<P> Commonly available material grades in the U.S. are A2, D2, M2, M42, O1, S7, W1, and high speed steel (including M2 / M7). </P> <P> Ground flat stock is annealed steel that has been ground to close tolerances (compare to drill rod). There are four types of materials available: O - 1 tool steel, A-2 tool steel, A-6 tool steel, and 1018 steel (low - carbon or low - carb steel). Lengths are either 18 or 36 in (457 or 914 mm) long, various widths up to 16 in (406 mm) are available, and thicknesses range from ⁄ to 2.875 in (0.40 to 73.03 mm). </P> <P> Some geometrical sizes are known as gauge plate . </P>

The diameter of a round bar with close tolerances is quickly measured by