Coffee grinders What s the difference between conical 12 05 2020· A grinder with flat burrs can get very close to the conical temperatures if it s built with the necessary technical precautions such as proper ventilation and speed of grinding he says He uses the Dalla Corte burrs as an example telling me that the 65 mm burr diameter and the 1400 RPM of the motor are important for obtaining a not high peripheral speed and lower heat