Thread identifier
Three questions, working from geometry rather than dimensions — taper, thread angle and seat. Answer them with a caliper and a pitch gauge.
Step 1
Measure across the thread crests at the first thread and at the last. Does the diameter change?
This single measurement separates the two tapered families from everything else.
This narrows a fitting to a family, not a part number. Size and series still need measuring, and on a port you cannot easily re-machine it is worth confirming before you commit the joint.
For the full method, including what each family seals on and the pairing that leaks, read how to identify any hydraulic fitting in four steps.
Every port thread in this catalogue
118 thread designations across 5,714 stocked parts, taken from the port of every fitting we carry. Most thread charts are textbook extracts; this one is what actually turns up on parts, so the sizes you meet most often are the ones at the top of each group.
A designation identifies the thread, not the fitting. JIC, ORFS and SAE O-ring boss all run the same UNF threads, and an unprefixed 1/2"-14 is NPT or BSP taper with nothing in the label to say which. The notes under each heading say what is still open rather than picking for you.
Metric37 designations
A 60° metric thread. On a hydraulic port it is normally a 24° cone (DIN 2353 / ISO 8434-1) or a metric O-ring port — the seat decides, not the thread.
| Designation | Nominal size | Pitch | Parts |
|---|---|---|---|
| M18×1.5 | M18 | 1.5 mm | 244 |
| M16×1.5 | M16 | 1.5 mm | 239 |
| M22×1.5 | M22 | 1.5 mm | 226 |
| M14×1.5 | M14 | 1.5 mm | 208 |
| M36×2 | M36 | 2 mm | 175 |
| M30×2 | M30 | 2 mm | 129 |
| M52×2 | M52 | 2 mm | 121 |
| M45×2 | M45 | 2 mm | 103 |
| M24×1.5 | M24 | 1.5 mm | 102 |
| M20×1.5 | M20 | 1.5 mm | 97 |
| M42×2 | M42 | 2 mm | 92 |
| M26×1.5 | M26 | 1.5 mm | 86 |
| M12×1.5 | M12 | 1.5 mm | 85 |
| M27×1.5 | M27 | 1.5 mm | 78 |
| M30×1.5 | M30 | 1.5 mm | 68 |
| M39×2 | M39 | 2 mm | 45 |
| M33×2 | M33 | 2 mm | 33 |
| M36×2.0 | M36 | 2.0 mm | 25 |
| M10×1 | M10 | 1 mm | 20 |
| M30×2.0 | M30 | 2.0 mm | 20 |
| M52×2.0 | M52 | 2.0 mm | 18 |
| M33×1.5 | M33 | 1.5 mm | 16 |
| M12×1.25 | M12 | 1.25 mm | 14 |
| M42×2.0 | M42 | 2.0 mm | 9 |
| M42×1.5 | M42 | 1.5 mm | 8 |
| M45×2.0 | M45 | 2.0 mm | 8 |
| M36×1.5 | M36 | 1.5 mm | 7 |
| M27×2 | M27 | 2 mm | 6 |
| M48×2 | M48 | 2 mm | 5 |
| M60×2 | M60 | 2 mm | 3 |
| M64×2 | M64 | 2 mm | 3 |
| M10×1.0 | M10 | 1.0 mm | 1 |
| M12×1 | M12 | 1 mm | 1 |
| M24×1.6 | M24 | 1.6 mm | 1 |
| M27×2.0 | M27 | 2.0 mm | 1 |
| M33×2.0 | M33 | 2.0 mm | 1 |
| M48×2.0 | M48 | 2.0 mm | 1 |
BSP parallel — G10 designations
Parallel, 55° Whitworth form, ISO 228. It never seals on the thread: the seal is a 60° cone in the port or a bonded washer under the hex.
| Designation | Nominal size | Pitch | Parts |
|---|---|---|---|
| G3/8"-19 | G3/8" | 19 TPI | 163 |
| G1/2"-14 | G1/2" | 14 TPI | 161 |
| G3/4"-14 | G3/4" | 14 TPI | 157 |
| G1/4"-19 | G1/4" | 19 TPI | 153 |
| G1"-11 | G1" | 11 TPI | 129 |
| G1.1/4"-11 | G1.1/4" | 11 TPI | 94 |
| G1.1/2"-11 | G1.1/2" | 11 TPI | 71 |
| G5/8"-14 | G5/8" | 14 TPI | 68 |
| G1/8"-28 | G1/8" | 28 TPI | 58 |
| G2"-11 | G2" | 11 TPI | 40 |
BSP taper — R and Rc24 designations
Taper, 55° Whitworth form, ISO 7. R is the male taper, Rc the female. It seals on the thread itself, so it wants sealant and it is not reusable indefinitely.
