Camlock coupling standards and norms - A-A-59326D & EN 14420-7

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What is the history of Camlock couplings?

The history of Camlock couplings is not well documented. However, various sources state that they were developed in the early 20th century. The first Camlock couplings were created from metal and were used for a number of applications, including firefighting and aircraft refuelling.

In the 1950s, a new version of the product appeared - in plastic. This has made couplings lighter and made them more popular in various industries.

Today, Camlock systems are made from a variety of materials, including stainless steel, brass and polypropylene. They are available in a wide range of sizes and varieties, making them suitable for use with a wide variety of hoses.

You can read about the types, material versions and sizes of Camlock couplings in a separate article on our website.

Although the exact origin of Camlock couplings is not known, there are several theories about their origins. One theory is that they were developed by firefighters in the early 20th century as a way of quickly and easily connecting/disconnecting hoses. While another theory holds that aviation mechanics were behind the development of the couplings, where the Camlock makes refuelling aircraft easier and faster.

The second story seems more likely, as the first standard for Camlock couplings originated in the US military.

What are the standards for Camlock couplings?

There are two standards for Camlock couplings: the American one, namely A-A-59326D (formerly Mil-C-27487), and the European one, namely EN 14420-7. We have a closer look at each of these below.

What is A-A-59326D (Mil-C-27487) Standard?

A-A-59326D standard is a federal standard according to which the majority of Camlock couplings are made in the US. Prior to this, they were manufactured to US military specification Mil-C-27487, which specified Camlock fitting dimensions and moulding methods, pressure ratings and tolerances, and inspection procedures.

The Mil-C-27487 specification ensured that products from different manufacturers were compatible with each other.

However, the Mil-C-2487 standard is now obsolete as it has been replaced by the A-A59326D standard. As with its predecessor, the new specification guarantees compatibility with other couplings that have also been developed along its lines.

What is the EN 14420-7 Standard?

EN 14420-7 Standard is a standard according to which Camlock couplings are made in the Europe. The European EN 14420-7 standard came into force in September 2004 and worked alongside the US standard. However, the US specification only applies to the connecting side of Camlock couplings and does not cover the hose/thread stub.

Significantly, the European standard is compatible with Camlock versions conforming to the original military specification Mil-C-27487. Only the threads and the design of the hose stub differ.

A smooth hose stub, which complies with the European EN 14420-7 standard (as well as the German DIN 2828 standard), has been added for fitting with RK safety clamps (these to comply with EN 14420-3 and DIN 2817). A flat thread seal has also been added to the female threaded part of the Camlock coupling.

What are the key differences between A-A-59326D and EN 14420-7?

The key difference between A-A-59326D and EN 14420-7 is the often different design of hose ends and threads in Camlock couplings. Also, as they are all manufactured to a single standard, they are compatible with each other regardless of manufacturer.

However, there are some exceptions. These apply mainly to the 1/2-inch, 5-inch and 8-inch sizes.

The military specification A-A59326A does not apply to the 5-inch and 8-inch sizes, so there are two types of coupling available.

The 1/2-inch size, on the other hand, also has two versions - one works in the US and the other in Europe and Australia. The European version has a thinner “lip” on the male part of the coupling (plug).

In practice, this means that the American female version (socket) is compatible with the European male Camlock couplings, but the connection has more play, making it easy to close the arms of the coupling.

In the other direction, it will no longer work. The European female versions of the Camlock will not accept the American male Camlock couplings, because the lip of the latter will be too large for you to close the arms of the coupling.

For the 8-inch Camlock varieties, you have two versions available - PTK and NAE:

  • PTK stands for: PT Coupling & Kuriyama.
  • NAE stands for: Neco, "Dixon" Andrews and Evertite.

To determine the type of 8-inch Camlock you have, do the following:

  • Measure the outside diameter of the male plug (or the inside diameter of the female socket). 
  • The PTK version has a diameter of less than 9 inches, while the NAE version has a diameter of more than 9 inches.


You already know what standards apply to Camlock couplings. In most cases they are compatible with each other, but there are some exceptions that you should be aware of.

Also consider that the standards refer primarily to metal couplings.  Therefore, polypropylene products, for example, do not have an international standard, so socket sizes can vary from manufacturer to manufacturer.

Always make sure they comply with the standards before you buy couplings.

Photo of Bartosz Kułakowski - CEO of Hosetech sp. z o. o.

Articles author

Bartosz Kułakowski

CEO of Hosetech Sp. z o.o.

Bartosz Kulakowski is an industrial hoses and couplings specialist with over 10 years of experience. Bartosz has been present in the technical industry since 2013. He gained experience as a technical and commercial advisor in the sector of plastic conveyor belts, steel structures, industrial hoses, and connectors. Since 2016, he has specialized exclusively in hoses and connectors. In 2019 he opened his own business under the HOSETECH Bartosz Kulakowski brand and since July 2022 he has been the CEO of the capital company HOSETECH Sp z o. o. (LLC).


What is the history of Camlock couplings?

What are the standards for Camlock couplings?

What is A-A-59326D (Mil-C-27487) Standard?

What is the EN 14420-7 Standard?

What are the key differences between A-A-59326D and EN 14420-7?