Threads and Fasteners - Cabarrus County Schools

Jan 13, 2005 · Standard screw threads consist of the Unified inch series and the Metric series. Unified inch series, dominant in the US, are based on the major (outermost) diameter and the number of threads per inch. The three standard series are designated UNC (coarse), UNF (fine), and UNEF (extra fine). Typical specifications are. 1/4-20 UNC or 1/2-20 UNF, ................
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