Michael,
>>> When 2 pieces do not join together, it means their edges are more than 0.005 units apart from one another, so that's kind of an indication that the surfaces are not all that accurately hugging one another.

Never know about this, now I clear undertand why you use to be to advise to small down object to make join.
A lot of things are now clear for me... Thank you very much for explonation!

And one thing I'd like to know, in his model was an issue when I made sweep between 4 edges, but can not join becouse of one of edge has one little segment in edge in the corner, so I run command rebuild edge and repaeir it. My question is what happen with this small segment when we small down object and join it and then scale it up. This segment will just deasapere?