I am designing a pan-tilt camera mount using standard hobby servos. Many existing designs use the servo shaft as a revolute joint, as opposed to simply a torque producing element. As a revolute joint the servo mechanism is subject to different torques and forces. Is using a servo shaft as a revolute joint recommended practice or should a bearing be used?
A bearing should be used, as it is a basic principle of mechanical engineering, but many times it is not. It is often avoided as a cost benefit result, hobby servos are cheap.
Servos themselves may have bearings and even metal gears. Brackets are available that have opposing bearing blocks. You have to decide if it worth the costs or is a mechanical necessity.