Which kind of grinding burrs are better? How can we choose between flat or conical burrs? There is often a lack of knowledge when we hear people talking about this topic: most of the time people don’t think they need to know about what’s inside a grinder.
Whether we like it or not, we are in the final stage of the supply chain so if we don’t care about it, we are going to ruin all of what has been done before.
So, which are the elements that have to be considered?
First of all, we need to have a clear idea of the final product we want to obtain in term of quality.
Firstly, conical and flat grinding burrs have different cutting shape; in conical burrs, we have an outer burr and a cone-shaped burr that sits inside the other one. The conical one has a non-uniform distribution with two different ground sizes, a smaller one and a larger one. The larger particles need more time to saturate cause of the smaller ones that restrict the flow of the water.
That’s why we are going to find an unbalanced cup with bitterness flavors and as well the chance to cause channeling. As regards the flat burrs, the beans are grinding between two horizontally rings of burrs that faced each other.
For this reason, there will be some retention of grounds coffee between the teeth in which coffee comes out (affecting the freshness of the following shots).
In conical burrs, it never happens cause coffee literally flow down relying on gravity. Secondly, conical burrs have lower rpm-grinder instead of flat ones which means less overheating (and less noise too).
Overheating the grinding chamber, could affect the flavors and the aromas for the final cup and also produce a static charge. But now we can avoid these problems keeping the grinding chamber on a stable temperature.
We have already talked about this on a previous article. Here you can have a look. However, flat ones provide a uniform distribution of ground size, which means better quality with a cleaner cup.
So, in the end, I do prefer the flat ones.
And just remember this:
more diameter of grinding burrs means fewer rotations of them and fewer seconds of grinding the dose. So less heater, less static charge and clumping.