This invention relates to the art of processing and treating molten metal. More particularly, this invention relates to a new and improved coupling design for a molten metal processing system to provide coupling design for rotor/shaft systems which has a heat break to prevent heat flow to a motor. This disclosure deals with a cross sectional area reduction heat break which provides a restriction prevent heat transmission through a conductive material by providing a coupling for connecting a motor to a shaft in a molten metal processing system to restrict heat flow to a motor, which will ultimately extend the life of the motor.