A grass trimmer is a machine used for mowing grass and small trees. There are two types: ride-on grass trimmers and self-propelled grass trimmers (walk-behind grass trimmers), and the cutting blades are classified into rotary knife type and hammer knife type. For the free knife type classified as a rotary knife type, it has a strong structure against obstacles because the free knife can escape when hitting obstacles such as stones.

• Areas that require frequent inspection for safe work.
• Areas that require regular replacement of parts.
• Areas where it is not possible to tighten too strongly.

• It is now possible to prevent loosening with low axial force.
• The burden on workers has been reduced.
• The maintenance cycle has been significantly extended, and maintenance costs have also been reduced.