The most common cause of hydraulic leaks is mismatched threads. Use this guide to correctly identify NPT, BSP, JIC, ORFS, SAE ORB, and Metric thread types before ordering fittings.
Important: Never mix BSP (55°) threads with NPT (60°) threads, they may appear to fit but will leak under pressure. Always verify thread type, angle, and seal method before assembly.
Follow these six steps before ordering any fitting or adapter.
Use calipers to measure the outside diameter of male threads or inside diameter of female threads. This gives you the nominal size.
Use a thread pitch gauge or count threads over a 1-inch span. This determines TPI (imperial) or pitch in mm (metric).
NPT/JIC/SAE use 60°. BSP uses 55°. A thread gauge or close visual inspection can reveal this. Mixing 60° and 55° causes leaks.
Look at the end of the fitting. Flat face with O-ring groove = ORFS. 37° cone = JIC. Tapered threads = NPT/BSPT. O-ring on thread body = SAE ORB.
Run your finger along the threads. If the diameter changes (gets smaller toward the end), it's tapered (NPT/BSPT). Constant diameter = parallel (BSPP, JIC, ORFS).
Use the tables below or contact our specialists. Misidentified threads are the #1 cause of hydraulic leaks. When in doubt, bring the fitting in.
Side-by-side thread type comparison for fast field identification.
| Thread Type | Angle | Profile | Seal Method | Standard | Region |
|---|---|---|---|---|---|
| NPT / NPTF | 60° | 1:16 | Thread interference (taper) | ASME B1.20.1 | Most Common in NA |
| BSP / BSPP / BSPT | 55° | BSPT: 1:16 / BSPP: Parallel | BSPP: O-ring or bonded seal / BSPT: Thread interference | ISO 228 / BS 21 | European Standard |
| JIC | 37° flare | N/A, straight thread with flare | 37° flare metal-to-metal | SAE J514 | High Pressure Rated |
| ORFS | Flat face | N/A, straight thread | O-ring in face groove | SAE J1453 | Zero-Leak Standard |
| SAE / ORB | N/A | Straight UNF thread | O-ring on OD of male thread | SAE J1926 | Port Connection |
| Metric (DIN) | 60° | Straight metric thread | O-ring or bonded seal | DIN 3852 / ISO 6149 | European Metric |
Bring your fitting to our Cleveland, TN location or call our specialists. We carry adapters, crosses, and transitions for every thread type combination.