So I needed a 1/2 npt male to 1/4 npt male adapter to try and use the extreme heat threaded tube that I got from Mcmaster Carr for the run between the air compressor pump and the inlet on the radiator....and I saw this one on amazon, did not need two, but it was only $9...so I was dumb and tried it:
www.amazon.com/dp/B0B1TYWK3T?...
That was the "SDTC Tech 2-Pack Brass Pipe Fitting 1/2-Inch NPT Male Thread to 1/4-Inch NPT Male Thread Reducer Adapter Straight Hex Nipple Connectors" pack....and it arrived quickly and I looked forward to finally being able to finish my air compressor after cooler build....and then neither of the two fitting 1/4 npt male ends would screw into the air compressor and grab the threads in there....where all my other 1/4 npt fitting ends that I had used grabbed the threads in the air compressor head just fine.
After fighting with it for a while, I finally measured it and found it is almost half a millimeter (0.1 inches or 0.4mm) smaller in the out thread diameter than the working fittings. Unfortunately for me, the other fittings with the 1/4 npt had other ends on that would not work for the final 1/2 npt to 1/2 npt hose that I got from mcmaster-carr:
Extreme-Temperature Air and Steam Hose, 321 Stainless Steel with 304 Stainless Steel NPT Female Fittings, 1/2 x 1/2, 36" Long
I probably should have gone with smaller (ie 1/4 npt for that leg of the hose...but I figured I would stay with 1/2" ID for all the extra hose and part sections I added as part of the after cooler project....to future proof it.
In any case these SDTC fittings suck...they do not fit into the compressor like they should, or rather they slide right in (vs screwing in) but with far too much space around the too small threads to work.
I got fed up and went to home depot before they closed and got this pack and by using one of the male 1/4 npt to male 1/4 npt and one female 1/4 npt to female 1/4 npt , I was able to go from the compressor into a female 1/4 npt to the SDTC 1/4 npt, by screwing the SDTC fitting the entire way into it while using teflon tape, ie right up to the nut flange..and then it finally sealed. So if you don't have that much room to screw these fittings in...don't buy them. So instead of using this right in my compressor and then the hose, I now have two extra fittings just to use this undersized fitting which should have just worked but did not.
That means I can finally start the edit on the 3 hrs of video for the air compressor after cooler project...and I could try and replace those three fittings with another single 1/4 npt male to 1/2 npt male...but I am tired of fighting with it and since it doesn't leak...it stays for now.