Anangle grinder, also known as aside grinder ordisc grinder, is a handheldpower tool used forgrinding (abrasive cutting),polishing, sanding, and similar applications. Its use is especially prevalent inmetalwork.
The high-speed angle grinder was invented in 1954[1] by German company Ackermann + Schmitt (FLEX-Elektrowerkzeuge GmbH) inSteinheim an der Murr.[2] Before the high speed angle grinder of 1954, many other inventors from the early 20th century had produced grinders and similar cutting tools for use in metalwork. As electricpower tools became more available and affordable, the prevalence of angle grinders inworkshops increased, and they also became a popularDIY tool, especially after the invention of battery-poweredcordless angle grinders.[3]
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". This originates with Ackermann + Schmitt's use of a flexibile shaft between the motor drive and the tool.[4] The name "flex" proved so enduring that Ackermann + Schmitt changed their company's name to FLEX.
InSwitzerland it is known as "Perles" from a popular brand ofcutting tools. In Finnish, angle grinders are colloquially known as "rälläkkä", an onomatopoeia for the distinctive sound they make when cutting (the Estonian name "relakas" comes from the Finnish name). In Polish it is also known as "kątówka"[5] or "gumówka"[6] (literally "rubber thing"), which refers to the elasticity of certain types of disks (however these are never made out of true rubber due to fire hazard). In Russian, the tool is known as "болгарка" ("bolgarka")[7] (literally "Bulgarian" of the feminine gender), since the first angle grinders in theUSSR were Bulgarian-made.[8]
Angle grinders are sometimes confused with cut-off saws, though these have less variable applications.
Angle grinders can be powered by anelectric motor orcompressed air. The motor drives a geared head at a right-angle, on which is a spindle for mounting discs. The nature of these discs varies based on their intended use.Abrasivedisc or thinner cut-off discs are the most common, and both can be replaced when worn. Angle grinders typically have an adjustable guard and a side-handle for two-handed operation. Many brands of angle grinders have two-stage trigger switch (also known as a "deadman's switch") to prevent the user accidentally switching the tool on, especially when changing discs.
Depending on their speed range, angle grinders can be used assanders, 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. Wheels are most often added or removed using an angle grinder wrench, a distinctive two-pin spanner used to attach discs to the grinder's spindle.
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 are used inmetal fabrication shops, onconstruction sites[citation needed] and inmachine shops, along withdie grinders andbench grinders.[citation needed]
There are different discs for different tasks, cut-off discs (diamond blade), abrasive grinding discs,grinding stones, sanding discs,wire brush wheels and polishing pads.[citation needed] Typically, cut-off discs are disposable and will be discarded once they are worn down. Angle grinders have largebearings to counter the side forces generated, unlike a powerdrill, where the force is axial. This versatility give angle grinders a wide variety of uses, including cutting, sanding, grinding, demolition, polishing, and stripping. Though they can be used on other materials, they are predominantly used on metal andmasonry.
Angle grinders are widely used inmetalworking,construction, emergency rescue, and the theft of bicycles, and can be 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 orpneumatic. Other variables include the motor power and speed,rpm, andarbor 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 4.5 and 5" size. OutsideNorth America, the most common sizes for angle grinder discs are 115 and 125 millimetres.
Discs for pneumatic grinders are much smaller, and pneumatic grinders tend to be used for lighter-duty jobs in which moreprecision is required. This is because pneumatic grinders can be powerful while being small and light, because they do not contain heavycopper motorwindings. 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 removewheel clamps from vehicles.[9][10]
Use of angle grinder can emit a large amount of small respirable dust.[11][12][13] Excessive dust emission is regulated byair pollution laws andviolation can result in fines. Proper use of well-designeddust collectors (e.g.dust collection hoods) can reduce dust concentration significantly (up to 80-90%).[11]
The disc type (fibre disc or grinding wheel) affects the dust's size distribution. The dust emitted can be as small asPM1.[14]
Angle grinders can produce considerable volumes of harmful sparks, fumes andparticulates, especially when compared to using areciprocating saw orband saw.[15] Angle grinders producesparks when cuttingferrous metals, and can also produceshards when cutting other materials. The blades themselves may break, which is a hazard to theface andeyes especially, as well as other parts of the body - in these instances debris moving at high speed may cause penetrating injuries.[16]
A grinder disc becoming lodged or jammed can cause kickback, a dangerous phenomenon where the tool will jump or thrust back towards the user. Consequently, a full face shield and otherprotective clothing such as cut resistant gloves must be worn at all times. Cutting discs often have arrows or marking specifying which direction they should be used in, and it is recommended to adjust the guard so sparks fly away from the angle grinder operator. Sparks can also make angle grinders afire hazard, especially in enclosed spaces.
Angle grinders should never be used without their guard or handle attached. Allworkpieces should be securely clamped or held firmly in avise.[17] In asound pressure level andvibration study conducted by the USNational Institute for Occupational Safety and Health, grinders under an unloaded condition created noise which ranged from 91 to 103dBA.[18]
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