Fittings and Threaded Adapters

Fittings and Threaded Adapters – AN/NPT/ORB/metric solutions for leak-free plumbing, tidy routing and easy servicing

Fittings and Threaded Adapters is built for making fuel and oil plumbing consistent across hoses, hardlines, rails and regulators, so sealing is determined by standards rather than guesswork. The category is organised into 14 main groups and totals 643 items, which is why it is often the fastest way to finish an install without improvising adapter stacks.

Typical jobs covered here include elbows for packaging, banjo connections where height is limited, union joins for straight-line extensions, tee and Y splitter branches for take-offs, and caps/plugs for unused ports. A reliable result starts with identifying the receiving port (AN flare seat, ORB O-ring boss, tapered NPT, or a specific metric pitch) before choosing size and geometry.

Technical Basics

AN connections typically seal on a 37° flare seat, so sealing depends on clean, undamaged seats rather than thread sealant. NPT is commonly tapered and often seals on the thread, while ORB ports seal via an O-ring, making O-ring condition and seating critical. With metric ports, pitch and the intended sealing face (washer/O-ring/seat) must match exactly.

For custom tanks, sumps or piping, weld-on ports are usually the cleanest approach: use Steel Weld-On Threaded Bungs for steel work and Aluminium Weld-On Threaded Bungs for aluminium parts. If you are converting between standards, Brass Adapters and Fittings (NPT/BSP/Metric/AN) is a practical place to start, and for instrumentation take-offs Sensor-Port AN Nipples and Adapters (1/8 NPT) helps keep layouts compact.

One short warning: near-matching threads (for example NPT vs BSP variants, or “close enough” metric pitches) can damage ports and still leak under pressure. If thread ID is not certain, confirm the component specification first, then choose the adapter that matches the sealing method.

Selection Criteria

Start with routing: if you need a gentler change of direction, 45° AN Elbow Fittings can help avoid hose kinks and reduce side-load at the joint. If you are building with hardline, AN Retaining Nuts, Tube Nuts and Tube Sleeves are the proper way to terminate and adapt the tube to AN-style connections.

Where clearance is tight, Banjo Fittings and Banjo Bolts can provide a lower-profile connection with controlled orientation. For frequent servicing or OEM-style fuel interfaces, Quick Connects and Special Fuel Adapters are worth considering, while straight-through joins or controlled disconnects are covered by Conical (Flare) Union Adapters (AN/NPT) and Dry Break Connectors.

If the job is specifically oil cooler plumbing, begin with Oil Cooler Fittings so you can match typical cooler ports and hose-end styles first. When comparing parts, prioritise the sealing method (flare seat vs O-ring vs thread seal), then select geometry that leaves spanner access and keeps hoses relaxed.

Installation & Maintenance

Most leaks come from cross-threading, damaged sealing faces, or hoses pulling sideways on the fitting. For branches, T-Fittings and Y-Splitters (AN/NPT) work best when you plan tool access and hose bend radius, then pressure-test and re-check after heat cycling.

With weld-on bungs, correct surface preparation and matching material (steel-to-steel, aluminium-to-aluminium) set the baseline, then the fitting choice finishes the joint. Keep assemblies clean, and use thread sealant only where the design seals on the thread.

FAQ

How do AN, NPT and ORB differ in sealing?
AN typically seals on a 37° flare seat, so seat condition is critical. NPT is tapered and often seals on the thread. ORB seals with an O-ring, so O-ring fit and seating are what make it leak-free.

How can I tell if a port is NPT or BSP?
They can look similar, but thread form and sealing behaviour differ. The safest route is the component specification or accurate thread measurement (diameter, pitch, taper). Avoid forcing a near-match thread, as damaged ports can leak permanently.

When should I choose a banjo fitting?
Use a banjo where height is limited or you need a low-profile, orientable connection. It is common in tight packaging where a conventional elbow would foul nearby parts. Always verify bolt thread and washer/seal type for the application.

Steel or aluminium weld-on bung: which one should I use?
Match the bung material to the part you are welding into: steel for steel components and aluminium for aluminium components. Correct welding practice and preparation matter as much as the bung itself. After welding, choose the fitting that matches the port standard and sealing method.

What AN size is most common for fuel and oil lines?
Many builds use AN-6, AN-8 and AN-10, but the correct choice is the one that matches your hose ends and component ports. Do not downsize the main run purely for convenience, as it can affect flow. Use the product page interface description as the final reference.

Why does a new joint weep after assembly?
On AN joints, a nicked or dirty flare seat is a common cause; on NPT, incorrect thread ID or poor thread-seal practice can be the issue. On ORB, a pinched or hardened O-ring is typical. Pinpoint the sealing surface first, then correct the root cause instead of adding more torque.

Choose fittings by port standard, sealing method and packaging, then order the adapters you need to complete your plumbing.