🔍 Key Concepts

• Purpose of resurfacing a commutator (what are you trying to correct on an eccentric/uneven commutator?) • Difference between shaping/removing metal and smoothing/polishing while in operation • Manufacturer and USCG training guidance on methods that prevent further eccentricity and damage to the windings/brushes

💭 Think About

• Think about which method allows you to true up the commutator surface evenly around its full circumference, not just touch high spots randomly. • Consider which method is normally done with the armature removed vs. left in place and running, and how that affects precision and risk of damage. • Ask yourself which tool is specifically designed for commutator work on small DC motors in the field, and which tools are more general-purpose metalworking tools.

✅ Before You Answer

• Verify which options involve the motor running vs. stopped and removed from the machine. • Check which method minimizes the risk of undercutting, grooving, or creating flat spots on the commutator bars. • Confirm which tool/technique is commonly recommended in marine electrical maintenance manuals for small DC motor commutators that are slightly eccentric.