Threads

ISO METRIC THREADING

threads_iso

  P (mm) Screw with 6g tolerance Nut screw with 6H tolerance
Ø major d Ø pitch dm Ø core dn Ø pitch Dm Ø core DN
max min max min max min max min max min
M4 0.7 3.978 3.383 3.523 3.433 3.220 2.979 3.545 3.663 3.242 3.422
M5 0.8 4.976 4.826 4.456 4.361 4.110 3.842 4.480 4.605 4.134 4.334
M6 1.0 5.974 5.974 5.324 5.212 4.891 4.563 5.350 5.500 4.917 5.153
M8 1.25 7.972 7.760 7.160 7.042 6.619 6.230 7.188 7.348 6.647 6.912
M10 1.5 9.968 9.732 8.994 8.862 8.344 7.888 9.026 9.206 8.376 8.676
M12 1.75 11.966 11.701 10.829 10.679 10.072 9.543 10.863 11.063 10.106 10.441
M14 2.0 13.962 13.682 12.663 12.503 11.797 11.204 12.701 12.913 11.835 12.210
M16 2.0 15.962 15.682 14.663 14.503 13.797 13.204 14.701 14.913 13.835 14.210
M18 2.5 17.958 17.623 16.334 16.164 15.252 14.541 16.376 16.600 15.294 15.744
M20 2.5 19.958 19.623 18.344 18.164 17.252 16.541 18.376 18.600 17.294 17.744

UK WHITWORTH THREADING (BSW-BSF)

threads_bs

 

  Thread per inch Major
diameter d
Pitch
diameter dm
Core
diameter dn
BSW
1/4 (0.25) 20 0.2500 0.2180 0.1860
5/16 (0.3125) 18 0.3125 0.2769 0.2413
3/8 (0.375) 16 0.3750 0.3350 0.2950
1/2 (0.5) 12 0.5000 0.4466 0.3932
5/8 (0.625) 11 0.6250 0.5668 0.5086
3/4 (0.75) 10 0.7500 0.6860 0.6220
 
BSF
1/4 (0.25) 26 0.2500 0.2254 0.2008
5/16 (0.3125) 22 0.3125 0.2834 0.2534
3/8 (0.375) 20 0.3750 0.3430 0.3110
1/2 (0.5) 16 0.5000 0.4600 0.4200
5/8 (0.625) 14 0.6250 0.5793 0.5336
3/4 (0.75) 12 0.7500 0.6966 0.6432

Fractions (of an inch) are expressed as decimals in the table.

 

AMERICAN STANDARD THREADING UNC-UNF

threads_unc

 

  Threads
per
inch
Screw with tolerance 2 Nut screw with tolerance 2B
Ø major d Ø pitch dm Ø core dn Ø minor D Ø pitch Dm Ø major Dn
max min max min max min min max min max min max
UNC
8-32 32 0.1631 0.1571 0.1428 0.1399 0.1259   0.130 0.139 0.1437 0.1475 0.1640  
10-24 24 0.1890 0.1818 0.1619 0.1586 0.1394   0.145 0.156 0.1629 0.1692 0.1900  
1/4 20 0.2489 0.2408 0.2164 0.2127 0.1894   0.196 0.207 0.2175 0.2224 0.2500  
5/16 18 0.3113 0.3026 0.2752 0.2712 0.2452   0.252 0.265 0.2764 0.2817 0.3125  
3/8 16 0.3737 0.3643 0.3331 0.3287 0.2992   0.307 0.321 0.3344 0.3401 0.3750  
1/2 13 0.4985 0.4876 0.4485 0.4435 0.4069   0.417 0.434 0.4500 0.4565 0.5000  
5/8 11 0.6234 0.6113 0.5644 0.5589 0.5152   0.527 0.546 0.5660 0.5732 0.6250  
3/4 10 0.7482 0.7353 0.6832 0.6773 0.6291   0.642 0.663 0.6850 0.6927 0.7500  
1 8 0.9980 0.9830 0.9168 0.9100 0.8492   0.865 0.890 0.9188 0.9276 1.0000  
 
UNF
8-32 36 0.1632 0.1577 0.1452 0.1424 0.1301   0.134 0.142 0.1460 0.1496 0.1640  
10-32 32 0.1891 0.1831 0.1688 0.1658 0.1519   0.156 0.164 0.1697 0.1736 0.1900  
1/4 28 0.2490 0.2392 0.2258 0.2208 0.2064   0.211 0.220 0.2268 0.2333 0.2500  
5/16 24 0.3114 0.3042 0.2843 0.2806 0.2618   0.267 0.277 0.2854 0.2902 0.3125  
3/8 24 0.3739 0.3667 0.3468 0.3430 0.3243   0.330 0.340 0.3479 0.3528 0.3750  
1/2 20 0.4987 0.4906 0.4662 0.4619 0.4392   0.446 0.457 0.4675 0.4731 0.5000  
5/8 18 0.6236 0.6105 0.5875 0.5805 0.5575   0.565 0.578 0.5889 0.5980 0.6250  
3/4 10 0.7485 0.7391 0.7079 0.7029 0.6740   0.682 0.696 0.7094 0.7159 0.7500  
1 12 0.9982 0.9868 0.9441 0.9382 0.8890   0.910 0.928 0.9459 0.9535 1.0000  

Fractions (of an inch) are expressed as decimals in the table.