SAE ORB (O-Ring Boss) Tube Fittings: Stainless & High-Nickel Alloy

A SAE ORB fitting terminates in a male straight-thread stud end. It seals against a machined port spotface with an elastomer O-ring, standardized as SAE J1926. Crestflo builds this O-Ring Boss end connection on stainless-steel and high-alloy instrumentation fittings, dimensionally to SAE J1926 (part of SAE J514, with ISO 11926 as the ISO equivalent), across dash -2 to -32. Standard items sit ready in stock, specials are made to order, and delivery runs 6–8 weeks. Here, "ORB" means the SAE O-Ring Boss straight-thread port connection under SAE J1926, and nothing else. It isn't the O-Ring Face Seal (ORFS), the SAE 45° flare, or the JIC 37° flare. These parts come in instrumentation-grade stainless and high-nickel alloys, not carbon-steel hydraulic grades. Request a quote or request a free sample to specify yours.

Also Known As: O-Ring Boss, SAE J1926, STOR & Straight-Thread O-Ring Designations

Buyers and specifiers call this connection by a lot of different names. It's commonly known as an O-ring boss fitting, ORB fitting, SAE O-ring boss, or straight-thread O-ring boss. It also turns up as SAE straight thread (STOR), male O-ring boss (MORB), and adjustable O-ring boss (AORB). In standards language, it's designated SAE J1926 for ports and stud ends, sits within SAE J514, and carries ISO 11926 as its ISO equivalent. Reversed and spec-driven phrasings show up too: O-ring boss port, O-ring boss thread, SAE J1926 fitting, SAE J514 O-ring boss, and dash-numbered forms like #6 ORB or #8 SAE ORB. All of them point back to the same J1926 straight-thread seat with its elastomer O-ring.

What Is a SAE O-Ring Boss (ORB) Fitting and How the Straight-Thread O-Ring Seal Works

SAE ORB fittings seal through a simple mechanical trick: an elastomer O-ring sits on a male straight-thread stud end, and when that stud is tightened, the O-ring compresses against the machined spotface of a matching boss port. The straight, parallel thread does the heavy lifting mechanically. Sealing, though, comes entirely from the O-ring. That split is what makes the joint leak-free, reusable, and repeatable, with no thread sealant and no tapered-thread interference needed.

This is also the key thing separating ORB from NPT. An ORB port depends on a soft-seal O-ring riding a straight thread. Make-up stays consistent, and rework stays clean, even after many assemblies. SAE J1926 exists as a standardized, non-proprietary port form, so any J1926-compliant O-ring boss stud end will mate with its matching port under the standard. Brand doesn't matter.

Why Choose ORB Over NPT Tapered Thread

NPT seals by tapered-thread interference, needs sealant, and wears with repeated make-up; ORB seals with an O-ring on a straight thread, so it is leak-free at high working pressures, reusable, and repeatable without galling the seal path. The O-ring absorbs the sealing duty while the straight thread sets consistent, torque-controlled clamp load, which is why ORB is favored on high-pressure ports where a re-makeable, high-integrity connection matters. To tell a straight-thread O-ring boss apart from an NPT or BSP port, see the thread identification guide; for the ORB-versus-JIC decision, see JIC vs ORB.

SAE ORB Size Chart: Dash-Size, Thread & Dimensions Chart, Dash -2 to -32 (SAE J1926)

SAE ORB sizes come down to two things: dash size and a straight (parallel) UN/UNF thread. This SAE ORB size chart lists the standard, published SAE J1926 dash sizes alongside their UN/UNF straight-thread callouts. Values follow SAE J1926, though they can be adjusted to fit specific requirements. SAE ORB fitting dimensions, along with the O-ring boss port dimensions each dash size mates with, follow SAE J1926 too. A compliant stud end and its mating port share the same thread and spotface geometry, no exceptions. On the tube side of ORB×tube fittings, you'll find both imperial and metric sizes.

Take a #8 (dash-8) SAE ORB: it runs on a 3/4-16 straight thread. Sealing depends on the boss port too. The mating spotface and counterbore need to be machined to the SAE J1926 port standard, or it won't seal correctly.

