Moving machine parts have the potential to cause severe workplace injuries, such as crushed fingers or hands, amputations, burns, or blindness. In addition, amputations, lacerations, and abrasions are costly and potentially increase workers' compensation premiums.  (Amputation is one of the most severe and crippling types of injuries in the occupational workplace, often resulting in permanent disability.) Due to this fact, OSHA (Occupational Safety & Health Administration) has established a set of standards around machine guarding. The purpose of machine guarding is to protect the machine operator and other employees in the work area from hazards created during the machine's regular operation.  That would include risks of concern such as ingoing nip points, rotating parts, reciprocating, trans versing, and flying chips & sparks. 

Any machine part, function, or process that might cause injury must be safeguarded. When the operation of a machine or accidental contact with it could injure the operator or others in the vicinity, the hazards must be controlled or eliminated.