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Thread Standard Practices
 

 
Nominal
Pipe
Size		 Outside
Diameter
of
Pipe
(D)		 Threads
(Inches)
(n)		 Pitch of
Thread		 Pitch
Diameter at beginning of External
Thread		 Handtight Engagement Effective Thread, External
Length˛ (L1) Diameter
(E1)		 Length (L2) Diameter
(E2)
Inch Threads Inch Threads
1 2 3 4 5 6 7 8 9 10 11
 
1/2 0.840 14 0.07143 0.75843 0.320 4.48 0.77843 0.5337 7.47 0.79179
3/4 1.050 14 0.07143 0.96768 0.339 4.75 0.98887 0.5457 7.64 1.00179
1 1.315 11.5 0.08696 1.21363 0.400 4.60 1.23863 0.6828 7.85 1.25630
1 1/4 1.660 11.5 0.08686 1.55713 0.420 4.83 1.58338 0.7068 8.13 1.60130
1 1/2 1.900 11.5 0.08696 1.79609 0.420 4.83 1.82234 0.7235 8.32 1.84130
2 2.375 11.5 0.08696 2.26902 0.436 5.01 2.29627 0.7565 8.70 2.31630
2 1/2 2.875 8 0.12500 2.71953 0.682 5.46 2.76216 1.1375 9.10 2.79062
3 3.500 8 0.12500 3.34062 0.766 6.13 3.38850 1.2000 9.60 3.41562
3 1/2 4.000 8 0.12500 3.83750 0.821 6.57 3.88881 1.2500 10.00 3.91562
4 4.500 8 0.12500 4.33438 0.844 6.75 4.38712 1.3000 10.40 4.41562
5 5.563 8 0.12500 5.39073 0.937 7.50 5.44929 1.4063 11.25 5.47862
6 6.625 8 0.12500 6.44609 0.958 7.66 6.50597 1.5125 12.10 6.54062
8 8.625 8 0.12500 8.43359 1.063 8.50 8.50003 1.7125 13.70 8.54062
10 10.750 8 0.12500 10.54531 1.210 9.68 10.62094 1.9250 15.40 10.66562
12 12.750 8 0.12500 12.53281 1.360 10.88 12.61781 2.1250 17.00 12.66562
 

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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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