SAE ORB O-Ring Seal & Elastomer Options: Nitrile, FKM (Viton) & EPDM

Each SAE dash size seats a specific O-ring that compresses against the boss spotface. It's the O-ring that does the sealing, not the thread. Nitrile (Buna-N) serves as the standard general-service elastomer. FKM (Viton) is available for high-temperature and hydrocarbon service, and EPDM covers steam, water, and polar media. Elastomer selection depends on the media and the operating temperature, and it can be customized to your requirements. O-ring size for each dash size follows the SAE J1926 O-ring boss series, so every dash seats its own standard O-ring. Both the elastomer and the alloy govern temperature capability, so match the seal to the service using the seal material temperature selection guide. Specify your elastomer on the RFQ, or ask our engineering team for the full ORB O-ring chart, which lists O-ring size and elastomer for each dash.

Adjustable vs Non-Adjustable SAE ORB Fittings

A non-adjustable ORB is a fixed male connector. The stud end threads home and seats the O-ring at a set position, nothing more to it. An adjustable ORB, the kind used on orientable elbows, tees, and run tees, carries a locknut and backup washer instead, so the port end can be clocked to whatever angle the job requires and then locked down with the O-ring fully compressed against the spotface. Adjustable O-ring boss (AORB) forms let a fabricator aim a run without breaking the seal. Non-adjustable forms, on the other hand, suit straight male-connector runs where orientation simply doesn't matter.

SAE ORB Configurations & End Combinations: Male Connector, Elbow, Tee & ORB-to-NPT/JIC

The SAE ORB line spans the entire configuration set. It pairs an O-ring boss end with a second connection built to match the assembly.

The ORB×tube compression end takes single or double ferrules, hardened or non-hardened, built to requirement, and handles tube up to 2" (50 mm) OD. It pairs with the wider Crestflo compression range. Crestflo supplies the SAE ORB end as a male straight-thread O-ring boss stud end that threads into a machined female O-ring boss port. Need a fitting with a female O-ring boss port instead, or a port-to-port ORB adapter? Just state the mating end on your RFQ, and our engineering team will confirm availability. For the ORB-versus-face-seal distinction, the VCO O-ring face seal fittings page covers the ORFS side of things.

SAE ORB Fitting Materials: 316/316L, 904L, Duplex, Inconel & Titanium

SAE ORB fittings come in the full stainless and high-alloy range, and that's exactly what separates an instrumentation-grade ORB fitting from a generic carbon-steel hydraulic part. Standard stainless grades run 304/304L, 316/316L, and 904L. Corrosion-resistant and super-austenitic options include Duplex 2205, Super Duplex 2507, 254 SMO (6Mo), AL-6XN, and Alloy 20. Nickel alloys cover Inconel 600/601/625/718/825, Incoloy 800/800H/825, Monel 400/K500, Hastelloy C-276/C-22/B-2/B-3/X, and Nickel 200/201. Titanium Grade 2 rounds out the list. Buyers tend to ask for these by name: a 316 ORB fitting or stainless-steel ORB fitting for general chloride service, a duplex or super-duplex ORB fitting when chloride SCC is the concern, and an Inconel, Monel, or Hastelloy ORB fitting for sour or high-temperature media. Sour service calls for alloys compliant with NACE MR0175 / ISO 15156-, and those are what get supplied. Brass isn't part of the US line. Stainless and alloy only.

You'll find the material background covered on the grade pages above. Crestflo supplies these grades as instrumentation fittings, not mill forms, and that distinction matters for how they're specified. Available finishes are material finish, electropolish, passivation, and silver anti-galling plating for stainless thread make-up. O2-cleaning is available on request.

