Flat vs. conical burrs in coffee grinders, which is best?

In this blog post, we will provide a brief overview and attempt to answer the question: What is best, flat burrs or conical burrs?


At Kaffa, we offer a selection of grinders with both options, to provide alternatives for our customers' many preferences.
And as usual, there isn't a right or wrong answer for everyone; it's like comparing apples and oranges. Similar, but different.

NOT ONLY THE TYPE OF BURR MATTERS

The main function of a grinder is to force coffee beans through a gap between two burrs, which work in a combination of two processes that both crush and cut the beans into particles you can brew with. A quality grinder is a carefully assembled combination of components. The burrs themselves are a critical element, but they are not the only factor. Other systems on the grinder also affect the grinding of the coffee. The drive train and adjustment mechanism are also important for the result. You can read more about grind size and grinder adjustment in our blog post here.

DESIGN

When it comes to burr types, the two most common main types are flat and conical. Flat burr sets have two compatible shapes that lie parallel to each other. Conical burr sets consist of an outer ring and an inner cone shape that fit into each other. Both types, in their simplest form, have holes at the top and a narrow opening at the bottom or side to allow ground particles to pass through. That gap is, for simplicity's sake, your grind setting.


Essentially, the purpose of grinding coffee is for the burrs to crush and cut the beans into smaller pieces, so that flavor can be extracted when water eventually comes into contact with these particles. Read more about extraction in our article here. It is in this complex process that we find the differences between flat and conical burrs.

 

THERE ARE DIFFERENCES

Conical burrs have several advantages over flat burrs. They require less adjustment and a simpler adjustment mechanism. The overall design is better for dispensing ground coffee, and makes cleaning easier. The slower motor limits noise, overheated coffee beans, and clogged grinders. This makes them the obvious choice for hand grinders. In short, conical burrs will be a good choice for most people.
A flat burr requires more power to ensure that the beans are pushed into the grinding chamber and then ejected from the sides. As a result, flat burrs tend to produce more noise and require more maintenance in the form of cleaning. Flat burrs also generate more heat than conical burrs because they use more mechanical force. If flat burrs get too hot, they can change the consistency of the result. The heat produced by friction can have a negative effect on the coffee beans and alter the taste. Therefore, flat burrs should ideally be of a certain physical size to minimize these disadvantages, which in turn requires a stronger motor and drives up the cost.

 

RETENTION

The difference in design can affect how coffee particles flow out of the grinder. Although the overall design of the grinder, grinding chamber, and the exit tunnel from the grinding chamber can also influence this. A common misconception is that flat burrs lead to greater retention, or coffee residue in the grinder. This is not necessarily true. Due to the distribution process in flat burrs where ground particles mostly exit by extrusion at the sides, some of the coffee can get trapped in the middle. Barazza's grinders with flat burrs therefore have a dome-like surface in the center of the bottom burr holder that helps to push beans and large particles towards the teeth of the burrs themselves, ensuring minimal retention occurs in the center of the burrs.
Conical burrs, on the other hand, primarily use gravity and their screw shape to push/screw out ground coffee particles. Retention will depend more on the design of the grinding chamber itself and the funnel leading out of it. The Sette series implemented a revolutionary gearbox and burr design where the outer burr or ring spins, allowing the ground coffee particles to fall freely out of the grinder. The result is fast grinding and virtually zero retention.

GRIND SIZES AND PARTICLE DISTRIBUTION

Another confusing difference when it comes to flat burrs vs. conical burrs can be the range of grind sizes. Here too, it's the sum of the physical properties of the systems in the grinder, more than the type of burr, that determines the outcome. Nevertheless, it can be said that flat burrs produce more uniform coffee particles, but conical burrs can be more consistent.

As we learned in our article on extraction here, this means that you can potentially get greater extraction from flat burrs, and thus extract more aroma and flavor. Some coffee enthusiasts therefore swear by this type of grinder. While a conical grinder, on the other hand, will potentially generate a consistent result more easily from time to time, which can be an advantage in a home setting where you want the best possible and stable result and a quiet, compact grinder.

What is most important to you? We at Kaffa can help you find the right grinder for your needs, but always remember that the coffee itself is the most important thing for good coffee!