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SAE O-Ring Boss (ORB) Ports and Fittings

SAE O-ring boss (ORB) is a straight-thread port that seals with an O-ring compressed into a chamfer at the top of the port. This sheet covers how ORB ports and fittings work, the adjustable and non-adjustable styles and how to identify them.

Ref HY-0015SAE J1926SAE J514ISO 11926

Draft, open for review. Check every value against the governing standard and the manufacturer’s data before use.

What it is

An ORB port is a straight UN/UNF thread with a spot face and a chamfer at its mouth, defined in SAE J1926 and ISO 11926. The male fitting has a matching straight thread with an O-ring seated at the base. When the fitting is tightened, the O-ring is squeezed into the chamfer and seals. The thread holds the fitting; it does not seal. ORB ports are common on pumps, valves, cylinders and manifolds because they seal better and are less likely to crack a casting than tapered pipe threads. SAE J514 covers the fittings that go into these ports.

How to identify

Look for an O-ring at the base of a straight male thread. On the port, look for a smooth spot face and a chamfer at the top of a straight thread. ORB uses the same thread sizes as JIC 37° by dash number, so check that the male end has no 37° flare. Measure thread OD and pitch and match them on the JIC 37° thread size chart. The O-ring for each dash size is the AS568 900-series ring with the same last digits, for example a -8 port takes a 908 ring. See the AS568 chart for ring dimensions.

ORB fitting styles

Style	How it seats	Typical use	Notes
Non-adjustable (straight)	Hex shoulder bottoms on the spot face	Straight connectors, plugs, adapters	Tighten to the maker's value; no orientation needed
Adjustable (elbows, tees)	Locknut and backup washer push the O-ring into the chamfer	Elbows and tees that must point a set way	Orient first, then tighten the locknut
Plug, hex or internal hex	Same as non-adjustable	Closing unused ports	Use the matching ring, not a generic one
Adapter, ORB to JIC	ORB end into port, JIC flare out	Most common pump and valve connection	Two different sealing methods on one part

Key points

The O-ring must be the right size and the right compound for the fluid and temperature. Nitrile 90 durometer is common for petroleum fluids; check for other fluids.
Lubricate the O-ring with system fluid before assembly.
For adjustable fittings: back the locknut off fully, thread in until the washer touches the spot face, back out to orient (no more than one turn), then hold the body and tighten the locknut.
Assembly torque values come from SAE J1926, SAE J514 or the fitting maker. Do not guess.
Never use thread sealant or tape on an ORB thread.

Common mistakes

Mistaking an ORB port for a JIC male because the threads match.
Reusing a flattened or nicked O-ring.
Rolling or cutting the O-ring on the threads during assembly.
Over-orienting an adjustable elbow so the O-ring is no longer trapped in the chamfer.
Forcing a tapered pipe fitting into an ORB port.

Governing standards: SAE J1926 and ISO 11926 (straight thread O-ring ports); SAE J514 (hydraulic tube fittings, including straight thread O-ring fittings); SAE AS568 (O-ring sizes).

Reference only. Verify against the current governing code or standard, the manufacturer's data and the project documents before use. Apps for Distributors disclaims liability arising from reliance on this reference.

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