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any one of a group of machines with built-in motors used in technology; during operation, the weight of a power tool is totally or partially supported by the hands of the operator feeding and controlling the machine. Power tools weigh between 1.5 and 10 kg. The working member is usually actuated by means of a pneumatic or electric (less often, hydraulic) drive from an internal-combustion engine or powder charge. There are more than 100 different types of power tools, classified in separate groups according to their use.
Drills are used for making holes. General-purpose drills are used for straight drilling, and there are designs for angled work in difficult-to-reach places. Power drills may have one, two, or multiple speeds, variable control of the bit’s rotation speed, and reversing or nonreversing drive. This group also includes hammer drills, in which impacts along the tool’s axis are transmitted to the bit as it rotates, thus increasing the working force and, consequently, efficiency, particularly when working with concrete, brick, and similar materials. Power drills may be equipped with specialized tools or accessories and are used for trimming, cutting, grinding and polishing, sawing, milling, and other work.
Grinders and polishers are used not only for grinding but also for sanding and polishing various materials. They may be designed for straight or angled operation; those designed for straight operation and equipped with cylindrical abrasive disks are most commonly used. Grinders and polishers designed for angled operation in sanding, cutting off, and polishing usually use various working tools, such as cup-shaped abrasive wheels, metal brushes, abrasive disks, and elastic lining disks with abrasive cloth or paper. Belt sanders, which have an endless abrasive belt, are often used for woodworking. Large wood or metal surfaces are worked with surface grinders having a platform-type working member, whose circular motion is parallel to the plane of the surface being worked; the working tool is usually an abrasive cloth or paper. Tools in which the working member is rotated by means of a flexible shaft drive are used for trimming castings and weld joints and for finishing the edges of parts prior to welding. Many types of power grinders are equipped with dust-suction devices.
Power screwdrivers and nut drivers are designed for assembling threaded connections. Nut drivers have become widely used. This group also includes drivers for wood screws and studs and power tools for screwing and unscrewing screws, studs, and pipe couplings.
Hammers and other percussive power tools, such as riveters, trimmers, and chippers, are used in assembly and metalworking operations. Old paint, rust, and scale are removed from metal parts by means of special hammers, whose working tool is a group of hardened steel rods. Mechanical picks are used in construction, mining, and other branches of industry for demolishing concrete and rocks. Drills with working tools that rotate and transmit impact at the same time are used for making holes of a given size in rocks, concrete, and brick. Bushhammers, which have a working tool in the form of a steel shoe with hardened pins, are used for working and trimming stone and concrete. Nail drivers and staplers are also classified as percussive power tools.
Cutting machines are used in making grooves, recesses, and various types of depressions in metal, wood, and plastic. The working tool of these machines is usually a shank-type end cutter. This group of machines includes planes, slotting machines, scrapers, and files.
Shears are designed for cutting sheet material in straight or irregular lines; the material may be of steel, nonferrous metal alloy, plastic, or rubber. The shears are used in assembly, erection and repair, roofing, and plumbing work and in heating, ventilation, and air-conditioning engineering. There are knife, blanking, circular, and lever (alligator) shears.
Saws are used for cutting wood, plastics, soft building materials, and, sometimes, small rolled metal stock, fittings, and pipes. Power saws include circular saws, chain saws, fretsaws, and hacksaws.
REFERENCESBarmash, V. N., D. I. Levin, and V. Z. Freidberg. Ruchnye mashiny dlia montazhnykh i otdelochnykh rabot. Moscow, 1960.
Sudakovich, D. I., and G. I. Bernadskii. Spravochnik po mekhanizirovannomu ruchnomu instrumentu, 2nd ed. Moscow-Leningrad, 1961.
Pnevmaticheskie ruchnye mashiny: Spravochnik. Leningrad, 1968.
M. L. GELFAND