printing working threads on an Ultimaker II extended

Even at 20 micron and less layer height, most theads have too many threads-per-millimeter/threads-per-inch to be reasonably 3D printed.
I'm regularly using a thread cutter on 3D printed parts to do this instead.

Now I have some  solenoid valves with a very strange NPT1/2 thread.
This is a very rare imperial sized, trapezoidal (getting smaller, not staying at one diameter)
thread with only 1,814mm per thread instead of 1mm.
(BTW NPT1/2 isn't even near 1/2" in size. )
So it looks like a perfect test to 3D print the thread without cutting.

Due to the extreme heat recently, I had some issues with my Ultimaker II extended at first.

But int he end it worked out.
Here is the same thread printed in normal quality,  high quality(at 200% speed) and ulti quality (40 micron).
The (at first) strange result it, that the thread printed at normal quality was far more clean then the other ones.
...that is until you think about a thread as one giant overhang. A thicker layer-height seems to work better for overhangs as it's not as compressed by the next layer. This is no problem in solid areas bu when there is air below the layer...you can guess.

Fits perfectly!