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How do you describe an ADAPTER so that you get what you want ?

Adapter terminology and expressions explained


If you are ordering adapters, it is probably for an application where you are trying to connect a hose to a machine, reducing flow, changing threads or connecting two hose assemblies together and you don’t quite have the right part, so an adapter will help you out and do the job ! But you do need the correct one… Would it be helpful to have adapter terminology and expressions explained in simpler terms?

Maybe you have a description but you have no idea what it means,
or are you having trouble describing what you need ?
Are you unsure what the right word is to describe the part ?
Are you worried that what you have ordered may not be what you need ?

Basic Information

It is essential to provide the following basic information to a supplier to be sure that you get what you want:

  • Geometry / Configuration
  • Size for each end (inside diameter, generally)
  • Orientation for each end (male or female)
  • Threads for each end (NPT, JIC, BSPP, SAE/ORB, etc)
  • Material (Stainless steel, Carbon steel, Brass and many more)
  • And the supplier’s part number (if you have it !)

These are all described in further detail in the paragraphs below.

In many cases, it is also important to know the application (fluid), the temperature and the pressure of the application to ensure that the requested material can withstand the application specifications.

And then there is all of the terminology that goes along with the world of adapters. If you are new to the industry it may seem like everyone is talking in a foreign language. Does it seem like there are different terms for the same part ? (you are generally correct !) If someone uses a term that you are not familiar with, just ask them what it means because you probably aren’t the only one who doesn’t know what it is!  But in the meantime, here is some of the terminology explained:


Geometry / Configuration

Adapters come in many shapes: straight, tees, elbows 90 or 45 degrees and crosses.
People may also refer to :

adjustable ORBs (which has a nut that is adjustable to attach the adapter to the wall of a machine / port.  See ORB or SAE for further information)
bushing (where the part is made up of a male thread which is larger and a female thread inside of that which is smaller, generally with a hex on the end of the adapter)
cap (which has female threads on one end only, can be hex or smooth)
compression (which is a method of compressing the end of the adapter onto tubing, so no threads, there are different types of compression fittings depending on the application)
connector (which is just another name for adapter)
conversion (which is an adapter with two different threads, to convert from one type of thread to another).
expanders (the first end is smaller than the second) ,
face seals (which has a groove in the very end of the adapter with an o-ring usually in it)
flareless (which is another word from compression fitting)
hollow-hex plugs (which has a hole in the hex – or top –  so that you can tighten it with an Allen key)
jump sizes (which is a different size for each end)
NPSM (which is a female NPT Swivel end)
ORB (which is an oring boss, meaning that there is an elastomeric o-ring on the thread, see thread section for more details)
reducers (the first end is bigger than the second end),
plug (which has male threads on one end only with a Hex.  They can be hollow-hex, hex standard or just hex. Hex standard plugs are not bored out on the inside, whereas a hex plug is bored out with a chamfer to allow it to be used with an NPSM fitting. There are also others such as square heads in plumbing applications.)
SAE (which is also known as an O-ring boss / ORB fitting, it actually stands for Society of American Engineers)
swivel (which means the part spins 360 degrees, can be a male swivel or a female swivel – which would be a swivel nut, some swivels are super-swivels / live-swivels which move in all directions as they have a ball bearing)
swivel nut (which is a nut that is crimped onto the body which can spin 360 degrees, generally for a female end, as opposed to a solid end)
tube ends (which means no threads, just tubing instead – that will generally accept a compression fitting)
unions (which are straight adapters with the same threads on both sides),

There are many more types of adapters (such as banjo), the above ones are the most common ones that we are presented with at Aerocom Specialty Fittings Inc.

Sizes for each end

Sizes are generally the inside diameter and are presented in 16ths or inches (or other dimensions if metric).  So, ends can be 3/4″ but can also be identified as -12 size (only the numerator of the fraction over 16 is mentioned).  However, some threads are described as #12 (JIC or AN, SAE ORB threads have the # in front of them) while others, such as NPT threads, are never described with the # symbol, but rather in fractions (3/4”).  So, if #12 is mentioned then you know that it is a JIC or ORB thread and not an NPT thread.   If the adapter has a tube end (no threads), then it is the Outside Diameter that is measured and described in fractions.  For metric ends, it is a bit more complicated as they have their own numbering and description system.


