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NPT to AN Conversion Chart

22K views 6 replies 4 participants last post by  The Big Al 
#1 ·
Can someone post up a conversion chart between AN and NPT. I need to know what 1/16" NPT and 1/8" NPT would convert to for AN.

I think it would be handy if this conversion chart was stickied for everyone!(Hey John, Might be a good addition to Jollyrodder.com)

Thanks!

John
 
#3 ·
AN is tube size expressed in 1/16th's of an inch. An AN-8 is 8/16th's or a half inch line. AN-6 is 6/16th's ==>3/8th's line. NPT is national pipe thread which is tapered. Some AN fittings have a NPT on the other end. All AN (Army/Navy or mil spec standardized during WWII) fittings use a 37° taper to seal, which is not compatible with SAE compression fittings which use a 45° angle. Bear in mind only the tube size has the inside diameter of the AN fitting, not the fitting itself which is much more restrictive. Another problem is the hose was designed to be light weight (aviation quality) hydraulic lines and do not work with alcohol (the lining material is made of natural gum rubber) or gasahol.

AN fittings became popular back in the good old days when we were scrapping out tens of thousands ex-military air craft. Now that you actually have to buy this stuff new (at $16 to $27 a fitting) I much prefer to use a Bridgeport high yellow brass SAE (Society of Automotive Engineers) fittings as they are a lot cheaper and work just as well without the bling.


Sorry I couldn't help.

Big Dave
 
#4 ·
NOPE!! You both helped ALOT!

So Dave....going by what you say that would mean that a 1/16" NPT would be a -1AN and 1/8" NPT would be a -2AN?

*****EDIT***** John, I just found it on your site! What a knucklehead I am!

John
 
#5 ·
There isn't a direct correlation between NPT (National Pipe Thread) and the size of the tube. I have seen from an AN-12 to an AN-4 fitting screwed into a 3/8th pipe plug hole.

Smallest AN line I have seen is an AN 4==> 4/16th's or 1/4" ID tube. For 1/8th inch inside diameter line, even on an aircraft, a copper tube with compression fittings is still the best route (has to be supported or the metal will fatigue if not supported and break) Though most aviation tubing I saw that size was stainless steel on old war birds.

Big Dave
 
#6 ·
as stated AN fittings have a 37* pitch on a straight thread to make a leak proof seal to the mating surface loosing the need for a thread sealant . national pipe thread locks as the threads fall short along the major diameter of the taper. they are not compatible but jegs has alot of adapters like 3/8 npt to 6 an etc. etc. 4.00 bucks each i think
 
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