Nominal Diameter NC & UNC NF & UNF NPT & NPS NS NEF Fractional TPI Drill Size in mm TPI Drill Size in mm TPI Drill Size in mm TPI Drill Size in mm TPI Taping with Reamer Taping without Reamer 1/16" - - - -- 27 6.00 6.30 64 1.20 - 3/32" - -- - - - - - 48 1.85 - 1/8" - - - - 27 8.40 8.70 40 2.60 - 5/32" - - - - - - - 32 & 35 3.20 & 3.30 - 3/16" - - - - - - - 24 & 32 3.80 & 4.00 - 7/32" - - - - - - - 24 & 32 4.50 & 4.80 - 1/4" 20 5.10 28 5.50 18 10.70 11.10 24 &32 5.30 &  5.60 32 5/16" 18 6.60 24 6.90 - - - 20 & 32 6.70 & 7.20 32 3/8" 16 8.00 24 8.50 18 14.25 14.50 20 8.30 32 7/16" 14 9.40 20 9.90 - - - 24 10.00 28 1/2" 13 10.80 20 11.50 14 17.50 18.00 12 & 24 10.50 & 11.50 28 9/16" 12 12.20 18 12.90 - - - - - 24 5/8" 11 13.50 18 14.50 - - - 12 13.90 24 11/16" - - - - - - - 11 & 16 15.00 & 15.90 24 3/4" 10 16.50 16 17.50 14 22.75 23.25 12 16.70 20 13/16" - - - - - - - - - 20 7/8" 9 19.50 14 20.40 -- - - 12 20.20 20 15/16" - 19.50 14 20.40 - - - 12 20.20 20 1" 8 22.25 12 23.25 11.50 28.50 29.00 14 23.50 20 1.1/8" 7 25.00 12 26.50 - - - - - 18 1.1/4" 7 28.00 12 29.50 11.50 37.50 38.00 - - 18 1.3/8" 6 3.075 12 32.75 - - - - - 18 1.1/2" 6 34.00 12 36.00 11.50 43.50 44.00 - - 18 1.5/8" - - - - - - - 5.5 36.90 18 1.3/4" 5 39.50 - - - - - - - 16 1.7/8" - - - - - - - 5 42.90 - 2" - - - - 11.50 55.00 56.00 - - 16   NC NF U.N.C U.N.F Size no. TPI Drill Size in mm TPI Drill Size in mm TPI Drill Size in mm TPI Drill Size in mm 0 - - 80 1.25 - - - - 1 34 1.55 72 1.55 -- - - - 2 56 1.85 64 1.90 - - - - 3 48 2.10 56 2.15 - - - - 4 4. 2.35 48 2.40 40 2.35 - - 5 40 2.65 44 2.70 - - - - 6 32 2.85 40 2.95 32 2.85 - - 8 32 3.50 36 3.50 32 3.50 - - 10 24 3.90 32 4.10 24 3.90 32 4.10 12 24 4.50 28 4.70 - - - -

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