You shouldn't need to file or sand the flat faces of the shells. Usually those faces are separated by shims. Usually those Myford shims are actually stacks of thin aluminium foil that can be peeled off layer by layer. Each layer is about 2 thou thick. So if you have 0.1mm up and down movement, you might try peeling off two layers from each side.
If yours does not have the aluminium foil stack type shims, you can either buy them from Myford's website or just make your own solid shims from shim stock in whatever size is needed.
It is common practice for shims to be thicker on one side of than the other. It's a way of getting one thou of adjustment, roughly, by removing a two thou foil layer on one side only.
YOu can leave the shims out when doing the bluing and just use light pressure on the bolts to make shell contact shaft.
Most of the time they do not need scraping, just the shims reducing.
There will eventually be an article in MEW on scraping the bearings, but couild be some time away as there is another article on completing the wide guide conversion to come first and they seem to run every second month.
Edited By Hopper on 21/11/2019 11:32:03