Then comes the fun part involving power tools--polishing the copper commutator. This can be done with a pencil eraser, but the sandpaper works great to clean and polish the copper. Clean copper is a good conductor, and that makes your motor work better. (There is a lot of good information about how motors work on the internet if you are interested in the technical details).
First, load the armature shaft into your drill or drill press. This is probably easier with a drill press, but I don't have one.
I don't have a bench clamp either, so I have to use my knees for this part. I also had to use rig something to keep the drill on while I use both hands to hold the sandpaper strip. Start with the 400 grit. While the armature is spinning in the drill, hold the sandpaper strip around the commutator. This will remove a lot of grime. Get it down to the shiny copper. Now, repeat this process with the 1500 grit paper strips. This really puts a nice polish on the commutator. Now that your armature is all clean, set it aside to keep from getting it dirty again!
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