-6 JIC Fitting Size and Dimensions
A -6 JIC fitting is for 3/8 in tube and has a 9/16-18 UNF thread. Here are its measurements, look-alikes and tightening values.
Last updated October 30, 2026. Reference values; verify against manufacturer specifications.
The -6 JIC is one of the most common hydraulic fitting sizes. It turns up on loaders, log splitters, tractors, power units and many other machines. It is also one of the easiest to misidentify, because its 9/16-18 thread is shared with three other fitting families. This page gives the full -6 dimensions, the fittings it is most often confused with, and the published tightening values.
-6 JIC at a glance
- Tube size: 3/8 in OD (9.53 mm). The dash number is the tube OD in sixteenths of an inch: 6/16 in = 3/8 in.
- Thread: 9/16-18 UNF: 0.5625 in major diameter, 18 threads per inch.
- Male OD: about 0.56 in (14.29 mm). Female ID: about 0.51 in (13.0 mm).
- Seat: 37° flare, metal-to-metal.
-6 JIC fitting dimensions
| Dimension | Inch | Metric |
|---|---|---|
| Tube OD | 3/8 in (0.375 in) | 9.53 mm |
| Thread | 9/16-18 UNF | pitch 1.411 mm |
| Threads per inch | 18 | 1.411 mm per thread |
| Male thread OD | 0.5625 in | 14.29 mm |
| Female thread ID (approx.) | 0.51 in | 13.0 mm |
| Seat angle | 37° from centreline (74° included) | same |
| Hex size | Varies by maker and part | check the catalog |
Thread and tube sizes per SAE J514 as published by Parker and Eaton. Female ID is the approximate value in the Eaton and McGill identification guides. Metric values are converted from inch at 25.4 mm/in. Hex sizes are not standardised across makers, so they are not listed.
Note that "-6" describes the tube, not the thread. A -6 JIC fitting does not have a 3/8 in thread; its thread is 9/16 in across. This is the single most common source of ordering errors with this size.
How to confirm a -6 JIC fitting
- Check the seat. A male -6 JIC has a convex cone nose. If you have a seat gauge, it should sit flush at 37°.
- Measure the thread. A male should read close to 0.56 in (14.3 mm). A female should read about 0.51 in (13.0 mm) across the inner crests. See how to measure JIC fittings.
- Check the pitch. The 18 TPI leaf of an inch thread gauge should sit flush. The pitch is 1.41 mm, which is not a standard metric pitch, so every leaf of a metric gauge will rock.
- Rule out look-alikes using the table below, or enter your numbers in the finder on the JIC identification page.
Fittings that look like -6 JIC
The 9/16-18 thread is used on -6 JIC, -6 ORB and -4 ORFS fittings. A male of any of these will thread into a female of the others, so the seat is the only reliable test. Two other fittings come close in diameter:
| Fitting | Thread | OD (in / mm) | TPI or pitch | How to tell |
|---|---|---|---|---|
| -6 ORB (SAE J1926) | 9/16-18 (same) | 0.56 / 14.29 | 18 TPI | O-ring under the hex, no cone |
| -4 ORFS (SAE J1453) | 9/16-18 (same) | 0.56 / 14.29 | 18 TPI | Flat face with an O-ring groove |
| -6 SAE 45° flare | 5/8-18 | 0.63 / 15.88 | 18 TPI | 45° cone; about 1.6 mm larger |
| 1/4 NPT | 1/4-18 NPT | about 0.54 / 13.7 | 18 TPI | Tapered thread, no seat |
| M14x1.5 metric | M14x1.5 | 0.55 / 14.0 | 1.5 mm (about 16.9 TPI) | Pitch; usually a 24° or 30° seat |
Look-alike threads from the Eaton and McGill thread identification guides, which agree on these sizes; metric threads are nominal.
The 1/4 NPT and M14x1.5 cases need the most care. M14x1.5 is within about 0.3 mm of the -6 JIC diameter, and 1/4 NPT within about 0.6 mm. 1/4 NPT also has 18 TPI, so only its taper and lack of a seat give it away. Comparisons in detail: JIC vs ORB, JIC vs ORFS, JIC vs NPT, JIC vs SAE 45°.
Torque and flats for -6 JIC
Parker recommends tightening steel JIC fittings by flats from wrench resistance (FFWR) and gives torque as a reference. Published torque ranges for the same size differ between sources:
| Source | Value | Notes |
|---|---|---|
| Parker Catalog 4400, swivel nut | 1-1/2 flats; reference 22 ft-lb (30 N·m) | FFWR is the recommended method |
| Tameson JIC assembly guide, flared tube nut / swivel nut | 2 flats / 1-1/2 flats | Tube nuts take more rotation than swivels |
| Hose and Fittings assembly chart, tube / swivel | 1-1/2 flats / 1-1/4 flats; 20–22 ft-lb | A lower flats count from a second chart |
| SAE J514 range (as published by distributors) | 18–20 ft-lb (24–27 N·m) | Torque range, steel |
Bring the nut to finger-tight, then wrench-tight until you feel resistance. Mark the nut and the fitting, and turn the nut the stated number of flats; one flat is 60°. The full table, with material adjustments, is on the JIC torque chart.
-6 JIC next to its neighbouring sizes
There is no -7 JIC in common use, so the next size up is -8. The -5 is close to the -6 in diameter, and a worn -6 female can read close to a -5 male, so check the pitch: 20 TPI for -5, 18 TPI for -6.
| Dash | Tube OD (in) | Thread | Male OD (mm) | Female ID (mm, approx.) |
|---|---|---|---|---|
| -5 | 5/16 | 1/2-20 | 12.70 | 11.4 |
| -6 | 3/8 | 9/16-18 | 14.29 | 13.0 |
| -8 | 1/2 | 3/4-16 | 19.05 | 17.5 |
Hose, tube and adapters
On hydraulic hose, a -6 dash number normally means a 3/8 in inside diameter. A -6 hose often has -6 JIC ends, but not always: adapters and reducing ends are common, so measure the end itself. To connect a -6 JIC hose to a port of a different type, use an adapter with a male -6 JIC end and the matching port end, for example -6 ORB or 1/4 NPT. For metric equivalents of every size, see the JIC metric conversion chart, and for the full range, the JIC fitting size chart.
Other single-size pages: -4 JIC fitting size, -8 JIC fitting size, -10 JIC fitting size, -12 JIC fitting size, -16 JIC fitting size. All sizes in one table: the JIC dash size chart. To check which half of a joint you are holding, see male vs female JIC fittings.
References
SAE J514 dimensions as published by Parker and Eaton; Eaton Thread Identification Guide; McGill Hose thread identification guide; Parker Catalog 4400 assembly methods. Values are reference only.
Frequently asked questions
What thread is a -6 JIC fitting?
9/16-18 UNF: 9/16 in (14.29 mm) major diameter with 18 threads per inch.
What tube size is -6 JIC?
3/8 in OD tube (9.53 mm). The dash number is the tube OD in sixteenths of an inch.
Is -6 JIC the same as 3/8 JIC?
Yes. "3/8 JIC" refers to the tube size. The thread is 9/16-18, not 3/8.
Will a -6 JIC fit a -6 ORB port?
The threads match (both 9/16-18), but they seal differently. A JIC cone cannot seal an ORB port, so use a -6 ORB to -6 JIC adapter.
How much torque does a -6 JIC need?
Parker gives 1-1/2 flats from wrench resistance for a steel swivel, with a reference torque of 22 ft-lb (30 N·m). Published SAE J514 ranges list 18–20 ft-lb. Follow your fitting maker's instructions.