The thread area is NOT anodized, we place grease on them to protect them from the acid.
If we did not, the threads would not be sharp, as the acid causes them to round off or build, and this will cause problems with sealing plastic fittings.
The order was place with plastic fittings, and we opitimized for the fittings we provided.
Yes, there is a taper, if there was not, the fitting would not get tite.
You guys should know, NPT standard is NOT followed very well. Try placing 4 different brand / material 1/4 NPT fittings side by side, and you will see the starting diameter varies.
At first we designed for metal fittings, but people where forcing plastic fittings all the way into the impeller (no joke). The feedback we had, showed 90% of the people where using plastic fittings, so we cut back a bit, to have best fit with plastic.
If you have a metal fitting, do as suggested above, and run it in and out a bit.
Most of the confusion comes from our European customers, which will no longer be a problem, as we now ship to Europe with 1/4 G straight ports
** AGIACOBBI, you worked on injection molds with NPT threads, could use some advise on three peice mold with interior NPT threads. Having a bitch finding an example
