Quote Originally Posted by njhussey View Post
If the fit of the bearings on the ER11 shaft aren't a press fit then there would be a problem. I've just discovered my bearings slide up and down the shaft!
If the bearings were a press fit the belleville washers wouldn't do anything - you must have a sliding fit so that the springs can apply a preload.

Quote Originally Posted by njhussey View Post
Isn't the spindle up pressing up against the inner race of the lower bearing? So wouldn't this mean that any axial load is applied to the inner race of the lower bearing and the Bellville washers would transmit the load to the upper bearing?
Yes for an 'upwards' axial force it's constrained - but not downwards. If it wasn't for the normal bearings and grubscrew the shaft could just fall out.