NPT vs AN Fittings and Lines

[Bartman]

Was surfing around looking for a good chart that compares sizes and what not, found this article from a shop called Verocious Motorsports. It explains the sizing conventions pretty well, which can be confusing when you're building fuel or brake lines that are using both NPT and AN fittings.

AN vs. NPT: Understanding Threads and Line Sizes | Verocious Motorsports

Guidelines for selecting AN and NPT port threads, adapter fittings, and line sizes for your custom application.

www.verociousmotorsports.com

I still haven't found a solid chart that sums it all up, NPT, AN, hard lines, hoses, etc. but this article definitely makes sense of the two conventions which covers a lot of it.

If anyone has a chart, please post it or a link to it. Thanks

 

[Bartman]

Another good article

"AN" vs. "NPT" Fittings and How They Relate

AN and NPT style fittings are popular thread measurements, and this article covers the differences between AN fittings and NPT threads, including how they relate to one another.

www.onallcylinders.com

The trick seems to be, AN size is number of 16th's OD of a thin walled tube which determines ID of fittings and hoses. Match the AN nominal dimension to the NPT size to have continuity of the ID through assemblies of fittings.

An AN-4 fitting or hose would have a nominal ID of 4/16ths, or 1/4". A 1/4" NPT male fitting will have a 1/4" ID hole going through it. A fitting with 1/4" NPT on one end and AN-4 on the other should have about the same size ID on each end.

AN-6 being 6/16th's, or 3/8" OD of a thin walled tube, a 3/8" NPT fitting would be its size equivalent for fittings and hose assemblies.

I think what makes this confusing is the tendency to also think about the sizes of the threads. The OD of the AN-6 and 3/8" NPT male plug is about 3/4's of an inch. That's a lot different than the ID of the port through the fitting. It works out though to just stick to the AN size and the nominal size of the NPT fitting to match pieces.

This stuff isn't difficult but until you clear your head, read through it and figure it out, it can be confusing!