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Unified Coarse

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 TPI 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. 1 64 0.073 0.0629 0.0538 0.0561 1.55 1.95
No.2 56 0.086 0.0744 0.0641 0.0667 1.85 2.3
No. 3 48 0.099 0.0855 0.0734 0.0764 2.1 2.65
No.4 40 0.112 0.0958 0.0813 0.0849 2.35 2.95
No. 5 40 0.125 0.1088 0.0943 0.0979 2.65 3.3
No.6 32 0.138 0.1177 0.0997 0.1042 2.85 3.6
No 8 32 0.164 0.1437 0.1257 0.1302 3.5 4.3
No. 10 24 0.19 0.1629 0.1389 0.1449 3.9 4.9
No. 12 24 0.216 0.1889 0.1649 0.1709 4.5 5.6
1 4 20 0.25 0.2175 0.1887 0.1959 5.1 6.5
5/16 18 0.3125 0.2764 0.2443 0.2524 6.6 8.1
3/8 16 0.375 0.3344 0.2983 0.3073 8 9.7
7/16 14 0.4375 0.3911 0.3499 0.3602 9.4 11.3
1/2 13 0.5 0.45 0.4056 0.4167 10.8 13
9/16 12 0.5625 0.5084 0.4603 0.4723 12.2 14.5
5/8 11 0.625 0.566 0.5135 0.5266 13.5 16.25
3/4 10 0.75 0.685 0.6273 0.6417 16.5 19.25
7/8 9 0.875 0.8028 0.7387 0.7547 19.5 22.5
1 8 1 0.9188 0.8466 0.8647 22.25 25.75
1,1/8 7.00 1.125 1.0322 0.9497 0.9704 25 29
1,1/4 7.00 1.25 1.1572 1.0747 1.0954 28 32
1,3/8 6 1.375 1.2667 1.1705 1.1946 30.75 35.5
1,1/2 6.00 1.5 1.3917 1.2955 1.3196 34 38.5
1,3/4 5 1.75 1.6201 1.5046 1.5335 39.5 45
2 4.50 2 1.8557 1.7274 1.7594 45 51
2,1/4 4.50 2.25 2.1057 1.9774 2.0094 52 58
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Last modified: SolFlu  Fri, 26 Jun 2009 21:15:35 GMT