Originally Posted by
juvela
"spins on easily" is not necessarily a good sign. metric f/w thread has a pitch diameter of 34.7mm which is smaller than BSC or Italian so a BSC or Italian thread f/w body will thread on very easily indeed. alas there is a possibility of stripping the thread. not even a good "class b" fit.
one must measure...
okay......checked the hub profile using a known ISO/rt BB cup. They clearly do not match up telling me this is a French threaded hub. Then I threaded the BB cup into my Simplex freewheel..........goes all the way in...........clearly not French. Tried the BB cup into an Atom 66 fw.......only goes in a couple of threads then tightens up.......clearly French. I did this per Sheldon Brown.......
....."A bottom-bracket cup can serve as a thread gauge for a freewheel: Dimensions are usually marked on cups. Hold the threads of the bottom-bracket cup against those of the hub, and look in between, against the light. If the threads engage tightly all the way across, the thread pitch is the same. If they rock across each other, it is different. You may check the thread pitch of a freewheel by threading an ISO
left bottom-bracket cup into it (not a right cup, which is left-threaded). The cup will go in easily if the thread pitch is the same -- but do have a freewheel extractor tool handy so you can unscrew the cup."