I did not read the entire thread as that would take way too long. The screen size on the various kief sifters I have been investigating is 145 to 150 microns. Nylon is easier to use because you don't have the static issue. It does wear out quicker though. You can get stainless screen that is that fine but you would have to make sure it is anti static. It is much more durable than nylon.

The kief sifters I have seen would be ridiculously easy to make at home. Some have just 4 2x4's about 18" long with the screen attached to the bottom. It would not be that hard to make a tumbler either. I saw one listed for about $400 that could be easily made in a garage for far less. They usually have hand and electric motor power but the good kief is the stuff that comes out the first 10 or 12 minutes of tumbling. If you keep going longer than that you start getting leaf material in the kief and the quality goes down.

I hope someone out there can add a site where you can acquire the nylon or antistatic stainless screen. I would like to make one soon. I have mountains of trim. I would like to see how the kief compares to the bubble hash I have been making.