Hydraulic Fitting Thread Types & Compatibility FAQ
What is the difference between NPT and BSP threads?
NPT threads use a 60-degree angle and are common in North America, while BSP threads use a 55-degree angle and are common internationally. They are not interchangeable.
Are NPT and BSPP threads interchangeable?
No, NPT and BSPP threads are not interchangeable because they differ in thread angle and sealing method, and forcing them together causes leaks or damage. NPT is tapered while BSPP is parallel.
What is an ORB fitting?
An ORB (O-Ring Boss) fitting seals with an o-ring compressed against a machined seat, providing a reliable leak-free connection in hydraulic systems. It's preferred where high-pressure sealing is critical.
How do I identify thread type on a fitting?
Measure the thread diameter and pitch, check whether the threads are tapered or parallel, and compare the results against a thread chart. A thread gauge speeds up identification.
What does JIC stand for?
JIC stands for Joint Industry Council, and JIC fittings use a 37-degree flare seal that remains one of the most common hydraulic connection standards. They're valued for reliability and wide availability.
What is the difference between BSPP and BSPT?
BSPP threads are parallel and seal with an o-ring or bonded washer, while BSPT threads are tapered and seal on the threads themselves. Choosing the right one prevents leaks.
Can you connect JIC to NPT fittings?
No, JIC and NPT fittings cannot be directly connected because JIC seals on a 37-degree flare and NPT seals on tapered threads. An adapter is required to join them.
What is a 37 degree flare fitting?
A 37-degree flare fitting, such as JIC, seals when the flared tube face presses against a matching 37-degree seat, creating a metal-to-metal seal. It's a hydraulic industry standard.
How do I measure thread size on a hydraulic fitting?
Measure the outside diameter of male threads or the inside diameter of female threads, plus the thread pitch, then match them to a thread chart. Calipers and a pitch gauge give the most accurate reading.
Can you mix metric and NPT threads?
No, you should never mix metric and NPT threads because they differ in pitch, angle, and sealing method. Even a small mismatch can cause cross-threading or immediate leakage.
What is the difference between JIC and NPT fittings?
JIC fittings seal with a 37-degree flare and metal-to-metal contact, while NPT fittings seal through tapered threads that wedge together. They are not interchangeable and require different mating components.
Do stainless steel fittings need thread sealant?
It depends on the thread type: tapered threads like NPT often need PTFE tape or sealant, while flare and o-ring fittings seal mechanically without it. Using sealant on the wrong fitting type can actually cause leaks.
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