and the hub shaft by frictionally engaging the key on the hub spacer to the slot opening in the hub shaft; and inserting the assembly of the hub shaft and the hub spacer into the center aperture in the hub frame such that any rotational torque of the hub frame is transferred to the hub shaft.
The method for transferring a torque from a hub frame to a hub shaft may further include the step of providing the opening in the hub shaft in a rectangular shape for receiving a rectangular-shaped key on the first surface of the hub spacer, or the step of providing the opening in the hub shaft in a trapezoidal-shape for receiving a trapezoidal-shaped key on the first surface of the hub spacer. The methodmay further include the step of providing a slot recess in the center aperture for receiving the pin on the hub spacer. The method may further include the step of transferring a rotational motion from the hub frame to the hub shaft and driving a conditioning disc mounted on the circular disc, or the step of transferring an up-and-down motion from the hub frame to the hub shaft and engaging or disengaging a conditioning disc mounted on the circular disc to or from a polishing pad. The method may further include the step of forming the key on the hub spacer to a length of at least 20 mm for transferring the rotational torque. The method may further include the step of providing the pin on the hub