What does “gage” (or “gauge”) mean?
Webster’s seems to prefer “gauge”, but Machinery’s Ready Reference uses “gage” for sheet, and “gauge” for wire. Strictly speaking, “gauge” is a measuring device, and “gage” a measurement system, but common usage has corrupted the distinction. An arbitrary assignment of numbers to size, used on sheet, wire, and many other things (tubing, shotgun bore, needles, and so on). Unfortunately there are so many different standards that using gage to specify a material is almost useless, and perhaps even dangerous. If in doubt, use decimals. For example, in U.S. gage, the standard for sheet metal is based on the weight of the metal, not on the thickness. 16-gage is listed as approximately .0625 inch thick and 40 ounces per square foot (the original standard was based on wrought iron at .2778 pounds per cubic inch; steel has almost entirely superseded wrought iron for sheet use, at .2833 pounds per cubic inch). Smaller numbers refer to greater thickness. There is no formula for converting gage to
