[Tom Wesenberg]

Does one spot on the armature rub as it passes each pole shoe, or does one spot on the pole shoe rub all the way around on the armature?
The first would be a bad armature, and the second could be a pole shoe not tight enough to the case.

Here's the armature exploded view. Assemble the top picture from right to left, and the first lock ring must be tight to the shaft or it can scrape on the thin bearing retainer, which must not be bent, or it will scrape and make noise.