AN Oil Fitting Guide

AN (Army-Navy) fittings for oil lines use a straight thread with a 37-degree flare for a leak-tight seal. The size of the fitting is indicated by an “AN” number, which corresponds to a specific tube outside diameter and thread size. For example, an AN-8 fitting has a 1/2″ tube outside diameter and a 3/4″-16 thread size

GDX PERFOREMANCE offer Offer a variety of custom oil fittings , Aluminum alloy and anodizing are used, and corresponding O-rings are provided.

Here’s a breakdown of some common AN oil fitting sizes: 

• AN-4: 7/16″-20 thread
• AN-6: 9/16″-18 thread
• AN-8: 3/4″-16 thread
• AN-10: 7/8″-14 thread
• AN-12: 1-1/16″-12 thread
• AN-16: 1-5/16″-12 thread

Key things to remember about AN fittings:

• Straight Thread: AN fittings use a straight thread, unlike tapered pipe threads like NPT.
• 37-degree Flare: The sealing surface is a 37-degree flare on both the fitting and the mating part.
• Standard: AN fittings are a military standard, widely used in automotive and aerospace applications.
• Compatibility: Ensure the thread size and pitch match when connecting AN fittings

AN-fitting male (outer diameter)

Below, the thread is presented in inches / metric dimensions in the thread / metric outer diameter.

AN4 = 7/16″ -20 = ~9,1mm in threads = ~11,8mm OD
AN6 = 9/16″ -18 = ~11,6mm in threads = ~14,2mm OD
AN8 = 3/4″ -16 = ~16,6mm in threads = ~ 19,0mm OD
AN10 = 7/8″ -14 = ~19,5mm in threads = ~22,3mm OD
AN12 = 1-1/16″ -12 = ~23,8mm in threads = ~26,9mm OD
AN16 = 1-5/16″ -12 = ~30,2mm in threads = ~33,3mm OD
AN20 = 1-5/8″ -12 = ~38,2mm n threads = ~41,4mm OD

AN-fitting female (inside diameter)

Here, the thread is presented in inches / metric inner diameter.

AN4 = 7/16″ -20 = ~9,9mm ID
AN6 = 9/16″ -18 = ~12,9mm ID
AN8 = 3/4″ -16 = ~17,5mm ID
AN10 = 7/8″ -14 = ~20,6mm ID
AN12 = 1-1/16″ -12 = ~24,9mm ID
AN16 = 1-5/16″ -12 = ~31,2mm ID
AN20 = 1-5/8″ -12 = ~39,1mm ID

AN-hose end inner diameter

An approximate internal dimension of AN hose ends is presented here. Note that the internal dimensions of hose ends and fittings may differ depending on the type, material manufacturer, etc. Therefore, these internal measurements should only be used as guidelines.

AN4 = ~3,7mm
AN6 = ~6,0mm
AN8 = ~8,6mm
AN10 = ~11,1mm
AN12 = ~14,3mm
AN16 = ~19mm
AN20 = ~25mm

Corresponding AN adapters generally have a 1 mm larger inner diameter. Should an adapter be reduced to a smaller thread, the inner diameter will also shrink.

Braided rubber hose measurement (-1950)

AN3 = 3/16″ hose id = ~4,76mm
AN4 = 1/4″ hose id = ~6,35mm
AN5 = 5/16″ hose id = ~7,9mm
AN6 = 3/8″ hose id = ~9,5mm
AN8 = 1/2″ hose id = ~12,7mm
AN10 = 5/8″ hose id = ~15,9mm
AN12 = 3/4″ hose id = ~19,05mm
AN16 = 1″ hose id = ~25,4mm
AN20 = 1-1/4″ hose id = ~31,75mm

Braided rubber hose measurement (nowdays)

AN4 = 7/32″ ~5,4mm
AN5 = 5/16″ ~7,9mm
AN6 = 11/32 ~8,7mm
AN8 = 7/16″ ~11,1mm
AN10 = 9/16″ ~14,2mm
AN12 = 11/16″ ~17,4mm
AN16 = 7/8″ ~22,2mm
AN20 = 1-1/8″ ~28,5mm

Braided PTFE hose measurement (nowdays)

AN4 = 3/16″ ~4,8mm
AN6 = 21/64″ ~8,1mm
AN8 = 27/64″ ~10,7mm
AN10 = 33/64″ ~13,0mm
AN12 = 41/64″ ~16,3mm
AN16 = 7/8″ ~22,2mm

AN-pipe / tube measurements:

AN pipe size is measured on the pipe outer diameter. The thickness varies between manufacturers and therefore the inner dimension is different. But overall, an AN4 pipe has ~ 1.5mm wall thickness and an AN12 pipe ~ 2.5mm wall thickness.

AN4 = 1/4″ pipe OD = ~6,35mm
AN5 = 5/16″ pipe OD = ~7,9mm
AN6 = 3/8″ pipe OD = ~9,5mm
AN8 = 1/2″ pipe OD = ~12,7mm
AN10 = 5/8″ pipe OD = ~15,9mm
AN12 = 3/4″ pipe OD = ~19,05mm

AN-key grip measurements

The key grip on AN fittings is also measured in inches and since European sizes are metric (millimeters), an adjustable socket wrench or inch tools is recommended during assembly so you get the correct engagement. There are special tools just for AN fittings, but a standard adjustable wrench works great.

AN3 = 1/2″ = ~12,7mm
AN4 = 9/16″ = ~14,3mm
AN6 = 11/16″ = ~17,48mm
AN8 = 7/8″ = ~22,23mm
AN10 = 1″ = ~25,4mm
AN12 = 1-1/4″ = ~31,75mm
AN16 = 1-1/2″ = ~38,1mm
AN20 = 1-13/16″ = ~46,0mm