Hydraulic hose fitting identification
A fitting is named by three things you can measure: the thread's diameter over the crests, its pitch, and the seat. Fourteen millimetres at 18 threads per inch with a 37° nose cone is a -6 JIC.
Enter what you measured; the sizes within reach are ranked, the best match is drawn with its diameter, pitch and seat, and the look-alikes that share a thread are named.
SAE J514: the pitch, the diameter and the seat agree.
- JIC 37° flare
- Thread
- Male OD, table
- 14.30mm
- Pitch
- 18 TPI (1.41 mm)
- Tube OD
- 3/8 in
- Hose ID, same dash
- 9.5mm
How it’s calculated
Caliper the thread over the crests (a male's outside, a female's inside), on the fourth or fifth full thread of a taper thread. Gauge the pitch with inch and metric gauges. Lay a seat gauge on the seat: the one that sits parallel to the axis is the angle. A pipe thread measures about 1/4 in over its nominal size. A match is within 0.5 mm at the same pitch and seat.
Sizes within 1.2 mm of the OD
| Fitting | Thread | OD, mm | Off, mm | Pitch | Seat |
|---|---|---|---|---|---|
| JIC 37° flare -6 | 9/16-18 UNF | 14.30 | −0.10 | same | same |
| O-ring face seal (ORFS) -4 | 9/16-18 UNF | 14.20 | ±0.00 | same | differs |
| O-ring boss (ORB) -6 | 9/16-18 UNF | 14.30 | −0.10 | same | differs |
| NPT / NPTF 1/4 | 1/4-18 NPT | 13.54 | +0.66 | same | differs |
| Metric 24° cone, light (L) 8L | M14 × 1.5 | 14.00 | +0.20 | differs | differs |
| Metric 24° cone, heavy (S) 6S | M14 × 1.5 | 14.00 | +0.20 | differs | differs |
| BSPP (G), 60° cone 1/4 | G 1/4-19 | 13.16 | +1.04 | differs | differs |
| BSPT (R) 1/4 | R 1/4-19 | 13.16 | +1.04 | differs | differs |
JIC 37° flare (SAE J514): every size
| Size | Thread | Male OD, mm | Female ID, mm | Pitch | Hose ID, mm |
|---|---|---|---|---|---|
| -2 | 5/16-24 UNF | 7.94 | 6.90 | 24 TPI | 3.2 |
| -3 | 3/8-24 UNF | 9.50 | 8.60 | 24 TPI | 4.8 |
| -4 | 7/16-20 UNF | 11.10 | 10.00 | 20 TPI | 6.4 |
| -5 | 1/2-20 UNF | 12.70 | 11.60 | 20 TPI | 7.9 |
| -6 | 9/16-18 UNF | 14.30 | 13.00 | 18 TPI | 9.5 |
| -8 | 3/4-16 UNF | 19.10 | 17.60 | 16 TPI | 12.7 |
| -10 | 7/8-14 UNF | 22.20 | 20.50 | 14 TPI | 15.9 |
| -12 | 1 1/16-12 UN | 27.00 | 24.60 | 12 TPI | 19.0 |
| -14 | 1 3/16-12 UN | 30.10 | 28.30 | 12 TPI | 22.2 |
| -16 | 1 5/16-12 UN | 33.30 | 31.30 | 12 TPI | 25.4 |
| -20 | 1 5/8-12 UN | 41.30 | 39.20 | 12 TPI | 31.8 |
| -24 | 1 7/8-12 UN | 47.60 | 45.60 | 12 TPI | 38.1 |
| -32 | 2 1/2-12 UN | 63.50 | 61.50 | 12 TPI | 50.8 |
How do you measure a hydraulic fitting?
Caliper the thread over the crests: a male's outside diameter, a female's inside. On a taper thread, measure the fourth or fifth full thread. Gauge the pitch with both inch and metric gauges: 16 threads per inch and 1.5 mm are close. Then lay a seat gauge on the cone: the gauge that sits parallel to the fitting's axis gives the angle.
JIC or SAE 45°?
In the -2 to -5, -8 and -10 sizes the two share a thread, so only the seat tells them apart: 37° from the axis for JIC, 45° for SAE, and the seats are not interchangeable.
Why does a 1/2 in pipe thread measure 21 mm?
A pipe thread's size is nominal, not its diameter: BSP and NPT threads measure about 1/4 in over their nominal size, so a 1/2 BSPP is about 21 mm over the crests. Subtract 1/4 in from what you measure for the size.