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UNC | Size | Tapping Drill mm | Pitch mm | TPI | OD mm | | 2-56 UNC | 1.85 | 0.45 | 56 | 2.18 | | 3-48 UNC | 2.10 | 0.53 | 48 | 2.51 | | 4-40 UNC | 2.35 | 0.64 | 40 | 2.84 | | 6-32 UNC | 2.84 | 0.79 | 32 | 3.51 | | 8-32 UNC | 3.50 | 0.79 | 32 | 4.17 | | 10-24 UNC | 3.90 | 1.06 | 24 | 4.83 | | 12-24 UNC | 4.55 | 1.06 | 24 | 5.49 | | 1/4-20 UNC | 5.30 | 1.27 | 20 | 6.35 | | 5/16-18 UNC | 6.60 | 1.41 | 18 | 7.94 | | 3/8-16 UNC | 8.00 | 1.59 | 16 | 9.53 | | 7/16-14 UNC | 9.40 | 1.81 | 14 | 11.11 | | 1/2-13 UNC | 10.80 | 1.95 | 13 | 12.70 | | 9/16-12 UNC | 12.25 | 2.12 | 12 | 14.29 | | 5/8-11 UNC | 13.50 | 2.31 | 11 | 15.88 | | 3/4-10 UNC | 16.50 | 2.54 | 10 | 19.05 | | 7/8-9 UNC | 19.45 | 2.82 | 9 | 22.23 | | 1-8 UNC | 22.25 | 3.18 | 8 | 25.40 |
See also: British Association Threads, British Standard Whitworth, Thread, UNF.
  
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