Commutators of armatures for electric motors or other dynamo-electric machines are finished by subjecting them to inspection and turning operations. The first inspection operation determines the minimum amount of material that can be cut while producing a high quality armature. This determination may indicate that no formal turning is required, only finishing. The turning operation, if applicable, cuts the commutator to a substantially cylindrical shape which is substantially concentric with the axis of rotation of the armature. The finishing operation, which may be performed by the same mechanism as the turning operation, imparts a desired axial roughness to the cylindrical commutator surface. The commutators may be inspected after the turning and finishing operations to generate data useful for such purposes as automatically modifying the turning and finishing operations performed on subsequent commutators.