Steel Hydraulic Pipe Fittings



We stock a wide variety of Hydraulic Fittings: JIC, SAE BOSS, Pipe, Flat Face, Compression and Metrics.  We specialize in all types and sizes, and carry an extensive stock of Hydraulic Fittings.

Can’t identify the hydraulic fitting you need?  See our extensive thread identification page or call our expert sales people to help you.  


Tapered Pipe Thread (NPT)

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Pipe Fittings

Hydraulic Pipe Fitting GroupThis fitting uses basic metal to metal sealing design for achieving a seal.  NPT Threads, when assembled without a sealant, leave a spiral leak path when tightened.  To seal pressurized fluid, NPT threads require a suitable sealant applied to the threads.  The seal fills all imperfections in the surfaces affecting the seal and also provides lubrication to ease assembly and minimize galling.

While a pipe thread connection can be disassembled and reassembled in low pressure system, it is not intended to be a frequently assembled and disassembled connection.


Hydraulic Pipe Thread Feature-Advantage-Benefit



Tapered Thread Connections have the following limitations which should be considered when specifying port connections:

  • Poor Dynamic Sealing Characteristics
  • Possible Expansion, and Even Cracking, of the Port
  • Orientation is a Concern in Shaped Connectors
  • Larger Threads are More Prone to Leakage because of More Potential Leak Points
  • System Contamination Due to Thread Sealant
  • Prone to Galling
  • Limited Remakeability


Straight Swivel Pipe Thread (NPSM)


How Straight Pipe WorkNPSM Pipe Swivel

Pipe swivels are manufactured to SAE J514 specifications.  Unlike most pipe thread connections, NPSM swivel adapters do not seal on the threads.  NPSM swivel connections incorporate parallel threads, as opposed to tapered.  Sealing is accomplished between the nose of the swivel and the mating seat of the NPT pipe thread.  This creates a metal to metal seal.  A mating NPT male connector must have this 30° seat to ensure proper sealing.  A full internal 30° seat with surface finish requirements of 125 Ra or better is required.  Not all male NPT ends have the 30° seat.  Make sure the one being used with a NPSM swivel does.



Reference Information from Parker Hannifin Tube Division 4300 Catalog

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