TOP-3 designations of the cylindrical pipe thread standard

When doing plumbing work at home, everyone will come across the concept of “pipe thread”. Without an engineering/specialty education, it may not be possible to understand all the nuances of pipe connections on your own.

Running to the nearest plumbing store for help is no longer relevant these days; it’s much easier to type the relevant query into the search bar. Next, comprehensive information will be presented regarding pipe thread sizes + their classification by type.

Applications and features of inch threads for pipes

Pipe threads are used on pipes and other elements of the pipeline system: fittings, shut-off and control valves, flanges.
Standardized by international specifications. Products with threads are widely used on the following systems:

• where the use of welding is undesirable or impossible;
• where it is necessary to form a dismountable connection;
• which are not subject to pressure or temperature surges, etc.

Previously, each manufacturer applied its own thread, which corresponded to paired parts manufactured in the same production. The need for unification arose when a discrepancy between various parts with threads from different manufacturers was discovered and, as a result, it became impossible to sell or exchange threaded metal products.

The thread differs in such parameters as

• profile angle (55°, 60°);
• shape of protrusions and depressions (sharp, flat, round);
• step (large, small);
• shape (conical, cylindrical);
• number of threads per inch.

In order to satisfy the needs of all industries, there are several types of threads. Moreover, the USA and Europe have their own standard pipe threads, which were created independently of each other. Despite some similarities in parameters, dimensions, and scope of application, threaded pipe fittings of different types cannot be used, since the only result of such a combination is damage to the products and poor quality of connections of pipeline elements.

NPT – National Pipe Taper – American tapered thread

*May also refer to NPS (National Parallel) threads, which are not similar or equivalent to NPT pipes.

NPT pipe threads are common in various types of industries. Provides a strong and tight connection of pipeline fittings. For operation under high pressure conditions, installation with a gasket is required.

NPTF threads are regulated by ASME B1.20.3. The dimensions of the two types are almost the same (except for the diameter of the protrusions and recesses). NPTF pipes are in demand in systems transporting liquid substances. The NPTF thread is more airtight and does not require the use of sealing materials.

Standard Tapered NPT Thread Size Chart

Correspondence table for various types and standards of threads

TABLE OF CORRESPONDENCE

Notes:
1. UNC, UNF, UNEF

– threads with appropriate pitch for different diameters:
UNC
– coarse pitch;
UNF
– small step;
UNEF
is a particularly small step;
UN
– threads with one pitch value for different diameters. 2. Threads with a taper of 1:16 are similar in profile to OTTM and OTTG threads (GOST 632-80). Threads are not interchangeable. However, under certain conditions for choosing a tool, it is possible to process external threads in accordance with GOST 632-80. 3. API RD 8 TPI thread (pitch 3.175) is interchangeable with tubing threads according to GOST 631-75, GOST 632-80 and GOST 633-80.

Related documents:

GOST 3469-91 - Microscopes. Lens thread. Dimensions GOST 4608-81 - Metric thread. Interference fits GOST 5359-77 - Ocular threads for optical instruments. Profile and dimensions GOST 6042-83 - Edison round thread. Profiles, dimensions and maximum dimensions GOST 6111-52 - Conical inch thread with a profile angle of 60 degrees GOST 6211-81 - Conical pipe thread GOST 6357-81 - Cylindrical pipe thread GOST 8762-75 - Round thread with a diameter of 40 mm for gas masks and calibers for her. Main dimensions GOST 9000-81 - Metric thread for diameters less than 1 mm. Tolerances GOST 9484-81 - Trapezoidal thread. Profiles GOST 9562-81 - Single-start trapezoidal thread. Tolerances GOST 9909-81 - Tapered thread of valves and cylinders for gases GOST 10177-82 - Persistent thread. Profile and main dimensions GOST 11708-82 - Thread. Terms and definitions GOST 11709-81 - Metric thread for parts made of plastic GOST 13535-87 - Reinforced thrust thread 45 degrees GOST 13536-68 - Round thread for sanitary fittings. Profile, main dimensions, tolerances GOST 16093-2004 - Metric thread. Tolerances. Clearance fits GOST 16967-81 - Metric threads for instrument making. Diameters and pitches GOST 24737-81 - Single-start trapezoidal thread. Main dimensions GOST 24739-81 - Multi-start trapezoidal thread GOST 25096-82 - Persistent thread. Tolerances GOST 25229-82 - Metric conical thread GOST 28487-90 - Conical locking thread for drill string elements. Profile. Dimensions. Tolerances

BSP – British Standard Pipe – British pipe thread

BSP pipe thread is also called Whitworth thread after its creator. Joseph Whitworth suggested sticking to the following parameters:

• profile angle – 55°;
• protrusions and depressions should be round;
• One of the main values ​​is TPI (threads per inch).

BSPP British Straight Pipe Thread Sizes

To improve the tightness of the joint, BSPP threaded pipes should be installed with a gasket. Some fittings come with rings or other types of seals.

Standard Tapered BSPT Thread Dimensions in mm

BSPT tapered threads are self-sealing and are used for connections with increased tightness requirements. BSPT male thread pipes can be used in conjunction with BSPT and BSPP fittings and pipes.

Thread R, pipe tapered

Compatible with BSPT threads

Pipe conical thread used in conical threaded connections, as well as in connections with external conical threads and internal cylindrical threads in accordance with GOST 6357-81. Based on BSW (British Standard Whitworth) threads and compatible with BSPT (British Standard Pipe Tapered Thread).

• GOST 6211-81 - Basic standards of interchangeability. Conical pipe thread.
• ISO R7
• DIN 2999
• BS 21
• JIS B 0203

Thread parameters

Inch thread with a taper of 1:16 (taper angle 3°34'48″). The profile angle at the apex is 55°. Symbol: letter R for external threads and Rc for internal threads (GOST 6211-81 - Basic standards of interchangeability. Conical pipe threads), numerical value of the nominal thread diameter in inches (inch), letters LH for left-hand threads. For example, a thread with a nominal diameter of 1 1/4″ is designated as: R 1 1/4″. For more information about threads, thread pitch and other parameters, see Wikipedia.org.

Comparison table of pipe thread types

In the catalog of the European Metallurgical Company you can buy pipes and fittings with NPT-F, NPT-M, BSP threads made of carbon and stainless steel. To order metal products according to international standards EN, ASTM, ANSI, DIN, ISO, etc., you can leave a request on the website or contact our operators online.

Thread G, cylindrical pipe

Compatible with BSP threads

Pipe cylindrical thread used in cylindrical threaded connections, as well as in connections of internal cylindrical threads with external conical threads in accordance with GOST 6211-81. Based on BSW (British Standard Whitworth) thread and compatible with BSP (British standard pipe thread).

• GOST 6357-81 - Basic standards of interchangeability. Cylindrical pipe thread.
• ISO R228
• EN 10226
• DIN 259
• BS 2779
• JIS B 0202

Thread parameters

Inch thread with a profile angle at the tip of 55°. Cuts on pipes up to 6″ size, pipes over 6″ are welded. Symbol according to GOST 6357-81: letter G, numerical value of the nominal diameter of the pipe in inches (inch). For more information about threads, thread pitch and other parameters, see Wikipedia.org.