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A chainsaw (or chain saw) is a portable, mechanical saw which cuts with a set of teeth attached to a rotating chain that runs along a guide bar. It is used in activities such as tree felling, limbing, bucking, pruning, to fell snags and assist in cutting firebreaks in wildland fire suppression, and to harvest firewood. Chainsaws with specially designed bar and chain combinations have been developed as tools for use in chainsaw art and chainsaw mills. Specialist chainsaws are used for cutting concrete. Chainsaws are sometimes used for cutting ice, for example for ice sculpture and in Finland for winter swimming. Someone who uses a saw is a sawyer. == Construction == A chainsaw consists of several parts: *Engine — almost always a two-stroke gasoline (petrol) internal combustion engine, usually with a cylinder volume of 30–120 cm3 or an electric motor. *Drive mechanism — typically a centrifugal clutch and sprocket. *Guide bar — an elongated bar with a round end of wear-resistant alloy steel typically 40 to 90 cm (16 to 36 in) in length. An edge slot guides the cutting chain. Specialized loop-style bars, called bow bars, were also used at one time for bucking logs and clearing brush, although they are now rarely encountered due to increased hazards of operation. *Cutting chain — Usually each segment in this chain (which is constructed from riveted metal sections similar to a bicycle chain, but without rollers) features small sharp cutting teeth. Each tooth takes the form of a folded tab of chromium plated steel with a sharp angular or curved corner and two cutting edges, one on the top plate and one on the side plate. Left-handed and right-handed teeth are alternated in the chain. Chains come in varying pitch and gauge; the pitch of a chain is defined as half of the length spanned by any three consecutive rivets (e.g., 8 mm, 0.325 inch), while the gauge is the thickness of drive link where it fits into the guide bar (e.g., 1.5 mm, 0.05 inch). Conventional "full complement" chain has one tooth for every two drive links. "Full skip" chain has one tooth for every three drive links. Built into each tooth is a depth gauge or "raker" which rides ahead of the tooth and limits the depth of cut, typically to around 0.5 mm (0.025"). Depth gauges are critical to safe chain operation. If left too high they will cause very slow cutting, if filed too low the chain will become more prone to kick back. Low depth gauges will also cause the saw to vibrate excessively. Vibration is not only uncomfortable for the operator but is also detrimental to the saw. *Tensioning mechanism - some way to adjust the tension in the cutting chain so that it neither binds on nor comes loose from the guide bar. The underside of each link features a small metal finger called a "drive link" which locates the chain on the bar, helps to carry lubricating oil around the bar, and engages with the engine's drive sprocket inside the body of the saw. The engine drives the chain around the track by a centrifugal clutch, engaging the chain as engine speed increases under power, but allowing it to stop as the engine speed slows to idle speed. Dramatic improvements, chainsaw safety devices and overall design have taken place since the chainsaw's invention, saving many lives and preventing countless serious injuries. These include chainbrake systems, better chain design and anti-vibration systems. As chainsaw carving has become more popular, chainsaw manufacturers are making special short, narrow-tipped bars for carving. These are called "quarter tipped," "nickel tipped" or "dime tipped" bars, based on the size of the round tip. Chainsaw manufacturer Echo sponsors a carving series,〔(ECHO Carving Series )〕 as well as carvers such as former Runaways singer Cherie Currie.〔(Chainsaw carving page. )〕 Some chainsaws such as the RedMax G3200 CV are built specifically for carving applications.〔(Masters of the Chainsaw - Chainsaw Competitions )〕 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「chainsaw」の詳細全文を読む スポンサード リンク
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