ed the Imperial ones.</p>
<p><a href="//en.wikipedia.org/wiki/Unified_Thread_Standard" title="Unified Thread Standard">American Unified Coarse</a> was originally based on almost the same imperial fractions. The Unified thread angle is 60° and has flattened crests (Whitworth crests are rounded). From 1/4&#160;in up to 1 1/2&#160;in, thread pitch is the same in both systems except that the thread pitch for the 1/2&#160;in bolt is 12 threads per inch (tpi) in BSW versus 13 tpi in the UNC.</p>
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