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Unified Fine

Thread Form

Unified Thread Form
  • p = Pitch = 1/TPI
  • hn = Height of internal thread = 0.54127p
  • hs = Height of external thread = 0.61344p
  • r = Basic Radius = 0.1443p

Thread Tables

Nominal Size T.P.I. Basic Major Diameter Basic Effective Diameter Basic Minor Diameter of External Threads Basic Minor Diameter of Internal Threads Tapping Drill Clearance Drill
(n/a) (n/a) (inch) (inch) (inch) (inch) (mm) (mm)
No. 0 80 0.06 0.0519 0.0447 0.0465 1.25 1.6
No. 1 72 0.073 0.064 0.056 0.058 1.55 1.96
No. 2 64 0.086 0.0759 0.0668 0.0691 1.9 2.3
No. 3 56 0.099 0.0874 0.0771 0.0797 2.15 2.65
No. 4 48 0.112 0.0985 0.0864 0.0894 2.4 2.95
No. 5 44 0.125 0.1102 0.0971 0.1004 2.7 3.3
No. 6 40 0.138 0.1218 0.1073 0.1109 2.95 3.6
No. 8 36 0.164 0.146 0.1299 0.1339 3.5 4.3
No. 10 32 0.19 0.1697 0.1517 0.1562 4.1 4.9
No. 12 28 0.216 0.1928 0.1722 0.1773 4.7 5.6
1/4 28 0.25 0.2268 0.2062 0.2113 5.5 6.5
5/16 24 0.3125 0.2854 0.2614 0.2674 6.9 8.1
3/8 24 0.375 0.3479 0.3239 0.3299 8.5 9.7
7/16 20 0.4375 0.405 0.3762 0.3834 9.9 11.3
1/2 20 0.5 0.4675 0.4387 0.4459 11.5 13
9/16 18 0.5625 0.5264 0.4943 0.5024 12.9 14.5
5/8 18 0.625 0.5889 0.5568 0.5649 14.5 16.25
3/4 16 0.75 0.7094 0.6733 0.6823 17.5 19.25
7/8 14 0.875 0.8286 0.7874 0.7977 20.4 22.5
1 12 1 0.9459 0.8978 0.9098 23.25 25.75
1, 1/8 12 1.125 1.0709 1.0228 1.0348 26.5 29
1, 1/4 12 1.25 1.1959 1.1478 1.1598 29.5 32
1, 3/8 12 1.375 1.3209 1.2728 1.2848 32.75 35.5
1, 1/2 12 1.5 1.4459 1.3978 1.4098 36 38.5
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Last modified: SolFlu  Fri, 26 Jun 2009 21:15:35 GMT