How to Measure Hydraulic Hoses & Fittings Before Ordering?

4 Mins read

Hydraulic cylinders are hugely important for industrial purposes. If it weren’t for the invention of the hydraulic cylinder, several forms of machinery would not be in operation today.

Entire industries may have to operate differently and less efficiently if hydraulic cylinders disappeared overnight. The type of force produced when hydraulic cylinders are working in unison is a big reason why massive construction projects can be completed.

In order to maximize the capabilities of those cylinders, you need to pair them with the right hydraulic fittings. We’ll get to that later in this article, but first, let’s take the time to examine the origins of the hydraulic cylinder.

Who Invented the Modern Hydraulic Cylinder?

To better understand how modern hydraulics came to be, it helps to remember the work done by the French mathematician Blaise Pascal. Pascal devoted much of his time to studying how fluids, pressures, and vacuums interacted with one another, according to Living History Farm.

Through his studies, Pascal discovered that liquids reacted a certain way to pressure whenever they were contained within an enclosed space. Pascal found that when pressure was applied to the liquid resting in one spot, the liquid would then transmit that force equally throughout the container in all directions. It was a discovery that eventually became known as Pascal’s Law.

As monumental as Pascal’s discovery was, it would be a while before it could be properly leveraged. During the late 1700s, inventor and locksmith Joseph Bramah began working with hydraulics. His work eventually led to the creation of what was termed back in 1795 as a “hydrostatic machine.” We know that hydrostatic machines are better today as a hydraulic press.

Guided by the principles of Pascal’s Law, Bramah leaned on hydraulic cylinders to create the hydraulic press. In turn, he made use of that hydraulic press to invent what was seen at the time as an unpickable lock.

The hydraulic press proved to be a hugely significant invention. Due in large part to inventing it, Bramah became known as one of the two pioneers of hydraulic engineering along with William George Armstrong, per Wikipedia.

Over the coming decades, numerous other innovators would improve upon the hydraulic press. They would tinker with the interplay of the hydraulic cylinders to broaden their capabilities.

It’s far from hyperbole to say that the modern industries would look very different were it not for the earlier discoveries and inventions of brilliant minds such as Blaise Pascal and Joseph Bramah.

How Do I Know Which Type of Fitting I’m Working With?

The right fittings need to be in place for a hydraulic system to work properly. If you’re not using the correct type of fitting, chances are that something will go wrong with the connections at some point.

Parker suggests utilizing simple steps to identify the fittings.

You can start by checking whether the fitting features a parallel or tapered thread. Parallel threads will feature the same diameter throughout the fitting while their threaded counterparts get smaller closer to the end.

Next, you will have to ascertain the pitch of the particular fitting you’re looking at. You will need a tool known as a pitch gage for this.

Finding out the size of the fitting is next on your agenda. Before doing that though, you must first check if you have a pipe thread or a non-pipe thread. The size of pipe threads can be measured by comparing one with a nominal size profile while a non-pipe thread’s size is measured by using a caliper to check its outside diameter.

With the information you’ve obtained, you should be able to identify what type of fitting you’re looking at.

Now let’s name some common pipe thread types.


The National Pipe Tapered (NPT) fittings are the ones you’ll encounter the most in North America. NPTF or National Pipe Tapered Fuel fittings are known for preventing leaks even better than their NPT counterparts.

BSP Types

BSP stands for British Standard Pipe and you’ll often see these fittings used in Europe. They come in parallel (BSPP) and tapered (BSPT) variants.

Metric Types

Similar to BSP fittings, Metric fittings are also found throughout the continent of Europe. You can usually tell if you’re looking at a Metric fitting if you see a capital “M” printed on it, according to Trimantec. The Metric tapered fittings in particular are great for distributing force throughout a hydraulic system.

JIS Types

The Japanese Industrial Standard fittings are mainly used in Japan and Korea. Thread sealants may sometimes be needed to close connections that use these fittings.

SAE Types

SAE or Society of Automotive Engineers fittings stand out from the other options because they use O-rings. Those O-rings allow these fittings to create tight seals more consistently.

Four-Bolt Flange Fittings

Last up are the four-bolt flange fittings and these are the types typically used for sealing fluid power systems, according to Hydraulics Direct.

What Are the Most Common Fitting Shapes?

Hydraulic fittings come in different shapes and sizes.

These shapes include adapters, bushings, caps, couplings, elbows, flanges, nipples, tees, unions, and eyes. Note that tees can come in the form of saddle tees and crosses as well.

Make sure that you get the shape of the fitting right before purchasing a replacement.

What Are the Most Common Fitting Sizes?

Here in the United States, you’ll often hear the term “nominal pipe size” mentioned when discussing fittings. Determining the nominal pipe size is important because it helps you figure out the diameter and thickness of the pipe that will wear the fittings.

Common nominal pipe sizes here in the country include 1/8, 1/4, 3/8, 1/2, 3/4, 1, and 1 1/4. Don’t neglect the size when choosing replacement fittings or else you could create a nightmarish situation for yourself.

The information included in this article should help guide you the next time you need replacement fittings. Still, the selection process can get confusing.

If you’re trying to buy hydraulic hoses and you want to eliminate the chances of making the wrong purchase, contact us at Sapphire Hydraulics. We’ll be the ones to take a look at your fittings and address the problem. Call us today to learn more about our services.