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Technical

Thread Dimensions

Tapered Threads Straight Threads
Size Pipe OD NPT BSPTr Acme 3A ODM -- Outside Diameter of
TPI TPI TPI ODM (max) IDF (min) the Male
1/8" .405 27 28 IDF -- Inside Diameter of the
1/4" .504 18 19 Female
3/8" .675 18 19
1/2" .840 14 14 TPI -- Threads Per Inch
3/4" 1.050 14 14
1" 1.315 11.5 11 8 1.462 1.352 GHT (3/4") -- 1.0625 ODM,
1-1/4" 1.660 11.5 11 11-1/2 TPI
1-1/2" 1.900 11.5 11 8 1.994 1.884
2" 2.375 11.5 11 8 2.526 2.416 NPT = National Pipe Taper
2-1/2" 2.875 8 11 8 3.058 2.948 BS = British Standard
3" 3.500 8 11 8 3.590 3.480
4" 4.500 8 11 6 4.695 4.544
5" 5.563 8 11
6" 6.625 8 11
8" 8.625 8
10" 10.750 8
12" 12.750 8

Normal Engagement Length of NPT Thread in Inches (A) *

Pipe Size A Pipe Size A
1/8" 1/4" 2-1/2" 15/16"
1/4" 3/8" 3" 1"
3/8" 3/8" 4" 1-1/8"
1/2" 1/2" 5" 1-1/4"
3/4" 9/16" 6" 1-5/16"
1" 11/16" 8" 1-7/16"
1-1/4" 11/16" 10" 1-5/8"
1-1/2" 11/16" 12" 1-3/4" * Dimensions given do not allow for
2" 3/4" variations in tapping or threading.

Identifying Threads

DIN knuckle threads for sanitary applications have a unique The threads for RJT fttings are British Standard Whitworth.
round shape making them easy to identify. There is a 30° These look similar to straight threads but have a 55° angle and
included angle between the threads. There are 6 to 8 threads small radii on the tips rather than the fat tips and 60° angle
per inch for sanitary fttings. Measuring the ID of the round found on U.S. standard straight threads. There are 6 to 8
nut or the OD of the threads on the weld liner will help with threads per inch for the sanitary fttings.
identifcation. As Dixon Sanitary will be offering inch sizes, the
best size identifcation is the OD of the tube.
277 Z

Dixon Sanitary 2014 800.789.1718