Confusing nail system dates to ancient Rome

  • By Jim Kjeldsen / Herald Columnist
  • Wednesday, August 23, 2006 9:00pm
  • Life

T hey hold our empire together as well.

The types of nails used in modern construction almost defy counting.

They include box nails, common nails, finishing nails, casing nails, brads and sprigs, to name a few.

Most countries quite intelligently use the metric system to describe nail sizes. For example, a “50 x 3.0” nail refers to a nail 50 mm long and 3 mm in diameter, with the lengths rounded to the nearest millimeter. Canada uses a similar system, except that nail lengths are given in inches.

But not the United States. Here, the length of a nail is designated by its “penny” size. This system began in England about the time carpenters were hammering stages together around Shakespeare’s ears as he was furiously working on “Hamlet.” In the U.S., we still walk into a store and ask for six-penny nails or 12-penny nails, with the size of the nail getting progressively larger.

Just why this is goes back to the Romans. D is a designation for denarius, a Roman coin sort of like a penny. In Elizabethan England, nails were sold by the pence, which adopted the “d” for shorthand because the Romans once invaded England and left behind a lot of nails along with their forts. Under this system, you could get 100 4d nails for 4 pence, 100 16d nails for 16 pence, 100 60d nails for 60 pence and so on.

Today in the U.S., the “d’ refers to the length of the nail, prices having changed a bit. This incredibly confusing system remains.

Just so you know, a three-penny nail is 1 inches long, an eight-penny nail is 2 inches long and a 20-penny nail is 4 inches long.

Here are a few nail varietals and what they are used for, more or less in order of popularity:

Box nails: Round wire nails with a head, somewhat smaller in diameter than a common nail.

Common nail: A typical construction nail with a head for pounding into boards.

Casing nail: A wire nail with a slightly larger head than a finishing nail. Casing nails are often used for such things as flooring.

Finishing nail: A wire nail without a head that can be punched down, puttied over and concealed.

Galvanized nail: Dipped in zinc for resistance to corrosion and weather exposure.

Ring-shank nail: Nails with little rings on the shank so you can never pull them out again.

Screw-shank nails: Nails with a spiral shank for easy pounding into soft wood.

Brads: Small nails of about 2 inches or less. These can be broken down into slight-headed brads, medium-headed brads, headless brads and such.

Masonry nails: Made of hardened steel, these are used to fix wood to brick, concrete blocks or hardened concrete.

Sprig: A small nail without a head, used mainly to hold glass in window frames before applying glaze to cover them up.

Upholstery nail: The round-headed nails, usually decorative, that hold cloth and leather onto furniture.

Square nail: Last but not least, this is the original nail that the Romans made in vast quantities. Well, the Romans probably didn’t make them, but their slaves did. Square nails are still being made in some parts of the world because they have approximately four times the holding power of modern round nails.

Carpenters today generally build houses using pneumatic nail guns to save time and wear and tear on their muscles. The nails are arranged in long clips that look like ammunition belts and are fired into the wood with a bang. The air-gun nail resembles the square nail of old with the exception that the head is T-shaped rather than battened on all four sides, according to the Appalachian Blacksmiths Association. Only it doesn’t hold as well.

So much for progress.

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