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[July 2017]

Beware of accidents when using a grass cutter!

Summer is the season when many people trim their gardens, often using a grass cutter (a machine for cutting grass with a fast-rotating blade).

The Consumer Affairs Agency received 140 reports on harmful incidents during use of a grass cutter (e.g. finger severance, fracture) from September 2009 through the end of June 2017. About half of the victims were aged 60 or more.

A grass cutter is a convenient machine, which consumers can easily buy at DIY stores or on the Internet. It has a sharp cutting blade, which rotates rapidly during operation. Careless use may lead to a serious and irreversible injury, such as breaking or cutting off a finger or foot.

Remember the following points when using a grass cutter.

  • Be sure to put on protectors (e.g. helmet, protective goggles, vibration-proof gloves) and check a grass cutter before use.
  • Check the ground and remove any hard objects such as stones and twigs beforehand.
  • Beware of the blade bounce caused by bumping an obstacle or the ground (kickback phenomenon).
  • Be sure to turn off the engine before removing any obstacle such as grass and foreign objects caught by the blade.
  • Family members or neighbors are encouraged to check if a user took safety measures before using a grass cutter and to pay attention to the user while using it to see if there's any abnormality.

Test results

If a rotating blade touches an obstacle such as a stone, the obstacle or a broken piece of blade may fly and hit the user or a person nearby, who may be injured, or may hit and damage something.

NCAC conducted a series of tests of engine-driven grass cutters (four-edged blade, eight-edged blade, chip saw, and nylon cord cutter). Each type of blade was contacted with stones (size of about 20-30 mm) to determine the scattering distance and the scattering speed of a stone or any broken blade. In addition, a car was hit by scattered stones to check the impact of a scattered stone.

  • The longest scattering distance was: about 67.8 m in case of four-edged blade; about 30.2 m in case of eight-edged blade; and about 16.9 m in case of nylon cord cutter. No stone was scattered in case of chip saw under the test conditions.
  • The scattering speed was: about 130 km/h in case of four-edged blade; about 76 km/h in case of eight-edged blade; and about 48 km/h in case of nylon cord cutter. No stone was scattered in case of chip saw under the test conditions.
  • In case of four-edged blade and eight-edged blade, stones were prone to be caught by the blade, and the scattering distance was longer and the scattering speed was faster than those in other cases.
  • In case of chip saw, stones were scarcely caught by the blade and were seldom scattered. When a stone was small enough to enter between chip saw blades, the small stone was flung away at high speed, and the edge of the chip saw blade was broken and flung away in some cases.
  • In case of nylon cord cutter, nylon cords greatly deformed when contacting with a stone, so the scattering distance was short and the scattering speed was slow. On the other hand, sand nearby was scattered in some cases. When nylon cords were contacted with a test dummy, the dummy was not cut by the cords, contrary to the case of metal blade.
  • When a car 10 m away from a grass cutter with four-edged blade was hit by scattered stones of 20-30 mm, the contact surface of the car was deformed and the coating was peeled off. In some cases, the window glass was broken.

Advice based on test results

Keep the following in mind to avoid accidents from objects scattered by a grass cutter.

  • If a grass cutter is used near a car or a house, or if there's any person nearby, take a sufficient anti-scattering measure. Don't come close to the user.
  • Apply the anti-scattering cover. Be sure to wear protectors.
  • When cutting grass in a place full of debris, use a nylon cord cutter.


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