Hydraulic Thread Identifier
Answer three questions to identify an unknown hydraulic fitting against all 7 standards.
Verify before connecting. This tool narrows the probable standard based on measurements you enter. It is not a definitive identification. Always confirm thread type with a thread identification gauge and check the manufacturer's specifications before assembling hydraulic connections. Incorrect fitting identification can cause leaks, blowouts, or high-pressure injection injuries.
Optional: Verify by Measurement
If you have calipers, enter the thread OD to narrow results further.
How to Identify Hydraulic Fittings
The fastest way to identify an unknown fitting is to check three things in order: thread taper, thread type (imperial vs metric), and seal mechanism. Thread taper is checked by feel or by eye. Thread type is checked with a pitch gauge. The seal mechanism is checked visually by looking at the fitting nose: flare cone, O-ring groove, cutting ring, or flat face.
If you have digital calipers, measuring the thread OD and counting TPI gives you a definitive match against the lookup table. The measurement approach is especially useful when the seal area is worn or damaged and hard to read visually.
Common Questions
How do I identify an unknown hydraulic fitting?
Start by determining if the thread is tapered or straight. Then measure the thread OD with calipers and count the threads per inch (TPI) or measure the metric pitch. Finally, examine the seal area: look for a flare cone, O-ring groove, cutting ring, or flat face. These three observations narrow the fitting to one or two possible standards.
What is the difference between JIC and NPT threads?
JIC has straight (non-tapered) threads with a 37-degree flare cone that seals metal-to-metal. NPT has tapered threads that seal by thread deformation and require sealant tape or compound. They are not interchangeable.
How do I tell BSP from NPT?
Both can be tapered, but the thread angle is different: NPT is 60 degrees, BSP is 55 degrees. At 1/8 inch nominal size, NPT has 27 TPI while BSP has 28 TPI. A thread pitch gauge is the most reliable way to distinguish them.
How do I tell DIN from JIS fittings?
Both use metric threads, but DIN has a 24-degree cone with a separate cutting ring on the tube, while JIS has a 30-degree flare without a cutting ring. If you see a cutting ring, it is DIN.
Reference data only. Verify thread dimensions with a thread identification gauge before making connections. Working with pressurized hydraulic systems involves serious injury risks including high-pressure injection, burns, and crushing hazards. This site does not replace manufacturer specifications, proper training, or employer safety procedures. See full terms of use.