JIC Fittings Guide › -6 JIC Fittings

-6 JIC Fittings: 9/16-18 UNF Thread for 3/8" Tube

A -6 JIC fitting is the 37° flare connection sized for 3/8" (9.53 mm) OD tube. Per SAE J514 and ISO 8434-2 it uses a 9/16-18 UNF straight thread. The dash number is the tube OD in sixteenths of an inch (6/16" = 3/8"), not the thread size, which is why a -6 measures larger across the threads than its name suggests. This page covers the dimensions, how to confirm you have a -6, common configurations and what to specify when you order. For every size from -2 to -32, see the main JIC fittings guide.

-6 JIC Dimensions

Measured values run slightly under nominal on plated or worn parts. Hex sizes are not fixed by the thread size alone, so confirm against the manufacturer's catalog if wrench size matters.

How to Confirm a Fitting Is -6 JIC

1. Measure the thread OD of a male (or the ID of a female) with calipers. Expect about 0.56" on a male -6.
2. Check pitch with an inch thread gauge: -6 JIC is 18 TPI.
3. Check the seat angle with a seat gauge. JIC is 37°; SAE 45° flare and 24° metric cones look similar.
4. Rule out neighbors. The sizes most often confused with -6 are -5 (1/2-20) and -8 (3/4-16).

The full process is in our guide on how to identify a JIC fitting.

Common Mix-Ups at -6

The -6 SAE 45° flare uses 5/8-18, not 9/16-18, so -6 JIC and -6 SAE 45° parts do not thread together. Note that -6 ORFS uses 11/16-16, and a 9/16-18 thread is also used on -4 ORFS, which is a common source of confusion. For reference, the ORFS (SAE J1453) thread at the same tube size is 11/16-16, so a -6 ORFS nut will not go onto a -6 JIC male. See JIC vs SAE 45° flare and JIC vs ORFS.

Where -6 JIC Is Typically Used

Typical applications include pilot lines, return and drain lines, small actuator and power-steering circuits, and many hose assemblies on tractors and compact loaders. Hose dash numbers generally refer to hose inside diameter, and a crimped hose end may carry the same or a different JIC size, so check the hose layline and the fitting separately.

Common -6 JIC Configurations

• Male JIC × male JIC straight unions and bulkhead unions
• Male JIC × male SAE O-ring boss (ORB) straight, 45° and 90° adapters
• Male JIC × male NPT adapters
• Female JIC swivel × male JIC adapters, elbows (45°/90°) and tees, including run and branch tees
• Caps and plugs, tube nuts and sleeves for flared tube
• Reducers to neighboring sizes
• Crimp hose ends with female JIC swivel (straight, 45°, 90°)

Descriptions of each shape are in our JIC fitting types guide.

Buying Tips for -6 JIC Fittings

• Describe both ends. For example: "-6 JIC male × -6 ORB male, 90° elbow, zinc-plated steel."
• Choose material to suit the fluid and environment — zinc-plated carbon steel for most hydraulics, 316 stainless for corrosion, brass mainly for lower-pressure service. See JIC materials and pressure ratings.
• Check pressure ratings in the manufacturer's catalog for the exact part and material; elbows, tees and adapters can be rated differently from straight fittings.
• Plan assembly. Use the manufacturer's torque or flats-from-wrench-resistance values; our JIC torque specs page explains both methods.

FAQ

Related guides

• JIC Fittings Guide (main)
• JIC vs NPT
• JIC vs ORFS
• JIC vs AN
• How to Identify a JIC Fitting
• JIC Thread Size Chart
• -4 JIC Fittings
• -8 JIC Fittings
• -10 JIC Fittings
• -12 JIC Fittings
• -16 JIC Fittings
• JIC vs SAE 45° Flare
• JIC vs BSPP
• JIC vs Metric (DIN 24°)
• JIC Torque Specs
• JIC Fitting Types
• JIC Materials & Pressure Ratings

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