Burr mill

Burr mills do not heat the ground product by friction as much as blade grinders ("choppers"), and produce particles of a uniform size determined by the separation between the grinding surfaces.

Food burr mills are typically designed for a specific purpose, such as grinding coffee beans, dried peppercorns, coarse salt, various spices, or poppy seeds as an example. Coffee mills for volume consumption are usually powered by electric motors, but fast and precise manual mills have experienced an uptick in popularity in the 2020s for individual-serving pour-over and espresso. Domestic pepper, salt, and spice mills, used to sprinkle a little seasoning on food, are usually operated manually, sometimes by a battery-powered motor.

Coffee grinders

The uniform particle size and variable settings of a burr grinder make it well-suited for coffee preparation, as different methods of coffee preparation require different size grinds. The size of the grind is determined by the separation between the two burrs, into which the coffee beans fall and are ground a few at a time. A finer grind allows a larger surface area to come into contact with the water, which yields a more complete extraction of caffeine and flavor. The grind spectrum ranges from Turkish coffee and espresso on the finer end to a French press, Karlsbad coffee and cold brew extraction on the coarse/extra coarse end, with pour-overs and drip coffee in the medium-fine to medium range. Blade mills are also used, but produce an undesirable wide range of particle sizes.

Burr coffee grinders can keep the flavor and aroma of the coffee beans intact if they operate at relatively low rotational speeds, producing less heat from friction than faster grinders and blade mills; "The oils and aromas can easily dissipate if the beans become too hot during grinding, although most grinders will not heat the beans to a high enough temperature to risk this occurring."

Electrically powered burr grinders obtain these lower speeds and even grind through two mechanisms. Lower-cost models generally use a small electric motor to drive a series of reduction gears, while heavy-duty commercial grinders use "direct drive", a large motor and a belt rather than gear reduction to spin the burrs. The reduction gear versions are noisier and usually do not have the lifespan of the direct drive units.

Electrically powered burr grinders are available in many variations. Some grinders allow fineness of grind to be adjusted in discrete steps, marked with numbers to allow a particular setting to be repeated, while stepless varieties use a worm drive or other mechanism to provide continuous variation without jumps between steps. Commercial grinders may include a doser, a catch bin to collect the ground coffee and release a specified amount at a time; doserless versions deliver the ground coffee into a container, which may be an espresso machine portafilter. Doserless grinders may implement weight-based or advance time-based grinding to deliver the right amount of coffee for an espresso shot or other beverage in a coffeehouse.

Manual coffee grinders have been largely supplanted by electrically powered ones for speed and convenience. Manual grinders, usually but not always less costly than electric models, continue in occasional use for cost, convenience, size, and aesthetic reasons. The powder-fine grind required for Turkish coffee cannot be achieved in an inexpensive home electric grinder without overstraining the motor and potentially damaging the plastic gears, or in a simple manual grinder; special precise manual grinders, often costly, are used.