An electric motor is provided including a stator and an armature received within the stator for rotational movement within the stator. The armature includes an armature shaft on which a commutator is mounted, and a lamination stack also mounted on the armature shaft and having radially extending teeth. The armature includes an end insulator arranged at an end of the lamination stack, the end insulator having a base portion fitted around the armature shaft and insulating teeth corresponding to the radially extending teeth of the lamination stack. A set of coils are wound in the lamination stack slots and the end insulator slots. At least a portion of the insulating teeth has a greater thickness than at least a portion of the base portion. Alternatively, at least one of the insulating teeth has a greater thickness than at least another of the insulating teeth.