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 today are usually made of steel. Formerly they were usually of wrought iron, but for some purposes nails are made of copper or (rather) brass.
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:
- brass tack
- bullethead nail
- canoe tacks
- carpet tack
- casing - similar to finish nails but on a larger scale
- coffin nail
- fiber cement
- masonry - fluted nail for use in concrete
- oval brad
- floor brad (aka 'stigs') - flat, tapered and angular, for use in fixing floor boards
- panel pin
- plastic strip
- gutter spikes
- roofing tack
- shake - small headed nails to use for nailing sidewall shakes
- Teco - 1-1/2 x .148 shanks nails used in metal connectors
- veneer pin
- wire-weld collated
Most countries, except the United States
, use a metric system
for describing nail sizes. A "50 x 3.0" indicates a nail 50 mm long (not including the head) and 3 mm in diameter. Lengths are rounded to the nearest millimeter.
USA uses a similar system except nail lengths are given in inches.
United States penny sizes
Nails are usually sold by weight (either in bulk or in boxes). In the US, the length of a nail is designated by its penny size
. It is commonly believed that the origin of the term "penny" in relation to nail size is based on the old custom in England
of selling nails by the hundred. A hundred nails that sold for six pence
were "six penny" nails. The larger the nail, the more a hundred nails would cost. Thus the larger nails have a larger number for its penny size
. This classification system was still used in England in the 18th century, but is obsolete there.
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.
| penny size
|| 25 |
|| 32 |
|| 38 |
|| 51 |
|| 57 |
|| 65 |
|| 70 |
|| 76 |
|| 83 |
|| 89 |
|| 102 |
|| 115 |
|| 127 |
|| 140 |
|| 152 |
- Box - a wire nail with a head; box nails have a smaller shank than common nails of the same size
- Bright - no surface coating; not recommended for weather exposure or acidic or treated lumber
- Casing - a wire nail with a slightly larger head than finish nails; often used for flooring
- CC or Coated - "cement coated"; nail coated with adhesive (cement) for greater holding power; also resin- or vinyl-coated; coating melts from friction when driven to help lubricate then hardens when cool; color varies by manufacturer (tan, pink, are common)
- Common - a common construction wire nail with a head: common nails have larger shanks than box nails of the same size
- Duplex - a common nail with a second head, allowing for easy extraction
- Finish - a wire nail that does not have a "head"; can be easily concealed
- Galvanized - treated for resistance to corrosion and/or weather exposure
- *Electrogalvanized - provides a smooth finish with some corrosion resistance
- *Mechanically galvanized - deposits more zinc than electrogalvanizing for increased corrosion resistance
- *Hot-dip galvanized - provides a rough finish that deposits more zinc than other methods, resulting in very high corrosion resistance that is suitable for some acidic and treated lumber; often easier to bend than other types of nails
- Head - round flat metal piece affixed to the top of the nail; for increased holding power
- Helix - the nail has a square shank that has been twisted this makes the nail very difficult to pull out; often used in decking
- Length - distance from the head to the point of a nail
- Phosphate-coated - a dark grey to black finish providing a surface that binds well with paint and joint compound and minimal corrosion resistance
- Point - sharpened end opposite the "head" for greater ease in driving
- Ring Shank - small rings on the shank to prevent the nail from being worked back out often used in flooring
- Shank - the body the length of the nail between the head and the point; may be smooth, or may have rings or spirals for greater holding power
- Sinker - Same thin diameter as a box nail, cement coated (see above), the funnel shaped head is easier to nail flat and the head has a grid on the strike surface to keep the hammer strike from slipping; these are the common nails used in framing today
- Spike - a large nail (usually over 4" - 100 mm)