After a certain time, depending on the conditions of use, lawnmowers blades, although they are designed and manufactured to last, will start to wear and may become deformed.

A deformed blade must be replaced. The same applies to a blade worn past the wear indicator. These wear indicators take the form of small lateral notches at both ends of the cutting edge. After any knock to the blade, it must be replaced. Micro-cracks caused by such a knock can lead to the blade breaking later.