Thread pitch – what is it and what does it mean?

Threads are one of the most commonly used ways of joining components in engineering, plumbing systems, industry, and mechanics. There are many thread standards (e.g. BSP, NPT, or SAE). One of the most important parameters of a thread is its pitch. Many people come across this term when installing screws, fittings, or system components, but do not always know exactly what it means. In this article, we explain what thread pitch is, how it is measured, and why it is so important in practice.

What is thread pitch?

Thread pitch is the distance between two adjacent thread crests, measured parallel to the axis of the screw or pipe. In other words, it is the distance a screw advances during one full turn in a thread.

This parameter is crucial for the proper matching of threaded components. If two components have a different thread pitch, it may be difficult to connect them together.

Thread pitch therefore determines how densely the thread turns are arranged on a given component.

How is thread pitch measured?

Thread pitch can be determined in several ways. The simplest method is to measure the distance between two successive thread crests using a caliper or a special tool called a thread pitch gauge.

In the case of metric threads, pitch is given directly in millimeters. For example, an M10 thread may have a pitch of 1.5 mm, which means that the distance between successive thread turns is exactly 1.5 mm.

In imperial systems, such as BSP inch threads, instead of pitch, the number of threads per inch is often given. This parameter is abbreviated as TPI (Threads Per Inch).

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Thread pitch in metric threads

In metric threads, thread pitch is one of the basic parameters describing a given thread. A thread designation usually consists of the letter M and the thread diameter in millimeters.

For example, the designation M12 means a thread with a diameter of 12 mm. In the standard version, an M12 thread has a pitch of 1.75 mm, although in some applications fine threads with a smaller pitch are also used.

Threads with a smaller pitch allow for more precise adjustment of the connection and often provide greater resistance to self-loosening.

Thread pitch in pipe threads

In plumbing systems, pipe threads such as BSP or NPT are very commonly used. In Europe, BSP is definitely the dominant standard. In these systems, thread pitch is most often specified by the number of threads per inch (TPI).

For example, a 1/2" NPT thread has 14 threads per inch. This means that there are 14 thread turns over a length of one inch.

In practice, this also means a specific distance between successive thread turns, but in technical documentation, the TPI value is more commonly used.

Why is thread pitch important?

Thread pitch is simply important for the functioning of threaded connections - that is, for their tightness. Above all, it determines whether two components will fit each other.

If the thread pitch is incompatible, the components will not be able to be screwed together properly, and an attempt to connect them may lead - sometimes even to thread damage.

Thread pitch also affects:

• the speed of screwing in the component

• the clamping force in the connection

• resistance to self-loosening

• adjustment precision

That is why, in many technical applications, selecting the right thread pitch is very important.

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How to identify thread pitch?

Identifying thread pitch may be necessary when repairing equipment, replacing fittings, or matching installation components.

Most often, special thread gauges are used for this purpose, allowing the correct pitch to be matched quickly. In workshop conditions, you can also measure the distance across several thread turns and divide the result by their number.

Thanks to this, you can determine the approximate thread pitch and choose the correct component.

Summary – what is thread pitch?

Thread pitch is one of the basic parameters describing every thread. It defines the distance between successive thread turns and determines how threaded components will work together.

Knowledge of thread pitch is particularly important in mechanics, plumbing, and when assembling technical systems. Thanks to the correct selection of this parameter, it is possible to achieve a durable, tight, and safe connection, regardless of whether you are connecting a valve, a pump, a pump group, a heat exchanger, a hydraulic separator - or just an ordinary fitting.

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