Thread table - inch thread dimensions

Threads, which are screw cuts on a cylindrical or conical face, inside or outside. Among them, metric threads and pipe threads can be distinguished. They belong to triangular threads, depending on the needs, they can be divided into fine, coarse, normal, right or left threads. The mechanics of the thread are the same as the mechanics of the incline, and therefore threaded connections can be classified as simple machines.

The screw mechanism allows us to multiply the applied force. We apply a force in the form of a rotary motion and we obtain a much greater longitudinal force, much like an inclined plane. In addition to the connecting function, the use of a screw is also used in elements such as drives for presses, machine tools or lifts.

Threaded connections are detachable connections where the connecting element is a bolt, screw or nut. Additionally, threaded connections may contain elements such as washers or split pins. Regardless of the type and nature of the threaded connection, the most important issue is to guarantee a high pressing force, which will ensure a durable and safe connection, as well as trouble-free disassembly. Each threaded connection should be selected to withstand the loads to which it was applied.

The strength of threaded connections depends on many factors.

Some of them cause corrosion processes, others destabilize the connection. Additionally, factors such as:

• large fluctuations and extreme temperatures
• influence of weather conditions
• aggressive environment (chemicals)

Inch thread table

In the metric system, threads that are multiples of a millimeter are used, such as M5, M6, M7, etc. The second important criterion is the thread pitch. All these features of metric threads have been standardized. In order to be able to easily and clearly select the thread size, please refer to the standardized metric thread table.

However, there are areas such as gas, hydraulics and pneumatics where inch connections are dominant.

Cylindrical "G" threads and Whitworth "W" threads are most commonly used.

Common inch threads

BSP - British Standard Pipe thread, Whitworth pipe thread

This group of threads is standard in many countries except the United States. This type of thread is characterized by a V-groove with a 55 ° slope and a rounded crest.

There are two types of BSP threads, namely:

• cylindrical BSPP, where both the male and female sides are parallel to each other.

Connections of this type are used in countries such as Great Britain, Australia, or in Europe and Asia. These types of threaded connections require additional sealing in the form of, for example, Teflon tape.

• tapered BSPT, where the external threads get tighter and the internal threads are most often parallel.

Conical threads seal on the cone and therefore do not require additional seals.

Thread tightness acc. To ISO standards

• ISO 228 - pipe threads where no additional seals are required
• ISO 7 - pipe threads where seals are required

BSP thread types and standards (letter designation)

• G - parallel BSPP internal and external thread, cylindrical acc. To ISO 228
• R - BSPT conical male thread acc. To ISO 7
• Rp - BSPT parallel female thread acc. To ISO 7
• Rc - BSPT internal thread acc. To ISO 7

Briggs NPT / NPS pipe thread

NP - or National Thread Pipe, a V-shaped pipe thread with a slope angle of 60 ° with a flattened crest, very popular in Canada and the United States.

There are two types of NP threads, namely:

• NPS - thread where the male and female parts of the thread are parallel (straight thread), which results in a lack of sealing.
• NPT - conical thread that gives us a seal on the thread (more popular than NPS)

BSP and NPT threads do not match and do not connect between them.

Metric threads acc. ISO standards

V-shaped thread with a slope of 60 °, the outer and inner parts are parallel to each other.

These threads have different sizes of the thread pitch for a given diameter, i.e. we can distinguish the usual thread pitch and the so-called thread. fine-threaded.

Standard metric threads have a default pitch size, and are selected only by diameter, e.g. M12

Fine threads have smaller pitches, and are not as popular as regular metric threads.

They are recognized by the diameter and the size of the scale , i.e. pitch, which means that for a given diameter they are available in two sizes of the scale (pitch)

Dimensions of inch BSP threads

NPT thread sizes

Compare NPT / NPS Threads to BSP Threads