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Cable Gland Thread Standards Explained: NPT, Metric, and PG

Author    |    hongxiang_admin    |    March 20, 2026
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Cable connectors play a crucial role in securing and sealing cables as they enter electrical equipment. These components help maintain the enclosure’s protection, preventing dust and moisture ingress and ensuring the long-term reliability of the system.

One of the most important aspects of cable connectors is the thread type. The choice of thread directly affects compatibility, sealing performance, and installation efficiency. Globally, three main thread systems are available on the market: metric threads, PG threads, and NPT threads. Understanding how each thread works will help us make more informed decisions.

Why thread type matters?

Thread type determines how a cable gland connects to an enclosure or panel. A mismatch can lead to loose fittings, leakage, or even equipment failure. Proper thread selection ensures a secure fit, effective sealing, and compliance with regional standards.

In industrial environments, where exposure to water, dust, chemicals, or vibration is common, choosing the correct thread type is essential for maintaining system performance.

  Metric threads

Metric threads are the most widely used standard across the world. They are defined by diameter and pitch in millimeters, such as M20 with a pitch of 1.5 millimeters.

These threads have a sixty degree profile, which allows even force distribution during installation. This design helps create stable connections and consistent sealing performance.

Metric cable glands are commonly used in Europe, Asia, and many international markets. They are often preferred for export equipment because they align with global standards and offer broad compatibility.

Typical applications include industrial automation systems, control cabinets, and general electrical installations. Because of their versatility, metric threads are often considered the default choice for modern projects.

PG threads

Hoonsun ip 68 Metal Cable Gland- Length Type with UL

PG threads originated in Germany and were widely used in European equipment. The name comes from a German term that refers to armored conduit threads.

Unlike metric threads, PG threads feature an eighty degree flank angle. This larger angle results in a shorter thread profile and improved resistance to loosening under vibration.

PG sizes are identified by numbers such as PG9, PG16, or PG21. These numbers roughly correspond to cable diameter ranges rather than exact thread dimensions.

Although PG threads have been gradually replaced by metric standards in many applications, they are still widely used in existing equipment and certain industries. You may find them in machinery, control panels, and specialized European systems.

For maintenance or replacement projects, understanding PG threads remains important since many legacy installations still rely on this standard.

NPT threads

M/PG/G/NPT /NG Type Metal Cable Waterproof Cable Gland Of Ip68

NPT threads are commonly used in North America and are based on an inch measurement system. These threads have a tapered design, which means the diameter changes along the length of the thread.

The tapered structure allows the threads to form a tight seal as they are tightened. This makes NPT threads especially suitable for environments where protection against liquids, gases, or pressure is required.

NPT threads also use a sixty degree angle, similar to metric threads, but their sealing mechanism relies on the taper rather than a sealing ring alone.

Typical industries that use NPT cable glands include oil and gas, marine applications, and chemical processing. These environments demand strong sealing performance and durability under harsh conditions.

M/PG/G/NPT /NG Type Metal Cable Waterproof Cable Gland Of Ip68

Key differences between thread types

Each thread system has unique characteristics that influence its performance and application.

Thread Type Thread Shape Sealing Method Measurement System Typical Usage
Metric Straight thread Uses sealing components such as gaskets or O rings to achieve protection Millimeter based sizing Widely used in global projects, industrial automation, and modern equipment
PG Straight thread with a different profile Relies on sealing elements and offers strong resistance to vibration Nominal size numbering system Common in older systems and European machinery
NPT Tapered thread Forms a seal through thread compression during tightening Inch based sizing Suitable for harsh environments such as oil, gas, and marine applications

How to choose the right thread type?

Choosing the right thread type involves several practical factors that directly impact performance and long-term reliability.

Most importantly, compatibility with the housing is crucial. The thread type of the cable connector must match the inlet bore of the panel or equipment. Using a mismatched thread can lead to a weak connection, leaks, and potential damage during installation.

Compliance with regional standards is also important. Metric threads are widely accepted internationally, while North America typically requires NPT threads. PG threads are common in existing European equipment and may still be necessary for maintenance or replacement.

Environmental conditions should also be considered. In humid, stressed, or corrosive environments, NPT threads offer a strong seal due to their tapered design. For general industrial environments, metric threads offer consistent performance and ease of use.

Cable size is equally important. The connector must be correctly matched to the cable diameter to ensure a good seal and stress relief. A mismatched connector will compromise protection and shorten equipment lifespan.

By considering all these factors, you can choose a thread type that ensures both safety and application efficiency.

Conclusion

While the cable connector thread type may seem insignificant, it has a significant impact on system safety and performance. Metric, PG, and NPT threads each have specific uses depending on regional standards and application requirements.

Metric threads offer global compatibility and consistent performance. PG threads remain crucial for legacy systems. NPT threads provide superior sealing performance even in harsh environments.

Understanding these differences and choosing the correct thread type ensures reliable cable management, enhanced protection, and long-term operational stability.

For more guidance on selecting the right cable connector for your project, please visit the HXCableGland website to explore a full range of solutions designed for modern industrial applications.

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