Flat or conical burrs? That is the question

The coffee grinder is among the most important equipment for any barista and home barista. When it comes to choosing a coffee grinder we have many options to consider, but the main feature we need to evaluate is the real core: the burrs.

There are two main categories on the market: flat or conical.  

Let's see here the most important differences and how the choice can change the final result. 

Both flat and conical burrs are made of two parts, the upper stationary and the lower part that moves. 

Flat ones are both the same shape and size while conical burrs have the lower moving part in the shape of a truncated cone that rotates inside the hollow upper burr due to the driveshaft. 

Let's look at the main differences in detail. 

FLAT BURRS 

Flat burrs are mostly used because they are cheaper and have an easier maintenance and replacement process even for an unskilled user. They are distinguished by flat shape and the parallel alignment. 

As they have less cutting surface and release the ground coffee by centrifugal force, flat burrs spin at a higher speed (900-1400 rpm). However, more speed also means more heat, and this is definitely a drawback. In fact, this overheats the coffee before extraction. 

Flat burrs are cheaper however they also have a shorter lifespan; they should be replaced after grinding about 300-400 kg of coffee. This rate also varies depending on the type of coffee. 

One selling point is the greater precision. The driveshaft that moves the flat burrs is more aligned than in the conical ones; we refer to hundredths of a millimeter of misalignment, but this helps to produce a finer, more homogeneous grind with flat burrs. 

CONICAL BURRS 

As illustrated in the picture, the conical burrs are formed by a truncated shape part that rotates inside the stationary hollow upper one. The ground coffee falls by gravity from the top down between the space within the two burrs. 

With a larger cutting surface, they manage to grind the same coffee as flat burrs while spinning at lower speed (about 350-500 rpm). As anticipated, this stresses the coffee less and generates reduced overheating, thus preserving oils and flavors. 

Conical burrs are more expensive than flat ones but this is balanced by a longer lifespan requiring replacement after about 900-1000 kg of ground coffee.  

Finally, conical burrs are commonly considered less precise resulting in multimodal grinding, this meaning coarser  and finer particles all together. 

The most popular materials for both types are steel, titanium and ceramic.  

On our site you can find several coffee grinders with flat grinds, from the brand new EK OMNIA, to the Eureka Mignon Single Dose and many more.   

With conical grinds and a diameter of 40 mm there is Fellow Opus instead. 

To sum up, whichever type of burrs you prefer for your coffee grinder, it is essential to replace them regularly because the more worn burrs you use, the more your coffee will be heated before extraction, and that is never a good idea!