Burrs

BURRS
An introduction to burrs, what they are, what significance they have, their location in the grinder, etc.

When buying a coffee grinder, it is good if you know what you are getting. An important aspect are the burrs, which often differ between grinders. The absolute biggest difference is the shape of the burrs. Conical and flat burrs are the most common forms of burrs for semi-professional and professional use. That is why this article will address the differences and similarities between conical and flat grinding wheels.

TABLE OF CONTENT
Shape
Performance (evenness, sound, heat, waste)
Maintenance
Price
Conclusion

1. SHAPE
Conical and flat burrs grind the coffee in the same way. A serrated ring moves against another serrated ring. The coffee beans are crushed between the two rings. The difference between the burrs is the shape of the rings.

Conical burrs have a conical shaped ring inside another conical shaped ring which is hollow. In terms of shape, they resemble a hand-held citrus press. The beans are directed downwards at an extremely acute angle, the path is almost vertical. The coffee is passed through the first quite large opening and down to the significantly smaller opening at the bottom.

Flat burrs have two rings that are placed horisontally. The serrations on one of the rings are directed downwards, while the serrations on the other ring are directed upwards, so the serrations are directed towards eachother. The coffee beans are released vertically down the burrs and when they hit the bottom, they change direction 90 degrees and are pressed out horizontally into the saw teeth.

2. PERFORMANCE
EVENNESS
When using flat burrs, you always get the same size of the ground coffee. This means that every grain is extracted equally, and everything is uniform.

Bimodal grinding is the grinding conical burrs use and you get two different sized grains (small and large). The two different sizes means that the smaller grains limit the water supply, which makes water move to the larger grains where it can easily get through. This means that the coffee will be saturated differently, and thus the taste can be affected.

SOUND
Coffee grinders with conical burrs generally have a lower rpm (revolutions per minute) than grinders with flat burrs. The flat burrs need higher rpm to force all beans through the grinder, since the L-shaped path requires a horizontal force compared to the conical burr that lets gravity take care of moving the beans. This means that grinders with conical burrs don’t need an equally powerful motor and thus the sound level becomes lower.

HEAT
Like the sound, conical burrs produce less heat than flat burrs. A lower rpm means less friction and thus less heat is generated between the burrs.

WASTE
Coffee grinders with flat burrs have a tendency to accumulate coffee in the system. Depending on how often and thoroughly you clean the grinder, this can more or less affect the taste of the coffee. If you change the bean mixture often, the taste can be distorted a little more. But if you make sure to maintain the grinder and clean it continuously, this is not a problem.

Conical burrs don’t have the same problem and the waste is minimal. They are also easier to clean.

3. MAINTENANCE
Cleaning is always important and the burrs are no exception. Grinder cleaning in the form of cleaning crystals for coffee grinders is very suitable for general cleaning. Removing the bean holder and brushing clean with a grinder cleaning brush is also recommended. If you start to feel that the grinding is not going as well as usual, it may be because the coffee residues on the grinder prevent the saw teeth from crushing the beans in the correct way. Then you may need to open up the grinder and clean the burrs by hand, or hand it in to our service workshop and we will fix everything that may need to be fixed.

The easiest way to destroy burrs? Grinding foreign substance. Never grind anything else than coffee beans in the grinder. The burrs are specifically designed to crush the beans. Nothing else should be passed through the grinder.