Abstract: A mechanical coupling for transferring torque from a first component that rotates about an axis to a second component that also rotates about the axis is provided. The coupling allows different rates of expansion of the first and second components in the radial direction by permitting sliding in the radial direction of the components relative to one another. The coupling comprises first and second circular arrays of teeth formed on the first component and second component, respectively, and centered on the axis. The first circular array of teeth are intermeshed with the second circular array of teeth, wherein rotation of the first component causes first mating sides on the first circular array of teeth to bear against second mating sides on the second circular array of teeth transferring torque to the second component. The first and second mating sides extend both axially and radially and are essentially curved.