Note! Pipe sizes do not refer to any physical dimensions. The outside diameter of a pipe or fitting must be measured and compared to a table for size identification. A 3/4" NPT pipe thread has an outside diameter - OD - of 1.050 inches. Each thread size has a defined number of threads per inch - TPI, or pitch. The 3/4" NPT pipe thread has 14 threads per inch. Both the TPI and OD of the thread are required for positive identification of thread size because more than one size have the same TPI.
For full table with Tap Drill Sizes - rotate the screen!
|TPI||Approximate Length of Thread (inches)||Approximate Number of Threads to be Cut||Approximate Total thread Makeup, Hand and Wrench (inches)||Nominal Outside Diameter Pipe|
|3-1/2"||8||1 5/8||13||1 1/16||4.000||3-3/4|
|4"||8||1 5/8||13||1 1/16||4.500||4-1/4|
|5"||8||1 3/4||14||1 3/16||5.563||5-9/32|
|6"||8||1 3/4||14||1 3/16||6.625||6-11/32|
|8"||8||1 7/8||15||1 5/16||8.625|
|12"||8||2 1/8||17||1 5/8||12.750|
1) The taper rate is 1 in 16 inch (3/4 inch in a foot or 62.5 mm in a meter)
NPT threads are not interchangeable with NPS - National Pipe Straight - threads.
Example - Typical Designation of NPT thread:
NPT threads may look similar to ISO 7-1 threads. However, ISO and NPT threads should not be mixed. ISO threads have 55o taper angle versus 60o for NPT. The NPT root and crest configurations are also different from ISO. For ISO threads pitch is usually measured in millimeters (may be expressed in Inch). The pitch is different.
Note that both NPT and NPS have the same thread angle, shape, and pitch (threads per inch). However, NPT threads are tapered and NPS threads are straight (parallel). Both threads have a 60° included angle and flat peaks and valleys.
Sizes and dimensions of pipes and tubes, and their fittings - inside and outside diameter, weight and more.
Thread data - metric, unified, ACME and others.
ANSI provides a forum for development of American national standards.
NPS pressure tight straight pipe threads with lubricant or sealer.
British Brass Thread is an imperial unit based screw thread.
British Standard Cycle is a British Imperial screw thread standard.
BSPT - British Standard Pipe Taper threads & BSP or BSPF - British Standard Pipe Parallel (Straight) threads.
Pipe threads where pressure tight joints are made on the threads - Part 1: Taper external threads and parallel internal threads.
Requirements for thread form, dimensions, tolerances and designation for fastening pipe threads, thread sizes.
Metric threads spark plugs according ISO 28741.
Pressure-tight joints made on the pipe threads.
Dimensions of metric threads according ISO 724.
Minimum ultimate tensile and proof loads for metric bolts with coarse or fine threads.
NPT - Briggs Standard Pipe threads - Taps and Drill Sizes.
Applied threaded standards used for piping connections.
Piping thread standards.
BSPP (G) - British Standard Pipe Parallel and BSPT (R/Rp) – British Standard Tapered Pipe for pipes and tapered threads - G/R/Rp.
Taps and drill sizes used for Whitworth - ISO 7 and ISO 228 threads.
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