USA Standards Committee B32 had its beginning on November 27, 1928 when it was requested to take up the unification of the various systems employed in gaging wire and sheet metal. Although there were extended periods of inactivity, USAS Standard B32.1, Preferred Thicknesses for Uncoated Thin Flat Metals was issued in 1941. It was revised in 1952 and reaffirmed in 1959 and again in 1966.
An attempt at standardizing round wire sizes to replace arbitrary (gage) numbers in order to eliminate the multiplicity of gages for wires of various metals was made in a proposal in September 1941, This proposal was never balloted. There was no further activity until October 25, 1965 when it was agreed to again study a standard series of sizes for general purpose round wire. The result was a proposal covering sizes from 0.010-through 0.500-inch diameter.
In the initial proposal, sizes from 0.250-through 0.500-inch diameter followed the preferred fraction series, well established in the United States. Sizes under 0.250-inch diameter followed an arbitrary decimal fraction series of preferred inch values. Subsequently, to prevent significant future problems and since no precedent had been established for the decimal size of wire under 0.250 other than arbitrary gages, consideration was given to selecting sizes compatible between the two measuring systems. The resulting proposal established decimal inch sizes corresponding to the preferred millimeter sizes of ISO Recommendation R 388, Metric Series for Basic Thicknesses of Sheet and Diameters of Wire, for sizes under 0.250-inch diameter, and retained the well established preferred fraction inch sizes (expressed in decimals) for sizes from 0.250-through 0.500-inch diameter. This proposal received approval as a USA Standard on August 22, 1969.
Order online or call: Americas: +1 800 854 7179 | Asia Pacific: +852 2368 5733 | Europe, Middle East, Africa: +44 1344 328039