G.3.4. What is a 45° grooved nut?
The 45° grooved nut is used for all installations with cone rings. It centers the unit perfectly on the left side.
They are available in three different widths to compensate cone rings on the right side with additional width. If a wider cone ring is combined with the wrong nut on the left side, the left industrial ball bearing probably isn't guided and the unit has play in the bottom bracket shell.
The photos show a 45°- and a 90°- grooved nut (see also G.3.5.).
Grooved nuts for mountain-drives have a left hand thread, for speed- and high-speed-drive a right-hand thread.