UNC THREAD CHART

UNC thread chart including major diameter, pitch diameter and minor diameter dimensions of UNC screw threads according to ASME B1.1 standard.

External Thread Dimensions for UNC Screw Threads:

UNC Thread Chart — External Thread Dimensions
Nominal
Diameter
TPI Tolerance
Class
Major Dia. Pitch Dia. Max.
Minor
Diameter
max. min. max. min.
#1 - 64 64 2A 0.0724 0.0686 0.0623 0.0603 0.0538
#2 - 56 56 2A 0.0854 0.0813 0.0738 0.0717 0.0642
#3 - 48 48 2A 0.0983 0.0938 0.0848 0.0825 0.0734
#4- 40 40 2A 0.1112 0.1061 0.0950 0.0925 0.0814
#5 - 40 40 2A 0.1242 0.1191 0.1080 0.1054 0.0944
#6 - 32 32 2A 0.1372 0.1312 0.1169 0.1141 0.1000
#8 - 32 32 2A 0.1631 0.1571 0.1428 0.1399 0.1259
#10 - 24 24 2A 0.1890 0.1818 0.1619 0.1586 0.1394
#12 - 24 24 2A 0.2150 0.2078 0.1879 0.1845 0.1654
1/4” - 20 20 2A 0.2489 0.2408 0.2164 0.2127 0.1894
5/16" - 18 18 2A 0.3113 0.3026 0.2752 0.2712 0.2452
3/8" - 16 16 2A 0.3737 0.3643 0.3331 0.3287 0.2992
7/16" - 14 14 2A 0.4361 0.4258 0.3897 0.3850 0.3511
1/2" - 13 13 2A 0.4985 0.4876 0.4485 0.4435 0.4069
Nominal
Diameter
TPI Tolerance
Class
Major Dia. Pitch Dia. Max.
Minor
Diameter
max. min. max. min.
9/16" - 12 12 2A 0.5609 0.5495 0.5068 0.5016 0.4617
5/8" - 11 11 2A 0.6234 0.6113 0.5644 0.5589 0.5152
3/4" - 10 10 2A 0.7482 0.7353 0.6832 0.6773 0.6291
7/8" - 9 9 2A 0.8731 0.8592 0.8009 0.7946 0.7408
1" - 8 8 2A 0.9980 0.9830 0.9168 0.9100 0.8492
1 1/8" - 7 7 2A 1.1228 1.1064 1.0300 1.0228 0.9527
1 1/4" - 7 7 2A 1.2478 1.2314 1.1550 1.1476 1.0777
1 3/8" - 6 6 2A 1.3726 1.3544 1.2643 1.2563 1.1742
1 1/2" - 6 6 2A 1.4976 1.4794 1.3893 1.3812 1.2992
1 3/4" - 5 5 2A 1.7473 1.7268 1.6174 1.6085 1.5092
2" - 4 1/2 4.5 2A 1.9971 1.9751 1.8528 1.8433 1.7324
2 1/4" - 4 1/2 4.5 2A 2.2471 2.2251 2.1028 2.0931 1.9824
2 1/2" - 4 4 2A 2.4969 2.4731 2.3345 2.3241 2.1992
2 3/4" - 4 4 2A 2.7468 2.7230 2.5844 2.5739 2.4491
3" - 4 4 2A 2.9968 2.9730 2.8344 2.8237 2.6991
3 1/4" - 4 4 2A 3.2467 3.2229 3.0843 3.0734 2.9490
3 1/2" - 4 4 2A 3.4967 3.4729 3.3343 3.3233 3.1990
3 3/4" - 4 4 2A 3.7466 3.7228 3.5842 3.5730 3.4489
4" - 4 4 2A 3.9966 3.9728 3.8342 3.8229 3.6989
Nominal
Diameter
TPI Tolerance
Class
max. min. max. min. Max.
Minor
Diameter
Major Dia. Pitch Dia.
 

