Grinder Burrs/Blades
Grinding burrs/blades are an essential part of espresso preparation, as consistent particle size is crucial for espresso extraction. Generally burrs last about 200-300 kilos of coffee on domestic units and 600-800 kilos of coffee on commercial units however this varies depending on beans and roast profile. The lighter the roast the higher the ware to the blades/burrs, and foreign material such as small stones going through the grinder destroy the blades. Although most roasters now have destoners to run their coffee thought, some small foreign items still occasional make it thorough.
If you don't know how many kilos have been put through the grinder, then you will need to asses grinder blade ware by visually inspecting the blades. However symptoms of worn burrs/blades are a burnt taste on the espresso or an increase in particle size variance.
There are also grinder cleaning tablets which you can put through the grinders to remove the oil residue on the blades and prolong the burr/blade life. We highly recommend this, as well as noting down when the blades were last changed and estimating a date for the next change based on overage weekly volumes.