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Angle grinder

An angle grinder, also known as a side grinder, is a handheld power tool used for cutting, grinding and polishing.

Angle grinders can be powered by an electric motor, petrol engine or compressed air. The motor drives a geared head at a right-angle on which is mounted an abrasive disc that can be replaced when worn. Angle grinders typically have an adjustable guard and a side-handle for two-handed operation.



Angle grinders may be used both for removing excess material off a piece or simply cutting into a piece. There are many different kinds of discs that are used for various materials and 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, where the force is axial.

Angle grinders are widely used in metalworking and construction, as well as in emergency rescues. They are commonly 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 how powerful the motor is. Other factors include power source (pneumatic or electric), 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 U.S.A. include 4, 4.5, 5, 6, 7, 9 and 12 inches. Discs for pneumatic grinders also come much smaller. Pneumatic grinders are generally used for lighter duty jobs where more precision is required. This is likely because pneumatic grinders can be small yet remain powerful, 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. There are also small electric grinders and large pneumatic grinders.


Angle grinders can be dangerous due to the high rpm involved and the sparks and pieces of excess material that fly off as they cut and grind. Another dangerous aspect of angle grinders is that a bad cutting disk can shred when in use. A third risk is that if the edge of the grinding wheel binds in a corner the torque from the spinning wheel will jerk the tool violently.

These safety hazards can be mitigated. Proper personal protective equipment while using an angle grinder would include safety glasses, thick leather gloves, and in more heavy duty operations hearing protection and a face shield. While using an angle grinder can occasionally result in injury, use of proper equipment will greatly reduce the risk.

However, the piece of PPE that people most neglect is hearing protection through some form of earplug or earmuff. When using high-powered power tools, the noise levels can become hazardous very easily. Through a sound power level and vibrations study conducted by the National Institute for Occupational Safety and Health, grinders under an unloaded condition ranged from 91 to 103 A-weighting[1], well above the Occupational Safety and Health Administration's standard for noise of 85 dBA time-averaged for eight hours[2]. This is both the regulatory and the industry standard.

In the unloaded case for these grinders, the sound power levels reached a range of 95 to 107 dBA[1], a considerable increase considering the dBA is on a logarithmic scale. According to the OSHA standards, an increase from the unloaded case of four dBA from 91 to 95 dBA[1] greater than halves the allowable exposure time from 7 hours to 3 and an increase from the loaded case from 103 to 107 dBA[1] from less than one hour to 40 minutes. Because of this, proper hearing protection is required for the task at hand.

Related tools

The angle grinder can be contrasted with other varieties of grinders; see grinding machine, bench grinder,Concrete grinder and other diamond tools.


  1. ^ a b c d 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
  2. ^ Occupational Safety and Health (OSHA) Standard 1910.95, 2008

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