Q: I am curious what it means when a nail is called 6 penny.

A: This is a good question, as in the past, nails were almost always sold in penny sizes. The origination of penny sizes is from six centuries ago in England where the price of 100 nails cost the indicated number of pence (abbreviation is "d"). Today, the penny designation refers to the length; for example:

2d 1 inch

3d 1-1/4 inch

4d 1-1/2 inch

6d 2 inches

8d 2-1/2 inches

10d 3 inches

Conventionally, for a given nail type, there is an appropriate diameter for each length or penny size; there is a different diameter size for box nails. For example, a 6d common wire nail is 0.131 of an inch in diameter; a box nail is 0.098 of an inch in diameter; a threaded nail is 0.120 of an inch in diameter; and a finishing nail is 0.091 of an inch in diameter.

Today, you may still see the penny size, but the actual size in inches length and the diameter is almost always given. This change results because a good number of manufacturers outside the U.S. did and still do not adhere to this "penny" convention of sizes; hence, the term penny for nails is obsolete.

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