many types of diamond blade, and they have many uses, including cutting stone, concrete, asphalt, bricks, coal balls, glass, a ...
), abrasive grinding discs, grinding stones, sanding discs, wire brush wheels and polishing pads. The angle grinder has large bearings to counter side forces generated during cutting, unlike a power
drill A drill is a tool used for making round holes or driving fasteners. It is fitted with a bit, either a drill or driverchuck. Hand-operated types are dramatically decreasing in popularity and cordless battery-powered ones proliferating due to ...
, where the force is axial. Angle grinders are widely used in
metalworking Metalworking is the process of shaping and reshaping metals to create useful objects, parts, assemblies, and large scale structures. As a term it covers a wide and diverse range of processes, skills, and tools for producing objects on every scale ...
and
construction Construction is a general term meaning the art and science to form objects, systems, or organizations,"Construction" def. 1.a. 1.b. and 1.c. ''Oxford English Dictionary'' Second Edition on CD-ROM (v. 4.0) Oxford University Press 2009 and co ...
,emergency rescues and even for bicycle thefts. Generally, they are found in workshops, service garages and auto body repair shops. There are a large variety of angle grinders to choose from when trying to find the right one for the job. The most important factors in choosing the right grinder are the disc size and the power of the motor. Other factors include power source ( pneumatic or electric),
rpm Revolutions per minute (abbreviated rpm, RPM, rev/min, r/min, or with the notation min−1) is a unit of rotational speed or rotational frequency for rotating machines. Standards ISO 80000-3:2019 defines a unit of rotation as the dimensi ...
, and arbor size. Generally disc size and power increase together. Disc size is usually measured in inches or millimetres. Common disc sizes for angle grinders in the United States include 4, 4.5, 5, 6, 7, 9 and 12 inches, with the most popular sizes being the 4 and 4.5" size. In Europe the most common sizes for angle grinder discs are 115 and 125 millimeters. Discs for pneumatic grinders also come much smaller. Pneumatic grinders are generally used for lighter duty jobs where more
precision Precision, precise or precisely may refer to: Science, and technology, and mathematics Mathematics and computing (general) * Accuracy and precision, measurement deviation from true value and its scatter * Significant figures, the number of digit ...
is required. This is likely because pneumatic grinders can be small and light yet remain powerful, because they do not contain heavy copper motor windings, while it is harder for an electric grinder to maintain adequate power with smaller size. Electric grinders are more commonly used for larger, heavy duty jobs. However, there are also small electric grinders and large pneumatic grinders.


Safety

Through a sound pressure level and vibrations study conducted by the
National Institute for Occupational Safety and Health The National Institute for Occupational Safety and Health (NIOSH, ) is the United States federal agency responsible for conducting research and making recommendations for the prevention of work-related injury and illness. NIOSH is part of the C ...
, grinders under an unloaded condition ranged from 91 to 103 dBA.National Institute for Occupational Safety and Health (NIOSH) Division of Applied Research and Technology (DART), Hand-held Power Tools Sound Pressure and Vibrations Database, 2009 In addition, angle grinders produce sparks when cutting ferrous metals. They also produce shards cutting other materials. The blades themselves may also break. This is a great hazard to the face and eyes especially, as well as other parts of the body, and as such, a full face shield and other protective clothing must be worn. Angle grinders should never be used without their guard or handle attached. All workpieces should be securely clamped or held firmly in a vise.


History

The high-speed angle grinder was invented in 1954 by German company ''Ackermann + Schmitt ( FLEX-Elektrowerkzeuge GmbH)'' in Steinheim an der Murr. Owing to this, in German, Dutch, Slovak, Czech, Polish, Croatian, Romanian, Hungarian, Bulgarian and Latvian, an angle grinder is colloquially called just a "flex", in Italy and in spanish-speaking countries it is sometimes called "flexible". In Polish it is also known as "kątówka" or "gumówka" (= the rubber thing), which refers to the elasticity of certain types of disks. However they are never made out of true rubber due to fire hazard. In Russian, it is known as "болгарка" ("bolgarka") (literally "Bulgarian" of the feminine gender), since the first angle grinders in the USSR were Bulgarian made.


See also

*
Abrasive saw __NOTOC__ An abrasive saw, also known as a cut-off saw or chop saw, is a circular saw (a kind of power tool) which is typically used to cut hard materials, such as metals, tile, and concrete. The cutting action is performed by an abrasive disc, ...


References

{{DEFAULTSORT:Angle Grinder Grinding machines Hand-held power tools Articles containing video clips German inventions 1954 in science 1954 in Germany it:Smerigliatrice#Smerigliatrice angolare