Norm Abrams on “TLC for Power Tools”

Toolmonger: "“Most small power tools have two “brushes,” solid blocks of carbon graphite that conduct electricity to the motor’s spinning armature. Friction gradually wears these brushes away, and if they’re not replaced, the motor loses power and eventually quits. You can tell it’s time for new brushes when you see lots of arcing — small, harmelss sparks inside the motor housing as the tool is running.”"