Angle grinder
An angle grinder, also known as a side grinder or disc grinder, is a handheld power tool used for cutting, grinding, and polishing various materials including metal, stone, concrete, and masonry.[1] It features a rotating abrasive disc or wheel attached at a right angle to the motor, enabling precise and efficient material removal in industrial, construction, and fabrication settings.[2] The angle grinder was invented in 1954 by the German company Ackermann + Schmitt (now FLEX-Elektrowerkzeuge GmbH), with the launch of the DL 9 model as the first high-speed version, revolutionizing abrasive cutting by allowing handheld operation at speeds up to 9,000 RPM.[3] Over the decades, the tool has evolved significantly, incorporating innovations such as lightweight designs in the 1960s (e.g., the ZL 108 model), vibration-reducing handles in the early 2000s (e.g., the L 3406 VRG), and brushless motors with cordless battery options by the 2010s and 2020s (e.g., the L 125 18.0-EC in 2017 and LBP 125-15 18-EC in 2024).[3] These advancements have made angle grinders more ergonomic, portable, and versatile for professional use. Primarily employed in metalworking for tasks like weld seam removal, rust elimination, and edge deburring, angle grinders are also essential in construction for cutting tiles, concrete, and rebar, as well as in polishing surfaces to achieve smooth finishes.[2] They come in various types, including corded electric models for continuous power, cordless battery-powered variants for mobility, pneumatic air-driven units for precision in confined spaces, and variable-speed options to accommodate different materials and applications.[2] Disc sizes typically range from 4 to 9 inches, with power outputs from 500 to 2,500 watts, allowing adaptability across trades.[2] Due to their high rotational speeds—often exceeding 10,000 RPM—angle grinders pose significant safety risks, including disc fragmentation, kickback, and flying debris, which account for numerous workplace injuries annually.[1] Standard safety features include spindle locks for disc changes, electronic overload protection, and anti-restart mechanisms, while users must employ personal protective equipment such as goggles, gloves, and dust masks, along with proper guards and training to mitigate hazards.[2] Regulatory bodies like OSHA emphasize regular inspections and adherence to manufacturer guidelines to ensure safe operation.[1]Introduction
Definition and Purpose
An angle grinder is a handheld power tool equipped with a rotating abrasive disc or wheel, primarily used for grinding, cutting, polishing, and finishing various surfaces through abrasive action.[2][4] This versatile device enables precise material removal and surface preparation, making it essential in applications such as smoothing rough edges, removing rust, or shaping workpieces.[5][2] The core purpose of an angle grinder lies in its ability to handle diverse materials, including metals, stone, concrete, and masonry, by employing interchangeable discs tailored to specific tasks like heavy-duty cutting or fine polishing.[4][5] It facilitates efficient surface modification in industries such as metalworking, construction, and fabrication, where quick and controlled abrasion is required.[2] The name "angle grinder" derives from its distinctive design, featuring an angled head and internal gear system that positions the disc at a right angle to the tool's body, enhancing ergonomic access to confined or awkward spaces.[4] Typical models accommodate disc sizes ranging from 4 to 9 inches in diameter, with common options being 4.5 inches for general use and 9 inches for heavier tasks, while operating at speeds up to 12,000 RPM to achieve effective abrasive performance.[2][4]Nomenclature
The primary name "angle grinder" originates from the tool's distinctive 90-degree angled gearbox, which positions the handle perpendicular to the rotating abrasive disc, enabling ergonomic operation in tight spaces.[4] This design feature, introduced in the first commercial model in 1935, with the high-speed version launched in 1954, distinguishes it from straight-shaft grinders and has become the standard nomenclature in tool manufacturing and safety standards.[3][6] Alternative designations include "side grinder," reflecting the lateral mounting of the disc relative to the body, and "disc grinder," which highlights the central role of the abrasive disc in its function.[7] In some regions and trade contexts, the term "flex" persists as a generic reference, derived from the early manufacturer Ackermann + Schmitt (now FLEX), whose pioneering model popularized the tool and led to the brand name entering common usage.[3] Regional variations and contextual misnomers further diversify the terminology; Cut-off configurations, fitted with thin abrasive wheels for slicing, are sometimes erroneously called "chopsaws" or "portable chopsaws" by users, borrowing from stationary miter saw designs despite the handheld nature.[8] Historically, early 20th-century references often labeled these devices simply as "portable grinders" in catalogs and patents, encompassing a broader category of handheld abrasive tools before the angled design prompted the more specific "angle grinder" adoption in post-World War II industrial standardization.[9] This shift aligned with evolving tool ergonomics and the proliferation of electric models, solidifying contemporary terms in professional and retail contexts.[3]History
Invention
The high-speed angle grinder was invented in 1954 by the German company Ackermann + Schmitt, founded in 1922 by Hermann Ackermann and Hermann Schmitt in Stuttgart to produce handheld grinding machines.[10] Following the disruptions of World War II, the company resumed production in 1946 with a focus on electric tools, including grinders, amid Germany's post-war industrial rebuilding efforts that emphasized efficient metalworking equipment.[10] The inaugural model, designated DL 9, represented a breakthrough as the world's first high-speed angle grinder, featuring an innovative angled head with a gearbox that enabled compact, portable operation without the flexible shafts used in earlier straight-line grinders.[3] This design addressed the demand for a versatile, handheld tool suitable for precise cutting and grinding in industrial applications during the economic recovery period.[10] Prior to the DL 9, Ackermann + Schmitt had introduced a low-speed angle grinder in 1935, but the 1954 model marked the advent of high rotational speeds for enhanced performance.[10]Development and Evolution
