Has anyone figured out what the thread on the fittings are. I am looking at changing them out as I am having problems getting tubing to fit. 3/16"x14" does not clamp down properly and is very flow restrictive. 1/4x 3/8 wont fit in the ferrule nut.

I though they would be 1/16th NPT. The place I went today didn't have much in 1/16" but the one sample we looked at did not match.

A search on the web did not lead me to find anything.
diameter at 3rd thread seems to be ~ 7.8mm and pitch could be 1.0mm

Thanks
Dave