Basic lawnmowers are often fitted with plastic blades. These generally wear more quickly than metal blades which results in you needing to replace the lawnmower blades more often than a lawnmower that uses a metal blade.
Lawnmowers with metal blades are generally sharper and provide a cleaner cut to the grass blade, resulting in a neater, tidier and superior finish to your lawn and garden. Metal lawnmower blades in some cases can be sharpened unlike plastic blades.
Metal blades by their nature are stronger than plastic blades, therefore can withstand more ‘abuse’ from your lawn. When cutting the grass it is common for small stones to flick up and hit the blade. A metal blade is more likely to avoid bending or damage than a plastic blade, however because of their rigid structure they are more likely to become misaligned than lawnmowers that use plastic blades.
It is important that when using a lawnmower to cut the grass, that the blade is always sharp. Using a blunt or dull blade will result in you tearing the grass, rather than cutting it cleanly. Mowing the lawn is a stressful event for grass, and tearing it only stresses grass out further. This may cause the grass to wilt, turn brown and in extreme cases die. A dull blade also requires more power reducing efficiency of the lawnmower.
The way in which lawnmower blades are fixed to the lawnmower may also differ slightly depending on the material they are made from.
Plastic lawnmower blades are typically fixed to a plastic cutting disc that spins and keeps the blades in position. Metal lawnmower blades are typically fastened to the drive shaft connected to the motor/engine depending on the lawnmowers power type.