Nominal diameters and thread sizes in hydraulics

Tubes, hoses, and threads in hydraulic systems are described according to their external or internal diameter, as well as by other criteria. We shed light on the rules and regulations.

Hydraulic lines for the entire vehicle

In hydraulic systems, the lines can be implemented as hydraulic tubes or hydraulic hoses. However, their size is described in different ways.
Pipes are identified by their external diameter (in mm) and wall thickness (e.g. 15 x 2). For hoses, the nominal diameter (DN) and internal diameter (in mm) are used for identification.

Dimensions for threads

Screw connections ensure that piping parts and components such as pumps, valves and cylinders are connected. A distinction is made between metric dimensions and thread in inches. In metric systems, short designations of purpose are used alongside thread dimensions. The system is based on external tube diameters in the lightweight and heavy-duty series. The differences between the series are determined by their compression strength (PN) and nominal pressure in bar. (Files are only available in German.)


Short designation in the metric system
We have compiled an overview of the different pipes, thread designations, compressive strengths and other values in our clearly organized identification table. You will find everything at a glance here.


Thread in inches
For identifying thread in inches, three different system must be observed in addition to the external and internal diameters. They are BSP (British Standard Pipe Thread), JIC (Joint Industry Council) and ORFS (O-Ring faced seal).


Identification table
In our tables, we have compiled an overview of thread size values for a variety of thread designation in inches, the metric system and various other systems.

The suitable tools are essential

To correctly identify the thread, measuring instruments and other materials for determination are indispensable. winkler supplies an extensive product range of screw connections, couplings and hydraulic tubes and hoses. Take a look in our “Hydraulic Components” or “Piping Parts and Screw Connections” catalogs, for example. (Catalog is only available in German.)

Advice from professionals

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The winkler Hydraulics Magazine

In our hydraulics magazine, we cover a wide range of topics related to mobile hydraulics. You'll find everything here: field reports, expert tips from our hydraulics specialists and, of course, interesting technical info on hydraulic components, new products, and special offers from the winkler product range. (Magazine is only available in German.)

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