Gordon’s recent post about the strange and elusive numbering scheme for machine screws brought another one to mind, gleaned from Carroll Smith’s Nuts, Bolts, Fasteners and Plumbing Handbook. 37° AN lines are a pretty common sight for lots of high-performance and show vehicles these days, courtesy of their excellent sealing performance and reusability. But how do you plan line sizes without really knowing the dimensions of a given fitting and its hoses?
Turns out, it’s pretty simple. The lines are sized with labels like -3AN up to around -20AN (standards up to -32AN exist, but the fittings are very rare). To determine the hose inner diameter for a specific AN size, just multiply the prefix by 1/16″. For instance, -10AN:
10(1/16″) = 10/16″ = 5/8″ inner diameter.
Thread sizes and hex dimensions are also standardized, as Wikipedia and Powerhouse’s AN wrench selection show us.