Blade, flat or conical

Grinders are a lot like espresso machines themselves. There are 100s if not 1000s of options, all with different features and very different price points. You will eventually get to a point where you might want different types of grinders for different types of beans and flavor profiles, but if you are just starting out, you might not want to think about all of those options, and you might not be willing or able to spend the money required to get multiple grinders. So, for the time being, we are going to keep it simple. We are going to group grinders by burr type, and go over the three main types. We will also cover a few key features to look out for as well.

BURRS

If we group grinders by burrs, there are, in general, 3 main types of grinders. Blade, Conical Burr and Flat Burr. If you bring up the notion of a blade grinder in espresso forums you will most likely offend someone if not get asked to leave. These are generally used for spices, and coffee geeks would tell you this is no better than taking a knife to a coffee bean. A blade grinder operates by cutting beans where burr grinders operate more by pressure, crushing the beans. If at all possible I would highly advise staying away from blade grinders and sticking with burr grinders. As such, for our purposes, we won't discuss blade grinders, we will be focusing on burr grinders. 

So what is the difference between a flat burr grinder and a conical burr grinder? From a mechanical aspect there is one main difference, flat or conical burrs. Flat burrs look like two flat disks with teeth put on top of each other, where conical burrs look almost like two cupcake wrappers placed inside of each other. So how does the burr shape translate into extraction? 

There are a few key aspects to pay attention to. Grind consistency, coffee retention and ease of use. Grind consistency under ideal conditions will go to the flat burr grinders. This is largely due to the fact that flat burr grinders only have one dimension to monitor to keep the burrs aligned, whereas conical burrs have two. However, ideal conditions are hard to keep with flat burrs. To drastically over simplify, coffee falls though conical burns where coffee gets “spun” out of flat burs. In order for the coffee to get spun out, the burrs need to be spinning at a much higher rate. This leads to heat build up. The warmer the burrs, the warmer the coffee, the warmer the oils, and the faster the extraction. This is how you quickly move away from “ideal conditions”. Once the burrs start to heat up, you need to start adjusting grind, which can lead to a preserved inconsistency in grind. 

The second aspect to keep in mind is coffee retention, this is the amount of grounds that stay in the machine once all the coffee has been ground. This can be anything from 1 to a few grams. Generally speaking you want this amount to be as little as possible as old coffee will go stale and stick to the inside of the grinder. In conical machines you have gravity giving you quite a bit of help pulling the ground out, in flat, the burrs need to spin fast enough to throw the grounds out. Which means conical burrs will typically perform slightly better in the long run. 

Ease of use is the other thing to consider between these two burr types as well. Flat burrs are going to be a little more fussy if you are running quite a bit of coffee though them as you will need to manipulate grind side and motor speed as the burrs heat up. As conical burrs don’t heat up as fast, they will be a little easier to use.

So which burr type is better? It is really going to depend on use case and budget, but in a very general sense I would argue that conical burrs are going to be the best for most people to start with, though for enthusiast flat burrs may provide a larger amount of control.

OTHER CONSIDERATIONS

Outside of burrs there are a few other things to consider. Those being single dose vs hopper, sound level, burr material and so on. Largely these will all come down to preference. Most enthusiasts will tell you that the quieter the better, single doses are better than hopper loaded, and ceramics are better than metal. But each of those has their pros and cons will be covered in depth in the theory section.