| Designation | Nominal size | Pitch | Parts |
|---|---|---|---|
| R 1/2"-14 | 1/2" | 14 TPI | 26 |
| R 3/4"-14 | 3/4" | 14 TPI | 25 |
| R 3/8"-19 | 3/8" | 19 TPI | 24 |
| R 1/4"-19 | 1/4" | 19 TPI | 21 |
| R 1"-11 | 1" | 11 TPI | 19 |
| R 1.1/4"-11 | 1.1/4" | 11 TPI | 14 |
| R 1/8"-28 | 1/8" | 28 TPI | 13 |
| R 1.1/2"-11 | 1.1/2" | 11 TPI | 12 |
| R 2"-11 | 2" | 11 TPI | 10 |
| Rc 1/4"-19 | 1/4" | 19 TPI | 6 |
| Rc 3/8"-19 | 3/8" | 19 TPI | 6 |
| Rc 1/2"-14 | 1/2" | 14 TPI | 5 |
| Rc 1/8"-28 | 1/8" | 28 TPI | 5 |
| Rc 1"-11 | 1" | 11 TPI | 5 |
| Rc 3/4"-14 | 3/4" | 14 TPI | 5 |
| Rc 1.1/4"-11 | 1.1/4" | 11 TPI | 4 |
| Rc 1.1/2"-11 | 1.1/2" | 11 TPI | 3 |
| Rc 2"-11 | 2" | 11 TPI | 3 |
| 1.1/2"-11 | 1.1/2" | 11 TPI | 2 |
| 1.1/4"-11 | 1.1/4" | 11 TPI | 2 |
| 1"-11 | 1" | 11 TPI | 2 |
| 2"-11 | 2" | 11 TPI | 2 |
| 3/8"-19 | 3/8" | 19 TPI | 2 |
| 1/4"-19 | 1/4" | 19 TPI | 1 |
NPT16 designations
Taper, 60° form, ASME B1.20.1, sealing on the thread. Nothing in the label is prefixed here, but at these sizes BSP taper has a different pitch, so NPT is the only standard that fits.
| Designation | Nominal size | Pitch | Parts |
|---|---|---|---|
| NPT 3/4"-14 | 3/4" | 14 TPI | 46 |
| NPT 1/2"-14 | 1/2" | 14 TPI | 43 |
| NPT 1"-11.5 | 1" | 11.5 TPI | 41 |
| NPT 3/8"-18 | 3/8" | 18 TPI | 41 |
| NPT 1/4"-18 | 1/4" | 18 TPI | 40 |
| NPT 1.1/4"-11.5 | 1.1/4" | 11.5 TPI | 30 |
| NPT 1/8"-27 | 1/8" | 27 TPI | 27 |
| NPT 1.1/2"-11.5 | 1.1/2" | 11.5 TPI | 26 |
| NPT 2"-11.5 | 2" | 11.5 TPI | 18 |
| 3/8"-18 | 3/8" | 18 TPI | 14 |
| 1"-11.5 | 1" | 11.5 TPI | 10 |
| 1/4"-18 | 1/4" | 18 TPI | 7 |
| 1.1/4"-11.5 | 1.1/4" | 11.5 TPI | 5 |
| 1.1/2"-11.5 | 1.1/2" | 11.5 TPI | 4 |
| 2"-11.5 | 2" | 11.5 TPI | 3 |
| NPT 2.1/2"-8 | 2.1/2" | 8 TPI | 1 |
Inch pipe — NPT or BSP taper2 designations
At 1/2" and 3/4" both NPT and BSP taper are 14 TPI, so a designation with no prefix does not tell you which one you are holding. Measure the flank angle — 60° is NPT, 55° is BSP.
| Designation | Nominal size | Pitch | Parts |
|---|---|---|---|
| 3/4"-14 | 3/4" | 14 TPI | 17 |
| 1/2"-14 | 1/2" | 14 TPI | 15 |
Inch straight — UN/UNF29 designations
A straight UN/UNF thread. JIC 37° flare, ORFS and SAE O-ring boss all run these, so the thread narrows it to three and the seat picks between them.
| Designation | Nominal size | Pitch | Parts |
|---|---|---|---|
| 9/16"-18 | 9/16" | 18 TPI | 199 |
| 1.1/16"-12 | 1.1/16" | 12 TPI | 151 |
| 3/4"-16 | 3/4" | 16 TPI | 148 |
| 7/8"-14 | 7/8" | 14 TPI | 137 |
| 1.5/16"-12 | 1.5/16" | 12 TPI | 127 |
| 1.3/16"-12 | 1.3/16" | 12 TPI | 108 |
| 7/16"-20 | 7/16" | 20 TPI | 102 |
| 1.5/8"-12 | 1.5/8" | 12 TPI | 91 |
| 1/2"-20 | 1/2" | 20 TPI | 86 |
| 11/16"-16 | 11/16" | 16 TPI | 81 |
| 13/16"-16 | 13/16" | 16 TPI | 81 |
| 1.7/8"-12 | 1.7/8" | 12 TPI | 79 |
| 1.7/16"-12 | 1.7/16" | 12 TPI | 73 |
| 1.11/16"-12 | 1.11/16" | 12 TPI | 59 |
| 1"-14 | 1" | 14 TPI | 58 |
| 2"-12 | 2" | 12 TPI | 43 |
| 2.1/2"-12 | 2.1/2" | 12 TPI | 36 |
| 3/8"-24 | 3/8" | 24 TPI | 13 |
| 5/16"-24 | 5/16" | 24 TPI | 11 |
| 1/4"-14 | 1/4" | 14 TPI | 10 |
| 5/8"-18 | 5/8" | 18 TPI | 7 |
| 7/8"-18 | 7/8" | 18 TPI | 4 |
| 1.1/16"-14 | 1.1/16" | 14 TPI | 2 |
| 11/16"-18 | 11/16" | 18 TPI | 2 |
| 13/16"-18 | 13/16" | 18 TPI | 2 |
| 7/16"-24 | 7/16" | 24 TPI | 2 |
| 7/8"-16 | 7/8" | 16 TPI | 2 |
| 2"-13 | 2" | 13 TPI | 1 |
| 9/16"-24 | 9/16" | 24 TPI | 1 |
Counted from the live catalogue and refreshed hourly. Designations we could not read to a standard — bare sizes with no pitch, weld preps, and oilfield LP threads, whose label carries no pitch — are left out rather than guessed at.