The plumbing fittings have a closed face. There are two kinds that work well, both the compression fitting that Don Ward shows (face at 90 degrees to the flats, and you can also get a fitting for flared copper pipe connnections that has a cone shaped extension. Either work well.
You do not need the threads to be full depth, and they can taper with shallow at the tool end and deeper at the back (handle end). It only takes about 1/3 of the thread depth to "lock down the fitting" tightly.
High speed steel tools will cut brass easily. The surface is likely to be a bit rough, but either a lathe file or abrasives on a firm backing will produce the nice surface that Don shows. Work through the grits. I have had occasion to remove these, and a strap wrench worked.