Originally Posted by
Dean V
The spline on the cassette is not long enough or machined to a close enough tolerance to hold the sprockets square to the free hub by itself. It relies mainly on the back shoulder which if uneven will cause some side to side run out of the cassette. But as you say it probably isn't critical and will function ok anyway.
I believe the key point is that the entire surface of the cassette does not need to be cut at the correct depth. I think that it is important to have a few places on the cassette at very close to the right depth and that this can be accomplished by hand if care is taken and a suitable scale is used to measure the depth of the cut. Given about four carefully hand cut "legs" spaced around the cassette to allow for proper torque on the lock ring then the remaining 90-95% of the carrier could be cut unevenly at a deeper level.