Angle grinders are often referred to as side grinders or disc grinders. These are handheld devices used mainly for grinding and polishing. Angle grinders derive power from an electric motor that propels a geared head at a right angle on which an abrasive disc is mounted. The size of the abrasive disc varies from 4 inches to 9 inches depending upon the power the grinder is required to generate. Angle Grinders with 4 inches and 5 inches generate higher RPM (Revolutions Per Minute) and less power.