[39chevy]

Question: Is the threads on 3/8, hard fuel line, NPT? Thanks, Dana

 

[bobscogin]

Steel tubing is generally connected using SAE inverted flare fittings. Flare nut slipped over the tubing and a 45º single flare formed on the tube. From there, you could adapt to pipe if necessary by using an NPT x IFF adapter.

Bob

 

[powerrodsmike]

The threads on the actual "tube nut" that fits 3/8 hard line is 5/8-18 straight standard NF threads.

A 3/8" NPT pipe has 18 threads per inch also, but is tapered, and the threadform is different.



Hope this helps,
Mikey