NPT Thread & NPT Thread Dimensions with Size Chart

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NPT Thread & NPT Thread Dimensions with Size Chart

Feb 07, 2023

What is NPT Thread & NPT Thread Dimensions

NPT (National Pipe Taper) is a type of tapered thread commonly used in North America for joining pipes and fittings. NPT threads have a tapered design that provides a mechanical seal between the male and female threads, allowing for a secure and leak-proof connection.

NPT thread dimensions are standardized in the ASME B1.20.1 specification and include both the thread crest and root diameter, as well as the thread pitch. The dimensions vary based on the size of the pipe, with larger pipes having a larger thread diameter and a finer pitch. NPT threads are available in sizes ranging from 1/16" to 6".

It's important to note that NPT threads are not compatible with other types of thread standards, such as BSP (British Standard Pipe) or ISO (International Organization for Standardization). When selecting fittings and connections, it's crucial to ensure that the appropriate thread standard is used for the intended application.

What is NPT Thread - What Does NPT Thread Mean

NPT stands for National Pipe Thread, also known as American National Standard Pipe Thread, it is a U.S technical standard for measuring screw threads on threaded pipes and pipe fittings. NPT threads can be divided into tapered and straight thread series for different purposes. NPT is defined by ANSI/ASME standard B1.20.1.

Characteristics of NPT Threads (National Pipe Thread Tapered):

– Angle between the taper and the center axis of the pipe≈1.7899°≈ 1°47′24″

– Truncation of roots and crests are flat

– 60°thread angle

– Pitch is measured in threads per inch (TPI)

Pipe threads can be designed to various types for suiting both with or without thread sealants. For example, the National Standard Taper Pipe Thread allows them to form a seal when tightened, the larger diameter keeps compressing into a smaller diameter and finally forms a seal. 

Types of NPT Threads:

NPT: National pipe taper

NPS: National pipe straight

NPSC: National pipe straight-coupling

NPSF: National pipe straight-fuel

NPSH: National pipe straight-hose

NPSI: National pipe straight-intermediate

NPSL: National pipe straight-locknut

NPSM: National pipe straight-mechanical

NPTF: National pipe taper-fuel

NPTR: National pipe taper-railing

NPT threads can also be referred to as MPT (Male Pipe Thread) or NPT (M) for external threads, and FPT (Female Pipe Thread) or NPT (F) for internal threads. But MPT and FPT are not specified in the ANSI standard.

NPT Thread Sizes

– Commonly used NPT thread sizes including 1/8, 1/4, 3/8, 1/2, 3/4, 1, 1+1/4, 1+1/2, 2, 2+1/2, 3, 4, 5, and 6 inches, can be found on most U.S pipes and fittings. The thread sizes smaller than 1/8 inch and larger than 6 inches are occasionally used for specific purposes. 

– The pipe size in the NPT thread sizes chart does not refer to any physical dimensions, it is used as a trade size. 

– When identifying or determining a thread size, the threads-per-inch and outside diameter of the thread are necessary because there is more than one size has the same TPI. So the OD of a pipe or fitting must be measured and compared to a thread size table for identification. 

– The taper rate is 1 in 16 inch.

– Example of NPT thread designation: 1/8 – 27 NPT

– NPT and NPS threads are not interchangeable, NPT threads are tapered and NPS threads are straight, but both NPT and NPS have the same thread angle, shape and pitch.

NPT Thread Size Chart - NPT Thread Dimensions Table