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Thread Standard Practices
 

 
Nominal
Pipe
Size		 Length L1 Plane
to L 2 Plane
External Thread
(L2 - L1)		 Wrench Makeup Length for Internal Thread Vanish Thread
(V)		 Overall
Length
External
Thread
(L4)		 Nominal Complete
External Threads		 Height
of
Thread
(h)		 Increase
in diameter/
Thread
(h)		 Basic(6)
Minor Diameter
at small
End of
Pipe (Ko)
Inch Thread Length (L3) Diameter
(E3)		 Inch Thread Length
L5)		 Diameter
(E5)
Inch Thread
1 12 13 14 15 16 17 18 19 20 21 22 23 24
 
1/2 0.2137 2.99 0.2143 3 0.74504 0.2478 3.47 0.7815 0.3909 0.78286 0.05714 0.00446 0.7013
3/4 0.2067 2.89 0.2143 3 0.95429 0.2478 3.47 0.7935 0.4029 0.99286 0.05714 0.00446 0.9105
1 0.2828 3.25 0.2609 3 1.19733 0.3017 3.47 0.9845 0.5089 1.24543 0.06957 0.00543 1.1441
1 1/4 0.2868 3.30 0.2609 3 1.54083 0.3017 3.47 1.0085 0.5329 1.59043 0.06857 0.00543 1.4876
1 1/2 0.3035 3.49 0.2609 3 1.77978 0.3017 3.47 1.0252 0.5496 1.83043 0.06957 0.00543 1.7265
2 0.3205 3.69 0.2609 3 2.25272 0.3017 3.47 1.0582 0.5826 2.30543 0.06957 0.00543 2.1995
2 1/2 0.4555 3.64 0.2500 2 2.70391 0.4337 3.47 1.5712 0.8875 2.77500 0.100000 0.00781 2.6195
3 0.4340 3.47 0.2500 2 3.32500 0.4337 3.47 1.6337 0.9500 3.40000 0.100000 0.00781 3.2406
3 1/2 0.4290 3.43 0.2500 2 3.82188 0.4337 3.47 1.6837 1.0000 3.90000 0.100000 0.00781 3.7375
4 0.4560 3.65 0.2500 2 4.31875 0.4337 3.47 1.7337 1.0500 4.40000 0.100000 0.00781 4.2344
5 0.4693 3.75 0.2500 2 5.37511 0.4337 3.47 1.8400 1.1563 5.46300 0.100000 0.00781 5.2907
6 0.5545 4.44 0.2500 2 6.43047 0.4337 3.47 1.9462 1.2625 6.52500 0.100000 0.00781 6.3461
8 0.6495 5.20 0.2500 2 8.41797 0.4337 3.47 2.1462 1.4625 8.52500 0.100000 0.00781 8.3336
10 0.7150 5.72 0.2500 2 10.52969 0.4337 3.47 2.3587 1.6750 10.65000 0.100000 0.00781 10.4453
12 0.7650 6.12 0.2500 2 12.51719 0.4337 3.47 2.5587 1.8750 12.65000 0.100000 0.00781 12.4328
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Notes:
  1. The basic dimensions of the American National Standard Taper Pipe Thread are given in inches to four or five decimal places.  While this implies a greater degree of precision than is ordinarily attained, these dimensions are the basic gage dimensions and are so expressed for the purpose of eliminating errors in computations.
  2. Also length of thin ring gage and length from gagging notch to small end of plug gage.
  3. Also pitch diameter at gaging notch (handtight plane).
  4. Also length of plug gage.
  5. The length L5 from the end of the pipe determines the plane beyond which the thread form is incomplete at the crest.  The next two threads are complete at the root.  At this plane the cone formed by the crests of the thread intersects the cylinder forming the external surface of the pipe.  L5 = L2 - 2P
  6. Given as information for use in selecting tap drills.  (See Appendix)
  7. Military Specification MIL - P - 7105 gives the wrench makeup as three threads for sizes 3 and smaller.  The E3 dimensions are as follows:  Nominal pipe size 2 1/2 = 2.69609 and size 3 = 3.31719; sizes 2 and smaller same as above, column 16.
  8. Reference Dimension
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