Originally Posted by aggiegrads

They can be fiddly. It is similar to adjusting a one-piece crank. The spindle has a keyway in the threads, and on the threaded portion go a cone, a washer with a nub in the interior circumference, and a lock nut. Unlike a crank, however, there is no way to get a pin spanner on the locknut. You have to leave it a bit loose, then tighten down the lock nut until you get the bearing tension right.