I have been able to "start" many a cross-threaded bb cup by firstly threading in by hand to where it binds up, then observing the tilt of the face of the cup relative to the end of the bb shell.

With the tilt angle identified, I use a 3lb hammer and gently tap the face of the cup level, before putting a bit of rotation to it, this time using a wrench.

Using small increments of tapping and turning, the cup can usually be started in the damaged threads of the bb shell, keeping an ever-vigilant eye on any tilting of the cup in the bb shell.


If the cup threads are flattened, they should first be relieved, where needed, with the corner edge of a fine bastard or mill file, as the cup is usually made of a harder metal than the bb shell and thus could distort the entire inside threading of the bb shell.