diameter). The across-flats definition is the common standard today, and has been for many decades. The larger spanner in this photo is from the 1920s or earlier. Its face was polished to allow the size stamp to show well in the photograph. This example is American, but it illustrates the way that spanners for Whitworth fasteners were typically labeled.</div>
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<p>The <a href="//en.wikipedia.org/wiki/British_standard_fine_thread" title="British standard fine thread" class="mw-redirect">British S