... , 5, 7, 8, 9, 12,16 slots armatureSilicon-steel lamination with epoxy coatingHigh-carbon steel shaftCu-Ag alloy commutatorCopper-graphite brushesBe-Cu leaf ... , D-cut, stepped shaftShaft-mounted gears, eccentric gears, belt pulleysStainless steel (SS304, SS420) shaftBall bearingCage-brush commutating systemPrecious metal brush / commutatorHall ...