Final answer:
Projecting shaft ends and edges in engineering must be smooth and not project more than one-third the diameter of the shaft for safety purposes.
Step-by-step explanation:
In engineering, all projecting shaft ends and edges must be smooth and not project more than one-third the diameter of the shaft. This is important for safety purposes, as sharp edges or protruding shafts can cause injury or damage to machinery.
By ensuring that the projecting shaft ends and edges are smooth and within the specified limits, the risk of accidents can be minimized.