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A power tool is a tool that is actuated by an additional power source and mechanism other than the solely manual labour used with hand tools. The most common types of power tools use electric motors. Internal combustion engines and compressed air are also commonly used. Other power sources include steam engines, direct burning of fuels and propellants,〔e.g. in powder-actuated tools〕 or even natural power sources like wind or moving water. Tools directly driven by animal power are not generally considered power tools. Power tools are used in industry, in construction, in the garden, for housework tasks such as cooking, cleaning, and around the house for purposes of driving (fasteners), drilling, cutting, shaping, sanding, grinding, routing, polishing, painting, heating and more. Power tools are classified as either stationary or portable, where portable means hand-held. Portable power tools have obvious advantages in mobility. Stationary power tools however often have advantages in speed and accuracy,〔A typical table saw for instance not only cuts faster than a regular hand saw, but the cuts are smoother, straighter and more square than what is normally achievable with a hand-held power saw.〕 and some stationary power tools can produce objects that cannot be made in any other way.〔e.g. lathes produce truly round objects〕 Stationary power tools for metalworking are usually called ''machine tools''. The term ''machine tool'' is not usually applied to stationary power tools for woodworking, although such usage is occasionally heard, and in some cases, such as drill presses and bench grinders, exactly the same tool is used for both woodworking and metalworking. ==History== The lathe is the oldest power tool, being known to the ancient Egyptians (albeit in a hand-powered form). Early industrial revolution-era factories had batteries of power tools driven by belts from overhead shafts. The prime power source was a water wheel or (later) a steam engine.The introduction of the electric motor (and electric distribution networks) in the 1880s made possible the self-powered stationary and portable tools we know today.〔(【引用サイトリンク】url=http://www.history.com/videos/the-worlds-first-power-tools )〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「power tool」の詳細全文を読む スポンサード リンク
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