How is this done properly? Thin hacksaw blade??
Professional rebuilders had a small high speed saw that cut the mica between the commutator bars to a depth of about 1/16" or slightly less. It's a pretty difficult job without the proper tools. If you're very careful with a fine-toothed hacksaw blade with the kerf ground off the teeth, it's possible to undercut the mica that way, but it's a tedious job with a lot of room to make mistakes.
Jerry
