AN Retaining Nuts, Tube Nuts and Tube Sleeves covers TURBOWORKS aluminium hardware used to assemble and service AN connections in multiple sizes (e.g. AN-3 to AN-12). These small parts are commonly used across fuel, oil and water plumbing where you want a tidy, serviceable joint.
For related fittings, go back to Fittings and Threaded Adapters. Filter by Size, sort the results, then open the product page to confirm the exact spec for your AN-6 / AN-8 setup. Choose the right sizes and add the required items to your basket.
AN Retaining Nuts, Tube Nuts and Tube Sleeves – essential AN assembly parts for clean routing and easy servicing
This category is for the small AN components that make a plumbing build consistent and serviceable. The range is largely TURBOWORKS aluminium parts available across common sizes such as AN-3 through AN-12.
Retaining nuts are typically used where the fitting design calls for a separate nut on a hose-style assembly, while a tube nut and tube sleeve pair is most often associated with tube-end solutions. When you are building a fuel or oil system that may be dismantled for maintenance, choosing the correct nut/sleeve set keeps leaks and rework to a minimum.
Technical Basics
Most AN connections seal on a 37° flare seat, which means the thread is primarily for clamping rather than sealing. Size matching matters: an AN-6 nut must match the corresponding AN fitting so the sealing faces meet correctly.
On tubing, the tube nut and tube sleeve are commonly used with a properly formed 37° flare to create a repeatable seal at the cone. Do not mix 37° AN parts with 45° automotive flares (often found on brake lines), because they may thread together yet fail to seal.
Some retaining nuts list the thread designation (for example 7/8-12 or 9/16-18), which helps you verify the mating side. For hose builds, also confirm the intended hose type (such as rubber or nylon) before ordering.
Selection Criteria
Start with Size: choose AN-3, AN-4 or larger based on your existing fittings and the system’s flow and packaging requirements. Using the same size across the nut, sleeve and mating fitting is the quickest way to avoid mismatched sealing faces.
Next, decide whether you are building a tube-end or hose-end connection: tube nut + tube sleeve typically supports tube-end assemblies, while a retaining nut may be required for certain hose-type configurations. If your build includes adapters (NPT/ORB/metric), verify standards carefully because different thread families are not interchangeable.
Aluminium hardware is widely used in motorsport and tuning plumbing, but thread care matters. If you service the system often, keep threads clean, avoid cross-threading and rely on correct assembly rather than over-tightening.
Installation & Maintenance
For tube assemblies, the usual sequence is: prepare the tube, slide on the tube nut, fit the tube sleeve, then form a clean 37° flare with the correct tool. Deburr and keep the cut square, otherwise the flare can seat unevenly and seep under pressure.
For hose assemblies, confirm the chosen retaining nut matches the specified hose type (e.g. rubber or nylon) and always leak-check after installation. Fuel systems in particular should be checked under pressure, because small leaks may only show once the system is loaded.
During periodic inspection, look for damaged threads, nicks on sealing faces and any side-load from poorly routed lines. If a joint suddenly feels tight or “gritty” during assembly, stop and diagnose the cause instead of forcing it.
FAQ
What are AN tube nuts and tube sleeves used for?
A tube nut and tube sleeve are typically used to clamp a tube-end against an AN fitting’s 37° cone seat. Correct flare angle and clean surfaces are critical for sealing. Always match the size (for example AN-6) to the mating fitting.
What is the difference between a retaining nut and a tube nut?
A retaining nut is often used where a hose-style fitting design requires a separate nut, while a tube nut is commonly associated with tube-end assemblies. Check the product page for the thread designation (e.g. 7/8-12) to confirm fitment. If you are unsure, identify the fitting type you are assembling first.
Will an AN-6 tube nut fit an AN-6 fitting?
Usually yes, provided both are intended for the same AN standard and 37° sealing method. Confirm the size marking (AN-6) and avoid mixing with 45° flare systems. If the seat angles differ, it will not seal reliably.
Can these parts be used for fuel, oil and water plumbing?
Yes, these items are commonly used across fuel, oil and water systems as assembly hardware. Final compatibility depends on the complete joint (hose/tube type, fitting style and sealing faces). Pressure-test after installation to confirm leak-free operation.
How do I know if a retaining nut is for rubber or nylon hose?
It depends on the specific part, so check the product description for the intended rubber or nylon hose use. Size (e.g. AN-10) is only one of the checks; hose type is the other key factor. If either does not match, choose a different nut.
Filter by size, verify compatibility on the product page, and order the nuts and sleeves you need for your build.
