Conical Burr

Conical burrs are a grinding mechanism consisting of a cone-shaped inner burr that rotates inside a stationary ring-shaped outer burr. Beans enter from the top, are caught between the two burr surfaces, and are progressively broken down as they spiral toward the narrower gap at the bottom. The conical geometry naturally feeds beans through the grinding path using gravity, requiring lower rotational speed than flat burrs.

The lower RPM operation of conical burrs generates less heat and less noise than flat burrs, which is an advantage for preserving volatile aromatic compounds and for comfortable home use. The gravity-assisted feed also means conical burr grinders tend to have very low retention — less ground coffee stays trapped inside the grinding chamber between doses.

Conical burrs produce what is described as a bimodal particle size distribution: the output contains a peak of the target size particles plus a secondary peak of smaller fines. This distribution gives conical-ground coffee a slightly fuller body and richer mouthfeel compared to the more unimodal (single-peaked) distribution of flat burrs. Whether this is desirable depends on personal preference and brewing method.

Conical burrs dominate the hand grinder and single-dose grinder market because of their low retention and gravity feed. They are also common in commercial shop grinders designed for high-volume espresso service. The bimodal grind they produce works excellently for espresso, where some fines contribute to body and crema, and performs well across pour-over and other brewing methods.