A hose coupling is the connector that joins one length of hose to another. It is typically made of brass, stainless steel or aluminum and comes in a variety of sizes, thread standards and genders. For the connection to work the way you want it and not leak or fly off, it's important to choose the right coupling for your job.

There are a few things to consider when choosing the right fitting for your job:
First, you'll need to understand what type of thread your hose has. Different thread types have different pitch and spacing. This is what makes it easier to select a coupling for your specific application.
Second, you'll need to know if the thread is straight or angled. A straight thread is more common for fire hoses, and you'll also find it on some low-pressure water suction or discharge hoses.
Third, you'll need to know if you're using a permanent or returnable type of hose coupling. A permanent type uses a crimping tool and is used for new equipment, while a returnable hose coupling can be re-used or returned without the need for a crimping tool.

The next step in the qualification process is to determine a starting crimp OD, which is how much the ferrule will crimp when it's attached to the hose. Coupling development engineers estimate the target crimp OD by looking at the flat portions of the ferrule diameter and comparing it to historical data and material property calculations. Once they've developed a crimp specification, they can start sizing and assembling the components to fit the target hose and ensure proper functionality.