21. Thread Series Intro Unified Threads Conversion Table Size Nominal Dia. Threads per inchColumnColumn12inchmmCoarseFineExtra FineConstant pitch seriesUNCUNFUNEF4UN6UN8UN12UN16UN20UN28UN32UNThreads perinch(25.4mm)Pitch(mm) No. 0 0.0600 1.524 80No. 10.07301.8546472 100 0.2540800.3175 SP No. 2 0.0860 2.184 56 64 72 0.3528 No. 3 0.0990 2.515 48 56No. 40.11202.8454048No. 50.12503.1754044No. 60.13803.5053240No. 80.16404.1663236No. 100.19004.8262432No. 120.21605.486242832640.3969600.4233UNCUNCUNFUNFUNEF560.4536480.5292440.5773400.6350360.7056SL 1/4 0.2500 6.350 20 28 32 UNC UNF UNEF 32 0.7938 5/16 0.3125 7.938 18 24 32 20 28 UNEF 28 0.9071 3/8 0.3750 9.525 16 24 32 UNC 20 28 UNEF 27 0.9407 7/16 0.4375 11.112 14 20 28 16 UNF UNEF 32 24 1.0583 1/2 0.5000 12.700 13 20 289/160.562514.288121824 16 UNF UNEF 32UNC16202832 20 1.2700191.3368 PO 5/8 0.6250 15.875 11 18 24 12 16 20 28 32 18 1.4111 11/16 0.6875 17.462 24 12 16 20 28 32 16 1.5875 3/4 0.7500 19.050 10 16 2013/160.812520.638207/80.875022.2259142015/160.937523.8122011.000025.400812201 1/161.062526.988181 1/81.125028.575712181 3/161.187530.1621812UNFUNEF28321216UNEF28321216UNEF28321216UNEF2832UNCUNF16UNEF28328121620288UNF162028812162028141.8143131.9538122.116711.52.2087112.3091102.540092.8222ST 1 1/4 1.2500 31.750 7 12 18 8 UNF 16 20 28 8 3.1750 1 5/16 1.3125 33.338 18 8 12 16 20 28 7 3.6286 1 3/8 1.3750 34.925 6 12 18 UNC 8 UNF 16 20 28 6 4.2333 1 7/16 1.4375 36.512 18 6 8 12 16 20 28 5 5.0800 1 1/2 1.5000 38.100 6 12 18 UNC 8 UNF 16 20 281 9/161.562539.68818681216204.55.644446.3500ROLL 1 5/8 1.6250 41.275 18 6 8 12 16 20 1 11/16 1.6875 42.862 18 6 8 12 16 20 1 3/4 1.7500 44.450 5 6 8 12 16 20 1 13/16 1.8125 46.038 6 8 12 16 20 1 7/8 1.8750 47.625 6 8 12 16 20 1 15/16 1.9375 49.212 6 8 12 16 20 2 2.0000 50.800 4.5 6 8 12 16 202 1/82.125053.97568121620 CARBIDE 2 1/4 2.2500 57.150 4.5 6 8 12 16 20 2 3/8 2.3750 60.325 6 8 12 16 20 2 1/2 2.5000 63.500 4 UNC 6 8 12 16 20 2 5/8 2.6250 66.675 4 6 8 12 16 20 2 3/4 2.7500 69.850 4 UNC 6 8 12 16 20 2 7/8 2.8750 73.025 4 6 8 12 16 2033.000076.2004UNC68121620 LONG 3 1/8 3.1250 79.375 4 6 8 12 16 3 1/4 3.2500 82.550 4 UNC 6 8 12 16 3 3/8 3.3750 85.725 4 6 8 12 16 3 1/2 3.5000 88.900 4 UNC 6 8 12 16 3 5/8 3.6250 92.075 4 6 8 12 16 3 1/4 3.7500 95.250 4 UNC 6 8 12 163 7/83.875098.4254681216 HAND 4 4.0000 101.600 4 UNC 6 8 12 164 1/84.1250104.7754681216 TAPS 4 1/4 4.2500 107.950 4 6 8 12 16 4 3/8 4.3750 111.125 4 6 8 12 16 4 1/2 4.5000 114.300 4 6 8 12 16 4 5/8 4.6250 117.475 4 6 8 12 16 4 3/4 4.7500 120.650 4 6 8 12 16 4 7/8 4.8750 123.825 4 6 8 12 1655.0000127.0004681216 EG (STI) 5 1/8 5.1250 130.175 4 6 8 12 16 5 1/4 5.2500 133.350 4 6 8 12 16 5 3/8 5.3750 136.525 4 6 8 12 16 5 1/2 5.5000 139.700 4 6 8 12 16 5 5/8 5.6250 142.875 4 6 8 12 165 3/45.7500146.0504681216 SPECIAL 5 7/8 5.8750 149.225 4 6 8 12 1666.0000152.4004681216 THREADS,GAUGES General size list of metric trapezoidal threads THREAD 1.5 2 3 4 5 6 7 8 10 12Tr 181.5 MILLS Tr 19 1.5 2 Tr 10 1.5 2 Tr 11 2 3 Tr 12 2 3 Tr 14 2 3Tr 162 4 DIES Tr 18 2 4 Tr 20 2 4 Tr 22 3 5 8 Tr 24 3 5 8 Tr 26 3 5 8Tr 28358 CENTER Tr 30 3 6 10Tr 323610 DRILLS Tr 34 3 6 10 Tr 36 3 6 10 Tr 38 3 7 10 Tr 40 3 7 10 Tr 42 3 7 10 Technical Tr 44 3 7 12Tr 463812 info Tr 48 3 8 12 709