Which of the following is a common risk involved in using a bench grinder?

Using a bench grinder carries several inherent risks, with injury from rotating wheels being one of the most significant concerns. The rotating wheels operate at high speeds, and if proper safety precautions are not followed, users can easily sustain severe injuries, such as lacerations or abrasions to the skin or even more serious harm if a body part comes into contact with the wheel. The potential for these injuries emphasizes the need for wearing appropriate personal protective equipment (PPE), such as safety goggles and gloves, and following proper operational procedures while using the grinder to minimize the risk.

While the other options present valid hazards associated with bench grinders, the direct threat posed by the rotating wheels stands out due to the immediate and potentially life-altering injuries that can occur from mishandling or accidents during operation.