Internal Thread Dimensions for UNC Screw Threads:

UNC Thread Chart — Internal Thread Dimensions
Nominal
Diameter
TPI Tolerance
Class
Major Dia. Pitch Dia. Minor Dia.
min. max. min. max.  min
#1 - 64 64 2B 0.0730 0.0655 0.0629 0.0623 0.0561
#2 - 56 56 2B 0.0860 0.0772 0.0744 0.0737 0.667
#3 - 48 48 2B 0.0990 0.0855 0.0855 0.0845 0.0764
#4- 40 40 2B 0.1120 0.0991 0.0958 0.0939 0.0849
#5 - 40 40 2B 0.1250 0.1121 0.1088 0.1062 0.0979
#6 - 32 32 2B 0.1380 0.1214 0.1177 0.1140 0.1040
#8 - 32 32 2B 0.1640 0.1475 0.1437 0.1390 0.1300
#10 - 24 24 2B 0.1900 0.1672 0.1629 0.1560 0.1450
#12 - 24 24 2B 0.2160 0.1933 0.1889 0.1810 0.1710
1/4” - 20 20 2B 0.2500 0.2224 0.2175 0.2070 0.1960
5/16" - 18 18 2B 0.3125 0.2817 0.2764 0.2650 0.2520
3/8" - 16 16 2B 0.3750 0.3401 0.3344 0.3210 0.3070
7/16" - 14 14 2B 0.4375 0.3972 0.3911 0.3760 0.3600
1/2" - 13 13 2B 0.5000 0.4565 0.4500 0.4340 0.1470
Nominal
Diameter
TPI Tolerance
Class
Major Dia. Pitch Dia. Minor Dia.
min. max. min. max. min.
9/16" - 12 12 2B 0.5625 0.5125 0.5084 0.4900 0.4720
5/8" - 11 11 2B 0.6250 0.5732 0.5660 0.5460 0.5270
3/4" - 10 10 2B 0.7500 0.6927 0.6850 0.6630 0.6420
7/8" - 9 9 2B 0.8750 0.8110 0.8028 0.7780 0.7550
1" - 8 8 2B 1.0000 0.9276 0.9188 0.8900 0.8650
1 1/8" - 7 7 2B 1.1250 1.0416 1.0322 0.9980 0.9700
1 1/4" - 7 7 2B 1.2500 1.1668 1.1572 1.1230 1.0950
1 3/8" - 6 6 2B 1.3750 1.2771 1.2667 1.2250 1.1950
1 1/2" - 6 6 2B 1.5000 1.4075 1.3917 1.3500 1.3200
1 3/4" - 5 5 2B 1.7500 1.6317 1.6201 1.5680 1.5340
2" - 4 1/2 4.5 2B 2.0000 1.8681 1.8557 1.7950 1.7590
2 1/4" - 4 1/2 4.5 2B 2.2500 2.1183 2.1057 2.0450 2.0090
2 1/2" - 4 4 2B 2.5000 2.3511 2.3376 2.2670 2.2290
2 3/4" - 4 4 2B 2.7500 2.6013 2.5876 2.5170 2.4790
3" - 4 4 2B 3.0000 2.8515 2.8376 2.7670 2.7290
3 1/4" - 4 4 2B 3.2500 3.1017 3.0876 3.0170 2.9790
3 1/2" - 4 4 2B 3.5000 3.3519 3.3376 3.2670 3.2290
3 3/4" - 4 4 2B 3.7500 3.6021 3.5876 3.5170 3.4790
4" - 4 4 2B 4.0000 3.8523 3.8376 3.7670 3.7290
Nominal
Diameter
TPI Tolerance
Class
min. max. min. max. min.
Major Dia. Pitch Dia. Minor Dia.

General Note: All dimensions expressed in inches.

Supplements:

Reference:

  • ASME B1.1-2003, Unified Inch Screw Threads (UN and UNR Thread Form)
  • Oberg, E. , Jones ,F.D. , Horton H.L. , Ryffel H.H., (2016) . Machinery's Handbook . 30th edition.  Industrial Press Inc.
  • Oberg, E. , Jones ,F.D. , Horton H.L. , Ryffel H.H., (2012) . Machinery's Handbook . 29th edition.  Industrial Press Inc.