vacuser
Dwayne,
What you need to use to keep the armature from turning as you get the impeller fan off would be to use a special fan lock tool that Kirby supplies to its network of authorized service centers. Otherwise, you can use an ice pick. Regardless, make sure you insert it in the right place to prevent damage to the armature as you get the fan off.
For extremely rusty fans, you may want to use some WD-40 and let it cure before you get down to removing it.
~Ben