Adapters, as well as other piping connecting components, are usually described as being either male or female.  Male parts have the threads on the outside, whereas female parts have the threads on the inside. A male part threads into a female part.


It would take an entire series of blogs to properly describe threads, but the main threads that Aerocom Specialty Fittings Inc generally offer are:

JIC 37 degree  (is a type of flare thread which has a 37 degree flare seating surface and generally used in higher pressure applications)
JIC 45 degree (this type of thread is generally for brass parts)
NPT (are a tapered thread which should be used with Teflon tape or some type of sealing compound and are generally used in lower pressure applications)
NPSM (which is National Pipe Straight Mechanical – Aerocom offers female swivel fittings with a straight thread and a 30 degree cone which is where the seal is made when mated with Male NPT fittings which would then have a 30 degree chamfer)
ORB (or adjustable ORB or SAE) this has the same thread as the JIC thread but does not have the 37 degree flare at the end.  As well it has an o ’ring near the hex which is where the seal is made with other fittings.  For the adjustable ORB, there is a nut which is used to secure the adapter into a port (in a machine).
BSP (for British Standard Pipe) which can be tapered (BSPT) or parallel (BSPP). These are generally not interchangeable with NPT (although some applications may accept both).
Metric (is a type of thread which is measured in millimeters rather than inches.  When ordering adapters with this type of thread, additional details are required – fine / coarse, heavy/light etc.  There is a more complex way to describe these fittings/threads.)

And then there are:
AN threads which are similar to JIC 37 degree threads, but AN threads are of a higher precision (for aeronautic applications).  There are also MS, NAS, AS threads which are for aeronautic applications.

There are many more threads that exist to satisfy needs in other applications (such as Fuel, Fire hose, aeronautics, military, plumbing), but those listed above are the ones that Aerocom Specialty Fittings Inc generally offers.

Charts are available which provide all of the details about each type of thread described above (and many more). They provide all of the details required for the machinists and programmers to machine the threads.


Adapters generally come in Carbon Steel, Stainless steel or Brass.  There are many different types of each of these materials.  It is critical to select the correct material as some fluids interact with materials in very different ways.  Chemical Resistance Charts can be consulted to ensure that the selected material is resistant to the fluid going through the adapters.

Generally Brass adapters will have a 45 degree flare (instead of a 37 degree JIC flare). Some sizes of the 45 degree flare can be used in the 37 degree application but not all, so if a 37 degree JIC flare is required on a brass adapter, it is critical to confirm that when ordering.

For very special applications, there are other materials that may be required (such as Hastelloy).  These materials are required to provide the needed lifespan of the part or to prevent degradation and contamination of the application fluid.

Temperature and Pressure

Hydraulic adapters are designed to withstand the highest pressure possible.  Some stainless adapters can withstand a working pressure of up to 6000 psi, but not all sizes and types. So, if your application runs at a high pressure, it is critical to mention that when ordering.  There are charts that exist by series, material and size which provide the design pressure of  each fitting.

Temperature is also a factor when making an adapter selection.  Certain materials can only withstand up to a certain temperature.  There are temperature correction factor tables which provide the information required to calculate the corrected working pressure for applications at higher temperatures.


There are many standards that have to be followed in order to provide customers with the adapters that they want.  These can be thread (NPT, JIC) standards or SAE standards such as SAE J514. They provide guidelines for machinists and engineers so that there is uniformity of parts from one supplier to another.  Some applications require compliance to these standards.


There are many more terms that people use to describe adapters.  Some are further discussed in our posts specifically about elbows, tees, conversion fittings which are available on our website. Hopefully having the adapter terminology and expressions explained will help you better understand the world of adapters and provide you with the terminology that you need to get the adapters that you want.  If you aren’t sure about how to describe something or need some information about adapters, please do not hesitate to reach out to Aerocom Specialty Fittings Inc and we would be happy to help you out.


The Aerocom Team