Following the initial invention of the high-speed angle grinder in 1954 by Ackermann + Schmitt (now FLEX), the tool underwent significant iterative improvements in the 1960s and 1970s, expanding its capabilities for broader industrial applications.[3] Variable speed controls also emerged, allowing operators to adjust rotational speeds for diverse materials and reducing the risk of disc damage or overheating. These advancements were influenced by OSHA regulations enacted in the 1970s, particularly the 1970 adoption of ANSI B7.1 standards, which mandated safety guards on grinding machines to cover the spindle end, nut, and flange, prompting redesigns for better operator protection and compliance in U.S. markets.[11] Pneumatic versions, first introduced in the mid-20th century, became more widely used in industrial environments by the 1980s, where compressed air power offered advantages in durability and reduced electrical hazards in wet or explosive settings.[12] Safety guards became a standard feature across models, evolving from basic metal shields to adjustable designs that complied with international standards, minimizing exposure to flying debris and wheel fragments.[13] This period marked a shift toward more robust, user-focused tools, with ergonomic improvements like streamlined housings introduced by FLEX in models such as the ZL 108.[3] The 1990s and 2000s brought a focus on portability, culminating in the rise of cordless battery-powered angle grinders powered by lithium-ion technology, which provided longer runtime and lighter weight compared to earlier nickel-cadmium batteries.[14] Although initial cordless prototypes appeared in the late 1960s for other tools, angle grinders remained corded until advancements in battery density enabled viable models in the 2000s, with full market penetration by the mid-2010s; FLEX launched its first 18V cordless variant, the L 125 18.0-EC, in 2017, significantly improving mobility for field work.[3] These developments enhanced usability in remote or extension-cord-free scenarios, such as automotive repair and site preparation. From the 2010s to the present, angle grinders have incorporated smart features like brushless motors, which eliminate carbon brushes for greater efficiency, reduced maintenance, and up to 50% longer runtime; DeWalt introduced the first corded brushless model in 2018, followed by FLEX's 230V version in 2021.[15][3] Electronic overload protection automatically shuts down the tool during excessive load to prevent motor burnout, while integrated dust extraction systems—often with connectable vacuums—capture up to 90% of airborne particles, addressing health concerns in concrete and metalworking.[16] Market growth has been robust, particularly in construction and automotive sectors, where demand for versatile cutting and polishing tools has driven annual global sales exceeding 10 million units by the early 2020s, supported by a market value surpassing USD 3 billion.[17][18] In 2024, FLEX introduced the LBP 125-15 18-EC, a cordless model with a paddle switch for enhanced control.[3] Key milestones include the OSHA-influenced safety integrations of the 1970s and the transition to brushless, cordless designs, reflecting ongoing emphasis on performance, safety, and sustainability.[19]Types
By Power Source
Angle grinders are classified by their power sources into electric (corded), battery-powered (cordless), and pneumatic (air-powered) variants, each offering distinct performance characteristics and applications based on energy delivery methods.[20] Electric corded angle grinders draw power from a standard electrical outlet, providing consistent and high output for demanding tasks. These models typically range from 800 to 2500 watts, enabling prolonged operation without runtime limitations, making them ideal for heavy-duty professional use such as metal fabrication and construction site work. However, the attached power cord restricts mobility and poses tripping hazards in dynamic environments.[21][22] Battery-powered cordless angle grinders utilize rechargeable lithium-ion batteries, emphasizing portability for jobsites without reliable electricity access. Common battery voltages span 18 to 60 volts, delivering equivalent power suitable for medium-duty cutting and grinding, though runtime typically lasts 20 to 60 minutes per charge depending on load and battery capacity. While offering freedom from cords and enhanced safety in wet conditions, these tools are generally heavier and may experience power fade as the battery depletes.[22][21] Pneumatic angle grinders operate on compressed air supplied by an external compressor, achieving high rotational speeds and lightweight designs for specialized industrial settings. They equate to 0.5 to 1.5 horsepower (approximately 370 to 1100 watts), with RPM often reaching 13,500 or higher, and require 90 PSI air pressure for optimal performance. These tools excel in explosive or hazardous atmospheres due to the absence of electrical components, providing superior torque and durability, but necessitate a reliable air supply infrastructure.[23][24][25] The following table compares representative specifications across power sources, based on common 115-125 mm disc models:| Power Source | Power Output | Typical RPM | Weight (kg) | Torque Characteristics |
|---|---|---|---|---|
| Electric (Corded) | 800-2500 W | 8,000-12,000 | 2.0-4.0 | Consistent high torque under load[22][26][27] |
| Battery-Powered | 18-60 V (equiv. 500-1500 W) | 8,000-11,000 | 2.5-5.0 | Variable, decreases with battery drain[22][21][28] |
| Pneumatic | 0.5-1.5 HP (370-1100 W) | 8,000-13,500+ | 1.5-3.0 | High stall-resistant torque[23][24][29][25] |