In mechanical and civil engineering, a peg or bar designed to fasten machine and structural components together or to keep them aligned. Dowel pins are used to keep machine components aligned, sometimes without making a rigid joint (as in a pin-connected truss). Taper pins are used to fix the hub of a gear or a pulley to a shaft. Split cotter pins prevent nuts from turning on bolts and keep loosely fitting pins in place. The clevis pin has a ridge at one end and is kept in place by a cotter pin inserted through a hole in the other end. Many other types of pins are used in various machines.
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In engineering, woodworking and construction, a nail is a pin-shaped, sharp object of hard metal, typically steel, used as a fastener. Nails for specialized purposes may also be made of stainless steel, brass or aluminium.
Nails are typically driven into the workpiece by a hammer or by a nail gun driven by compressed air or a small explosive charge. A nail holds materials together by friction in the vertical direction and shear strength in lateral directions. The point of the nail is also sometimes bent over or clinched to prevent it from pulling out.
Nails are made in a great variety of forms for specialized purposes; the common everyday kind of nail is sometimes called a "wire nail" to distinguish it from nails in general. Some kinds of nails are referred to by other words, for example "pins", "tacks," "brads" and "spikes."
Nails go back at least to the Ancient Roman period. The provision of iron for nails by King David for Solomon's Temple is mentioned in the Bible. Until the end of the 18th century, they were always made by hand, a nailer providing them with a head and point. Until the early 17th century there were workmen called slitters who cut up iron bars to a suitable size for nailers to work on, but in 1590 the slitting mill was introduced to England, providing a mechanical means of producing rods of uniform cross-section. In the 19th century, after the invention of machines to make "cut nails", some nails continued to be made by hand, but the handmade nail industry gradually declined and was largely extinct by the end of that century.
Manufactured cut nails were first introduced in America at the end of the 18th century. Cut nails are machine-cut from flat sheets of steel (originally iron). They are also called square nails because of their roughly rectangular cross section. Though still used for historical renovations, and for heavy-duty applications, such as attaching boards to masonry walls, cut nails are much less common today than wire nails.
Types of nail include:
USA uses a similar system except nail lengths are given in inches.
The penny size is written with a number and the abbreviation d for penny (e.g. - 10d). D is an abbreviation for denarius, a Roman coin similar to a penny; this was the abbreviation for a penny in the UK before decimalisation. A smaller number indicates a shorter nail and a larger number indicates a longer nail. Nails under 1¼ in., often called brads, are sold mostly in small packages with only a length designation (e.g. ½" (12 mm), 1" (28 mm), etc.). In boxes of nails that are packaged for pneumatics nails are called 8 penny nails but have a length of 2-3/8. Some 16d nails are called 16d short and measure 3-1/4". Penny size is not always directly correlated to length because nails with larger shanks and shorter lengths will be the same weight as the standard penny designation.
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