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A hammer is a tool that delivers a blow (a sudden impact) to an object. Most hammers are hand tools used to drive nails, fit parts, forge metal, and break apart objects. Hammers vary in shape, size, and structure, depending on their purposes. Hammers are basic tools in many trades. The usual features are a head (most often made of steel) and a handle (also called a helve or haft). Most hammers are hand tools, but there are also many powered versions, called power hammers (such as steam hammers and trip hammers) for heavier uses, such as forging. Some hammers have other names, such as ''sledgehammer'', ''mallet'' and ''gavel''. The term "hammer" also applies to some other devices that deliver blows, such as the hammer of a firearm or the hammer of a piano. == History == The use of simple hammers dates to about 2,600,000 BCE when various shaped stones were used to strike wood, bone, or other stones to break them apart and shape them. Stones attached to sticks with strips of leather or animal sinew were being used as hammers with handles by about 30,000 BCE during the middle of the Paleolithic Stone Age. The hammer's archeological record shows that it may be the oldest tool for which definite evidence exists of its early existence.〔〔 File:StoneHammerDoverMN.JPG|An early stone hammer File:Hammer stone tapping.jpg|Stone tapping hammer File:Hammer stone head.jpg|Perforated hammer head of stone File:Sacrificial hammer Dodona Louvre Br1183 n2.jpg|Ancient Greek bronze sacrificial hammer, 7th century BCE, from Dodona File:Melencolia I (Durero) hammer crop.jpg|16th century claw hammer from Dürer's ''Melencolia I'' (1514) 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「Hammer」の詳細全文を読む スポンサード リンク
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