# Angle grinder

An angle grinder, also known as a side grinder or disc grinder, is a handheld power tool used for grinding (abrasive cutting) and polishing. 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 or compressed air. The motor drives a geared head at a right-angle, on which can be mounted an abrasive 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 used in metal fabrication shops and on construction sites. They are also common in machine shops, along with die grinders and bench grinders.

## Safety and health

The use of an angle grinder in cutting is not preferred, because large amounts of harmful sparks, fumes and particulates are generated when compared with using reciprocating saw or band saw. Angle grinders produce sparks when cutting ferrous metals. They also produce shards when cutting other materials. The blades themselves may break, which is a hazard to the face and eyes especially, as well as other parts of the body. Consequently, 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. In a sound pressure level and vibration study conducted by the US National Institute for Occupational Safety and Health, grinders under an unloaded condition created noise which ranged from 91 to 103 dBA.

### Regulation
## 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 tasks, such as cut-off discs (diamond blade), 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, in which the force is axial.
Angle grinders are widely used in metalworking and construction, emergency rescues, and even for the theft of bicycles. Generally, they are found in workshops, service garages and auto body repair shops. There are a large variety of angle grinders with different disc sizes and power sources: battery, corded or pneumatic. Other variables include the power of the motor, rpm, and arbor size. Generally, disc size and power increase together. Disc size is usually measured in inches or millimeters. 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 4.5 and 5" size. In Europe, the most common sizes for angle grinder discs are 115 and 125 millimeters.
Discs for pneumatic grinders are much smaller. Pneumatic grinders are generally used for lighter-duty jobs in which more precision is required. That is because pneumatic grinders can be powerful while being small and light, because they do not contain heavy copper motor windings. 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.
Angle grinders have been used to remove wheel clamps from vehicles.

## History

The high-speed angle grinder was invented in 1954 by German company Ackermann + Schmitt (FLEX-Elektrowerkzeuge GmbH) in Steinheim an der Murr. As a result, in German, Dutch, Slovak, Czech, Polish, Croatian, Romanian, Hungarian, Bulgarian and Latvian, an angle grinder is colloquially called a "flex", and in Italy and in Spanish-speaking countries it is sometimes called "flexible". In Switzerland it is known as "Perles" from a popular brand of cutting tools. 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.