By how much should the driver shaft be higher than the driven shaft?

The correct answer indicates that the driver shaft should be higher than the driven shaft by 15-thousandths of an inch (0.015). This specific amount creates an ideal alignment and clearance between the two shafts, which is essential for efficient operation and to minimize wear and tear.

When the driver shaft is positioned slightly higher, it helps to ensure that there is a proper load distribution across the components. This alignment is crucial since it prevents binding or excessive pressure on the bearings and gears, which can lead to premature failure. Additionally, this slight elevation helps accommodate for any slight movements or vibrations that may occur during operation, maintaining optimal performance and longevity of the machinery.

Balancing the heights appropriately minimizes the risk of misalignment issues that could lead to increased friction, potential overheating, and ultimately, component failure. Since 15-thousandths represents a recognized standard in mechanical practices for the space necessary for these factors, it is deemed the best choice.