Originally Posted by
JohnDThompson
It was a cost-saving decision to use right-hand thread on both sides of the bottom bracket (French thread does this as well). You only need one type of tap, run it in one side and all the way through to the other, and you can be certain that both sides of the shell are tapped concentrically. Use of thread adhesive and/or a tool that supplies suitable torque ensures that the cup will not come loose in use.
That, unfortunately, makes sense. At least the Brits, Swiss, Japanese and Americans did not follow suit.
I don't know about the Belgians, Dutch, Germans or Taiwanese, but since I have never heard anyone complain about a Merckx or a Gazelle or a Giant fixed cup coming loose in the middle of a ride, I'm guessing they went the left-hand threaded fixed cup route as well. And if I'm wrong about, someone will set me straight. (It would not be the first time, it would not be the last.)