A mill that reduces roasted coffee beans to grounds of the size a brewing method needs, from coarse for a French press to very fine for espresso. Burr grinders crush the beans between two abrasive surfaces set a fixed distance apart and give an even grind; blade grinders chop with a spinning blade and produce a mix of dust and chunks, which brews unevenly. Hand-cranked burr mills and electric models both exist.
Grinding just before brewing matters because ground coffee goes stale within minutes. The same machine can grind whole spices, but the oils of cumin or coriander linger in the burrs and flavour the next coffee, so cooks who grind spices often keep a second mill: see spice grinder.