All rotary cutters are inherently dangerous. Reputable manufacturers do all they can to reduce the risks associated with rotary cutters, but the ultimate safety responsibility rests with the operator. Hazards with rotary cutters include thrown objects, direct blade contact and PTO entanglement.

Thrown Objects Hazard
Of all the hazards inherent in a rotary cutter, the hazard of thrown objects is perhaps least recognized by operators and bystanders. The blades on a rotary cutter may have a tip speed of more than 150 mph. Objects such as stones, cans, bottles (or fragments), pieces of limbs or roots, and other debris can be thrown more than 300 feet. Too many people assume that a rotary cutter will not throw objects very far, but testing and documented accidents have demonstrated that objects can be thrown farther than the length of a football field – and still have enough velocity and momentum to cause serious injury.

Types of Injuries Possible from Thrown Objects
Objects thrown from a rotary cutter can injure you in several ways. Sharp objects can cause severe puncture wounds. Heavy objects can hit the head or body, causing concussion or death. The most common injury, however, is eye damage. Even small objects can injure an eye and cause blindness.

Equipment Safety Features to Reduce Thrown Objects
A properly designed and equipped rotary cutter can reduce the risk of injury. The cutter deck should be designed to conform to American Society of Agricultural Engineers Standard S474.1 – Agricultural Rotary Mower Safety. This standard prescribes several safety features for rotary cutters and also contains a procedure for testing rotary cutters for thrown objects by using nails dropped through tubes inserted in the deck. Conforming to this standard means the manufacturer has designed the machine to conform to the state of the art in thrown objects reduction. Nevertheless, the standard does not require or imply total elimination of thrown objects, just a significant reduction in their incidence.
 
Chain guards on the front and rear of the mower (Figures 1 and 2) can reduce the thrown objects hazard even more, but they will not eliminate the hazard. Chain guards will typically reduce the number of thrown objects by half and significantly reduce the velocity of those that are thrown. Other shielding such as rubber belting or metal bands are used on some machines but may interfere with mowing efficiency.

Most manufacturers offer chain guards; some make them standard equipment, but with a delete option. The cost of chain guards varies with the size of cutter and with the manufacturer. The cost of chain guards may range from less than $100 on small economy machines to well over $500 on larger heavy-duty cutters.

Operator and Bystander Responsibility
As an equipment operator, you must be aware of the hazards inherent in thrown objects and take steps to minimize the danger. The first and most important step is to operate a rotary cutter only if there are no people or animals within 300 feet (or more). If anyone approaches within that range, you should immediately turn off the tractor PTO to stop the cutter and not resume operation until the site is clear of bystanders. Using chain guards is recommended. It is imperative to use chain guards if you will be working in an area where bystanders might approach within 300 feet. Operating without chain guards is acceptable only in situations where there is no possibility of another person within 300 feet.

Bystanders also have an obligation to stay away from rotary cutters. Although rotary cutters are typically noisy and visibly dangerous, you should warn family members or anyone else who might conceivably approach of the dangers and tell them to stay back at least 300 feet. If a person must approach within several hundred feet of a rotary cutter, he or she should wear safety glasses. The most dangerous area is the rear of the machine.

The thrown object hazard with rotary cutters is not fully recognized by everyone. This very real hazard can cause injury, blindness or even death. You should buy and use a safe rotary cutter and should never operate if anyone gets within 300 feet (or more) of the machine.