SAE ORB Pressure & Temperature Ratings and Applications

An O-ring boss is a high-integrity port form: a high-pressure ORB built for demanding working pressures. The achievable rating isn't one fixed value. It's set by dash size, tube wall, material, and the O-ring elastomer, all working together. Working pressure follows the applicable standard and the tube-side rating of the ORB×tube compression end. Ratings can be tailored to what the job requires, so confirm the certified rating for your dash size, alloy, and elastomer on the RFQ. Related Crestflo high-pressure families extend to 15,000 PSI, and go higher still on the cone-and-thread range. The re-makeable straight-thread O-ring joint fits hydraulics, instrument-air ports, oil-and-gas process and sampling loops, offshore work, and analytical systems. Take a look at hydraulics, instrument air, and oil and gas.

Standards, Certifications & Traceability for SAE ORB Fittings

Crestflo SAE ORB fittings conform to SAE J1926 and SAE J514 for the O-ring boss end, with ISO 11926 as the ISO equivalent. The company's ISO 9001 / 14001 / 45001 and PED certified. It also holds the standard approvals that apply to compression tube fittings, including ASTM F1387 performance qualification, which governs the compression side of ORB×tube ends, and it supplies NACE MR0175 / ISO 15156-compliant alloys for sour service. Traceability comes standard as EN 10204 MTC 3.1, with 3.2 available on request, and every part carries a heat/lot number marking. Testing spans hydraulic proof, burst and impulse, pneumatic, flexure fatigue, rotary flex, vibration, thermal cycling, pull-out, and vacuum, plus PMI. In-house NDT is standard, and destructive testing runs through ISO/IEC 17025-accredited labs; third-party inspection is available on request. Certificates are stated here and held in full at quality; for more detail, see ASTM F1387 and NACE MR0175. The Crestflo Engineering Team reviewed this page.

Request a Quote, Sample or Cross-Reference for SAE ORB Fittings

Every order is quoted, not carted. End users and EPC contractors can request a quote or a free sample, and OEMs can ask about the private-label program. ORB is a standardized SAE J1926 port, so any compliant O-ring boss stud end interchanges by the standard. For a Parker, Swagelok, or Hoke part-by-part equivalent, request your cross-reference from our engineering team through the master interchange. Swagelok® is a trademark of Swagelok Company, and Parker® is a trademark of Parker Hannifin Corporation; Crestflo isn't affiliated with or endorsed by either company. Want the ordering-code guide for ORB series, dash, end, material, O-ring, and finish options? Just ask our engineering team on the RFQ. Distributors can request the SAE ORB line card. The ORB fittings catalog is available to download, and datasheets and CAD go out to customers on request.

Why Crestflo for SAE ORB Fittings

Crestflo supplies instrumentation-grade SAE ORB fittings to SAE J1926 dimensions across 316L through Inconel, duplex, and titanium. That's a depth of material options most hydraulic sellers simply don't carry. For US buyers hunting a SAE ORB fitting supplier close to home rather than importing directly overseas, Crestflo offers a domestic source: a Houston, TX sales contact, delivery nationwide, and a single RFQ covering every alloy listed above.

Standard items ship from ready stock. Specials are made to order. Either way, lead times run 6-8 weeks, well under the 20-plus weeks common among the major suppliers. Buyers can order in small MOQs, request private label, and choose imperial or metric sizing. Every part ships with a heat number and an EN 10204 MTC 3.1 certificate.

Manufacturing origin is India, though US or European melt is available on request, and full material traceability comes standard. Crestflo operates as the instrumentation division of a four-decade-old export house recognized by the Government of India, with a proven delivery record across the Middle East. Take a look at why Crestflo, lead time, and testing and inspection.

SAE ORB Fitting FAQ

Related Tube Fittings, Materials & Resources

• Parent line: instrumentation tube fittings
• Sibling connections: JIC 37° flare fittings · NPT-end tube fittings · ISO-parallel tube fittings · VCO O-ring face seal fittings
• Materials: 316/316L · Super Duplex 2507 · 254 SMO · Inconel 625 · Monel 400 · Hastelloy C-276 · Titanium Gr 2
• Decision guides: JIC vs ORB · thread identification guide · seal material temperature selection
• Standards: NACE MR0175 · EN 10204 MTC · ASTM F1387

Reviewed by the Crestflo Engineering Team